ADS5294IPFPT [TI]
八通道、14 位、80MSPS 模数转换器 (ADC) | PFP | 80 | -40 to 85;型号: | ADS5294IPFPT |
厂家: | TEXAS INSTRUMENTS |
描述: | 八通道、14 位、80MSPS 模数转换器 (ADC) | PFP | 80 | -40 to 85 转换器 模数转换器 |
文件: | 总67页 (文件大小:2460K) |
中文: | 中文翻译 | 下载: | 下载PDF数据表文档文件 |
ADS5294
www.ti.com
SLAS776B –NOVEMBER 2011–REVISED JULY 2012
Octal Channel 14-Bit, 80 MSPS High-SNR and Low-Power ADC
Check for Samples: ADS5294
1
FEATURES
DESCRIPTION
Using CMOS process technology and innovative
circuit techniques, the ADS5294 is a low power
80MSPS 8-Channel ADC. Low power consumption,
high SNR, low SFDR, and consistent overload
recovery allow users to design high performance
systems.
•
•
Maximum Sample Rate: 80 MSPS/14-Bit
High Signal-to-Noise Ratio
–
–
75.5-dBFS SNR at 5 MHz/80 MSPS
78.2-dBFS SNR at 5 MHz/80 MSPS and
Decimation Filter Enabled
The ADS5294 has a digital processing block that
integrates several commonly used digital functions for
improving system performance. It includes a digital
filter module that has built-in decimation filters (with
low-pass, high-pass and band-pass characteristics).
The decimation rate is also programmable (by 2, by
4, or by 8). This makes it useful for narrow-band
applications, where the filters can be used
conveniently to improve SNR and knock-off
harmonics, while at the same time reducing the
output data rate. The device includes an averaging
mode where two channels (or even four channels)
can be averaged to improve SNR.
–
84-dBc SFDR at 5 MHz/80 MSPS
•
•
Low Power Consumption
–
–
58 mW/CH at 50 MSPS
77 mW/CH at 80 MSPS (2 LVDS Wire Per
Channel)
Digital Processing Block
–
Programmable FIR Decimation Filter and
Oversampling to Minimize Harmonic
Interference
–
Programmable IIR High Pass Filter to
Minimize DC Offset
Serial LVDS outputs reduce the number of interface
lines and enable the highest system integration. The
digital data from each channel ADC can be output
over one or two wires of LVDS output lines
depending on the ADC sampling rate. This 2-wire
interface helps keep the serial data rate low, allowing
low cost FPGA based receivers to be used even at
high sample rate. The ADC resolution can be
programmed to 12 bit or 14 bit through registers. A
very unique feature is the programmable mapping
module that allows flexible mapping between the
input channels and the LVDS output pins. This helps
greatly reduce the complexity of LVDS output routing
and can potentially result in cheaper system boards
by reducing the number of PCB layers.
–
–
Programmable Digital Gain: 0 dB to 12 dB
2- or 4- Channel Averaging
•
Flexible Serialized LVDS Outputs:
–
–
–
One or Two Wires of LVDS Output Lines
per Channel Depending on ADC Sampling
Rate
Programmable Mapping Between ADC
Input Channels and LVDS Output Pins-
Eases Board Design
Variety of Test Patterns to Verify Data
Capture by FPGA/Receiver
•
•
•
•
Internal and External References
1.8V Operation for Low Power Consumption
Low-Frequency Noise Suppression
The device integrates an internal reference trimmed
to accurately match across devices. Best
performance is expected to be achieved through the
internal reference mode. The device can be driven
with external references as well.
Recovery From 6-dB Overload within 1 Clock
Cycle
•
Package: 12-mm × 12-mm 80-Pin QFP
The device is available in a 12 mm × 12 mm 80-pin
QFP. It is specified over a –40°C to 85°C operating
temperature range. ADS5294 is completely pin-to-pin
and register compatible to ADS5292.
APPLICATIONS
•
•
•
Ultrasound Imaging
Communication Applications
Multi-channel Data Acquisition
1
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of
Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
Copyright © 2011–2012, Texas Instruments Incorporated
ADS5294
SLAS776B –NOVEMBER 2011–REVISED JULY 2012
www.ti.com
This integrated circuit can be damaged by ESD. Texas Instruments recommends that all integrated circuits be handled with
appropriate precautions. Failure to observe proper handling and installation procedures can cause damage.
ESD damage can range from subtle performance degradation to complete device failure. Precision integrated circuits may be more
susceptible to damage because very small parametric changes could cause the device not to meet its published specifications.
Figure 1. Block Diagram
2
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SLAS776B –NOVEMBER 2011–REVISED JULY 2012
PACKAGING/ORDERING INFORMATION(1)
PRODUCT
PACKAGE TYPE
OPERATING
ORDERING NUMBER
TRANSPORT MEDIA, QUANTITY
Tray, 480 (MOQ)
ADS5294IPFP
ADS5294
PFP
–40°C to 85°C
ADS5294IPFPR
ADS5294IPFPT
Tape and Reel, 1000
Tape and Reel, 250
(1) For the most current package and ordering information see the Package Option Addendum at the end of this document, or see the TI
web site at www.ti.com.
PIN CONFIGURATION
80-PIN TQFP WITH THERMAL PAD
PFP PACKAGE (TOP VIEW)
80 79 78 77 76
74
71 70 69 68 67 66 65 64 63 62 61
60
75
73 72
IN2p
IN2n
1
IN7n
IN7p
59
58
57
2
AGND
3
4
5
6
7
AGND
IN6n
Thermal Pad
IN3p
IN3n
56
55
54
53
IN6p
AGND
IN4p
AGND
IN5n
8
IN4n
IN5p
9
52
51
50
49
48
47
46
AVDD
PD
AVDD
RESET
LGND
ADS529X
80 TQFP
10
11
12
LVDD
LGND
LVDD
OUT8A_n
OUT1A_p
OUT1A_n
13
14
15
16
17
OUT8A_p
OUT8B_n
OUT8B_p
OUT7A_n
OUT7A_p
OUT1B_p
OUT1B_n
45
44
OUT2A_p
OUT2A_n
43
42
41
18
19
20
OUT2B_p
OUT2B_n
OUT7B_n
OUT7B_p
21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40
PIN FUNCTIONS
PIN
NUMBER
OF PINS
DESCRIPTION
NAME
AVDD
AGND
VCM
NUMBER
5
6
1
9, 52, 66, 71, 74
Analog power supply, 1.8V
3, 6, 55, 58, 61, 80 Analog ground
68
Common-mode output pin, 0.95 V output. This pin can be configured as the external reference
voltage (1.5 V) input pin as well. See Reg 0x42.
1
1
2
2
2
CLKN
CLKP
73
72
Negative differential clock –Tie CLKN to GND for single-ended clock
Positive differential clock
IN1P, IN1N
IN2P, IN2N
IN3P, IN3N
78, 79
1, 2
4, 5
Differential input signal, Channel 1
Differential input signal, Channel 2
Differential input signal, Channel 3
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PIN FUNCTIONS (continued)
PIN
NUMBER
OF PINS
DESCRIPTION
NAME
NUMBER
7, 8
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
1
1
1
1
1
1
1
IN4P, IN4N
Differential input signal, Channel 4
Differential input signal, Channel 5
Differential input signal, Channel 6
Differential input signal, Channel 7
Differential input signal, Channel 8
Differential LVDS bit clock (7X)
Differential LVDS frame clock (1X)
IN5P, IN5N
53, 54
56, 57
59, 60
62, 63
31, 32
29, 30
13, 14
15, 16
17, 18
19, 20
21, 22
23, 24
25, 26
27, 28
35, 36
33, 34
39, 40
37, 38
43, 44
41, 42
47, 48
45, 46
10
IN6P, IN6N
IN7P, IN7N
IN8P, IN8N
LCLKP, LCLKN
ACLKP, ACLKN
OUT1A_P, OUT1A_N
OUT1B_P, OUT1B_N
OUT2A_P, OUT2A_N
OUT2B_P, OUT2B_N
OUT3A_P, OUT3A_N
OUT3B_P, OUT3B_N
OUT4A_P, OUT4A_N
OUT4B_P, OUT4B_N
OUT5A_P, OUT5A_N
OUT5B_P, OUT5B_N
OUT6A_P, OUT6A_N
OUT6B_P, OUT6B_N
OUT7A_P, OUT7A_N
OUT7B_P, OUT7B_N
OUT8A_P, OUT8A_N
OUT8B_P, OUT8B_N
PD
Differential LVDS data output, wire 1, channel 1
Differential LVDS data output, wire 2, channel 1
Differential LVDS data output, wire 1, channel 2
Differential LVDS data output, wire 2, channel 2
Differential LVDS data output, wire 1, channel 3
Differential LVDS data output, wire 2, channel 3
Differential LVDS data output, wire 1, channel 4
Differential LVDS data output, wire 2, channel 4
Differential LVDS data output, wire 1, channel 5
Differential LVDS data output, wire 2, channel 5
Differential LVDS data output, wire 1, channel 6
Differential LVDS data output, wire 2, channel 6
Differential LVDS data output, wire 1, channel 7
Differential LVDS data output, wire 2, channel 7
Differential LVDS data output, wire 1, channel 8
Differential LVDS data output, wire 2, channel 8
Power down control input. Active High. The pin has an internal 220-kΩ pulldown resistor.
Negative reference input/ output
REFB
69
REFT
70
Positive reference input/ output
RESET
51
Active HIGH RESET input. The pin has an internal 220-kΩ pulldown resistor.
Serial clock input. The pin has an internal 220-kΩ pulldown resistor.
Serial data input. The pin has an internal 220-kΩ pulldown resistor.
SCLK
77
SDATA
76
SDOUT
64
Serial data readout. This pin is in the high-impedance state after reset. When the <READOUT> bit
is set, the SDOUT pin becomes active. This is a CMOS digital output running from the AVDD
supply.
1
1
CSZ
75
65
Serial enable chip select – active low digital input
SYNC
Input signal to synchronize channels and chips when used with reduced output data rates. If it is
not used, add a ≤ 10 KΩ pull-down resistor.
2
2
1
LVDD
LGND
NC
11, 49
12, 50
67
Digital and I/O power supply, 1.8V
Digital ground
No Connection. Must leave floated
4
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ABSOLUTE MAXIMUM RATINGS(1)
over operating free-air temperature range (unless otherwise noted)
VALUE
UNIT
MIN
–0.3
–0.3
–0.3
–0.3
–0.3
–0.3
MAX
2.2
Supply voltage AVDD
LVDD
V
V
2.2
between AGND and LGND
0.3
V
at analog inputs
at digital inputs, CLKN, CLKP(2), RESET, SCLK, SDATA, CSZ
min[2.2, AVDD+0.3]
V
Voltage
min[2.2, AVDD+0.3]
V
at digital outputs
Maximum junction temperature (TJ), any condition
Storage temperature range
min[2.2,LVDD+0.3]
V
105
150
85
°C
°C
°C
V
–55
-40
Operating temperature range
Human Body Model (HBM)
ESD Ratings
2000
500
Charged Device Model (CDM)
V
(1) Stresses above those listed under absolute maximum ratings may cause permanent damage to the device. These are stress ratings
only and functional operation of the device at these or any other conditions beyond those indicated under “recommended operating
conditions” is not implied Exposure to absolute maximum rated conditions for extended periods may degrade device reliability.
(2) When AVDD is turned off, it is recommended to switch off the input clock (or ensure the voltage on CLKP, CLKN is < |0.3V|. This
prevents the ESD protection diodes at the clock input pins from turning on.
THERMAL INFORMATION
ADS5294
THERMAL METRIC(1)
UNITS
PFP (80 PINS)
θJA
Junction-to-ambient thermal resistance
30.8
6.3
8.3
0.2
8.2
0.3
θJCtop
θJB
Junction-to-case (top) thermal resistance
Junction-to-board thermal resistance
°C/W
ψJT
Junction-to-top characterization parameter
Junction-to-board characterization parameter
Junction-to-case (bottom) thermal resistance
ψJB
θJCbot
(1) For more information about traditional and new thermal metrics, see the IC Package Thermal Metrics application report, SPRA953.
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UNIT
RECOMMENDED OPERATING CONDITIONS
MIN
TYP
MAX
SUPPLIES
AVDD Analog supply voltage
LVDD Digital supply voltage
ANALOG INPUTS/OUTPUTS
Differential input voltage range
Input common-mode voltage
REFT External reference mode
REFB External reference mode
1.7
1.7
1.8
1.8
1.9
1.9
V
V
2
0.95±0.05
1.45
VPP
V
V
0.45
V
VCM
Common-mode voltage output
External Reference mode Input
0.95
V
1.5
V
(1)
Maximum Input Frequency
2 VPP amplitude
80
MHz
CLOCK INPUTS
ADC Clock input sample rate
10
0.2
0.2
0.2
80
MSPS
VPP
Sine wave, AC-coupled
LVPECL, AC-coupled
LVDS, AC-coupled
1.5
1.6
Input Clock amplitude differential (V(CLKP)
V(CLKN)) peak-to-peak
-
0.7
VIL
VIH
<0.3
>1.5
50%
V
V
Input Clock CMOS single-ended (V(CLKP)
Input clock duty cycle
)
35%
65%
DIGITAL OUTPUTS
1x (sample
rate)
ACLKP and ACLKN outputs (LVDS), 1-wire interface
LCLKP and LCLKN outputs (LVDS), 1-wire interface
ACLKP and ACLKN outputs (LVDS), 2-wire interface
LCLKP and LCLKN outputs (LVDS), 2-wire interface
MSPS
MSPS
MSPS
MSPS
7x (sample
rate)
0.5x (sample
rate)
3.5x (sample
rate)
Maximum data rate, 2-wire interface
560
700
5
Mbps
Mbps
pF
Maximum data rate, 1-wire interface
CLOAD Maximum external capacitance from each output pin to LGND
RLOAD Differential load resistance between the LVDS output pairs
100
Ω
TA
Operating free-air temperature
-40
85
°C
(1) See the Large and Small Signal Input Bandwidth section.
6
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SLAS776B –NOVEMBER 2011–REVISED JULY 2012
ELECTRICAL CHARACTERISTICS DYNAMIC PERFORMANCE
Typical values are at 25°C, AVDD = 1.8 V, LVDD = 1.8 V, 50% clock duty cycle, –1 dBFS differential analog input, Sample
rate = 80 MSPS, ADC is configured in internal reference mode (unless otherwise noted). MIN and MAX values are across the
full temperature range TMIN = –40°C to TMAX = 85°C, AVDD = 1.8 V, LVDD = 1.8 V.
PARAMETERS
CONDITIONS
MIN
TYP
MAX
UNITS
AC PERFORMANCE
fin = 10 MHz, 65 MSPS
fin = 5 MHz, TA = 25°C
75.6
75.5
dBFS
dBFS
dBFS
dBFS
dBFS
dBFS
dBFS
dBFS
dBFS
dBFS
Bits
72.8
71.8
fin = 5 MHz, Across temperatures
SNR
Signal-to-noise ratio
fin = 5 MHz, -60 dBFS Input signal amplitude
77.3
78.2
74.2
71.7
74.8
73.4
70
fin = 5 MHz, Decimation by two enabled
fin = 30 MHz
fin = 65 MHz
fin = 5 MHz
SINAD
Signal-to-noise and distortion ratio
fin = 30 MHz
fin = 65 MHz
ENOB
DNL
INL
Effective number of bits
Differential nonlinearity
Integral nonlinearity
fin = 5 MHz
12.2
±0.5
2.2
84
fin = 5 MHz
–0.96
72
1.7
5.5
LSB
LSB
dBc
fin = 5 MHz
fin = 5 MHz
SFDR
THD
HD2
HD3
Spurious-free dynamic range
Total harmonic distortion
fin = 30 MHz
81
dBc
fin = 65 MHz
74
dBc
fin = 5 MHz
70.5
73
82
dBc
fin = 30 MHz
80
dBc
fin = 65 MHz
73.5
93
dBc
fin = 5 MHz
dBc
Second-harmonic distortion
Third-harmonic distortion
fin = 30 MHz
88
dBc
fin = 65 MHz
85
dBc
fin = 5 MHz
72
84
dBc
fin = 30 MHz
81
dBc
fin = 65 MHz
74
dBc
fin = 5 MHz
91
dBc
Worse spur excluding HD2, HD3
fin = 30 MHz
83
dBc
fin = 65 MHz
76
dBc
IMD3
Intermodualtion distortion
Overload recovery
fin = 8 MHz at –7 dBFS, f2 = 10 MHz at –7 dBFS
84.5
dBc
Recovery to within 1% of full-scale for 6-dB overload with
sine wave input
1
Clock Cycle
fin = 10 MHz, -1 dBFS signal applied on
aggressor channel no signal applied on
victim channel
far channel
90
85
dBc
dBc
XTALK
Cross-talk
near channel
Phase noise
5 MHz, 1 kHz off carrier
–138
dBc/Hz
ANALOG INPUT / OUTPUT
Differential input voltage range
(0-dB gain)
2
VPP
RIN
CIN
Differential Input Resistance
Differential Input Capacitance
Analog input bandwidth
At DC
2
3.2
kΩ
pF
At DC
With a 50 Ωsource impedance
550
MHz
Analog input common-mode current
(per input pin)
1.6
µA/MSPS
VCM common-mode output voltage
VCM output current capability
0.95
5
V
mA
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ELECTRICAL CHARACTERISTICS DYNAMIC PERFORMANCE (continued)
Typical values are at 25°C, AVDD = 1.8 V, LVDD = 1.8 V, 50% clock duty cycle, –1 dBFS differential analog input, Sample
rate = 80 MSPS, ADC is configured in internal reference mode (unless otherwise noted). MIN and MAX values are across the
full temperature range TMIN = –40°C to TMAX = 85°C, AVDD = 1.8 V, LVDD = 1.8 V.
PARAMETERS
CONDITIONS
MIN
TYP
MAX
UNITS
DC ACCURACY
Offset error
Across devices and across channels within a device
–15
15
mV
Temperature coefficient of offset error
<0.01
mV/ °C
Gain error due to internal reference
inaccuracy alone
E(GREF)
Across devices
-2
2
%FS
E(GCHAN)
Gain error of channel alone
0.5
%FS
Temperature coefficient of E(GCHAN)
<0.01
%FS/ °C
POWER SUPPLY
80 MSPS, 14 Bit, 2-wire LVDS
50 MSPS, 1-wire LVDS
77
58
52
33
mW/CH
mW/CH
mW/CH
mW/CH
40 MSPS, 14 Bit, 1-wire LVDS
10 MSPS, 14 Bit, 1-wire LVDS
Power consumption
fin = 10 MHz, 80 MSPS, 14 Bit,
Decimation filter = 2, 1-wire LVDS
100
mW/CH
14 Bit, 80 MSPS
230
200
155
111
80
265
122
mA
mA
mA
mA
mA
mA
AVDD
LVDD
14 Bit, 65 MSPS
14 Bit, 40 MSPS
80 MSPS, 14 Bit, 2-wire LVDS
50 MSPS, 14 Bit, 1-wire LVDS
40 MSPS, 14 Bit, 1-wire LVDS
73
80 MSPS, 1 Bit, Decimation filter = 2,
1-wire LVDS
210
175
mA
Partial Power Down (80 MSPS, 2-wire)
Complete Power Down
mW
mW
dB
Power-down power consumption
60
Power supply modulation ratio
Power supply rejection ratio
Carrier = 5 MHz, f(PSRR) = 10 kHz, 50 mVpp on AVDD
AC power supply rejection ratio f = 10 kHz
35
55
dB
8
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DIGITAL CHARACTERISTICS
The DC specifications refer to the condition where the digital outputs are not switching, but are permanently at a valid logic
level 0 or 1. AVDD = 1.8V, LVDD = 1.8V
PARAMETERS
CONDITION
MIN
TYP
MAX
UNITS
DIGITAL INPUTS/OUTPUTS
All digital inputs support 1.8-V and 3.3-V CMOS
logic levels.
VIH
Logic high input voltage
1.3
V
VIL
IIH
Logic low input voltage
Logic high input current
Logic low input current
Logic high output voltage
Logic low output voltage
0.4
V
µA
µA
V
VHIGH = 1.8 V
VLOW = 0 V
6
< 0.1
IIL
VOH
VOL
AVDD - 0.1
0.2
V
LVDS OUTPUTS
High-level output differential
voltage
VODH
100 Ω external termination
100 Ω external termination
245
350
405
mV
Low-level output differential
voltage
VODL
VOCM
–245
900
–350
1100
–405
1300
mV
mV
Output common-mode voltage
OUTP
Logic 0
Logic 0
V = +350 mV*
ODH
V
= -350 mV*
ODL
OUTM
V
OCM
GND
GND
*With external 100-W termination
Figure 2. LVDS Output Voltage Levels
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TIMING REQUIREMENTS(1)(2)(3)
Typical values are at 25°C, AVDD = 1.8 V, LVDD = 1.8 V, sampling frequency = 80 MSPS, 14-bit, sine wave input clock = 1.5
Vpp clock amplitude, CLOAD = 5 pF, RLOAD = 100 Ω, unless otherwise noted. MIN and MAX values are across the full
temperature range TMIN = –40°C to TMAX = 85°C, AVDD = 1.8 V, LVDD = 1.7 V to 1.9 V
PARAMETERS
CONDITIONS
MIN
TYP
MAX
UNITS
The delay in time between the rising edge of the input
sampling clock and the actual time at which the sampling
occurs
ta
Aperture delay
4
ns
Aperture delay variation
Across channels within the same device
±175
2.5
ps
ns
Across devices at the same temperature and LVDD supply
tj
Aperture jitter RMS
Data latency
320
fs rms
Clock
cycles
1-wire LVDS output interface
2-wire LVDS output interface
11
15
td
Clock
cycles
tSU
tH
Data setup time
Data hold time
80 MSPS, 2 wire LVDS, 7x serialization
80 MSPS, 2 wire LVDS, 7x serialization
0.34
0.55
0.57
0.8
ns
ns
Input clock rising edge(zero cross) to frame clock rising
edge(zero cross)
Clock propagation delay
See Table 1 and Table 2
tPROP
Variation of tPROP
LVDS bit clock duty cycle
Data rise time
Between two devices at same temperature and LVDD supply
±0.75
48%
0.24
0.24
0.20
0.20
ns
tRISE
Rise time is from -100 mV to + 100 mV, 10 ≤ Fs ≤ 80 MSPS
Fall time is from +100 mV to -100 mV, 10 ≤ Fs ≤ 80 MSPS
Rise time is from -100 mV to +100 mV, 10 ≤ Fs ≤ 80 MSPS
Fall time is from +100 mV to -100 mV, 10 ≤ Fs ≤ 80 MSPS
ns
ns
ns
ns
tFALL
Data fall time
tCLKRISE
tCLKFALL
Output clock rise time
Output clock fall time
Time to valid data after coming out of COMPLETE POWER-
DOWN mode
tWAKE
Wake-up Time
100
5
µs
µs
Time to valid data after coming out of PARTIAL POWER-
DOWN mode (with clock continuing to run during power-
down)
(1) Timing parameters are ensured by design and characterization and not tested in production.
(2) Measurements are done with a transmission line of 100-Ω characteristic impedance between the device and the load. Setup and hold
time specifications take into account the effect of jitter on the output data and clock.
(3) Data valid refers to logic HIGH of 100 mV and logic LOW of –100 mV.
10
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(1)
Table 1. LVDS Timing at Different Sampling Frequencies - 2 Wire Interface, 7x Serialization
LVDS Output Rate (MSPS)
Setup Time (tsu), ns
Hold Time (tH), ns
tPROG = (6/7) × T + tdelay, ns(2)
Zero-Crossing of LCLKP to
Data Becoming Invalid
Data Valid to Zero-
Crossing of LCLKP
(both edges)
tPROG = delay from Input clock zero-cross
rising edge to frame clock zero cross (rising
edge)
Fs = 1/T
(both edges)
MIN
TYP
0.57
0.64
0.9
1.3
2
MAX
MIN
0.55
0.8
1.2
1.6
2
TYP
0.8
1.1
1.5
1.85
2.3
3.5
7
MAX
MIN
8
TYP
9.5
9.5
9.5
9.5
9.5
9.5
9.5
MAX
11
80
65
50
40
30
20
10
0.34
0.35
0.7
1
8
11
8
11
8
11
1.7
2.9
6.5
8
11
3.2
6.7
3.2
6.7
8
11
8
11
(1) Bit clock and Frame clock jitter has been included in the Setup and hold timing.
(2) Values below correspond to tdelay, NOT tPROG
(1)
Table 2. LVDS Timing at Different Sampling Frequencies - 1 Wire Interface, 14x Serialization
LVDS Output Rate (MSPS)
Setup Time (tsu), ns
Hold Time (tH), ns
tPROG = (5/7) × T + tdelay, ns(2)
Zero-Crossing of LCLKP to
Data Becoming Invalid
Data Valid to Zero-
Crossing of LCLKP
(both edges)
tPROG = delay from Input clock zero-cross
rising edge to frame clock zero cross (rising
edge)
Fs = 1/T
(both edges)
MIN
TYP
0.48
0.68
0.8
MAX
MIN
0.28
0.54
1
TYP
0.6
MAX
MIN
7.5
7.5
7.5
7.5
7.5
TYP
MAX
10.5
10.5
10.5
10.5
10.5
50
40
30
20
10
0.28
0.5
9
9
9
9
9
0.8
0.62
1.2
1.25
1.9
1.4
1.6
3.3
3.1
3.3
3.5
(1) Bit clock and Frame clock jitter has been included in the Setup and hold timing.
(2) Values below correspond to tdelay, NOT tPROG
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LVDS TIMING DIAGRAM
Figure 3. 14-Bit 1 wire LVDS Timing Diagram
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Figure 4. Enlarged 1 wire LVDS Timing Diagram (14bit)
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Figure 5. 14-Bit 2 wire LVDS Timing Diagram
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Figure 6. Enlarged 2 wire LVDS Timing Diagram (14bit)
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Figure 7. Definition of Setup and Hold Times tSU = min(tSU1, tSU2); tH = min(tH1, tH2
)
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SLAS776B –NOVEMBER 2011–REVISED JULY 2012
TYPICAL CHARACTERISTICS
Typical values are at 25°C, AVDD = 1.8 V, LVDD = 1.8V, 50% clock duty cycle, –1 dBFS differential analog input, 14 Bit/80
MSPS, ADC is configured in the internal reference mode, unless otherwise noted.
0
−10
0
−10
SNR = 76.1 dBFS
SINAD = 75.7 dBFS
SFDR = 87 dBc
THD =84.7 dBc
SNR = 75.5 dBFS
SINAD = 74.4 dBFS
SFDR = 80.3 dBc
THD =79.7 dBc
−20
−20
−30
−30
−40
−40
−50
−50
−60
−60
−70
−70
−80
−80
−90
−90
−100
−110
−120
−130
−140
−100
−110
−120
−130
−140
10
20
30
40
10
20
30
40
Frequency (MHz)
Frequency (MHz)
Figure 8. FFT for 5 MHz Input Signal,
Sample Rate = 80 MSPS
Figure 9. FFT for 15 MHz Input Signal,
Sample Rate = 80 MSPS
0
−10
0
−10
SNR = 70.7 dBFS
SNR = 76.5 dBFS
SINAD =69.5 dBFS
SFDR = 74.9 dBc
THD =74.55 dBc
SINAD = 76.5 dBFS
SFDR = 90.23 dBc
THD = 87 dBc
−20
−20
−30
−30
−40
−40
−50
−50
−60
−60
−70
−70
−80
−80
−90
−90
−100
−110
−120
−130
−140
−100
−110
−120
−130
−140
10
20
30
40
5
10
15
20
Frequency (MHz)
Frequency (MHz)
Figure 10. FFT for 65 MHz Input Signal,
Sample Rate = 80 MSPS
Figure 11. FFT for 5 MHz Input Signal,
Sample Rate = 40 MSPS
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TYPICAL CHARACTERISTICS (continued)
Typical values are at 25°C, AVDD = 1.8 V, LVDD = 1.8V, 50% clock duty cycle, –1 dBFS differential analog input, 14 Bit/80
MSPS, ADC is configured in the internal reference mode, unless otherwise noted.
0
0
SNR = 76.5 dBFS
SINAD = 76.5 dBFS
SFDR = 88.4 dBc
THD = 87 dBc
fIN1 = 8 MHz
fIN2 = 10 MHz
Each Tone at −7dBFS Amplitude
Two Tone IMD = −91.4 dBFS
−10
−10
−20
−20
−30
−30
−40
−40
−50
−50
−60
−60
−70
−70
−80
−80
−90
−90
−100
−110
−120
−130
−140
−100
−110
−120
−130
−140
5
10
15
20
10
20
30
40
Frequency (MHz)
Frequency (MHz)
Figure 12. FFT for 15 MHz Input Signal,
Sample Rate = 40 MSPS
Figure 13. Two Tone Intermodulation
77
76
75
74
73
72
71
70
86
84
82
80
78
76
74
72
70
5
15
25
35
45
55
65
75
85
5
15
25
35
45
55
65
75
85
Input Signal frequency (MHz)
Input Signal frequency (MHz)
Figure 14. Signal -To-Noise Ratio vs. Input Signal
Frequency
Figure 15. Spurious-Free Dynamic Range vs. Input Signal
Frequency
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TYPICAL CHARACTERISTICS (continued)
Typical values are at 25°C, AVDD = 1.8 V, LVDD = 1.8V, 50% clock duty cycle, –1 dBFS differential analog input, 14 Bit/80
MSPS, ADC is configured in the internal reference mode, unless otherwise noted.
80
76
72
68
64
60
90
86
82
78
74
70
Input frequency = 10 MHz
Input frequency = 70 MHz
Input frequency = 10 MHz
Input frequency = 70 MHz
0
1
2
3
4
5
6
7
8
9
10 11 12
0
1
2
3
4
5
6
7
8
9
10 11 12
Digital gain (dB)
Digital gain (dB)
G001
G001
Figure 16. SNR vs. Digital Gain
Figure 17. SFDR vs. Digital Gain
120
110
100
90
80
70
60
50
40
30
20
10
0
80
88
87
86
85
84
83
82
78
77
76
75
74
73
72
SFDR
SNR
79.5
79
78.5
78
77.5
77
76.5
76
75.5
75
SNR
SFDR(dBc)
SFDR(dBFS)
74.5
74
−96 −86 −76 −66 −56 −46 −36 −26 −16 −6
Input amplitude (dBFS)
0
0.2 0.4 0.6 0.8
1
1.2 1.4 1.6 1.8
2
2.2 2.4
Input Clock Amplitude, differential (Vp−p)
Figure 18. Performance vs. Input Amplitude
Figure 19. Performance vs. Clock Input Amplitudes
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TYPICAL CHARACTERISTICS (continued)
Typical values are at 25°C, AVDD = 1.8 V, LVDD = 1.8V, 50% clock duty cycle, –1 dBFS differential analog input, 14 Bit/80
MSPS, ADC is configured in the internal reference mode, unless otherwise noted.
86
85.5
85
77
90
89
88
87
86
85
84
83
82
81
80
78
SFDR
SNR
Fin = 5 MHz
SFDR
SNR
77.5
77
76.5
76
76.5
76
84.5
84
75.5
75
75.5
75
83.5
83
74.5
74
74.5
74
82.5
82
73.5
73
73.5
73
1.10
35
40
45
50
55
60
65
0.80
0.85
0.90
0.95
1.00
1.05
Input Clock Duty Cycle (%)
Analog Input Common−mode voltage (V)
Figure 20. Performance vs. Input Clock Duty Cycle
Figure 21. Performance vs. Input VCM
77.0
88
87
86
85
84
83
82
81
80
79
78
AVDD=1.65V
AVDD=1.7V
AVDD=1.8V
AVDD=1.9V
AVDD=1.95V
AVDD=1.65V
AVDD=1.7V
AVDD=1.8V
AVDD=1.9V
AVDD=1.95V
76.5
76.0
75.5
75.0
74.5
74.0
−40
−20
0
20
40
60
80
−40
−20
0
20
40
60
80
Temperature (°C)
Temperature (°C)
Figure 22. Signal -To-Noise Ratio vs. Temperature
Figure 23. Spurious-Free Dynamic Range vs. Temperature
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TYPICAL CHARACTERISTICS (continued)
Typical values are at 25°C, AVDD = 1.8 V, LVDD = 1.8V, 50% clock duty cycle, –1 dBFS differential analog input, 14 Bit/80
MSPS, ADC is configured in the internal reference mode, unless otherwise noted.
100
95
90
85
80
75
70
−110
−120
−130
−140
−150
−160
Far Channel
Near Channel
10
20
30
40
50
60
70
0.01
0.1
1
10
100
Frequency of Aggressor Channel (MHz)
Frequency Offset (kHz)
Figure 24. Crosstalk vs. Frequency
Figure 25. Phase Noise for 5 MHz Input Signal,
Sample Rate = 80 MSPS
0.8
0.7
0.3
0.2
0.6
0.5
0.4
0.3
0.1
0.2
0.1
0.0
0.0
−0.1
−0.2
−0.3
−0.4
−0.5
−0.6
−0.7
−0.8
−0.1
−0.2
−0.3
900
3900
6900
9900
12900
15900
900
3900
6900
9900
12900
15400
Output_codes (dB)
Output_codes (LSB)
Figure 26. Integral Non-Linearity
Figure 27. Differential Non-Linearity
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TYPICAL CHARACTERISTICS (continued)
Typical values are at 25°C, AVDD = 1.8 V, LVDD = 1.8V, 50% clock duty cycle, –1 dBFS differential analog input, 14 Bit/80
MSPS, ADC is configured in the internal reference mode, unless otherwise noted.
80
With 50mVpp signal superimposed on input common−mode
45.5
Fin = 3 MHz
70
31.53
60
50
16.18
40
5.55
0.1
0.11
0.03
30
0
10
20
30
40
50
60
70
Frequency of CMRR signal (MHz)
Figure 28. Histogram of Output Code with Analog Inputs
Shorted
Figure 29. Common Mode Rejection Ratio vs. Frequency
−10
20
With 50mVpp signal
PSMR
PSRR
Low Pass
High pass
superimposed on AVDD supply
PSMR: 3MHz input signal applied
PSRR: No input signal applied
10
−20
−30
−40
−50
−60
−70
−80
0
−10
−20
−30
−40
−50
−60
−70
−80
0.01
0.1
1
10
70
0.0
0.1
0.2
0.3
0.4
0.5
Frequency of signal on supply (MHz)
Normalized Frequency (fin/fs)
Figure 30. Power Supply Rejection Ratio vs. Frequency
Figure 31. Filter Response, Decimate by 2
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TYPICAL CHARACTERISTICS (continued)
Typical values are at 25°C, AVDD = 1.8 V, LVDD = 1.8V, 50% clock duty cycle, –1 dBFS differential analog input, 14 Bit/80
MSPS, ADC is configured in the internal reference mode, unless otherwise noted.
40
0
Low Pass
SNR = 78.2 dBFS
SINAD = 78.2 dBFS
Decimate by 2 Filter Enabled
−10
30
Band−Pass1
Band−Pass2
High Pass
−20
20
−30
10
−40
0
−50
−10
−20
−30
−40
−50
−60
−70
−80
−60
−70
−80
−90
−100
−110
−120
−130
−140
0.0
0.1
0.2
0.3
0.4
0.5
0
5
10
Frequency (MHz)
15
20
Normalized frequency (fin/fs)
Figure 32. Filter Response, Decimate by 4
Figure 33. FFT for 5 MHz Input Signal, Sample
Rate = 80 MSPS with Decimation Filter = 2
0
−10
3
0
SNR = 77.9 dBFS
SINAD = 77.9 dBFS
SFDR = 93.13 dBc
THD = −96 dBc
−3
−20
−6
−30
2 Channels averaged
−9
−40
−12
−15
−18
−21
−24
−27
−30
−33
−36
−39
−42
−45
−50
−60
−70
−80
K=2
K=3
K=4
K=5
K=6
K=7
K=8
K=9
K=10
−90
−100
−110
−120
−130
−140
0
5
10
15
20
25
30
35
40
0.02
0.1
1
10 15
Frequency (MHz)
Input Signal Frequency (MHz)
Figure 34. FFT for 5 MHz Input Signal, Sample
Rate = 80 MSPS by Averaging 2 Channels
Figure 35. Digital High-Pass Filter Response
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TYPICAL CHARACTERISTICS (continued)
Typical values are at 25°C, AVDD = 1.8 V, LVDD = 1.8V, 50% clock duty cycle, –1 dBFS differential analog input, 14 Bit/80
MSPS, ADC is configured in the internal reference mode, unless otherwise noted.
0
0
−5
HPF_DISABLED
HPF_ENABLED
−10
−15
−25
−20
−30
−40
−35
−50
−45
−60
−55
−70
−65
−80
−90
−75
−100
−110
−120
−130
−140
−150
−85
−95
−105
−115
−125
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
0
5
10
15
20
25
30
35
40
Input Signal Frequency (MHz)
Frequency (MHz)
Figure 36. FFT with HPF Enabled and Disabled, No Signal
Figure 37. FFT (Full-Band) for 5 MHz Input Signal, Sample
Rate = 80MSPS with Low Frequency Noise Suppression
Enabled
0
0
LF noise suppression enabled
LF noise suppression disabled
LF noise suppression enabled
LF noise suppression disabled
−10
−10
−20
−30
−20
−30
−40
−40
−50
−50
−60
−60
−70
−70
−80
−80
−90
−90
−100
−110
−120
−130
−140
−100
−110
−120
−130
−140
0
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
Frequency (MHz)
1
39 39.1 39.2 39.3 39.4 39.5 39.6 39.7 39.8 39.9 40
Frequency (MHz)
Figure 38. FFT (0 to 1 MHz) for 5 MHz Input Signal, Sample
Rate = 80 MSPS with Low Frequency Noise Suppression
Enabled
Figure 39. FFT (39 MHz to 40 MHz) for 5 MHz Input Signal,
Sample Rate = 80 MSPS with Low Frequency Noise
Suppression Enabled
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TYPICAL CHARACTERISTICS (continued)
Typical values are at 25°C, AVDD = 1.8 V, LVDD = 1.8V, 50% clock duty cycle, –1 dBFS differential analog input, 14 Bit/80
MSPS, ADC is configured in the internal reference mode, unless otherwise noted.
450
400
350
300
250
200
150
350
325
300
275
250
225
200
175
150
125
100
75
2−wire
1−wire
1−wire Decimate by 2
50
10
20
30
40
50
60
70
80
10 15 20 25 30 35 40 45 50 55 60 65 70 75 80
Sampling Frequency (MSPS)
Sampling Frequency (MSPS)
Figure 40. Power Consumption on Analog Supply
Figure 41. Power Consumption on Digital Supply
240
190
170
150
130
110
90
2−wire
1−wire
1−wire Decimate by 2
220
200
180
160
140
120
100
80
70
50
30
10
20
30
40
50
60
70
80
10
20
30
40
50
60
70
80
Sampling Frequency (MSPS)
Sampling Frequency (MSPS)
Figure 42. Supply Current on Analog Supply
Figure 43. Supply Current on Digital Supply
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SERIAL INTERFACE
ADS5294 has a set of internal registers that can be accessed by the serial interface formed by pins CSZ (Serial
interface Enable – Active Low), SCLK (Serial Interface Clock) and SDATA (Serial Interface Data).
When CSZ is low,
•
•
•
Serial shift of bits into the device is enabled.
Serial data (SDATA) is latched at every rising edge of SCLK.
SDATA is loaded into the register at every 24th SCLK rising edge
If the word length exceeds a multiple of 24 bits, the excess bits are ignored. Data can be loaded in multiples of
24-bit words within a single active CSZ pulse. The first eight bits form the register address and the remaining 16
bits the register data. The interface can work with SCLK frequencies from 15 MHz down to very low speeds (few
Hertz) and also with non-50% SCLK duty cycle.
Register Initialization
After power-up, the internal registers must be initialized to the respective default values. Initialization can be done
in one of two ways:
1. Through a hardware reset, by applying a high pulse on the RESET pin; or
2. Through a software reset; using the serial interface, set the RST bit high. Setting this bit initializes the
internal registers to the respective default values and then self-resets the bit low. In this case, the RESET pin
stays low (inactive).
REGISTER DATA
REGISTER ADDRESS
SDATA
SCLK
A7
A6
A5
A4
A3
A2
A1
A0
D15 D14 D13 D12 D11 D10
D9
D8
D7
D6
D5
D4
D3
D2
D1
D0
t
DH
t
DSU
t
SLOADH
t
SCLK
t
SLOADS
CSZ
RESET
Figure 44. Serial Interface Timing
SERIAL INTERFACE TIMING CHARACTERISTICS
Typical values at 25°C, MIN and MAX values across the full temperature range TMIN = –40°C to TMAX = 85°C, AVDD = 1.8 V,
LVDD = 1.8 V, unless otherwise noted.
PARAMETER
MIN
> DC
33
TYP MAX
UNIT
MHz
ns
fSCLK
tSLOADS
tSLOADH
tDS
SCLK frequency (= 1/ tSCLK
CS to SCLK setup time
SCLK to CS hold time
SDATA setup time
)
15
33
ns
33
ns
tDH
SDATA hold time
33
ns
26
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RESET TIMING
Typical values at 25°C, MIN and MAX values across the full temperature range TMIN = –40°C to TMAX = 85°C (unless
otherwise noted)
PARAMETER
TEST CONDITIONS
Delay from power up of AVDD and LVDD to RESET pulse active
Pulse duration of active RESET signal
MIN TYP MAX UNIT
t1
t2
t3
Power-on delay
1
ms
ns
ns
Reset pulse duration
Register write delay
50
Delay from RESET disable to CSZ active
100
POWER SUPPLY
AVDD, LVDD
t
1
RESET
t
2
t
3
SEN
NOTE: A high-going pulse on RESET pin is required in serial interface mode in case of initialization through hardware reset.
For parallel interface operation, RESET has to be tied permanently HIGH.
Figure 45. Reset Timing Diagram
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Serial Register Readout
The device includes a mode where the contents of the internal registers can be read back on SDOUT pin. This
may be useful as a diagnostic check to verify the serial interface communication between the external controller
and the ADC.
By default, after power up and device reset, the SDOUT pin is in the high-impedance state. When the readout
mode is enabled using the register bit <READOUT>, SDOUT outputs the contents of the selected register
serially, described as follows.
•
Set register bit <READOUT> = 1 to put the device in serial readout mode. This disables any further writes
into the internal registers, EXCEPT the register at address 1. Note that the <READOUT> bit itself is also
located in register 1.
The device can exit readout mode by writing <READOUT> to 0.
Only the contents of register at address 1 cannot be read in the register readout mode.
•
•
•
•
Initiate a serial interface cycle specifying the address of the register (A7-A0) whose content is to be read.
The device serially outputs the contents (D15–D0) of the selected register on the SDOUT pin.
The external controller can latch the contents at the rising edge of SCLK.
To exit the serial readout mode, reset register bit <READOUT> = 0, which enables writes into all registers of
the device. At this point, the SDOUT pin enters the high-impedance state.
A) Enable Serial Readout (<READOUT> = 1)
REGISTER DATA (D15:D0) = 0x0001
REGISTER ADDRESS (A7:A0) = 0x01
SDATA
SCLK
0
0
0
0
0
0
0
1
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
CSZ
Pin SDOUT Becomes
Active and Forces Low
Pin SDOUT is tri-stated
SDOUT
B) Read Contents of Register 0x0F.
This Register has been Initialized with 0x0200
(The Device was earlier put in global power down)
REGISTER DATA (D15:D0) = XXXX (don’t care)
D9
D3 D2 D1 D0
REGISTER ADDRESS (A7:A0) = 0x0F
A7 A6 A5 A4 A3 A2 A1 A0
SDATA
SCLK
D13
D10
D8
D4
D15 D14
D12 D11
D7 D6
D5
CSZ
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
0
SDOUT
SDOUT Output Contents of Register 0x0F in the same cycle, MSB first
Figure 46. Serial Readout Timing
28
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DEFAULT STATES AFTER RESET
•
•
•
•
•
•
Device is in normal operation mode with 14-bit ADC enabled for all channels.
Output interface is 1-wire, 14× serialization with 7×bit clock and 1×frame clock frequency
Serial readout is disabled
PDN pin is configured as global power-down pin
Digital gain is set to 0 dB.
Digital modes such as LFNS, digital filters, and so on, are disabled.
Register Map
(1)(2)(3)(4)
Table 3. Summary of Functions Supported by Serial Interface
ADDR.
(HEX)
D15
D14
D13
D12
D11
D10
D9
D8
D7
D6
D5
D4
D3
D2
D1
D0
NAME
DESCRIPTION
1: Self-clearing software RESET; . After reset, this bit is set to 0
0: Normal operation.
00
X
X
RST
EN_READOUT
EN_HIGH_ADDRS
1: READOUT of registers mode;0: Normal operation
01
0 – Disable access to register at address 0xF0
1 – Enable access to register at address 0xF0
X
1:Enable SYNC feature to synchronize the test patterns;
0: Normal operation, SYNC feature is disabled for the test patterns.
Note: this bit needs to be set as 1 when software or hardware SYNC
feature is used. see Reg.0x25[8] and 0x25[15]
02
0A
X
X
EN_SYNC
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
RAMP_PAT_RESET_VAL
PDN_CH<8:1>
Ramp pattern reset value
1:Channel-specific ADC power-down mode;
0: Normal operation
1:Partial power-down mode - fast recovery from power-down;
0: Normal operation
PDN_PARTIAL
PDN_COMPLETE
PDN_PIN_CFG
LFNS_CH<8:1>
EN_FRAME_PAT
0F
1:Register mode for complete power-down - slower recovery;
0: Normal operation
1:Configures PD pin for partial power-down mode;
0:Configures PD pin for complete power-down mode
X
1: Channel-specific low frequency noise suppression mode enable;
0: LFNS disabled
14
X
X
X
X
X
X
X
X
1: Enables output frame clock to be programmed through a pattern;
0: Normal operation on frame clock
X
X
1C
23
24
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
ADCLKOUT<13:0>
PRBS_SEED<15:0>
14-bit pattern for frame clock on ADCLKP/ADCLKN pins
PRBS pattern starting seed value lower 16 bits
X
X
1: Swaps the polarity of the analog input pins electrically;
0: Normal configuration
X
X
X
X
X
X
X
X
INVERT_CH<8:1>
X
X
X
X
X
X
PRBS_SEED<22:16>
PRBS seed starting value upper 7 bits
(1) The unused bits in each register (identified as blank table cells) must be programmed as '0'.
(2) X = Register bit referenced by the corresponding name and description
(3) Bits marked as '0' should be forced to 0, and bits marked as '1' should be forced to 1 when the particular register is programmed.
(4) Multiple functions in a register can be programmed in a single write operation.
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Table 3. Summary of Functions Supported by Serial Interface (1)(2)(3)(4) (continued)
ADDR.
(HEX)
D15
D14
D13
D12
D11
D10
D9
D8
D7
D6
D5
D4
D3
D2
D1
D0
NAME
DESCRIPTION
1: Enables a repeating full scale ramp pattern on the outputs;
0: Normal operation
X
0
0
EN_RAMP
1:Enables mode wherein output toggles between 2 defined codes;
0: Normal operation
0
X
0
DUALCUSTOM_PAT
SINGLE_CUSTOM_PAT
1: Enables mode wherein output is a constant specified code;
0: Normal operation
0
0
X
2 MSBs for single custom pattern (and for the first code of the dual
custom patterns)
X
X
BITS_CUSTOM1<13:12>
BITS_CUSTOM2<13:12>
X
X
2 MSBs for second code of the dual custom patterns
1: Software sync bit for test patterns on all 8 CHs;
0: No sync. Note: in order to synchronize the digital filters using the
SYNC pin, this bit must be set as 0.
25
X
TP_SOFT_SYNC
1: PRBS test pattern enable bit;
0: PRBS test pattern disabled
X
PRBS_TP_EN
PRBS_MODE_2
X
PRBS 9 bit LFSR (23bit LFSR is default)
1: Enable PRBS seed to be chosen from register 0x23 and 0x24;
0: Disabled
X
PRBS_SEED_FROM_REG
1: Enable the external SYNC feature for syncing test patterns.
0: Inactive. Note: in order to synchronize the digital filters using the
SYNC pin, this bit must be set as 0.
X
TP_HARD_SYNC
12 lower bits for single custom pattern (and for the first code of the
dual custom pattern).
26
27
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
BITS_CUSTOM1<11:0>
BITS_CUSTOM2<11:0>
EN_BITORDER
12 lower bits for second code of the dual custom pattern
Enables the bit order output.
0 = Byte wise, 1 = Word wise
Selects between bytewise and bit wise
1: bit-wise, odd bits come out on one wire and even bits come out on
other wire
0: byte-wise, upper bits on one wire and lower bits on other wire
Note: D15 must be set to '0' for this mode
0
1
X
BIT_WISE
28
1: Output format is one sample on one LVDS wire and next sample
on other LVDS wire.
0: Data comes out in two-wire mode with upper set of bits on one
channel and lower set of bits on the other.
X
X
X
X
X
X
X
X
X
EN_WORDWISE__BY_CH<7:0>
Note: D15 must set '1' for this mode.
1: Enables filter blocks - global control;
0: Inactive
GLOBAL_EN_FILTER
EN_CHANNEL_AVG
29
2A
1: Enables channel averaging mode;
0: Inactive
X
X
X
X
X
GAIN_CH1<3:0>
GAIN_CH2<3:0>
GAIN_CH3<3:0>
GAIN_CH4<3:0>
Programmable gain - Channel 1
Programmable gain - Channel 2
Programmable gain - Channel 3
Programmable gain - Channel 4
X
X
X
X
X
X
X
X
X
X
X
X
30
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Table 3. Summary of Functions Supported by Serial Interface (1)(2)(3)(4) (continued)
ADDR.
(HEX)
D15
D14
D13
D12
D11
D10
D9
D8
D7
D6
D5
D4
D3
D2
D1
D0
NAME
DESCRIPTION
Programmable gain - Channel 5
X
X
X
X
GAIN_CH5<3:0>
GAIN_CH6<3:0>
X
X
X
X
Programmable gain - Channel 6
2B
2C
2D
X
X
X
X
X
X
GAIN_CH7<3:0>
Programmable gain - Channel 7
X
X
X
X
X
X
X
X
X
GAIN_CH8<3:0>
Programmable gain - Channel 8
X
X
X
X
X
AVG_CTRL4<1:0>
AVG_CTRL3<1:0>
AVG_CTRL2<1:0>
AVG_CTRL1<1:0>
AVG_CTRL8<1:0>
AVG_CTRL7<1:0>
AVG_CTRL6<1:0>
AVG_CTRL5<1:0>
FILTER1_COEFF_SET<2:0>
FILTER1_RATE<2:0>
ODD_TAP1
1: Averaging control for what comes out on LVDS output OUT4
Averaging control for what comes out on LVDS output OUT3
Averaging control for what comes out on LVDS output OUT2
Averaging control for what comes out on LVDS output OUT1
Averaging control for what comes out on LVDS output OUT8
Averaging control for what comes out on LVDS output OUT7
Averaging control for what comes out on LVDS output OUT6
Averaging control for what comes out on LVDS output OUT5
Select stored coefficient set for filter 1
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Set decimation factor for filter 1
X
X
X
Use odd tap filter 1
1: Enables filter for channel 1;
0: Disables
2E
2F
30
X
X
X
USE_FILTER1
HPF_CORNER _CH1
HPF_EN_CH1
X
X
X
X
X
X
X
X
X
X
X
X
HPF corner in values k from 2 to 10
1: HPF filter enable for the channel;
0: Disables
X
X
X
X
X
FILTER2_COEFF_SET<2:0>
FILTER2_RATE<2:0>
ODD_TAP2
Select stored coefficient set for filter 2
Set decimation factor for filter 2
Use odd tap filter 2
X
X
1: Enables filter for channel 2;
0: Disables
USE_FILTER2
HPF_CORNER _CH2
HPF_EN_CH2
HPF corner in values k from 2 to 10
1: HPF filter enabled for the channel;
0: Disabled
X
X
FILTER3_COEFF_SET<2:0>
FILTER3_RATE<2:0>
ODD_TAP3
Select stored coefficient set for filter 3
Set decimation factor for filter 3
Use odd tap filter 3
X
X
1: Enables filter for channel 3;
0: Disables
USE_FILTER3
HPF_CORNER _CH3
HPF_EN_CH3
HPF corner in values k from 2 to 10
1: HPF filter enabled for the channel;
0: Disabled
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Table 3. Summary of Functions Supported by Serial Interface (1)(2)(3)(4) (continued)
ADDR.
(HEX)
D15
D14
D13
D12
D11
D10
D9
D8
D7
D6
D5
D4
D3
D2
D1
D0
NAME
DESCRIPTION
Select stored coefficient set for filter 4
X
X
X
FILTER4_COEFF_SET<2:0>
FILTER4_RATE<2:0>
ODD_TAP4
X
X
X
Set decimation factor for filter 4
Use odd tap filter 4
X
1: Enables filter for channel 4;
0: Disables
31
X
USE_FILTER4
HPF_CORNER _CH4
HPF_EN_CH4
X
X
X
X
HPF corner in values k from 2 to 10
1: HPF filter enabled for the channel;
0: Disabled
X
X
X
X
FILTER5_COEFF_SET<2:0>
FILTER5_RATE<2:0>
ODD_TAP5
Select stored coefficient set for filter 5
Set decimation factor for filter 5
Use odd tap filter 5
X
X
X
X
1: Enables filter for channel 5;
0: Disables
32
X
USE_FILTER5
HPF_CORNER _CH5
HPF_EN_CH5
X
X
X
X
HPF corner in values k from 2 to 10
1: HPF filter enabled for the channel;
0: Disabled
X
X
X
X
X
X
X
X
X
X
FILTER_TYPE6<2:0>
DECBY8_6
Select stored coefficient set for filter 6
Enables decimate by 8 filter 6
Set decimation factor for filter 6
Use odd tap filter 6
X
X
X
X
X
X
X
X
X
FILTER_MODE6<1:0>
ODD_TAP6
33
X
X
X
X
USE_FILTER6
Enables filter for channel 6
X
X
X
X
HPF_CORNER _CH6
HPF_EN_CH6
HPF corner in values k from 2 to 10
Hpf filter enable for the channel
Select stored coefficient set for filter 7
Enables decimate by 8 filter 7
Set decimation factor for filter 7
Use odd tap filter 7
X
FILTER_TYPE7<2:0>
DECBY8_7
FILTER_MODE7<1:0>
ODD_TAP7
34
X
USE_FILTER7
Enables filter for channel 7
X
X
X
X
HPF_CORNER _CH7
HPF_EN_CH7
HPF corner in values k from 2 to 10
Hpf filter enable for the channel
Select stored coefficient set for filter 8
Enables decimate by 8 filter 8
Set decimation factor for filter 8
Use odd tap filter 8
X
FILTER_TYPE8<2:0>
DECBY8_8
FILTER_MODE8<1:0>
ODD_TAP8
35
38
1: Enables filter for channel 8;
0: Disables
X
X
USE_FILTER8
HPF_CORNER_CH8
HPF_EN_CH8
X
X
X
X
HPF corner in values k from 2 to 10
1: HPF filter enable for the channel;
0: Disables
X
X
DATA_RATE<1:0>
Select output frame clock rate
32
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Table 3. Summary of Functions Supported by Serial Interface (1)(2)(3)(4) (continued)
ADDR.
(HEX)
D15
D14
D13
D12
D11
D10
D9
D8
D7
D6
D5
D4
D3
D2
D1
D0
NAME
DESCRIPTION
Drive external reference mode through:
D15=D3=1: the VCM pin;
X
X
EXT_REF_VCM
D15=D3=0: REFT/REFB pins.
Note: 0xF[15] should be set as '1' to enable the external reference
mode
42
45
X
X
PHASE_DDR<1:0>
PAT_DESKEW
Controls phase of LCLK output relative to data
1: Enable deskew pattern mode;
0: Inactive
0
X
0
1: Enable sync pattern mode;
0: Inactive
X
PAT_SYNC
EN_2WIRE
BTC_MODE
MSB_FIRST
EN_SDR
1: 2 wire LVDS output;
0: 1 wire LVDS output
1
1
1
1
1
1
X
1: 2's complement; (ADC data output format)
0: Binary Offset (ADC data output format)
X
1: MSB First;
0: LSB First
X
1:SDR Bit Clock;
0: DDR Bit Clock
X
1: Enable 12 bit serialization mode;
0: Inactive
0
0
0
X
0
EN_12BIT
EN_14BIT
46
1: Enable 14 bit serialization mode;
0: Inactive
X
1: Enable 16 bit serialization mode;
0: Inactive
1
1
X
0
0
EN_16BIT
FALL_SDR
Note: 16 bit can be used when average mode or decimation mode is
enabled for better SNR.
1: Controls LCLK rising or falling edge comes in the middle of data
window when operating in SDR output mode; 0: At the edge of data
window.
X
50
51
1
1
1
1
1
1
1
1
1
1
1
1
1
1
X
X
X
X
X
X
X
X
MAP_Ch1234_to_OUT1A
MAP_Ch1234_to_OUT1B
MAP_Ch1234_to_OUT2A
MAP_Ch1234_to_OUT2B
MAP_Ch1234_to_OUT3A
MAP_Ch1234_to_OUT3B
MAP_Ch1234_to_OUT4A
MAP_Ch1234_to_OUT4B
MAP_Ch5678_to_OUT5B
MAP_Ch5678_to_OUT5A
MAP_Ch5678_to_OUT6B
MAP_Ch5678_to_OUT6A
MAP_Ch5678_to_OUT7B
MAP_Ch5678_to_OUT7A
OUT1A Pin pair to channel data mapping selection
OUT1B Pin pair to channel data mapping selection
OUT2A Pin pair to channel data mapping selection
OUT2B Pin pair to channel data mapping selection
OUT3A Pin pair to channel data mapping selection
OUT3B Pin pair to channel data mapping selection
OUT4A Pin pair to channel data mapping selection
OUT4B Pin pair to channel data mapping selection
OUT5B Pin pair to channel data mapping selection
OUT5A Pin pair to channel data mapping selection
OUT6B Pin pair to channel data mapping selection
OUT6A Pin pair to channel data mapping selection
OUT7B Pin pair to channel data mapping selection
OUT7A Pin pair to channel data mapping selection
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
52
53
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
54
X
X
X
X
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Table 3. Summary of Functions Supported by Serial Interface (1)(2)(3)(4) (continued)
ADDR.
(HEX)
D15
D14
D13
D12
D11
D10
D9
D8
D7
D6
D5
D4
D3
D2
D1
D0
NAME
DESCRIPTION
1
1
X
X
X
X
MAP_Ch5678_to_OUT8B
MAP_Ch5678_to_OUT8A
OUT8B Pin pair to channel data mapping selection
OUT8A Pin pair to channel data mapping selection
55
F0
X
X
X
X
1: Enable external reference mode. the voltage reference can be
applied on either REFP/B pins or VCM pin.
X
EN_EXT_REF
0: Default: internal reference mode.
34
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DESCRIPTION OF SERIAL REGISTERS
POWER-DOWN MODES
ADDR. D15 D14 D13 D12 D11 D10
(HEX)
D9
D8
D7
D6
D5
D4
D3
D2
D1
D0
NAME
0F
X
X
X
X
X
X
X
X
PDN_CH<8:1>
PDN_PARTIAL
PDN_COMPLETE
PDN_PIN_CFG
X
X
X
Each of the 8 channels can be individually powered down. PDN_CH<N> controls the power-down mode for ADC
channel <N>. In addition to channel-specific power-down, the ADS5294 also has two global power-down modes:
1. The partial power-down mode. It partially powers down the chip; recovery time from the partial power-down
mode is about 10 µs provided that the clock has been running for at least 50 µs before exiting this mode.
2. The complete power-down mode. It completely powers down the chip, and involves a much longer recovery
time 100 µs.
In addition to programming the chip in either of these two power-down modes (through either the PDN_PARTIAL
or PDN_COMPLETE bits), the PD pin itself can be configured as either a partial power-down pin or a complete
power-down pin control. For example, if PDN_PIN_CFG=0 (default), when the PD pin is high, the device enters
complete power-down mode. However, if PDN_PIN_CFG=1, when the PD pin is high, the device enters partial
power-down mode.
LOW FREQUENCY NOISE SUPPRESSION MODE
ADDR. D15 D14 D13 D12 D11 D10
(HEX)
D9
D8
D7
D6
D5
D4
D3
D2
D1
D0
NAME
14
X
X
X
X
X
X
X
X
LFNS_CH<8:1>
The low frequency noise suppression mode is specifically useful in applications where good noise performance is
desired in the frequency band of 0 to 1 MHz (around DC). Setting this mode shifts the low-frequency noise of the
ADS5294 to approximately Fs/2, thereby, moving the noise floor around DC to a much lower value.
LFNS_CH<8:1> enables this mode individually for each channel. See Figure 38 and Figure 39.
ANALOG INPUT INVERT
ADDR. D15 D14 D13 D12 D11 D10
(HEX)
D9
D8
D7
D6
D5
D4
D3
D2
D1
D0
NAME
24
X
X
X
X
X
X
X
X
INVERT_CH<8:1>
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Normally, INP pin represents the positive analog input pin, and INN represents the complementary negative input.
Setting the bits marked INVERT_CH<8:1> (individual control for each channel) causes the inputs to be swapped.
INN now represents the positive input, and INP the negative input.
LVDS TEST PATTERNS
ADDR.
(HEX)
D15 D14 D13 D12 D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0
NAME
23
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
PRBS_SEED<15:0>
PRBS_SEED<22:16>
EN_RAMP
X
0
0
0
X
0
0
0
24
25
DUALCUSTOM_PAT
SINGLE_CUSTOM_PAT
BITS_CUSTOM1<13:12>
BITS_CUSTOM2<13:12>
TP_SOFT_SYNC
X
X
X
X
X
PRBS_TP_EN
X
PRBS_MODE_2
X
PRBS_SEED_FROM_REG
TP_HARD_SYNC
X
X
X
26
27
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
BITS_CUSTOM1<11:0>
BITS_CUSTOM2<11:0>
PAT_DESKEW
0
X
0
45
X
PAT_SYNC
The ADS5294 can output a variety of test patterns on the LVDS outputs. These test patterns replace the normal
ADC data output. All these patterns can be synchronized across devices by the sync function either through the
hardware SYNC pin or the software sync bit TP_SOFT_SYNC bit in register 0x25. TP_HARD_SYNC bit when
set enables the Test patterns to be synchronized by the hardware SYNC Pin. When the software sync bit
TP_SOFT_SYNC bit is set, special timing is needed.
•
Setting EN_RAMP to 1 causes all the channels to output a repeating full-scale ramp pattern. The ramp
increments from zero code to full-scale code in steps of 1 LSB every clock cycle. After hitting the full scale
code, it returns back to zero code and ramps again.
•
The device can also be programmed to output a constant code by setting SINGLE_CUSTOM_PAT to 1, and
programming the desired code in BITS_CUSTOM1<13:0>. In this mode, BITS_CUSTOM1<13:0> take the
place of the 14-bit ADC data at the output, and are controlled by LSB-first and MSB-first modes the same way
as normal ADC data are.
•
•
The device may also be made to toggle between two consecutive codes, by programming
DUAL_CUSTOM_PAT to 1. The two codes are represented by the contents of BITS_CUSTOM1<13:0> and
BITS_CUSTOM2<13:0>.
In addition to custom patterns, the device may also be made to output two preset patterns:
–
–
–
Deskew patten – Set using PAT_DESKEW, this mode replaces the 14-bit ADC output D<13:0> with the
0101010101010101 word.
Sync pattern – Set using PAT_SYNC, the normal ADC word is replaced by a fixed 11111110000000
word.
PRBS patterns: The device can give 9 bit or 23 bit LFSR Pseudo random pattern on the channel outputs
that are controlled by the register 0x25. To enable the PRBS pattern PRBS_TP_EN bit in the register
0x25 needs to be set. Default is the 23 bit LFSR but 9 bit LFSR can be chosen by setting
PRBS_MODE_2 bit. The seed value for the PRBS patterns can be chosen by enabling the
PRBS_SEED_FROM_REG bit to 1 and the value written to the PRBS_SEED registers in 0x24 and 0x23.
Note that only one of the above patterns should be active at any given instant.
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BIT-BYTE-WORD WISE OUTPUT
ADDR. D15 D14 D13 D12 D11 D10 D9
(HEX)
D8
D7
D6
D5
D4
D3
D2
D1
D0
NAME
x
EN_BITORDER
BIT_WISE
0
x
28
1
X
X
X
X
X
X
X
X
EN_WORDWISE_B
Y_CH<7:>
Register 0x28 can select the LVDS ADC output as bit-wise,byte-wise or word-wise in the two wire mode.
Figure 47 and Figure 48 illustrate the details.
Figure 47. 12-Bit Word Wise
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Figure 48. 14-Bit Word Wise
DIGITAL PROCESSING BLOCKS
The ADS5294 integrates a set of commonly useful digital functions that can be used to ease system design.
These functions are shown in the digital block diagram of Figure 49 and described in the following sections.
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LVDS OUTPUTS
Test Patterns
-
Channel 1 ADC Data
Channel
1
14-BIT
Ramp
OUT 1A
OUT 1B
Serializer
Wire
Serializer
Wire
1
Average of 2
channels
Built-in Coefficients
2
24-tap filter
(Even Tap)
Decimation
by or
by
2
Channel
2
3
4
4
OUT 2A
OUT 2B
23-tap filter
(Odd Tap)
Serializer
Channel 2 ADC Data
Channel 3 ADC Data
Channel 4 ADC Data
Wire
Serializer
Wire
1
Average of 4
channels
Custom Coefficients
MAPPER
Decimation
2
24-tap filter
(Even Tap)
by
by
2
4
or
or
MULTIPLEXER
8 : 8
OUT 3A
OUT 3B
23-tap filter
(Odd Tap)
Channel
by
8
Serializer
GAIN
Wire
Serializer
Wire
1
(0 to 12 dB ,
1
dB steps )
12-tap filter
2
OUT 4A
OUT 4B
Channel
Serializer
Wire
Serializer
Wire
1
DIGITAL PROCESSING BLOCK for CHANNEL 1
2
½ ADS529x
Figure 49. Digital Processing Block Diagram
PROGRAMMABLE DIGITAL GAIN
ADDR.
D15 D14 D13 D12 D11 D10 D9
(HEX)
D8
D7
D6
D5
D4
D3
D2
D1
D0
NAME
2A
X
X
X
X
GAIN_CH1<3:0>
GAIN_CH2<3:0>
GAIN_CH3<3:0>
GAIN_CH4<3:0>
GAIN_CH5<3:0>
GAIN_CH6<3:0>
GAIN_CH7<3:0>
GAIN_CH8<3:0>
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
2B
X
X
X
X
X
X
X
X
In applications where the full scale swing of the analog input signal is much less than the 2 VPP range supported
by the ADS5294, a programmable gain can be set to achieve the full-scale output code even with a lower analog
input swing. The programmable gain for each channel can be individually set using a set of four bits, indicated as
GAIN_CHN<3:0> for Channel N. The gain setting is coded in binary from 0-12 dB as shown in Table 4.
Table 4. Gain Setting for Channel N
GAIN_CHN<3>
GAIN_CHN<2>
GAIN_CHN<1>
GAIN_CHN<0>
CHANNEL N GAIN SETTING
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0 dB
1 dB
2 dB
3 dB
4 dB
5 dB
6 dB
7 dB
8 dB
9 dB
10 dB
11 dB
12 dB
Do not use
Do not use
Do not use
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CHANNEL AVERAGING
ADDR.
D15 D14 D13 D12 D11 D10 D9
(HEX)
D8
D7
D6
D5
D4
D3
D2
D1
D0
NAME
29
X
EN_CHANNEL_AVG
AVG_CTRL4<1:0>
AVG_CTRL3<1:0>
AVG_CTRL2<1:0>
AVG_CTRL1<1:0>
AVG_CTRL8<1:0>
AVG_CTRL7<1:0>
AVG_CTRL6<1:0>
AVG_CTRL5<1:0>
2C
X
X
X
X
X
X
X
X
X
X
X
X
2D
X
X
X
X
In the default mode of operation, the LVDS outputs <8..1> contain the data of the ADC Channels <8..1>. By
setting the EN_CHANNEL_AVG bit to ‘1’, the outputs from multiple channels can be averaged. The resulting
outputs from the Channel averaging block (which is bypassed in the default mode) are referred to as Bins. The
contents of the Bins <8..1> come out on the LVDS outputs <8..1>. The contents of each of the 8 bins are
determined by the register bits marked AVG_CTRLn<1:0> where n stands for the Bin number. The different
settings are shown below:
AVG_CTRL1<1>
AVG_CTRL1<0>
Contents of Bin 1
Zero
0
0
0
1
ADC Channel 1
1
0
Average of ADC Channel 1, 2
Average of ADC Channel 1, 2, 3, 4
Contents of Bin 2
Zero
1
1
AVG_CTRL2<1>
AVG_CTRL2<0>
0
0
0
1
ADC Channel 2
1
0
ADC Channel 3
1
1
Average of ADC Channel 3, 4
Contents of Bin 3
Zero
AVG_CTRL3<1>
AVG_CTRL3<0>
0
0
0
1
ADC Channel 3
1
0
ADC Channel 2
1
1
Average of ADC Channel 1, 2
Contents of Bin 4
Zero
AVG_CTRL4<1>
AVG_CTRL4<0>
0
0
0
1
ADC Channel 4
1
0
Average of ADC Channel 3, 4
Average of ADC Channel 1, 2, 3, 4
Contents of Bin 5
Zero
1
1
AVG_CTRL5<1>
AVG_CTRL5<0>
0
0
0
1
ADC Channel 5
1
0
Average of ADC Channel 5, 6
Average of ADC Channel 5, 6, 7, 8
Contents of Bin 6
Zero
1
1
AVG_CTRL6<1>
AVG_CTRL6<0>
0
0
0
1
ADC Channel 6
1
0
ADC Channel 7
1
1
Average of ADC Channel 7, 8
Contents of Bin 7
Zero
AVG_CTRL7<1>
AVG_CTRL7<0>
0
0
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AVG_CTRL1<1>
AVG_CTRL1<0>
Contents of Bin 1
ADC Channel 7
0
1
1
0
ADC Channel 6
1
1
Average of ADC Channel 6, 5
Contents of Bin 8
AVG_CTRL8<1>
AVG_CTRL8<0>
0
0
1
1
0
1
0
1
Zero
ADC Channel 8
Average of ADC Channel 7, 8
Average of ADC Channel 5, 6, 7, 8
When the contents of a particular bin is set to Zero, then the LVDS buffer corresponding to that bin gets
automatically powered down.
DECIMATION FILTER
ADDR.
(HEX)
D15 D14 D13 D12 D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0
NAME
29
X
GLOBAL_EN_FILTER
FILTER1_COEFF_SET<2:0>
FILTER1_RATE<2:0>
ODD_TAP1
2E
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
USE_FILTER1
2F
30
31
32
33
34
35
FILTER2_COEFF_SET<2:0>
FILTER2_RATE<2:0>
ODD_TAP2
USE_FILTER2
FILTER3_COEFF_SET<2:0>
FILTER3_RATE<2:0>
ODD_TAP3
USE_FILTER3
FILTER4_COEFF_SET<2:0>
FILTER4_RATE<2:0>
ODD_TAP4
USE_FILTER4
FILTER5_COEFF_SET<2:0>
FILTER5_RATE<2:0>
ODD_TAP5
USE_FILTER5
FILTER6_COEFF_SET<2:0>
FILTER6_RATE<2:0>
ODD_TAP6
USE_FILTER6
FILTER7_COEFF_SET<2:0>
FILTER7_RATE<2:0>
ODD_TAP7
USE_FILTER7
FILTER8_COEFF_SET<2:0>
FILTER8_RATE<2:0>
ODD_TAP8
USE_FILTER8
The decimation filter is implemented as 24-tap FIR with symmetrical coefficients (each coefficient is 12-bit
signed). The filter equation is:
æ 1 ö
y(n) =
´ (h ´ x(n)+h ´ x(n -1)+h ´ x(n - 2)+...+h ´ x(n -11)+h ´ x(n -12)...+h ´ x(n - 22)+h ´ x(n - 23)
é ù
0 1 2 11 11 1 0
ç
÷
ë
û
11
è 2
ø
(1)
41
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By setting the register bit <ODD_TAPn> = 1, a 23-tap FIR is implemented:
æ
ö
1
y(n)=
´é(h ´x(n)+h ´x(n-1)+h ´x(n-2)+...+h ´x(n-10)+h ´x(n -11)+h ´x(n-12)...+h ´x(n-21)+h ´x(n -22)ù
ç
÷
0
1
2
10
11
10
1
0
ë
û
ç
÷
11
2
è
ø
(2)
In Equation 1 and Equation 2, h0, h1 …h11 are 12 bit signed representation of the coefficients, x(n) is the input
data sequence to the filter and y(n) is the filter output sequence.
A decimation filter can be introduced at the output of each channel. To enable this feature, the
GLOBAL_EN_FILTER should be set to ‘1’. Setting this bit to ‘1’ increases the overall latency of each channel to
20 clock cycles irrespective of whether the filter for that particular channel has been chosen or not (using the
USE_FILTER bit). The bits marked FILTERn_COEFF_SET<2:0>, FILTERn_RATE<2:0>, ODD_TAPn and
USE_FILTERn represent the controls for the filter for Channel n. Note that these bits are functional only when
the GLOBAL_EN_FILTER gets set to ‘1’. For illustration, the controls for channel 1 are listed in Table 5:
The USE_FILTER1 bit determines whether the filter for Channel 1 is used or not. When this bit is set to ‘1’, the
filter for channel 1 is enabled. When this bit is set to ‘0’, the filter for channel 1 is disabled but the channel data
passes through a dummy delay so that the overall latency of channel 1 is 20 clock cycles. With the
USE_FILTER1 bit set to ‘1’, the characteristics of the filter can be set by using the other sets of bits.
The ADS5294 has 6 sets of filter coefficients stored in memory. Each of these sets define a unique pass band in
the frequency domain and contain 12 coefficients (each coefficient is 12-bit long). These 12 coefficients are used
to implement either a symmetric 24-tap (even-tap) filter, or a symmetric 23-tap (odd-tap) filter. Setting the register
bit ODD_TAP1 to ‘1’ enables the odd-tap configuration (the default is even tap with this bit set to ‘0’) for Channel
1. The bits FILTER1_COEFF_SET<2:0> can be used to choose the required set of coefficients for Channel 1.
The passbands corresponding to of each of these filter coefficient sets is shown in Figure 50
Set 1
Set 2
H(f)
H(f)
0.2*Fs
0.3*Fs
0.2*Fs
0.3*Fs
0.5*Fs
f
f
Set 3
Set 4
H(f)
H(f)
0.1*Fs
0.15*Fs
0.075*Fs
0.275*Fs
f
f
0.225*Fs
0.125*Fs
Set 5
Set 6
H(f)
H(f)
0.275*Fs
0.4*Fs 0.5*Fs
f
f
0.375*Fs
0.225*Fs
0.35*Fs
Figure 50. Filter Types
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Coefficient Sets 1 and 2 are the most appropriate when Decimation by a factor of 2 is required, whereas
Coefficient Sets 3,4,5,6 are appropriate when Decimation by a factor of 4 is desired. The computation rate of the
filter output can be independently set using the bits FILTERn_RATE<2:0>. The settings are shown in Table 5.
Table 5. Digital Filters
<USE
FILTER
CHn>
<DATA
RATE>
FILTERn
RATE>
<FILTERn
COEFF SET>
<EN CUSTOM
FILT>
DECIMATION
TYPE OF FILTER
<ODD TAP>
Built-in low-pass odd-tap filter (pass band = 0 to fS/4)
Built-in high-pass odd-tap filter (pass band = 0 to fS/4)
Built-in low-pass even-tap filter (pass band = 0 to fS/8)
Built-in first band pass even tap filter(pass band = fS/8 to fS/4)
001
001
010
010
000
000
001
001
000
001
010
011
1
1
0
0
1
1
1
1
0
0
0
0
Decimate by 2
Decimate by 4
Built-in second band pass even tap filter(pass band = fS/4 to 3
fS/8)
010
001
100
0
1
0
Built-in high pass odd tap filter (pass band = 3 fS/8 to fS/2)
Custom filter (user programmablecoefficients)
Custom filter (user programmablecoefficients)
Custom filter (user programmablecoefficients)
Custom filter (user programmablecoefficients)
010
001
010
011
001
000
001
100
101
000
000
000
1
1
1
1
1
1
0
1
1
1
1
Decimate by 2
Decimate by 4
Decimate by 8
Bypass decimation
0 and 1
0 and 1
0 and 1
0 and 1
The choice of the odd/even tap setting, filter coefficient set and the filter rate uniquely determines the filter to be
used. In addition to the preset filter coefficients, the coefficients for each of the eight filter channels can be
programmed by the user. Each of the eight channels has 12 programmable coefficients, each 12-bit long. The 96
registers with addresses from 5A (Hex) to B9 (Hex) are used to program these 8 sets of 12 programmable
coefficients. Registers 5A to 65 are used to program the 1st filter, with the 1st coefficient occupying the bits
D11..D0 of register 5A, the 2nd coefficient occupying the bits D11..D0 of register 5B, and so on. Similarly
registers 66(Hex) to 71(Hex) are used to program the 2nd filter, and so on.
When programming the filter coefficients, the D15 bit of each of the 12 registers corresponding to that filter
should be set to ‘1’. If the D15 bit of these 12 registers is set to ‘0’, then the preset coefficient (as programmed by
FILTERn_COEFF_SET<2:0>) is used even if the bits D11..D0 get programmed. By setting or not setting the D15
bits of individual filter channels to ‘1’, some filters can be made to operate with preset coefficient sets, and some
others can be made to simultaneously operate with programmed coefficient sets.
HIGH PASS FILTER
ADDR.
D15 D14 D13 D12 D11 D10
D9
D8
D7
D6
D5
D4
D3
D2
D1
D0
NAME
(HEX)
2E
2E
2F
2F
30
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
HPF_corner_CH1
HPF_EN_CH1
X
X
X
X
X
X
X
X
HPF_corner_CH2
HPF_EN_CH2
HPF_corner_CH3
HPF_EN_CH3
30
31
HPF_corner_CH4
HPF_EN_CH4
31
32
HPF_corner_CH5
HPF_EN_CH5
32
33
HPF_corner_CH6
HPF_EN_CH6
33
34
HPF_corner_CH7
HPF_EN_CH7
34
35
HPF_corner_CH8
HPF_EN_CH8
35
This group of registers controls the characteristics of a digital high pass transfer function applied to the output
data, useing Equation 3:
2k
2k +1
y(n) =
[x(n) - x(n -1)+y(n -1)]
(3)
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Where k is set as described by the HPF_corner registers (one for each channel). Also the HPF_EN bit in each
register needs to be set to enable the HPF feature for each channel.
BIT CLOCK PROGRAMMABILITY
ADDR.
(HEX)
D15 D14 D13 D12 D11 D10 D9
D8
D7
D6
D5
D4
D3
D2
D1
D0
NAME
42
X
X
PHASE_DDR<1:0>
EN_SDR
46
1
X
46
1
X
FALL_SDR
The output interface of the ADS5294 is normally a DDR interface, with the LCLK rising edge and falling edge
transitions in the middle of alternate data windows. This default phase is shown in Figure 51.
PHASE_DDR<1:0> = 10
ADCLKp
LCLKp
OUTp
Figure 51. Default Phase of LCLK
The phase of LCLK can be programmed relative to the output frame clock and data using bits
PHASE_DDR<1:0>. The LCLK phase modes are shown in Figure 52.
PHASE_DDR<1:0> = 00
PHASE_DDR<1:0> = 10
ADCLKp
ADCLKp
LCLKp
OUTp
LCLKp
OUTp
PHASE_DDR<1:0> = 01
PHASE_DDR<1:0> = 11
ADCLKp
LCLKp
OUTp
ADCLKp
LCLKp
OUTp
Figure 52. Phase Programmability Modes for LCLK
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In addition to programming the phase of the LCLK in the DDR mode, the device can also be made to operate in
SDR mode by setting bit EN_SDR to 1. In the mode, the bit clock (LCLK) is output at 14X times the input clock,
or twice the rate as in DDR mode. Depending on the state of FALL_SDR, the LCLK may be output in either of
the two manners shown in Figure 53. As can be seen in Figure 53, only the LCLK rising (or falling edge) is used
to capture the output data in SDR mode. The SDR mode does not work well beyond 40 MSPS because the
LCLK frequency will become very high.
EN_SDR = 1, FALL_SDR = 0
ADCLKp
LCLKp
OUTp
EN_SDR = 1, FALL_SDR = 1
ADCLKp
LCLKp
OUTp
Figure 53. SDR Interface Modes
OUTPUT DATA RATE CONTROL
ADDR. D15 D14 D13 D12 D11 D10 D9
(HEX)
D8
D7
D6
D5
D4
D3
D2
D1
D0
38
DATA_RATE<1> DATA_RATE<0>
In the default mode of operation, the data rate at the output of the ADS5294 is at the sampling rate of the ADC.
This is true even when the custom pattern generator is enabled. In addition, both output data rate and sampling
rate can also be configured to a sub-multiple of the input clock rate.
With the DATA_RATE<1:0> control, the output data rate can be programmed to be a sub-multiple of the ADC
sampling rate. This feature can be used to lower the output data rate, for example when the decimation filter is
used. Without enabling the decimation filter, the sub-multiple ADC sampling rate feature still can be used.
The different settings are listed below:
DATA_RATE<1>
DATA_RATE<0>
Output data rate
0
0
1
1
0
1
0
1
Same as ADC sampling rate
1/2 of ADC sampling rate
1/4 of ADC sampling rate
1/8 of ADC sampling rate
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SYNCHRONIZATION PULSE
ADDR.
(HEX)
D15
D14
D13
D12 D11 D10
D9
D8
D7
D6
D5
D4
D3
D2
D1
D0
25
02
TP_HARD_SYNC
EN_SYNC
The SYNC pin can be used to synchronize the data output from channels within the same chip or from channels
across chips when decimation filters are used with reduced output data rate.
When the decimation filters are used (for example, the decimate by two filter is enabled), then, effectively, the
device outputs one digital code for every two analog input samples. If the SYNC function is not enabled, then the
filters are not synchronized (even within a chip) – this means that one channel may be sending out codes
corresponding to input samples N, N+1 and so on, while another may be sending out code corresponding to
N+1, N+2 and so on.
To achieve synchronization, the SYNC pulse must arrive at all the ADS529x chips at the same time instant (as
shown in the timing diagram of Figure 54
The ADS5294 generates an internal synchronization signal which is used to reset the internal clock dividers used
by the decimation filter.
Using the SYNC signal in this way ensures that all channels will output digital codes corresponding to the same
set of input samples.
SYNC Timings:
Synchronizing the filters using the SYNC pin is enabled by default. No register bits are required to be
written. Even EN_SYNC bit is not required.It is important for register bit TP_HARD_SYNC to be 0 for
this mode to work. As shown by Figure 54, the SYNC rising edge can be positioned anywhere within the
window. The width of the SYNC must be at least one clock cycle.
0ns
ADC Input
Clock
tCLK/2
-1ns
tCLK/2
t : -1ns< t < tCLK/2
d
d
SYNC
t
>
width
1clock cycle
Figure 54. Synchronization Pulse Timing
Note that the SYNC DOES NOT synchronize the sampling instants of the ADC across chips. All channels within
a single chip sample their analog inputs simultaneously. To ensure that channels across two chips will sample
their analog inputs simultaneously, the input clock needs to be routed to both chips with identical length. This
ensuring that the input clocks arrive at both the chips at the same time. This needs to be taken care of in the
board design and routing. The SYNC pin cannot be used to synchronize the sampling instants.
In addition to the above, the SYNC can also be used to synchronize the RAMP test patterns across channels. In
order to synchronize the test patterns, TP_HARD_SYNC must be set as 1. Setting TP_HARD_SYNC =1 actually
disables the sync of the filters.
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External Reference Mode of Operation
The ADS5294 supports an external reference mode of operation in one of two ways:
a. By forcing the reference voltages on the REFT and REFB pins.
b. By applying the reference voltage on VCM pin.
This mode can be used to operate multiple ADS5294 chips with the same (externally applied) reference voltage.
Using the REF pins:
For normal operation, the device requires two reference voltages, REFT and REFB. By default, the device
generates these two voltages internally. To enable the external reference mode, set the register bits as shown in
Table 6 . This powers down the internal reference amplifier and the two reference voltages can be forced directly
on the REFT and REFB pins as VREFT = 1.45V ± 50mV and VREFB = 0.45 V ±50 mV.
Note that the relation between the ADC full-scale input voltage and the applied reference voltages is
Full-scale input voltage = 2 x (VREFT – VREFB)
(4)
Using the VCM pin:
In this mode, an external reference voltage VREFIN can be applied to the VCM pin such that
Full-scale input voltage = 2 x VREFIN
(5)
To enable this mode, set the register bits as shown in Table 6. This changes the function of the VCM pin to an
external reference input pin. The voltage applied on VCM must be 1.5 V ±50 mV.
Table 6. External reference function
Function
EN_HIGH_ADDRS
EN_EXT_REF
EXT_REF_VCM
External reference using REFT/REFB pins
External reference using VCM pin
1
1
1
1
00
11
DATA OUTPUT FORMAT MODES
ADDR.
D15 D14 D13 D12 D11 D10
(HEX)
D9
D8
D7
D6
D5
D4
D3
D2
D1
D0
NAME
46
46
1
1
X
BTC_MODE
MSB_FIRST
X
The ADC output, by default, is in Straight offset binary mode. Programming the BTC_MODE bit to '1' inverts the
MSB, and the output becomes Binary 2’s complement mode. Also, by default, the first bit of the frame (following
the rising edge of CLKP) is the LSB of the ADC output. Programming the MSB_FIRST mode inverts the bit order
in the word, and the MSB is output as the first bit following CLKP rising edge.
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PROGRAMMABLE MAPPING BETWEEN INPUT CHANNELS AND OUTPUT PINS
ADDR.
D15 D14 D13 D12 D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0
(HEX)
NAME
50
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
X
X
X
X
MAP_CH1234_TO_OUT1A
MAP_CH1234_TO_OUT1B
MAP_CH1234_TO_OUT2A
MAP_CH1234_TO_OUT2B
MAP_CH1234_TO_OUT3A
MAP_CH1234_TO_OUT3B
MAP_CH1234_TO_OUT4A
MAP_CH1234_TO_OUT4B
MAP_CH5678_TO_OUT5B
MAP_CH5678_TO_OUT5A
MAP_CH5678_TO_OUT6B
MAP_CH5678_TO_OUT6A
MAP_CH5678_TO_OUT7B
MAP_CH5678_TO_OUT7A
MAP_CH5678_TO_OUT8B
MAP_CH5678_TO_OUT8A
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
51
X
X
X
X
52
53
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
54
55
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
The ADS5294 has 16 pairs of LVDS channel outputs. The mapping of ADC channels to LVDS output channels is
programmable to allow for flexibility in board layout. The 16 LVDS channel outputs are split in to 2 groups of 8
LVDS pairs. Within each group 4 ADC input channels can be multiplexed in to the 8 LVDS pairs depending on
the modes of operation whether it is 1 wire mode or 2 wire mode.
Input channels 1 to 4 can be mapped to any of the LVDS outputs OUT1A/B to OUT4A/B (using the
MAP_CH1234_TO_OUTnA/B). Similarly, input channels 5 to 8 can be mapped to any of the LVDS outputs
OUT5A/B to OUT8A/B (using the MAP_CH5678_TO_OUTnA/B). The block diagram of the mapping is listed in
Figure 55.
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Channel 8 data
MAP_CH5678_to_OUTn<3:0> = 0000
n = 5A, 5B, 6A, 6B, 7A, 7B, 8A, 8B
Channel 7 data
MAP_CH5678_to_OUTn<3:0> = 0010
OUTn
Channel 6 data
MAP_CH5678_to_OUTn<3:0> = 0100
MAP_CH5678_to_OUTn<3:0> = 1xxx, the
unused OUTn LVDS buffer is powered down.
Channel 5 data
MAP_CH5678_to_OUTn<3:0> = 0110
Channel 4 data
MAP_CH1234_to_OUTn<3:0> = 0110
Channel 3 data
MAP_CH1234_to_OUTn<3:0> = 0100
OUTn
Channel 2 data
MAP_CH1234_to_OUTn<3:0> = 0010
MAP_CH1234_to_OUTn<3:0> = 1xxx, the
unused OUTn LVDS buffer is powered down.
Channel 1 data
MAP_CH1234_to_OUTn<3:0> = 0000
(a) 1-wire mode
Channel 1 LSB Byte data<7:0>
MAP_CH1234_to_OUTn<3:0> = 0000
Channel 1 MSB Byte data<15:8>
MAP_CH1234_to_OUTn<3:0> = 0001
Channel 2 LSB Byte data<7:0>
MAP_CH1234_to_OUTn<3:0> = 0010
n = 1A, 1B, 2A, 2B, 3A, 3B, 4A, 4B
OUTn
Channel 2 MSB Byte data<15:8>
MAP_CH1234_to_OUTn<3:0> = 0011
Channel 3 LSB Byte data<7:0>
MAP_CH1234_to_OUTn<3:0> = 0100
MAP_CH1234_to_OUTn<3:0> = 1xxx, the
unused OUTn LVDS buffer is powered down.
Channel 3 MSB Byte data<15:8>
MAP_CH1234_to_OUTn<3:0> = 0101
Channel 4 LSB Byte data<7:0>
MAP_CH1234_to_OUTn<3:0> = 0110
Channel 4 MSB Byte data<15:8>
MAP_CH1234_to_OUTn<3:0> = 0011
Channel 8 LSB Byte data<7:0>
MAP_CH5678_to_OUTn<3:0> = 0000
Channel 8 MSB Byte data<15:8>
MAP_CH5678_to_OUTn<3:0> = 0001
Channel 7 LSB Byte data<7:0>
MAP_CH5678_to_OUTn<3:0> = 0010
n = 5A, 5B, 6A, 6B, 7A, 7B, 7A, 7B
OUTn
Channel 7 MSB Byte data<15:8>
MAP_CH5678_to_OUTn<3:0> = 0011
Channel 6 LSB Byte data<7:0>
MAP_CH5678_to_OUTn<3:0> = 0100
MAP_CH5678_to_OUTn<3:0> = 1xxx, the
unused OUTn LVDS buffer is powered down.
Channel 6 MSB Byte data<15:8>
MAP_CH5678_to_OUTn<3:0> = 0101
Channel 5 LSB Byte data<7:0>
MAP_CH5678_to_OUTn<3:0> = 0110
Channel 5 MSB Byte data<15:8>
MAP_CH5678_to_OUTn<3:0> = 0011
(b) 2-wire mode
Figure 55. Input and Output Channel Mapping
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Registers 0x50 to 0x55 control the multiplexing options as below:
MAP_CH1234_to_OUTn<3:0>
Mapping
Used in 1-wire mode?
Used in 2-wire mode?
0000
0001
ADC input channel IN1 to OUTn
Y
N
Y, for LSB byte
Y, for MSB byte
ADC input channel IN1 to OUTn (2-
wire only)
0010
0011
ADC input channel IN2 to OUTn
Y
N
Y, for LSB byte
Y, for MSB byte
ADC input channel IN2 to OUTn (2-
wire only)
0100
0101
ADC input channel IN3 to OUTn
Y
N
Y, for LSB byte
Y, for MSB byte
ADC input channel IN3 to OUTn (2-
wire only)
0110
0111
ADC input channel IN4 to OUTn
Y
N
Y, for LSB byte
Y, for MSB byte
ADC input channel IN4 to OUTn (2-
wire only)
1xxx
LVDS output buffer OUTn is powered
down
MAP_CH5678_to_OUTn<3:0> Mapping
Used in 1-wire mode?
Used in 2-wire mode?
Y, for LSB byte
0000
0001
ADC input channel IN8 to OUTn
Y
N
ADC input channel IN8 to OUTn (2-
wire only)
Y, for MSB byte
0010
0011
ADC input channel IN7 to OUTn
Y
N
Y, for LSB byte
Y, for MSB byte
ADC input channel IN7 to OUTn (2-
wire only)
0100
0101
ADC input channel IN6 to OUTn
Y
N
Y, for LSB byte
Y, for MSB byte
ADC input channel IN6 to OUTn (2-
wire only)
0110
0111
ADC input channel IN5 to OUTn
Y
N
Y, for LSB byte
Y, for MSB byte
ADC input channel IN5 to OUTn (2-
wire only)
1xxx
LVDS output buffer OUTn is powered
down
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The default mapping for 1-wire and 2-wire modes is:
Table 7. Mapping for 1-wire Mode
Analog Input channel
Channel IN1
Channel IN2
Channel IN3
Channel IN4
Channel IN5
Channel IN6
Channel IN7
Channel IN8
LVDS Output
OUT1A
OUT2A
OUT3A
OUT4A
OUT5A
OUT6A
OUT7A
OUT8A
Note: In the single wire mode with default register settings, ADC data is available only on OUTnA.
Table 8. Mapping for 2-wire Mode
Analog Input channel
Channel IN1
Channel IN2
Channel IN3
Channel IN4
Channel IN5
Channel IN6
Channel IN7
Channel IN8
LVDS Output
OUT1A, OUT1B
OUT2A, OUT2B
OUT3A, OUT3B
OUT4A, OUT4B
OUT5A, OUT5B
OUT6A, OUT6B
OUT7A, OUT7B
OUT8A, OUT8B
Note: In the 2-wire mode, the ADC data is available on both OUTnA and OUTnB.
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APPLICATION INFORMATION
THEORY OF OPERATION
The ADS5294 is an octal channel, 14-bit high-speed ADC with sample rate up to 80 MSPS that runs off a single
1.8 V supply. All eight channels of the ADS5294 simultaneously sample their analog inputs at the rising edge of
the input clock. The sampled signal is sequentially converted by a series of small resolution stages, with the
outputs combined in a digital correction logic block. At every clock, edge the sample propagates through the
pipeline resulting in a data latency of 11 clock cycles.
The 14 data bits of each channel are serialized and sent out in either 1-wire (one pair of LVDS pins are used) or
2-wire (two pairs of LVDS pins are used) mode, depending on the LVDS output rate. When the data is output in
the 2-wire mode, it can reduce the serial data rate of the outputs, especially at higher sampling rates. Hence, low
cost FPGAs can be used to capture 80 MSPS/14bit data. Alternately, at lower sample rates, the 14-bit data can
be output as a single data stream over one pair of LVDS pins (1-wire mode). The device outputs a bit clock at 7x
and frame clock at 1x times the sample frequency in the 14-bit mode.
This 14-bit ADC achieves approximately 76 dBFS SNR at 80 MSPS. Its output resolution can be configured as
12-bit and 10-bit if necessary. 70 dBFS and 61 dBFS SNRs are achieved when the ADS5294’s output resolution
is 12-bit and 10-bit respectively.
ANALOG INPUT
The analog inputs consist of a switched-capacitor based, differential sample and hold architecture. This
differential topology results in very good AC performance even for high input frequencies at high sampling rates.
The INP and INM pins are internally biased around a common-mode voltage of Vcm (0.95 V). For a full-scale
differential input, each input pin (INP and INM) must swing symmetrically between Vcm + 0.5V and Vcm - 0.5V,
resulting in a 2 VPP differential input swing. Figure 56 illustrates the equivalent circuit of the input sampling circuit.
Figure 56. Analog Input Circuit Model
DRIVE CIRCUIT
For optimum performance, the analog inputs must be driven differentially. This improves the common-mode
noise immunity and even order harmonic rejection. A 5 Ω to 15 Ω resistor in series with each input pin is
recommended to damp out ringing caused by package parasitic.
The drive circuit shows an R-C filter across the analog input pins. The purpose of the filter is to absorb the
glitches caused by the opening and closing of the sampling capacitors.
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0.1 mF
10 W
INP
Differential
Input
2 pF
INM
ADS259x
10 W
0.1 mF
Figure 57. Analog Input Drive Circuit
Large and Small Signal Input Bandwidth
The small signal bandwidth of the analog input circuit is high, around 550 MHz. When using an amplifier to drive
the ADS5294, the total noise of the amplifier up to the small signal bandwidth must be considered. The large
signal bandwidth of the device depends on the amplitude of the input signal. The ADS5294 supports 2 VPP
amplitude for input signal frequency up to 80 MHz. For higher frequencies (80 MHz), the amplitude of the input
signal must be decreased proportionally. For example, at 160 MHz, the device supports a maximum of 1 VPP
signal.
INPUT CLOCK
The ADS5294 is configured by default to operate with a single-ended input clock – CLKP is driven by a CMOS
clock and CLKM is tied to GND. The device can automatically detect a single-ended or differential clock. If CLKM
is grounded, the device treats clock as a single-ended clock. Operating with a low-jitter differential clock usually
gives better SNR performance, especially at input frequencies greater than 30 MHz. Typical clock termination
structures are listed in Figure 58 andFigure 59.
Clock buffer
Lpkg
~ 2 nH
5 Ω
CLKP
Cbond
~ 0.5 pF
Ceq
Ceq
6 pF
6 pF
5 kΩ
Resr
~ 200 Ω
VCM
5 kΩ
Lpkg
~ 2 nH
5 Ω
CLKM
Cbond
~ 0.5 pF
Resr
~ 200 Ω
Ceq is approximately 1 to 3 pF, equivalent input capacitance of clock buffer.
Figure 58. Equivalent Circut of the Input Clock Circuit
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SINGLE-ENDED CLOCK CONNECTIONS
CMOS
CLOCK IN
CLKP
VCM
CLKM
ADS529x
Figure 59. Single-Ended Clock Drive Circuit
DIFFERENTIAL CLOCK CONNECTIONS
DIFFERENTIAL CLOCK CONNECTIONS
0.1 mF
0.1 mF
CLKP
CLKM
CLKP
CLKM
R
Differential
LVPECL
term
Differential sine-
wave clock input
clock input
0.1 mF
R
ADS529x
0.1 mF
ADS529x
term
0.1 mF
CLKP
Differential
LVDS
R
term
clock input
CLKM
0.1 mF
ADS529x
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DIGITAL HIGH PASS IIR FILTER
DC offset is often observed at ADC input signals. For example, in ultrasound applications, the DC offset from
VGA (variable Gain amplifier) varies at different gains. Such a variable offset can introduce artifacts in ultrasound
images especially in Doppler modes. Analog filter between ADC and VGA can be used with added noise and
power. Digital filter achieves the same performance as analog filters and has more flexibility in fine tuning
multiple characteristics.
ADS5294 includes optional 1st order digital high-pass IIR filter. Its block diagram is shown in Figure 60 as well as
its transfer function
2k
2k +1
y(n) =
[x(n) - x(n -1)+y(n -1)]
(6)
Figure 60. HP Filter Block Diagram
Figure 61 shows its characteristics at k=2 to 10.
3
0
−3
−6
−9
−12
−15
−18
−21
−24
−27
−30
−33
−36
−39
−42
K=2
K=3
K=4
K=5
K=6
K=7
K=8
K=9
K=10
−45
0.02
0.1
1
10 15
Input Signal Frequency (MHz)
Figure 61. HP Filter Amplitude Response at K = 2 to 10
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DECIMATION FILTER
ADS5294 includes an option to decimate the ADC output data using filters. Once the decimation is enabled, the
decimation rate, frequency band of the filter can be programmed. In addition, the user can select either the pre-
defined or custom coefficients.
Table 9. Digital Filters
<USE
FILTER
CHn>
<DATA
RATE>
FILTERn
RATE>
<FILTERn
COEFF SET>
<EN CUSTOM
FILT>
DECIMATION
TYPE OF FILTER
<ODD TAP>
Built-in low-pass odd-tap filter (pass band = 0 to fS/4)
Built-in high-pass odd-tap filter (pass band = 0 to fS/4)
Built-in low-pass even-tap filter (pass band = 0 to fS/8)
Built-in first band pass even tap filter(pass band = fS/8 to fS/4)
001
001
010
010
000
000
001
001
000
001
010
011
1
1
0
0
1
1
1
1
0
0
0
0
Decimate by 2
Decimate by 4
Built-in second band pass even tap filter(pass band = fS/4 to 3
fS/8)
010
001
100
0
1
0
Built-in high pass odd tap filter (pass band = 3 fS/8 to fS/2)
Custom filter (user programmablecoefficients)
Custom filter (user programmablecoefficients)
Custom filter (user programmablecoefficients)
Custom filter (user programmablecoefficients)
010
001
010
011
001
000
001
100
101
000
000
000
1
1
1
1
1
1
0
1
1
1
1
Decimate by 2
Decimate by 4
Decimate by 8
Bypass decimation
0 and 1
0 and 1
0 and 1
0 and 1
DECIMATION FILTER EQUATION
In the default setting, the decimation filter is implemented as a 24-tap FIR filter with symmetrical coefficients
(each coefficient is 12-bit signed). By setting the register bit <ODD TAPn> = 1, a 23-tap FIR is implemented
Pre-defined Coefficients
The build-in filters (low pass, high pass an band pass) use pre-defined coefficients. The frequency responses of
the build-in decimation filters with different decimation factors are shown in Figure 62.
20
10
40
30
Low Pass
High pass
Low Pass
Band−Pass1
Band−Pass2
High Pass
20
0
10
−10
−20
−30
−40
−50
−60
−70
−80
0
−10
−20
−30
−40
−50
−60
−70
−80
0.0
0.1
0.2
0.3
0.4
0.5
0.0
0.1
0.2
0.3
0.4
0.5
Normalized Frequency (fin/fs)
Normalized frequency (fin/fs)
Figure 62. Decimation Filter Responses
(Decimate by 2)
Figure 63. Decimation Filter Responses
(Decimate by 4)
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Custom Filter Coefficients
The filter coefficients can also be programmed by the user (customized). For custom coefficients, set the register
bit <FILTER COEFF SELECT> and load the coefficients (h0 to h11) in registers 0x5A to 0xB9, using the serial
interface as:
Register content = real coefficient value x 211, i.e., 12 bit signed representation of real coefficient.
Board Design Considerations
Grounding
A single ground plane is sufficient to give good performance, provided the analog, digital, and clock sections of
the board are cleanly partitioned. See ADS5294VM Evaluation Module (SLAU355) for placement of components,
routing and grounding.
Supply Decoupling
Because the ADS5294 already includes internal decoupling, minimal external decoupling can be used without
loss in performance. For example, the ADS5294EVM uses a single 0.1 µF decoupling capacitor for each supply,
placed close to the device supply pins.
Packaging
Exposed Pad
The exposed pad at the bottom of the package is the main path for heat dissipation. Therefore, the pad must be
soldered to a ground plane on the PCB for best thermal performance. The pad must be connected to the ground
plane through the optimum number of vias.
Also, visit TI’s thermal website at www.ti.com/thermal.
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DEFINITION OF SPECIFICATIONS
Analog Bandwidth – The analog input frequency at which the power of the fundamental is reduced by 3 dB with
respect to the low-frequency value.
Aperture Delay – The delay in time between the rising edge of the input sampling clock and the actual time at
which the sampling occurs. This delay is different across channels. The maximum variation is specified as
aperture delay variation (channel-to-channel).
Aperture Uncertainty (Jitter) – The sample-to-sample variation in aperture delay.
Clock Pulse Width/Duty Cycle – The duty cycle of a clock signal is the ratio of the time the clock signal remains
at a logic high (clock pulse width) to the period of the clock signal. Duty cycle is typically expressed as a
percentage. A perfect differential sine-wave clock results in a 50% duty cycle.
Maximum Conversion Rate – The maximum sampling rate at which specified operation is given. All parametric
testing is performed at this sampling rate unless otherwise noted.
Minimum Conversion Rate – The minimum sampling rate at which the ADC functions.
Differential Nonlinearity (DNL) – An ideal ADC exhibits code transitions at analog input values spaced exactly
1 LSB apart. The DNL is the deviation of any single step from this ideal value, measured in units of LSBs.
Integral Nonlinearity (INL) – The INL is the deviation of the ADC transfer function from a best fit line determined
by a least squares curve fit of that transfer function, measured in units of LSBs.
Gain Error – Gain error is the deviation of the ADC actual input full-scale range from its ideal value. The gain
error is given as a percentage of the ideal input full-scale range. Gain error has two components: error as a
result of reference inaccuracy and error as a result of the channel. Both errors are specified independently as
EGREF and EGCHAN
To a first-order approximation, the total gain error is ETOTAL ~ EGREF + EGCHAN
For example, if ETOTAL = ±0.5%, the full-scale input varies from (1 – 0.5/100) x FSideal to (1 + 0.5/100) x FSideal
.
.
.
Offset Error – The offset error is the difference, given in number of LSBs, between the ADC actual average idle
channel output code and the ideal average idle channel output code. This quantity is often mapped into millivolts.
Temperature Drift – The temperature drift coefficient (with respect to gain error and offset error) specifies the
change per degree Celsius of the parameter from TMIN to TMAX. It is calculated by dividing the maximum deviation
of the parameter across the TMIN to TMAX range by the difference TMAX – TMIN
.
Signal-to-Noise Ratio – SNR is the ratio of the power of the fundamental (PS) to the noise floor power (PN),
excluding the power at dc and the first nine harmonics.
PS
SNR = 10Log10
PN
(7)
SNR is either given in units of dBc (dB to carrier) when the absolute power of the fundamental is used as the
reference, or dBFS (dB to full-scale) when the power of the fundamental is extrapolated to the converter full-
scale range.
Signal-to-Noise and Distortion (SINAD) – SINAD is the ratio of the power of the fundamental (PS) to the power
of all the other spectral components including noise (PN) and distortion (PD), but excluding dc.
PS
SINAD = 10Log10
PN + PD
(8)
SINAD is either given in units of dBc (dB to carrier) when the absolute power of the fundamental is used as the
reference, or dBFS (dB to full-scale) when the power of the fundamental is extrapolated to the converter full-
scale range.
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Effective Number of Bits (ENOB) – ENOB is a measure of the converter performance as compared to the
theoretical limit based on quantization noise.
SINAD - 1.76
ENOB =
6.02
(9)
Total Harmonic Distortion (THD) – THD is the ratio of the power of the fundamental (PS) to the power of the
first nine harmonics (PD).
PS
THD = 10Log10
PN
(10)
THD is typically given in units of dBc (dB to carrier).
Spurious-Free Dynamic Range (SFDR) – The ratio of the power of the fundamental to the highest other
spectral component (either spur or harmonic). SFDR is typically given in units of dBc (dB to carrier).
Two-Tone Intermodulation Distortion – IMD3 is the ratio of the power of the fundamental (at frequencies f1
and f2) to the power of the worst spectral component at either frequency 2f1 – f2 or 2f2 – f1. IMD3 is either given
in units of dBc (dB to carrier) when the absolute power of the fundamental is used as the reference, or dBFS (dB
to full-scale) when the power of the fundamental is extrapolated to the converter full-scale range.
DC Power-Supply Rejection Ratio (DC PSRR) – DC PSSR is the ratio of the change in offset error to a change
in analog supply voltage. The dc PSRR is typically given in units of mV/V.
AC Power-Supply Rejection Ratio (AC PSRR) – AC PSRR is the measure of rejection of variations in the
supply voltage by the ADC. If ΔVSUP is the change in supply voltage and ΔVOUT is the resultant change of the
ADC output code (referred to the input), then:
DVOUT
PSRR = 20Log10
(Expressed in dBc)
DVSUP
(11)
Voltage Overload Recovery – The number of clock cycles taken to recover to less than 1% error after an
overload on the analog inputs. This is tested by separately applying a sine wave signal with 6dB positive and
negative overload. The deviation of the first few samples after the overload (from the expected values) is noted.
Common-Mode Rejection Ratio (CMRR) – CMRR is the measure of rejection of variation in the analog input
common-mode by the ADC. If ΔVCM_IN is the change in the common-mode voltage of the input pins and ΔVOUT is
the resulting change of the ADC output code (referred to the input), then:
DVOUT
10
CMRR = 20Log
(Expressed in dBc)
DVCM
(12)
Crosstalk (only for multi-channel ADCs) – This is a measure of the internal coupling of a signal from an
adjacent channel into the channel of interest. It is specified separately for coupling from the immediate
neighboring channel (near-channel) and for coupling from channel across the package (far-channel). It is usually
measured by applying a full-scale signal in the adjacent channel. Crosstalk is the ratio of the power of the
coupling signal (as measured at the output of the channel of interest) to the power of the signal applied at the
adjacent channel input. It is typically expressed in dBc.
Copyright © 2011–2012, Texas Instruments Incorporated
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ADS5294
SLAS776B –NOVEMBER 2011–REVISED JULY 2012
www.ti.com
REVISION HISTORY
Changes from Original (November 2011) to Revision A
Page
•
Changed From: Product Preview To: Production ................................................................................................................. 1
Changes from Revision A (November 2011) to Revision B
Page
•
•
•
•
•
•
•
•
•
•
•
Changed the location of OUT A and OUT B in Figure 5 and Figure 6 ............................................................................... 14
Added EN_HIGH_ADDRS to Table 3 ................................................................................................................................. 29
Moved EN_EXT_REF From: 0x0F To: 0xF0 in Table 3 ..................................................................................................... 34
Added the section BIT-BYTE-WORD WISE OUTPUT. Added Figure 47 and Figure 48. .................................................. 37
Added section DIGITAL PROCESSING BLOCKS ............................................................................................................. 38
Replaced Table 5 and Table 6 with new Table 5 - Digital Filters ....................................................................................... 43
Changed the SYNCHRONIZATION PULSE section .......................................................................................................... 46
Added the External Reference Mode of Operation section ................................................................................................ 47
Added Figure 58 ................................................................................................................................................................. 53
Replaced Table 9 (Decimation Filter Modes) with new Table 9 - Digital Filters ................................................................. 56
Deleted section: Synchronization Pulse ............................................................................................................................. 57
60
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Copyright © 2011–2012, Texas Instruments Incorporated
Product Folder Link(s) :ADS5294
PACKAGE OPTION ADDENDUM
www.ti.com
25-Feb-2012
PACKAGING INFORMATION
Status (1)
Eco Plan (2)
MSL Peak Temp (3)
Samples
Orderable Device
Package Type Package
Drawing
Pins
Package Qty
Lead/
Ball Finish
(Requires Login)
ADS5294IPFP
ADS5294IPFPR
ADS5294IPFPT
ACTIVE
ACTIVE
ACTIVE
HTQFP
HTQFP
HTQFP
PFP
PFP
PFP
80
80
80
96
Green (RoHS
& no Sb/Br)
CU NIPDAU Level-3-260C-168 HR
1000
250
Green (RoHS
& no Sb/Br)
CU NIPDAU Level-3-260C-168 HR
CU NIPDAU Level-3-260C-168 HR
Green (RoHS
& no Sb/Br)
(1) The marketing status values are defined as follows:
ACTIVE: Product device recommended for new designs.
LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.
NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design.
PREVIEW: Device has been announced but is not in production. Samples may or may not be available.
OBSOLETE: TI has discontinued the production of the device.
(2) Eco Plan - The planned eco-friendly classification: Pb-Free (RoHS), Pb-Free (RoHS Exempt), or Green (RoHS & no Sb/Br) - please check http://www.ti.com/productcontent for the latest availability
information and additional product content details.
TBD: The Pb-Free/Green conversion plan has not been defined.
Pb-Free (RoHS): TI's terms "Lead-Free" or "Pb-Free" mean semiconductor products that are compatible with the current RoHS requirements for all 6 substances, including the requirement that
lead not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, TI Pb-Free products are suitable for use in specified lead-free processes.
Pb-Free (RoHS Exempt): This component has a RoHS exemption for either 1) lead-based flip-chip solder bumps used between the die and package, or 2) lead-based die adhesive used between
the die and leadframe. The component is otherwise considered Pb-Free (RoHS compatible) as defined above.
Green (RoHS & no Sb/Br): TI defines "Green" to mean Pb-Free (RoHS compatible), and free of Bromine (Br) and Antimony (Sb) based flame retardants (Br or Sb do not exceed 0.1% by weight
in homogeneous material)
(3) MSL, Peak Temp. -- The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder temperature.
Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is provided. TI bases its knowledge and belief on information
provided by third parties, and makes no representation or warranty as to the accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and
continues to take reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on incoming materials and chemicals.
TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited information may not be available for release.
In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI to Customer on an annual basis.
Addendum-Page 1
PACKAGE MATERIALS INFORMATION
www.ti.com
14-Jul-2012
TAPE AND REEL INFORMATION
*All dimensions are nominal
Device
Package Package Pins
Type Drawing
SPQ
Reel
Reel
A0
B0
K0
P1
W
Pin1
Diameter Width (mm) (mm) (mm) (mm) (mm) Quadrant
(mm) W1 (mm)
ADS5294IPFPR
ADS5294IPFPT
HTQFP
HTQFP
PFP
PFP
80
80
1000
250
330.0
330.0
24.4
24.4
15.0
15.0
15.0
15.0
1.5
1.5
20.0
20.0
24.0
24.0
Q2
Q2
Pack Materials-Page 1
PACKAGE MATERIALS INFORMATION
www.ti.com
14-Jul-2012
*All dimensions are nominal
Device
Package Type Package Drawing Pins
SPQ
Length (mm) Width (mm) Height (mm)
ADS5294IPFPR
ADS5294IPFPT
HTQFP
HTQFP
PFP
PFP
80
80
1000
250
367.0
367.0
367.0
367.0
45.0
45.0
Pack Materials-Page 2
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