LTC1606AIG#TRPBF [Linear]
LTC1606 - 16-Bit, 250ksps, Single Supply ADC; Package: SSOP; Pins: 28; Temperature Range: -40°C to 85°C;型号: | LTC1606AIG#TRPBF |
厂家: | Linear |
描述: | LTC1606 - 16-Bit, 250ksps, Single Supply ADC; Package: SSOP; Pins: 28; Temperature Range: -40°C to 85°C |
文件: | 总12页 (文件大小:173K) |
中文: | 中文翻译 | 下载: | 下载PDF数据表文档文件 |
Final Electrical Specifications
LTC1606
16-Bit, 250ksps,
Single Supply ADC
March 2000
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DESCRIPTION
FEATURES
The LTC®1606 is a 250ksps, sampling 16-bit A/D con-
verter that draws only 75mW (typical) from a single 5V
supply. This easy-to-use device includes sample-and-
hold, precision reference, switched capacitor successive
approximation A/D and trimmed internal clock.
■
Sample Rate: 250ksps
■
Single 5V Supply
■
Bipolar Input Range: ±10V
■
■
■
■
■
■
■
■
Signal-to-Noise Ratio: 90dB Typ
Power Dissipation: 75mW Typ
Integral Nonlinearity: ±2.0LSB Max
Guaranteed No Missing Codes
Operates with Internal or External Reference
Internal Synchronized Clock
The LTC1606’s input range is an industry standard ±10V.
Maximum DC specs include ±2.0LSB INL and 16 bits no
missing codes over temperature. An external reference
can be used if greater accuracy over temperature is
needed.
28-Pin SSOP Package
Improved 2nd Source to AD976A and ADS7805
The 90dB signal-to-noise ratio offers an improvement of
3dBovercompetingdevices,andtheRMStransitionnoise
is reduced (0.65LSB vs 1LSB) relative to competitive
parts.
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APPLICATIONS
■
Industrial Process Control
■
Multiplexed Data Acquisition Systems
The ADC has a microprocessor compatible, 16-bit or two
byte parallel output port. A convert start input and a data
ready signal (BUSY) ease connections to FIFOs, DSPs and
■
High Speed Data Acquisition for PCs
■
Digital Signal Processing
microprocessors.
, LTC and LT are registered trademarks of Linear Technology Corporation.
Low Power, 250kHz, 16-Bit Sampling ADC on 5V Supply
5V
10µF
0.1µF
28
27
V
V
DIG ANA
6 TO 13
15 TO 22
16-BIT
200Ω
7.35k
V
IN
1
±10V
INPUT
16-BIT
SAMPLING ADC
OR 2 BYTE
PARALLEL
BUS
D15 TO D0
33.2k
2.5k
9k
CAP
REF
4
3
4.096V
26
25
BUSY
CS
10µF
1.64x
BUFFER
DIGITAL
CONTROL
SIGNALS
CONTROL
LOGIC AND
TIMING
4k
R/C 24
2.5V
REFERENCE
BYTE
23
2.2µF
AGND1 AGND2
DGND
14
1606 TA01
2
5
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no represen-
tationthattheinterconnectionofitscircuitsasdescribedhereinwillnotinfringeonexistingpatentrights.
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LTC1606
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/O
PACKAGE RDER I FOR ATIO
ABSOLUTE AXI U RATI GS
(Notes 1, 2)
ORDER PART
TOP VIEW
VANA .......................................................................... 7V
VDIG to VANA ........................................................... 0.3V
NUMBER
V
1
2
3
4
5
6
7
8
9
28
27
V
V
IN
DIG
AGND1
REF
ANA
LTC1606ACG
LTC1606AIG
LTC1606CG
LTC1606IG
V
DIG ........................................................................... 7V
26 BUSY
25 CS
24 R/C
23 BYTE
22 D0
21 D1
20 D2
19 D3
18 D4
17 D5
16 D6
15 D7
Ground Voltage Difference
DGND, AGND1 and AGND2 .............................. ±0.3V
Analog Inputs (Note 3)
CAP
AGND2
D15 (MSB)
D14
VIN ..................................................................... ±25V
CAP ............................ VANA + 0.3V to AGND2 – 0.3V
REF....................................Indefinite Short to AGND2
Momentary Short to VANA
D13
D12
D11 10
D10 11
D9 12
Digital Input Voltage (Note 4) ........ VDGND – 0.3V to 10V
Digital Output Voltage........ VDGND – 0.3V to VDIG + 0.3V
Power Dissipation.............................................. 500mW
Operating Ambient Temperature Range
D8 13
DGND 14
LTC1606AC/LTC1606C............................ 0°C to 70°C
LTC1606AI/LTC1606I ......................... – 40°C to 85°C
Storage Temperature Range ................. –65°C to 150°C
Lead Temperature (Soldering, 10 sec).................. 300°C
G PACKAGE
28-LEAD PLASTIC SSOP
TJMAX = 125°C, θJA = 95°C/W
Consult factory for Military grade parts.
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CONVERTER CHARACTERISTICS
The ● indicates specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. (Notes 5, 6)
LTC1606
TYP
LTC1606A
TYP
PARAMETER
CONDITIONS
MIN
16
MAX
MIN
16
MAX
UNITS
Resolution
●
●
Bits
Bits
No Missing Codes
Transition Noise
15
16
0.65
0.65
LSB
RMS
Integral Linearity Error
Bipolar Zero Error
Bipolar Zero Error Drift
Full-Scale Error Drift
Full-Scale Error
(Note 7)
●
●
±3
±2
LSB
Ext. Reference = 2.5V (Note 8)
±10
±10
mV
±2
±7
±2
±5
ppm/°C
ppm/°C
%
Ext. Reference = 2.5V (Notes 12, 13)
Ext. Reference = 2.5V
●
±0.50
±8
±0.25
±8
Full-Scale Error Drift
Power Supply Sensitivity
±2
±2
ppm/°C
V
= V = V
V = 5V ±5% (Note 9)
DD
LSB
ANA
DIG
DD
2
LTC1606
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The ● indicates specifications which apply over the full operating temperature range, otherwise
ANALOG INPUT
specifications are at TA = 25°C. (Note 5)
LTC1606/LTC1606A
SYMBOL PARAMETER
CONDITIONS
4.75V ≤ V
MIN
TYP
±10
10
MAX
UNITS
V
V
C
Analog Input Range (Note 9)
Analog Input Capacitance
Analog Input Impedance
≤ 5.25V, 4.75V ≤ V ≤ 5.25V
●
IN
IN
ANA
DIG
pF
R
IN
10
kΩ
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DYNAMIC ACCURACY (Notes 5, 14)
LTC1606
TYP
LTC1606A
SYMBOL PARAMETER
CONDITIONS
MIN
MAX
MIN
TYP
MAX
UNITS
S/(N + D) Signal-to-(Noise + Distortion) Ratio 1kHz Input Signal (Note 14)
10kHz Input Signal
90
90
30
90
90
30
dB
dB
dB
87
20kHz, –60dB Input Signal
THD
Total Harmonic Distortion
1kHz Input Signal, First 5 Harmonics
10kHz Input Signal, First 5 Harmonics
–102
–94
– 102
–94
dB
dB
–89
Peak Harmonic or Spurious Noise 1kHz Input Signal
10kHz Input Signal
–102
–94
–102
–94
dB
dB
Full-Power Bandwidth
Aperture Delay
(Note 15)
275
40
275
40
kHz
ns
Aperture Jitter
Sufficient to Meet AC Specs Sufficient to Meet AC Specs
Transient Response
Overvoltage Recovery
Full-Scale Step (Note 9)
(Note 16)
2
2
µs
150
150
ns
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INTERNAL REFERENCE CHARACTERISTICS The ● indicates specifications which apply over the full
operating temperature range, otherwise specifications are at TA = 25°C. (Note 5)
LTC1606/LTC1606A
PARAMETER
CONDITIONS
MIN
TYP
2.500
±5
MAX
UNITS
V
V
Output Voltage
Output Tempco
I
I
= 0
= 0
●
2.470
2.520
V
REF
REF
OUT
OUT
ppm/°C
Internal Reference Source Current
External Reference Voltage for Specified Linearity
External Reference Current Drain
CAP Output Voltage
1
µA
V
(Notes 9, 10)
2.30
2.50
2.70
100
Ext. Reference = 2.5V (Note 9)
●
µA
V
I
= 0
4.096
OUT
3
LTC1606
DIGITAL INPUTS AND DIGITAL OUTPUTS
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The ● indicates specifications which apply over the full
operating temperature range, otherwise specifications are at TA = 25°C. (Note 5)
LTC1606/LTC1606A
SYMBOL PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
V
V
V
High Level Input Voltage
Low Level Input Voltage
Digital Input Current
V
V
V
= 5.25V
DD
= 4.75V
DD
= 0V to V
IN
●
●
●
2.4
IH
IL
0.8
V
I
±10
µA
pF
V
IN
DD
C
V
Digital Input Capacitance
High Level Output Voltage
5
IN
V
V
V
= 4.75V
= 4.75V
I = –10µA
4.5
OH
DD
O
I = –200µA
O
●
4.0
V
V
Low Level Output Voltage
I = 160µA
O
0.05
0.10
V
OL
DD
I = 1.6mA
O
●
●
●
0.4
±10
15
V
I
Hi-Z Output Leakage D15 to D0
Hi-Z Output Capacitance D15 to D0
Output Source Current
= 0V to V , CS High
µA
pF
mA
mA
OZ
OUT
DD
C
CS High (Note 9)
OZ
I
I
V
V
= 0V
–10
10
SOURCE
SINK
OUT
OUT
Output Sink Current
= V
DD
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TIMING CHARACTERISTICS The ● indicates specifications which apply over the full operating temperature
range, otherwise specifications are at TA = 25°C. (Note 5)
LTC1606/LTC1606A
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
kHz
µs
f
t
t
t
t
t
t
t
t
t
t
t
t
t
t
Maximum Sampling Frequency
Conversion Time
●
●
●
●
●
●
●
250
SAMPLE(MAX)
2.5
1.5
CONV
Acquisition Time
µs
ACQ
1
Convert Pulse Width
Data Valid Delay After R/C↓
BUSY Delay from R/C↓
BUSY Low
(Note 11)
(Note 9)
40
ns
2.5
65
µs
2
C = 30pF
L
ns
3
2.5
µs
4
BUSY Delay After End of Conversion
Aperture Delay
100
40
15
90
2
ns
5
ns
6
Bus Relinquish Time
BUSY Delay After Data Valid
Previous Data Valid After R/C↓
R/C to CS Setup Time
Time Between Conversions
Bus Access
●
●
50
ns
7
20
ns
8
µs
9
(Notes 9, 10)
●
●
●
●
5
4
ns
10
11
12
µs
C = 30pF, (Notes 10)
L
15
15
60
60
ns
Byte Delay
C = 30pF, (Notes 9, 10)
L
ns
4
LTC1606
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POWER REQUIREMENTS The ● indicates specifications which apply over the full operating temperature
range, otherwise specifications are at TA = 25°C. (Note 5)
LTC1606/LTC1606A
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
5.25
20
UNITS
V
V
Positive Supply Voltage
Positive Supply Current
Power Dissipation
(Notes 9, 10)
4.75
DD
I
●
●
15
75
mA
DD
P
100
mW
DIS
Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 9: Guaranteed by design, not subject to test.
Note 10: Recommended operating conditions.
Note 2: All voltage values are with respect to ground with DGND, AGND1
and AGND2 wired together (unless otherwise noted).
Note 11: With CS low the falling R/C edge starts a conversion. If R/C
returns high at a critical point during the conversion, it can create errors.
For best results, ensure that R/C returns high within 1µs after the start of
the conversion.
Note 3: When these pin voltages are taken below ground or above V
=
ANA
V
= V , they will be clamped by internal diodes. This product can
DIG
DD
handle input currents of greater than 100mA below ground or above V
without latch-up.
DD
Note 12: As measured with fixed resistors shown in Figure 4. Adjustable to
zero with external potentiometer.
Note 4: When these pin voltages are taken below ground, they will be
clamped by internal diodes. This product can handle input currents of
90mA below ground without latchup. These pins are not clamped to V
Note 13: Full-scale error is the worst-case of –FS or +FS untrimmed
deviation from ideal first and last code transitions, divided by the transition
voltage (not divided by the full-scale range) and includes the effect of
offset error.
.
DD
Note 5: V = 5V, f
= 250kHz, t = t = 5ns unless otherwise
r f
DD
SAMPLE
specified.
Note 14: All specifications in dB are referred to a full-scale ±10V input.
Note 6: Linearity, offset and full-scale specifications apply for a V input
with respect to ground.
Note 7: Integral nonlinearity is defined as the deviation of a code from a
straight line passing through the actual end points of the transfer curve.
The deviation is measured from the center of the quantization band.
IN
Note 15: Full-power bandwidth is defined as full-scale input frequency at
which a signal-to-(noise + distortion) degrades to 60dB or 10 bits of
accuracy.
Note 16: Recovers to specified performance after (2• FS) input
overvoltage.
Note 8: Bipolar offset is the offset voltage measured from –0.5 LSB when
the output code flickers between 0000 0000 0000 0000 and 1111 1111
1111 1111.
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PIN FUNCTIONS
VIN (Pin 1): Analog Input. Connect through a 200Ω
resistor to the analog input. Full-scale input range is
±10V.
DGND (Pin 14): Digital Ground.
D7 to D0 (Pins 15 to 22): Three-State Data Outputs.
Hi-Z state when CS is high or when R/C is low.
AGND1 (Pin 2): Analog Ground. Tie to analog ground
plane.
BYTE (Pin 23): Byte Select. With BYTE low, data will be
output with Pin 6 (D15) being the MSB and Pin 22 (D0)
being the LSB. With BYTE high the upper eight bits and
the lower eight bits will be switched. The MSB is output
on Pin 15 and bit 8 is output on Pin 22. Bit 7 is output on
Pin 6 and the LSB is output on Pin 13.
REF (Pin 3): 2.5V Reference Output. Bypass with 2.2µF
tantalum capacitor. Can be driven with an external refer-
ence.
CAP (Pin 4): Reference Buffer Output. Bypass with 10µF
tantalumcapacitor.Thecapacitoroutputvoltageis4.096V
when REF = 2.5V.
R/C (Pin 24): Read/Convert Input. With CS low, a falling
edge on R/C puts the internal sample-and-hold into the
hold state and starts a conversion. With CS low, a rising
edge on R/C enables the output data bits.
AGND2 (Pin 5): Analog Ground. Tie to analog ground
plane.
D15 to D8 (Pins 6 to 13): Three-State Data Outputs.
Hi-Z state when CS is high or when R/C is low.
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LTC1606
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PIN FUNCTIONS
CS (Pin 25): Chip Select. Internally OR’d with R/C. With
R/C low, a falling edge on CS will initiate a conversion.
With R/C high, a falling edge on CS will enable the output
data.
or another conversion will start without time for signal
acquisition.
V
ANA (Pin 27): 5V Analog Supply. Bypass to ground with
a 0.1µF ceramic and a 10µF tantalum capacitor.
BUSY (Pin 26): Output Shows Converter Status. It is low
when a conversion is in progress. Data valid on the rising
edge of BUSY. CS or R/C must be high when BUSY rises
VDIG (Pin 28): 5V Digital Supply. Connect directly to Pin
27.
TEST CIRCUITS
Load Circuit for Output Float Delay
Load Circuit for Access Timing
5V
5V
1k
1k
DBN
DBN
DBN
DBN
1k
30pF
30pF
1k
30pF
30pF
1606 TC02
1606 TC01
A. Hi-Z TO V AND V TO V
B. Hi-Z TO V AND V TO V
OL OH
A. V TO Hi-Z
OH
B. V TO Hi-Z
OL
OH
OL
OH
OL
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FUNCTIONAL BLOCK DIAGRA
C
C
SAMPLE
7.35k
V
IN
V
V
ANA
9k
2.5k
SAMPLE
DIG
ZEROING SWITCHES
4k
REF
2.5V REF
+
REF BUF
1.64x
COMP
16-BIT CAPACITIVE DAC
–
CAP
(4.096V)
16
D15
D0
SUCCESSIVE APPROXIMATION
REGISTER
•
•
•
OUTPUT LATCHES
AGND1
AGND2
DGND
INTERNAL
CLOCK
CONTROL LOGIC
1606 BD
CS
R/C
BYTE
BUSY
6
LTC1606
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APPLICATIONS INFORMATION
Conversion Details
Driving the Analog Inputs
The LTC1606 uses a successive approximation algorithm
and an internal sample-and-hold circuit to convert an
analog signal to a 16-bit or two byte parallel output. The
ADC is complete with a precision reference and an internal
clock. The control logic provides easy interface to micro-
processors and DSPs. (Please refer to the Digital Interface
section for the data format.)
The nominal input range for the LTC1606 is ±10V or
(±4•VREF)andtheinputisovervoltageprotectedto±25V.
Theinputimpedanceistypically10kΩ,therefore,itshould
be driven with a low impedance source. Wideband noise
coupling into the input can be minimized by placing a
1000pF capacitor at the input as shown in Figure 2. An
NPO-type capacitor gives the lowest distortion. Place the
capacitor as close to the device input pin as possible. If an
amplifier is to be used to drive the input, care should be
takentoselectanamplifierwithadequateaccuracy,linear-
ity and noise for the application. The following list is a
summary of the op amps that are suitable for driving the
LTC1606. More detailed information is available in the
LinearTechnologydatabooksandLinearViewTM CD-ROM.
Conversion start is controlled by the CS and R/C inputs. At
the start of conversion the successive approximation
register (SAR) is reset. Once a conversion cycle has
begun, it cannot be restarted.
During the conversion, the internal 16-bit capacitive DAC
output is sequenced by the SAR from the most significant
bit (MSB) to the least significant bit (LSB). Referring to
Figure 1, VIN is connected through the resistor divider to
the sample-and-hold capacitor during the acquire phase
andthecomparatoroffsetisnulledbytheautozeroswitches.
In this acquire phase, a minimum delay of 1.5µs will
provide enough time for the sample-and-hold capacitor to
acquire the analog signal. During the convert phase, the
autozero switches open, putting the comparator into the
compare mode. The input switch switches CSAMPLE to
ground, injecting the analog input charge onto the sum-
ming junction. This input charge is successively com-
pared with the binary-weighted charges supplied by the
capacitive DAC. Bit decisions are made by the high speed
comparator. At the end of a conversion, the DAC output
balances the VIN input charge. The SAR contents (a 16-bit
data word) that represents the VIN are loaded into the
16-bit output latches.
200Ω
A
IN
V
IN
1000pF
33.2k
CAP
1606 • F02
Figure 2. Analog Input Filtering
LT1007 - Low noise precision amplifier. 2.7mA supply
current ±5V to ±15V supplies. Gain bandwidth product
8MHz. DC applications.
LT1097 - Low cost, low power precision amplifier. 300µA
supply current. ±5V to ±15V supplies. Gain bandwidth
product 0.7MHz. DC applications.
LT1227-140MHzvideocurrentfeedbackamplifier. 10mA
supply current. ±5V to ±15V supplies. Low noise and low
distortion.
SAMPLE
SI
C
SAMPLE
R
SAMPLE
HOLD
IN1
LT1360 - 37MHz voltage feedback amplifier. 3.8mA sup-
ply current. ±5V to ±15V supplies. Good AC/DC specs.
V
IN
–
+
R
IN2
LT1363 - 50MHz voltage feedback amplifier. 6.3mA sup-
ply current. Good AC/DC specs.
C
V
DAC
COMPARATOR
DAC
DAC
S
A
R
LT1364/LT1365 - Dual and quad 50MHz voltage feedback
amplifiers. 6.3mA supply current per amplifier. Good AC/
DC specs.
16-BIT
LATCH
LT1468 - 90MHz 22V/µs 16-bit accurate amplifier.
1606 • F01
Figure 1. LTC1606 Simplified Equivalent Circuit
LinearView is a trademark of Linear Technology Corporation
7
LTC1606
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APPLICATIONS INFORMATION
is applied to VIN and R4 is adjusted until the output code
is changing between 0111 1111 1111 1110 and 0111
1111 1111 1111. Figure 6 shows the bipolar transfer
characteristic of the LTC1606.
Internal Voltage Reference
The LTC1606 has an on-chip, temperature compensated,
curvature corrected, bandgap reference, which is factory
trimmed to 2.50V. The full-scale range of the ADC is equal
to (±4 • VREF) or nominally ±10V. The output of the
reference is connected to the input of a buffer (1.64x)
througha4kresistor(seeFigure3). Theinputtothebuffer
or the output of the reference is available at REF (Pin 3).
The internal reference can be overdriven with an external
reference if more accuracy is needed. The buffer output
drives the internal DAC and is available at CAP (Pin 4). The
CAP pin can be used to drive a steady DC load of less than
2mA. Driving an AC load is not recommended because it
can cause the performance of the converter to degrade.
1
V
±10V INPUT
IN
2
200Ω
1%
AGND1
2.2µF
+
LTC1606
33.2k
1%
3
4
REF
CAP
+
10µF
5
AGND2
1606 • F04
Figure 4. ±10V Input Without Trim
4k
3
REF
(2.5V)
BANDGAP
REFERENCE
1
2.2µF
V
±10V INPUT
IN
2
+
–
200Ω
AGND1
R
1%
2.2µF
+
3
0.64R
33.2k
REF
5V
1%
LTC1606
4
CAP
(4.096V)
576k
R4
50k
INTERNAL
CAPACITOR
DAC
4
5
CAP
+
10µF
R3
50k
10µF
AGND2
1606 • F03
1606 • F05
Figure 3. Internal or External Reference Source
Figure 5. ±10V Input with Offset and Gain Trim
For minimum code transition noise, the REF pin and the
CAP pin should each be decoupled with a capacitor to
filter wideband noise from the reference and the buffer
(2.2µFtantalumfortheREFpinand10µFtantalumforthe
CAP pin).
011...111
BIPOLAR
011...110
ZERO
000...001
000...000
111...111
111...110
Offset and Gain Adjustments
TheLTC1606offsetandfull-scaleerrorshavebeentrimmed
at the factory with the external resistors shown in Figure
4. This allows for external adjustment of offset and full
scale in applications where absolute accuracy is impor-
tant. See Figure 5 for the offset and gain trim circuit. First,
adjust the offset to zero by adjusting resistor R3. Apply an
input voltage of –152.6µV (–0.5LSB) and adjust R3 so the
codeischangingbetween1111111111111111and0000
0000 0000 0000. The gain error is trimmed by adjusting
resistorR4. Aninputvoltageof9.999542V(+FS–1.5LSB)
100...001
FS = 20V
100...000
1LSB = FS/65536
–1 0V
LSB
INPUT VOLTAGE (V)
1
LSB
–FS/2
FS/2 – 1LSB
1606 • F06
Figure 6. LTC1606 Bipolar Transfer Characteristics
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LTC1606
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APPLICATIONS INFORMATION
DC Performance
Timing and Control
Onewayofmeasuringthetransitionnoiseassociatedwith
a high resolution ADC is to use a technique where a DC
signal is applied to the input of the ADC and the resulting
output codes are collected over a large number of conver-
sions. For example in Figure 7, the distribution of output
code is shown for a DC input that has been digitized 4096
times. The distribution is Gaussian and the RMS code
transition is about 0.65LSB.
Conversion start and data read are controlled by two
digital inputs: CS and R/C. To start a conversion and put
the sample-and-hold into the hold mode, bring CS and
R/C low for no less than 40ns. Once initiated, it cannot be
restarted until the conversion is complete. Converter
statusisindicatedbytheBUSYoutputandthisislowwhile
the conversion is in progress.
Therearetwomodesofoperation.Thefirstmodeisshown
in Figure 8. The digital input R/C is used to control the start
of conversion. CS is tied low. When R/C goes low, the
sample-and-hold goes into the hold mode and a conver-
sion is started. BUSY goes low and stays low during the
conversion and will go back high after the conversion has
been completed and the internal output shift registers
havebeenupdated.R/Cshouldremainlowfornolessthan
40ns. During the time R/C is low, the digital outputs are in
a Hi-Z state. R/C should be brought back high within 1µs
after the start of the conversion to ensure that no errors
occur in the digitized result. The second mode, shown in
Figure 9, uses the CS signal to control the start of a
conversion and the reading of the digital output. In this
mode the R/C input signal should be brought low no less
than 10ns before the falling edge of CS. The minimum
pulse width for CS is 40ns. When CS falls, BUSY goes low
and will stay low until the end of the conversion. BUSY will
go high after the conversion has been completed. The new
data is valid when CS is brought back low again to initiate
2500
2000
1500
1000
500
0
–3 –2 –1
0
1
2
3
4
CODE
1606 • F07
Figure 7. Histogram for 4096 Conversions
DIGITAL INTERFACE
Internal Clock
The ADC has an internal clock that is trimmed to achieve
a typical conversion time of 2.3µs. No external adjust-
mentsarerequiredand, withthetypicalacquisitiontimeof a read. Again, it is recommended that both R/C and CS
1µs, throughput performance of 250ksps is assured.
return high within 1µs after the start of the conversion.
t
1
R/C
t
11
t
2
t
4
t
3
BUSY
MODE
t
t
6
5
ACQUIRE
CONVERT
ACQUIRE
CONVERT
Hi-Z
t
t
ACQ
CONV
t
9
PREVIOUS
DATA VALID
PREVIOUS
DATA VALID
DATA
VALID
DATA
VALID
Hi-Z
NOT VALID
DATA MODE
1606 • F08
t
t
7
8
Figure 8. Conversion Timing with Outputs Enabled After Conversion (CS Tied Low)
9
LTC1606
APPLICATIONS INFORMATION
U
W U U
t
t
t
t
10
10
10
10
R/C
t
t
1
1
CS
t
3
t
4
BUSY
MODE
t
6
ACQUIRE
CONVERT
ACQUIRE
t
CONV
HI-Z
Hi-Z
DATA
VALID
DATA BUS
t
t
7
12
1606 • F09
Figure 9. Using CS to Control Conversion and Read Timing
t
t
10
10
R/C
CS
BYTE
Hi-Z
Hi-Z
Hi-Z
Hi-Z
PINS 6 TO 13
PINS 15 TO 22
HIGH BYTE
LOW BYTE
LOW BYTE
HIGH BYTE
t
t
t
7
12
12
1606 • F10
Figure 10. Using CS and BYTE to Control Data Bus Read Timing
10
LTC1606
U
W U U
APPLICATIONS INFORMATION
Output Data
expressed as:
The output data can be read as a 16-bit word or it can be
read as two 8-bit bytes. The format of the output data is
two’s complement. The digital input pin BYTE is used to
control the two byte read. With the BYTE pin low, the first
eight MSBs are output on the D15 to D8 pins and the eight
LSBs are output on the D7 to D0 pins. When the BYTE pin
is taken high, the eight LSBs replace the eight MSBs
(Figure 10).
2
2
2
2
√V2 + V3 + V4 ... + VN
THD = 20log
V1
where V1 is the RMS amplitude of the fundamental fre-
quency and V2 through VN are the amplitudes of the
second through Nth harmonics.
Board Layout, Power Supplies and Decoupling
Wire wrap boards and molded sockets are not recom-
mended for high resolution or high speed A/D converters.
To obtain the best performance from the LTC1606, a
printed circuit board is required. Layout for the printed
circuit board should ensure the digital and analog signal
linesareseparatedasmuchaspossible. Inparticular, care
should be taken not to run any digital track alongside an
analog signal track or underneath the ADC. The analog
input should be screened by AGND.
Dynamic Performance
FFT (Fast Fourier Transform) test techniques are used to
test the ADC’s frequency response, distortion and noise at
the rated throughput. By applying a low distortion sine
wave and analyzing the digital output using an FFT algo-
rithm, the ADC’s spectral content can be examined for
frequencies outside the fundamental.
Signal-to-Noise Ratio
Pay particular attention to the design of the analog and
digital ground planes. The DGND pin of the LTC1606
should be tied to the analog ground plane. Placing the
bypasscapacitorascloseaspossibletothepowersupply,
the reference and reference buffer output is very impor-
tant. Low impedance common returns for these bypass
capacitors are essential to low noise operation of the ADC,
and the foil width for these tracks should be as wide as
possible. Also, since any potential difference in grounds
between the signal source and ADC appears as an error
voltage in series with the input signal, attention should be
paid to reducing the ground circuit impedance as much as
possible.
The Signal-to-Noise and Distortion Ratio (SINAD) is the
ratiobetweentheRMSamplitudeofthefundamentalinput
frequency to the RMS amplitude of all other frequency
components at the A/D output. The output is band limited
tofrequenciesfromaboveDCandbelowhalfthesampling
frequency. A typical LTC1606 has a SINAD of 90dB and
THD of –102dB with a 250kHz sampling rate and a 1kHz
input.
Total Harmonic Distortion
Total Harmonic Distortion (THD) is the ratio of the RMS
sumofallharmonicsoftheinputsignaltothefundamental
itself. The out-of-band harmonics alias into the frequency
band between DC and half the sampling frequency. THD is
11
LTC1606
U
PACKAGE DESCRIPTION Dimensions in inches (millimeters) unless otherwise noted.
G Package
28-Lead Plastic SSOP (0.209)
(LTC DWG # 05-08-1640)
10.07 – 10.33*
(0.397 – 0.407)
28 27 26 25 24 23 22 21 20 19 18
16 15
17
7.65 – 7.90
(0.301 – 0.311)
5
7
8
1
2
3
4
6
9 10 11 12 13 14
5.20 – 5.38**
(0.205 – 0.212)
1.73 – 1.99
(0.068 – 0.078)
0° – 8°
0.65
(0.0256)
BSC
0.13 – 0.22
0.55 – 0.95
(0.005 – 0.009)
(0.022 – 0.037)
0.05 – 0.21
(0.002 – 0.008)
0.25 – 0.38
(0.010 – 0.015)
NOTE: DIMENSIONS ARE IN MILLIMETERS
*DIMENSIONS DO NOT INCLUDE MOLD FLASH. MOLD FLASH
SHALL NOT EXCEED 0.152mm (0.006") PER SIDE
**DIMENSIONS DO NOT INCLUDE INTERLEAD FLASH. INTERLEAD
FLASH SHALL NOT EXCEED 0.254mm (0.010") PER SIDE
G28 SSOP 1098
RELATED PARTS
PART NUMBER
LTC1274/LTC1277
LTC1415
DESCRIPTION
COMMENTS
Low Power 12-Bit, 100ksps ADCs
Single 5V, 12-Bit, 1.25Msps ADC
14-Bit, 200ksps ADC
10mW Power Dissipation, Parallel/Byte Interface
55mW Power Dissipation, 72dB SINAD
15mW, Serial or Parallel Interface
LTC1418
LTC1419
Low Power 14-Bit, 800ksps ADC
Micropower Precision Series Reference
Precision Bandgap Reference
Micropower 4-/8-Channel 12-Bit ADCs
16-Bit, 333ksps ADC
True 14-Bit Linearity, 81.5dB SINAD, 150mW Dissipation
0.075% Max, 10ppm/°C Max, Only 130µA Supply Current
0.04% Max, 3ppm/°C Max
LT1460-2.5
LT1461
LTC1594/LTC1598
LTC1604
Serial I/O, 3V and 5V Versions
±2.5V Input, 90dB SINAD, 100dB THD, No Missing Codes
Pin Compatible
LTC1605
16 Bits, 100kHz ADC
LTC1605-1/LTC1605-2 16 Bits, 100kHz ADC
0V to 4V/±4V Input Range, Pin Compatible with LTC1606
1606i LT/TP 0300 4K • PRINTED IN THE USA
LinearTechnology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
12
●
●
(408)432-1900 FAX:(408)434-0507 www.linear-tech.com
LINEAR TECHNOLOGY CORPORATION 2000
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