LTC1416 [Linear]

Low Power 14-Bit, 400ksps Sampling ADC; 低功耗,14位, 400ksps采样ADC
LTC1416
型号: LTC1416
厂家: Linear    Linear
描述:

Low Power 14-Bit, 400ksps Sampling ADC
低功耗,14位, 400ksps采样ADC

文件: 总20页 (文件大小:509K)
中文:  中文翻译
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LTC1416  
Low Power 14-Bit, 400ksps  
Sampling ADC  
U
DESCRIPTIO  
EATURE  
Sample Rate: 400ksps  
Power Dissipation: 70mW  
Guaranteed ±1.5LSB DNL, ±2LSB INL (Max)  
80.5dB S/(N + D) and 93dB THD at 100kHz  
80dB S/(N + D) and 90dB THD at Nyquist  
Nap and Sleep Shutdown Modes  
S
F
The LTC®1416 is a 2.2µs, 400ksps, 14-bit sampling A/D  
converter that draws only 70mW from ±5V supplies. This  
easy-to-usedeviceincludesahighdynamicrangesample-  
and-hold and a precision reference. Two digitally select-  
able power shutdown modes provide flexibility for low  
power systems.  
Operates with Internal or External Reference  
True Differential Inputs Reject Common Mode Noise  
15MHz Full Power Bandwidth Sampling  
±2.5V Bipolar Input Range  
The LTC1416’s full-scale input range is ±2.5V. Maximum  
DC specifications include ±2LSB INL, ±1.5LSB DNL over  
temperature.OutstandingACperformanceincludes80.5dB  
S/(N + D) and 93dB THD with a 100kHz input, and 80dB  
S/(N + D) and 90dB THD at the Nyquist input frequency of  
200kHz.  
28-Pin SSOP Package  
O U  
PPLICATI  
A
S
The unique differential input sample-and-hold can ac-  
quire single-ended or differential input signals up to its  
15MHz bandwidth. The 60dB common mode rejection  
allows users to eliminate ground loops and common  
mode noise by measuring signals differentially from the  
source.  
Telecommunications  
Digital Signal Processing  
Multiplexed Data Acquisition Systems  
High Speed Data Acquisition  
Spectrum Analysis  
The ADC has a µP compatible, 14-bit parallel output port.  
There is no pipeline delay in the conversion results. A  
separate convert start input and a data ready signal  
(BUSY) ease connections to FIFOs, DSPs and micropro-  
cessors.  
Imaging Systems  
, LTC and LT are registered trademarks of Linear Technology Corporation.  
U
O
TYPICAL APPLICATI  
Effective Bits and  
Signal-to-(Noise + Distortion)  
vs Input Frequency  
Complete, 70mW, 14-Bit ADC with 80.5dB S/(N + D)  
14  
13  
12  
11  
10  
9
86  
80  
74  
68  
62  
DV  
AV  
10µF  
DD  
DD  
LTC1416  
NYQUIST  
FREQUENCY  
14  
+
A
IN  
D13 (MSB)  
D0 (LSB)  
OUTPUT  
BUFFERS  
14-BIT ADC  
S/H  
8
7
A
IN  
REFCOMP  
22µF  
6
5
4
3
2
1
BUFFER  
4k  
BUSY  
CS  
CONVST  
RD  
SHDN  
TIMING  
AND  
LOGIC  
2.5V  
REFERENCE  
V
REF  
1µF  
f
= 400kHz  
10k  
SAMPLE  
V
0
SS  
AGND  
DGND  
1416 TA01  
1k  
100k  
1M 2M  
INPUT FREQUENCY (Hz)  
10µF  
–5V  
1416 TA02  
1
LTC1416  
W W W  
U
/O  
PACKAGE RDER I FOR ATIO  
ABSOLUTE AXI U RATI GS  
AVDD = DVDD = VDD (Notes 1, 2)  
ORDER  
TOP VIEW  
Supply Voltage (VDD)................................................ 6V  
Negative Supply Voltage (VSS)................................ 6V  
Total Supply Voltage (VDD to VSS) .......................... 12V  
Analog Input Voltage  
(Note 3) ......................... (VSS – 0.3V) to (VDD + 0.3V)  
Digital Input Voltage (Note 4) ..........(VSS – 0.3V) to 10V  
Digital Output Voltage....... (VSS – 0.3V) to (VDD + 0.3V)  
Power Dissipation............................................. 500mW  
Operating Temperature Range  
Commercial ............................................ 0°C to 70°C  
Industrial ........................................... 40°C to 85°C  
Storage Temperature Range ................ 65°C to 150°C  
Lead Temperature (Soldering, 10 sec)................. 300°C  
PART NUMBER  
+
A
A
1
2
3
4
5
6
7
8
9
28 AV  
DD  
IN  
27 DV  
IN  
DD  
LTC1416CG  
LTC1416IG  
V
26  
V
SS  
REF  
REFCOMP  
AGND  
D13(MSB)  
D12  
25 BUSY  
24 CS  
23 CONVST  
22 RD  
D11  
21 SHDN  
20 D0  
D10  
D9 10  
D8 11  
19 D1  
18 D2  
D7 12  
17 D3  
D6 13  
16 D4  
DGND 14  
15 D5  
G PACKAGE  
28-LEAD PLASTIC SSOP  
TJMAX = 110°C, θJA = 95°C/W  
Consult factory for Military grade parts and for A grade parts.  
U
CO VERTER  
With Internal Reference (Notes 5, 6)  
CHARACTERISTICS  
PARAMETER  
CONDITIONS  
MIN  
TYP  
MAX  
UNITS  
Bits  
Resolution (No Missing Codes)  
Integral Linearity Error  
Differential Linearity Error  
Offset Error  
13  
(Note 7)  
±0.8  
±0.7  
±5  
±2  
LSB  
±1.5  
±20  
LSB  
(Note 8)  
LSB  
Full-Scale Error  
Internal Reference  
External Reference = 2.5V  
±20  
±10  
±60  
±40  
LSB  
LSB  
Full-Scale Tempco  
I
= 0  
±15  
ppm/°C  
OUT(REF)  
U
U
(Note 5)  
A ALOG I PUT  
SYMBOL PARAMETER  
CONDITIONS  
MIN  
TYP  
MAX  
UNITS  
V
V
Analog Input Range (Note 9)  
4.75V V 5.25V, 5.25V V 4.75V  
±2.5  
IN  
DD  
SS  
I
Analog Input Leakage Current  
Analog Input Capacitance  
CS = High  
±1  
µA  
IN  
C
Between Conversions  
During Conversions  
15  
5
pF  
pF  
IN  
t
t
t
Sample-and-Hold Acquisition Time  
(Note 9)  
100  
–1.5  
2
400  
ns  
ns  
ACQ  
AP  
Sample-and-Hold Aperture Delay Time  
Sample-and-Hold Aperture Delay Time Jitter  
Analog Input Common Mode Rejection Ratio  
ps  
RMS  
jitter  
+
CMRR  
2.5V < (A = A ) < 2.5V  
60  
dB  
IN  
IN  
2
LTC1416  
U W  
DY A IC ACCURACY (Note 5)  
SYMBOL  
PARAMETER  
CONDITIONS  
MIN  
TYP  
MAX  
UNITS  
S/(N + D)  
Signal-to-(Noise + Distortion) Ratio  
100kHz Input Signal  
200kHz Input Signal  
77  
80.5  
80  
dB  
dB  
THD  
Total Harmonic Distortion  
100kHz Input Signal, First 5 Harmonics  
200kHz Input Signal, First 5 Harmonics  
93  
90  
86  
86  
dB  
dB  
SFDR  
IMD  
Spurious-Free Dynamic Range  
Intermodulation Distortion  
Full Power Bandwidth  
100kHz Input Signal  
95  
90  
15  
dB  
dB  
f
= 87.01172kHz, f = 113.18359kHz  
IN2  
IN1  
MHz  
MHz  
Full Linear Bandwidth  
(S/(N + D) 77dB)  
0.8  
U
U
U
I TER AL REFERE CE CHARACTERISTICS  
(Note 5)  
PARAMETER  
CONDITIONS  
MIN  
TYP  
2.500  
±15  
MAX  
UNITS  
V
V
V
V
Output Voltage  
Output Tempco  
Line Regulation  
I
I
= 0  
= 0  
2.480  
2.520  
REF  
REF  
REF  
OUT  
OUT  
ppm/°C  
4.75V V 5.25V  
5.25V V 4.75V  
0.05  
0.05  
LSB/V  
LSB/V  
DD  
SS  
V
Output Resistance  
0.1mA I  
0.1mA  
OUT  
4
kΩ  
REF  
COMP Output Voltage  
I
= 0  
4.06  
V
OUT  
U
U
(Note 5)  
DIGITAL I PUTS A D DIGITAL OUTPUTS  
SYMBOL PARAMETER  
CONDITIONS  
MIN  
TYP  
MAX  
UNITS  
V
V
High Level Input Voltage  
Low Level Input Voltage  
Digital Input Current  
V
V
V
= 5.25V  
= 4.75V  
= 0V to V  
2.4  
V
V
IH  
IL  
DD  
DD  
IN  
0.8  
I
±10  
µA  
pF  
IN  
DD  
C
V
Digital Input Capacitance  
High Level Output Voltage  
5
IN  
V
V
V
= 4.75V  
OH  
DD  
I
I
= 10µA  
4.5  
V
V
OUT  
OUT  
= 200µA  
4.0  
V
Low Level Output Voltage  
= 4.75V  
OL  
DD  
I
I
= 160µA  
0.05  
0.10  
V
V
OUT  
OUT  
= 1.6mA  
0.4  
±10  
15  
I
Hi-Z Output Leakage D13 to D0  
Hi-Z Output Capacitance D13 to D0  
Output Source Current  
= 0V to V , CS High  
µA  
pF  
OZ  
OUT  
DD  
C
CS High (Note 9 )  
OZ  
I
I
V
V
= 0V  
10  
10  
mA  
mA  
SOURCE  
SINK  
OUT  
OUT  
Output Sink Current  
= V  
DD  
W U  
POWER REQUIRE E TS  
(Note 5)  
SYMBOL PARAMETER  
CONDITIONS  
(Note 10)  
MIN  
4.75  
TYP  
MAX  
5.25  
UNITS  
V
V
Positive Supply Voltage  
Negative Supply Voltage  
V
V
DD  
SS  
(Note 10)  
4.75  
5.25  
I
Positive Supply Current  
Nap Mode  
7
0.8  
1
10  
mA  
mA  
µA  
DD  
SHDN = 0V, CS = 0V  
SHDN = 0V, CS = 5V  
1.2  
Sleep Mode  
I
Negative Supply Current  
Nap Mode  
7
20  
15  
10  
mA  
µA  
µA  
SS  
SHDN = 0V, CS = 0V  
SHDN = 0V, CS = 5V  
Sleep Mode  
3
LTC1416  
W U  
POWER REQUIRE E TS  
(Note 5)  
CONDITIONS  
SYMBOL  
PARAMETER  
MIN  
TYP  
MAX  
UNITS  
P
Power Dissipation  
Power Dissipation, Nap Mode  
Power Dissipation, Sleep Mode  
70  
4
0.1  
100  
6
mW  
mW  
mW  
DISS  
SHDN = 0V, CS = 0V  
SHDN = 0V, CS = 5V  
W U  
(Note 5, see Figures 15 to 21)  
CONDITIONS  
TI I G CHARACTERISTICS  
SYMBOL  
PARAMETER  
MIN  
TYP  
MAX  
UNITS  
kHz  
µs  
f
t
t
t
t
t
t
t
t
t
Maximum Sampling Frequency  
Conversion Time  
400  
1.5  
SAMPLE(MAX)  
1.9  
100  
2
2.2  
400  
2.5  
CONV  
Acquisition Time  
(Note 9)  
ns  
ACQ  
Acquisition + Conversion Time  
CS to RD Setup Time  
µs  
ACQ+CONV  
(Notes 9, 10)  
(Notes 9, 10)  
(Notes 9, 10)  
(Note 10)  
0
ns  
1
2
3
4
5
6
CSto CONVSTSetup Time  
CSto SHDNSetup Time  
SHDNto CONVSTWake-Up Time  
CONVST Low Time  
10  
10  
ns  
ns  
400  
ns  
(Notes 10, 11)  
40  
ns  
CONVST to BUSY Delay  
C = 25pF  
L
25  
ns  
ns  
50  
t
Data Ready Before BUSY↑  
75  
50  
100  
ns  
ns  
7
t
t
t
Delay Between Conversions  
Wait Time RDAfter BUSY↑  
Data Access Time After RD↓  
(Note 10)  
40  
ns  
ns  
8
–5  
9
C = 25pF  
L
15  
20  
8
25  
35  
ns  
ns  
10  
C = 100pF  
L
35  
50  
ns  
ns  
t
Bus Relinquish Time  
20  
25  
30  
ns  
ns  
ns  
11  
0°C T 70°C  
A
40°C T 85°C  
A
t
t
RD Low Time  
t
ns  
ns  
12  
13  
10  
CONVST High Time  
40  
The  
denotes specifications which apply over the full operating  
Note 6: Linearity, offset and full-scale specifications apply for a single-  
+
temperature range; all other limits and typicals at T = 25°C.  
ended A input with A grounded.  
A
IN IN  
Note 1: Absolute Maximum Ratings are those values beyond which the life  
Note 7: Integral nonlinearity is defined as the deviation of a code from a  
straight line passing through the actual endpoints of the transfer curve.  
The deviation is measured from the center of the quantization band.  
Note 8: Bipolar offset is the offset voltage measured from 0.5LSB when  
the output code flickers between 0000 0000 0000 00 and  
1111 1111 1111 11.  
Note 9: Guaranteed by design, not subject to test.  
Note 10: Recommended operating conditions.  
Note 11: The falling CONVST edge starts a conversion. If CONVST returns  
high at a critical point during the conversion it can create small errors. For  
best results ensure that CONVST returns high either within 900ns after the  
start of the conversion or after BUSY rises.  
of a device may be impaired.  
Note 2: All voltage values are with respect to ground with DGND and  
AGND wired together unless otherwise noted.  
Note 3: When these pin voltages are taken below V or above V , they  
SS  
DD  
will be clamped by internal diodes. This product can handle input currents  
greater than 100mA below V or above V without latchup.  
SS  
DD  
Note 4: When these pin voltages are taken below V , they will be clamped  
SS  
by internal diodes. This product can handle input currents greater than  
100mA below V without latchup. These pins are not clamped to V  
.
SS  
DD  
Note 5: V = 5V, V = 5V, f  
= 400kHz, t = t = 5ns unless  
r f  
DD  
SS  
SAMPLE  
otherwise specified.  
4
LTC1416  
U W  
TYPICAL PERFORMANCE CHARACTERISTICS  
S/(N + D) vs Input Frequency  
and Amplitude  
Signal-to-Noise Ratio  
vs Input Frequency  
Distortion vs Input Frequency  
90  
80  
70  
60  
50  
40  
30  
20  
10  
0
90  
80  
70  
60  
50  
40  
30  
20  
10  
0
0
–10  
–20  
–30  
–40  
–50  
–60  
–70  
–80  
–90  
–100  
–110  
V
= 0dB  
IN  
IN  
V
= –20dB  
V
= –60dB  
IN  
3RD  
THD  
2ND  
1k  
10k  
100k  
1M 2M  
1k  
1k  
10k  
100k  
1M 2M  
10k  
100k  
1M 2M  
INPUT FREQUENCY (Hz)  
INPUT FREQUENCY (Hz)  
INPUT FREQUENCY (Hz)  
1416 G02  
1416 G01  
1416 G03  
Spurious-Free Dynamic Range  
vs Input Frequency  
Differential Nonlinearity  
vs Output Code  
Intermodulation Distortion Plot  
0
–10  
–20  
–30  
–40  
–50  
–60  
–70  
–80  
–90  
–100  
1.0  
0.5  
0
–20  
f
= 400kHz  
V
= ±2.5V  
= 2.5V  
SAMPLE  
OUT  
REF  
f =87.01171876kHz  
a
V
f =113.1835938kHz  
b
–40  
–60  
0
–80  
–100  
–120  
–140  
–0.5  
–1.0  
1k  
10k  
100k  
1M 2M  
8192  
12288  
0
60  
100  
120 140 160 180 200  
0
16384  
20 40  
80  
4096  
INPUT FREQUENCY (Hz)  
FREQUENCY (Hz)  
OUTPUT CODE  
1416 G04  
1416 G05  
1416 G06  
Integral Nonlinearity  
vs Output Code  
Power Supply Feedthrough  
vs Ripple Frequency  
Input Common Mode Rejection  
vs Input Frequency  
0
–10  
–20  
–30  
–40  
–50  
–60  
–70  
–80  
–90  
–100  
80  
70  
60  
50  
40  
30  
20  
10  
0
1.0  
0.5  
V
= ±2.5V  
= 2.5V  
OUT  
REF  
V
0
DGND (V = 100mV)  
IN  
–0.5  
–1.0  
V (V = 10mV)  
SS IN  
V
(V = 10mV)  
DD IN  
1k  
10k  
100k  
1M 2M  
1k  
10k  
100k  
1M 2M  
8192  
12288  
0
16384  
4096  
RIPPLE FREQUENCY (Hz)  
INPUT FREQUENCY (Hz)  
OUTPUT CODE  
1416 G08  
1416 G09  
1416 G07  
5
LTC1416  
U U  
U
PI FU CTIO S  
+
A
A
V
(Pin 1): ±2.5V Positive Analog Input.  
(Pin 2): ±2.5V Negative Analog Input.  
(Pin 3): 2.5V Reference Output. Bypass to AGND  
CONVST (Pin 23): Conversion Start Signal. This active  
low signal starts a conversion on its falling edge.  
IN  
IN  
CS (Pin 24): The Chip Select input must be low for the  
ADC to recognize CONVST and RD inputs. CS also sets  
the shutdown mode when SHDN goes low. CS and  
SHDN low select the quick wake-up nap mode. CS high  
and SHDN low select sleep mode.  
BUSY (Pin 25): The BUSY output shows the converter  
status. It is low when a conversion is in progress. Data  
is valid on the rising edge of BUSY.  
REF  
with 1µF.  
REFCOMP (Pin 4): 4.06V Reference Output. Bypass to  
AGND with 22µF tantalum in parallel with 0.1µF  
ceramic, or 22µF ceramic.  
AGND (Pin 5): Analog Ground.  
D13 to D6 (Pins 6 to 13): Three-State Data Outputs.  
DGND (Pin 14): Digital Ground for Internal Logic. Tie to  
V
(Pin 26): 5V Negative Supply. Bypass to AGND  
SS  
AGND.  
with 10µF tantalum in parallel with 0.1µF ceramic, or  
10µF ceramic.  
D5 to D0 (Pins 15 to 20): Three-State Data Outputs.  
DV (Pin 27): 5V Positive Supply. Tie to Pin 28.  
DD  
SHDN (Pin 21): Power Shutdown Input. Low selects  
shutdown. Shutdown mode selected by CS. CS = 0 for  
nap mode and CS = 1 for sleep mode.  
RD (Pin 22): Read Input. This enables the output  
drivers when CS is low.  
AV (Pin 28): 5V Positive Supply. Bypass to AGND  
DD  
with 10µF tantalum in parallel with 0.1µF ceramic, or  
10µF ceramic.  
U
U
W
FU CTIO AL BLOCK DIAGRA  
C
C
SAMPLE  
SAMPLE  
+
A
IN  
AV  
DD  
DV  
DD  
A
V
IN  
SS  
4k  
ZEROING SWITCHES  
V
2.5V REF  
REF AMP  
REF  
+
COMP  
14-BIT CAPACITIVE DAC  
REFCOMP  
(4.06V)  
14  
D13  
D0  
SUCCESSIVE APPROXIMATION  
REGISTER  
OUTPUT LATCHES  
AGND  
DGND  
INTERNAL  
CLOCK  
CONTROL LOGIC  
1416 BD  
SHDN CONVST  
RD  
CS  
BUSY  
6
LTC1416  
TEST CIRCUITS  
Load Circuits for Access Timing  
Load Circuits for Output Float Delay  
5V  
5V  
1k  
1k  
DBN  
DBN  
DBN  
DBN  
1k  
C
C
1k  
100pF  
100pF  
L
L
(A) Hi-Z TO V AND V TO V  
(B) Hi-Z TO V AND V TO V  
OL  
(A) V TO Hi-Z  
OH  
(B) V TO Hi-Z  
OL  
OH  
OL  
OH  
OL  
OH  
1416 TC01  
1416 TC02  
U
W U U  
APPLICATIONS INFORMATION  
CONVERSION DETAILS  
Conversion start is controlled by the CS and CONVST  
inputs. At the start of the conversion the successive  
approximation register (SAR) is reset. Once a conversion  
cycle has begun, it cannot be restarted.  
The LTC1416 uses a successive approximation algorithm  
and an internal sample-and-hold circuit to convert an  
analog signal to a 14-bit parallel output. The ADC is  
complete with a precision reference and an internal clock.  
The control logic provides easy interface to microproces-  
sors and DSPs. (Please refer to the Digital Interface  
section for the data format.)  
During the conversion, the internal differential 14-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, the AIN+ and AINinputs are  
connected to the sample-and-hold capacitors (CSAMPLE  
)
during the acquire phase and the comparator offset is  
nulled by the zeroing switches. In this acquire phase, a  
minimum delay of 400ns will provide enough time for the  
sample-and-hold capacitors to acquire the analog signal.  
Duringtheconvertphasethecomparatorzeroingswitches  
open, putting the comparator into compare mode. The  
input switches connect the CSAMPLE capacitors to ground,  
transferring the differential analog input charge onto the  
summingjunction. Thisinputchargeissuccessivelycom-  
pared with the binary-weighted charges supplied by the  
differential capacitive DAC. Bit decisions are made by the  
high speed comparator. At the end of a conversion, the  
+
C
SAMPLE  
SAMPLE  
SAMPLE  
SAMPLE  
+
A
A
IN  
IN  
HOLD  
HOLD  
C
HOLD  
ZEROING SWITCHES  
+
C
DAC  
HOLD  
+
+
V
DAC  
C
DAC  
COMP  
V
DAC  
14  
D13  
D0  
OUTPUT  
LATCH  
SAR  
+
differential DAC output balances the AIN and AINinput  
charges. The SAR contents (a 14-bit data word) which  
represents the difference of AIN+ and AINare loaded into  
the 14-bit output latches.  
1416 F01  
Figure 1. Simplified Block Diagram  
7
LTC1416  
U
W U U  
APPLICATIONS INFORMATION  
DYNAMIC PERFORMANCE  
Signal-to-Noise Ratio  
The LTC1416 has excellent high speed sampling capabil-  
ity. FFT (Fast Fourier Transform) test techniques are used  
to testtheADC’sfrequency 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. Figure 2 shows a  
typical LTC1416 FFT plot.  
TheSignal-to-NoiseplusDistortionRatio[S/(N+D)]isthe  
ratiobetweentheRMSamplitudeofthefundamentalinput  
frequency to the RMS amplitude of all other frequency  
components at the A/D output. The output is band limited  
to frequenciesfromaboveDCandbelowhalfthesampling  
frequency. Figure 2a shows a typical spectral content with  
a 400kHz sampling rate and a 100kHz input. The dynamic  
performance is excellent for input frequencies up to and  
beyond the Nyquist limit of 200kHz, Figure 2b.  
0
f
f
= 400kHz  
SAMPLE  
IN  
= 101.5625kHz  
–20  
Effective Number of Bits  
SFDR = 95.2dB  
SINAD = 80.5dB  
–40  
TheEffectiveNumberofBits(ENOBs)isameasurementof  
the resolution of an ADC and is directly related to the  
S/(N + D) by the equation:  
–60  
–80  
ENOB = [S/(N + D) – 1.76]/6.02  
–100  
–120  
–140  
where ENOB is the Effective Number of Bits of resolution  
and S/(N + D) is expressed in dB. At the maximum  
samplingrateof400kHztheLTC1416maintainsnearideal  
ENOBs up to the Nyquist input frequency of 200kHz (refer  
to Figure 3).  
0
25 50 75 100 125  
FREQUENCY (kHz)  
150  
175 200  
1416 F02a  
Figure 2a. LTC1416 Nonaveraged, 4096 Point FFT,  
Input Frequency = 100kHz  
14  
13  
12  
11  
10  
9
86  
80  
74  
68  
62  
0
NYQUIST  
FREQUENCY  
f
f
= 400kHz  
SAMPLE  
= 189.9414kHz  
IN  
–20  
SFDR = 94.8dB  
SINAD = 80.2dB  
8
7
–40  
6
5
4
3
–60  
–80  
2
1
0
–100  
–120  
–140  
f
= 400kHz  
10k  
SAMPLE  
1k  
100k  
1M 2M  
INPUT FREQUENCY (Hz)  
1416 TA02  
0
25 50 75 100 125  
FREQUENCY (kHz)  
150  
175 200  
1416 F02b  
Figure 3. Effective Bits and Signal/(Noise + Distortion)  
vs Input Frequency  
Figure 2b. LTC1416 Nonaveraged, 4096 Point FFT,  
Input Frequency = 190kHz  
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Total Harmonic Distortion  
ence frequencies of mfa ± nfb, where m and n = 0, 1, 2, 3,  
etc. For example, the 2nd order IMD terms include (fa +  
fb). If the two input sine waves are equal in magnitude, the  
value (in decibels) of the 2nd order IMD products can be  
expressed by the following formula:  
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  
expressed as:  
Amplitude at fa+ fb  
(
)
IMD fa + fb = 20 log  
(
)
2
2
2
2
Amplitude at fa  
V2 + V3 + V4 +...Vn  
THD = 20 log  
V1  
0
–20  
f
a
= 400kHz  
SAMPLE  
where V1 is the RMS amplitude of the fundamental fre-  
quency and V2 through Vn are the amplitudes of the  
second through Nth harmonics. THD versus input fre-  
quency is shown in Figure 4. The LTC1416 has good  
distortion performance up to the Nyquist frequency and  
beyond.  
f =87.01171876kHz  
f =113.1835938kHz  
b
–40  
–60  
–80  
–100  
–120  
–140  
0
–10  
–20  
–30  
–40  
–50  
–60  
–70  
0
60  
20 40  
80  
100 120 140 160 180 200  
FREQUENCY (Hz)  
1416 G05  
Figure 5. Intermodulation Distortion Plot  
–80  
3RD  
–90  
–100  
–110  
THD  
Peak Harmonic or Spurious Noise  
2ND  
The peak harmonic or spurious noise is the largest spec-  
tral component excluding the input signal and DC. This  
value is expressed in decibels relative to the RMS value of  
a full-scale input signal.  
1k  
10k  
100k  
1M 2M  
INPUT FREQUENCY (Hz)  
1416 G03  
Figure 4. Distortion vs Input Frequency  
Full-Power and Full-Linear Bandwidth  
Intermodulation Distortion  
The full-power bandwidth is that input frequency at which  
the amplitude of the reconstructed fundamental is  
reduced by 3dB for a full-scale input signal. The full-linear  
bandwidth is the input frequency at which the S/(N + D)  
has dropped to 77dB (12.5 effective bits). The LTC1416  
has been designed to optimize input bandwidth, allowing  
the ADC to undersample input signals with frequencies  
above the converter’s Nyquist frequency. The noise floor  
stays very low at high frequencies; S/(N + D) becomes  
dominatedbydistortionatfrequenciesfarbeyondNyquist.  
If the ADC input signal consists of more than one spectral  
component, the ADC transfer function nonlinearity can  
produce intermodulation distortion (IMD) in addition to  
THD. IMD is the change in one sinusoidal input caused by  
the presence of another sinusoidal input at a different  
frequency.  
If two pure sine waves of frequencies fa and fb are applied  
to the ADC input, nonlinearities in the ADC transfer func-  
tion can create distortion products at the sum and differ-  
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Driving the Analog Input  
frequency. For example, if an amplifier is used in a gain of  
1 and has a unity-gain bandwidth of 50MHz, then the  
output impedance at 50MHz should be less than 100.  
Thesecondrequirementisthattheclosed-loopbandwidth  
must be greater than 10MHz to ensure adequate small-  
signal settling for full throughput rate. If slower op amps  
areused, moresettlingtimecanbeprovidedbyincreasing  
the time between conversions.  
The differential analog inputs of the LTC1416 are easy to  
drive.Theinputsmaybedrivendifferentiallyorasasingle-  
endedinput(i.e., theAINinputisgrounded). TheAIN+ and  
AIN inputs are sampled at the same instant. Any un-  
wanted signal that is common mode to both inputs will be  
reduced by the common mode rejection of the sample-  
and-hold circuit. The inputs draw only one small current  
spike while charging the sample-and-hold capacitors at  
the end of conversion. During conversion the analog  
inputs draw only a small leakage current. If the source  
impedance of the driving circuit is low, then the LTC1416  
inputs can be driven directly. As source impedance  
increases so will acquisition time (see Figure 6). For  
minimum acquisition time, with high source impedance, a  
buffer amplifier should be used. The only requirement  
is that the amplifier driving the analog input(s) must  
settle after the small current spike before the next  
conversion starts (settling time must be 400ns for full  
throughput rate).  
The best choice for an op amp to drive LTC1416 will  
depend on the application. Generally, applications fall into  
two categories: AC applications where dynamic specifica-  
tionsaremostcriticalandtimedomainapplicationswhere  
DC accuracy and settling time are most critical. The  
followinglistisasummaryoftheopampsthataresuitable  
for driving the LTC1416. More detailed information is  
available in the Linear Technology Databooks and the  
LinearViewTM CD-ROM.  
LT®1220: 30MHz unity-gain bandwidth voltage feedback  
amplifier. ±5V to ±15V supplies, excellent DC specifica-  
tions.  
LT1223: 100MHz video current feedback amplifier. 6mA  
supply current, ±5V to ±15V supplies, low distortion at  
frequencies above 400kHz, low noise, good for AC appli-  
cations.  
10  
1
LT1227: 140MHz video current feedback amplifier. 10mA  
supply current, ±5V to ±15V supplies, lowest distortion at  
frequencies above 400kHz, low noise, best for AC applica-  
tions.  
0.1  
0.01  
LT1229/LT1230:Dualandquad100MHzcurrentfeedback  
amplifiers. ±2V to ±15V supplies, low noise, good AC  
specs, 6mA supply current each amplifier.  
10  
100  
1k  
10k  
100k  
SOURCE RESISTANCE ()  
1416 F06  
LT1360:50MHzvoltagefeedbackamplifier. 3.8mAsupply  
current, good AC and DC specs, ±5V to ±15V supplies.  
Figure 6. Acquisition Time vs Source Resistance  
LT1363: 70MHz, 1000V/µs op amps. 6.3mA supply cur-  
rent, good AC and DC specs.  
Choosing an Input Amplifier  
Choosing an input amplifier is easy if a few requirements  
are taken into consideration. First, to limit the magnitude  
ofthevoltagespikeseenbytheamplifierfromchargingthe  
sampling capacitor, choose an amplifier that has a low  
output impedance (<100) at the closed-loop bandwidth  
LT1364/LT1365:Dualandquad70MHz,100V/µsopamps.  
6.3mA supply current per amplifier.  
LinearView is a trademark of Linear Technology Corporation.  
10  
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Input Filtering  
accommodate other input ranges often with little or no  
additional circuitry. The following sections describe the  
reference and input circuitry and how they affect the input  
range.  
The noise and the distortion of the input amplifier and  
other circuitry must be considered since they will add to  
the LTC1416 noise and distortion. The small-signal band-  
width of the sample-and-hold circuit is 15MHz. Any noise  
ordistortionproductsthatarepresentattheanaloginputs  
will be summed over this entire bandwidth. Noisy input  
circuitry should be filtered prior to the analog inputs to  
minimize noise. A simple 1-pole RC filter is sufficient for  
many applications. For example, Figure 7 shows a 1000pF  
capacitor from AIN+ to ground and a 200source resistor  
to limit the input bandwidth to 800kHz. The 1000pF  
capacitor also acts as a charge reservoir for the input  
sample-and-hold and isolates the ADC input from sam-  
pling glitch sensitive circuitry. High quality capacitors and  
resistors should be used since these components can add  
distortion. NPO and silver mica type dielectric capacitors  
have excellent linearity. Carbon surface mount resistors  
can also generate distortion from self-heating and from  
damage that may occur during soldering. Metal film  
surface mount resistors are much less susceptible to both  
problems.  
Internal Reference  
The LTC1416 has an on-chip, temperature compensated,  
curvature corrected, bandgap reference that is factory  
trimmedto2.500V.Itisconnectedinternallytoareference  
amplifier and is available at VREF (Pin 3). See Figure 8a. A  
4k resistor is in series with the output so that it can be  
easily overdriven by an external reference or other cir-  
cuitry (see Figure 8b). The reference amplifier gains the  
voltage at the VREF pin by 1.625 to create the required  
internal reference voltage. This provides buffering be-  
tween the VREF pin and the high speed capacitive DAC. The  
R1  
4k  
V
REF  
3
4
BANDGAP  
REFERENCE  
2.5V  
4.0625V  
REFCOMP  
AGND  
REF  
AMP  
R2  
200  
1
80k  
22µF  
ANALOG  
INPUT  
+
A
A
V
IN  
IN  
1000pF  
LTC1416  
2
3
4
5
5
R3  
128k  
LTC1416  
REF  
1416 F08a  
REFCOMP  
AGND  
22µF  
Figure 8a. LTC1416 Reference Circuit  
1416 F07  
Figure 7. RC Input Filter  
5V  
1
2
3
4
5
+
A
A
V
IN  
ANALOG  
INPUT  
V
IN  
IN  
LT1019A-2.5  
Input Range  
LTC1416  
V
OUT  
REF  
The±2.5VinputrangeoftheLTC1416isoptimizedforlow  
noise and low distortion. Most op amps also perform best  
over this same range, allowing direct coupling to the  
analog inputs and eliminating the need for special transla-  
tion circuitry.  
REFCOMP  
AGND  
22µF  
1416 F08b  
Some applications may require other input ranges. The  
LTC1416 differential inputs and reference circuitry can  
Figure 8b. Using the LT1019-2.5 as an External Reference  
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80  
70  
60  
50  
40  
30  
20  
10  
0
reference amplifier compensation pin, REFCOMP (Pin 4),  
must be bypassed with a capacitor to ground. The refer-  
ence amplifier is stable with capacitors of 1µF or greater.  
For the best noise performance, a 22µF ceramic or 22µF  
tantaluminparallelwitha0.1µFceramicisrecommended.  
The VREF pin can be driven with a DAC or other means  
shown in Figure 9. This is useful in applications where the  
peak input signal amplitude may vary. The input span of  
the ADC can then be adjusted to match the peak input  
signal, maximizing the signal-to-noise ratio. The filtering  
of the internal LTC1416 reference amplifier will limit the  
bandwidth and settling time of this circuit. A settling time  
of 5ms should be allowed for after a reference adjustment.  
1k  
10k  
100k  
1M 2M  
INPUT FREQUENCY (Hz)  
1416 G09  
Figure 10a. CMRR vs Input Frequency  
1
+
1
+
A
ANALOG INPUT  
A
IN  
IN  
ANALOG  
2
3
INPUT  
2
3
4
5
A
V
A
V
IN  
IN  
LTC1416  
LTC1416  
1.25V TO 3V  
±2.5V  
REF  
LTC1450  
REF  
0V TO 5V  
4
5
REFCOMP  
AGND  
REFCOMP  
AGND  
22µF  
22µF  
1416 F10b  
1416 F09  
Figure 9. Driving VREF with a DAC  
Figure 10b. Selectable 0V to 5V or ±2.5V Input Range  
converts a 0V to 5V analog input signal with no additional  
translation circuitry.  
Differential Inputs  
The LTC1416 has a unique differential sample-and-hold  
circuit that allows rail-to-rail inputs. The ADC will always  
Full-Scale and Offset Adjustment  
convert the difference of AIN – AINindependent of the  
+
Figure11ashowstheidealinput/outputcharacteristicsfor  
theLTC1416. Thecodetransitionsoccurmidwaybetween  
successive integer LSB values (i.e., FS + 0.5LSB, FS +  
1.5LSB, FS + 2.5LSB, . . . FS – 1.5LSB, FS – 0.5LSB). The  
output is two’s complement binary with 1LSB = FS –  
(FS)/16384 = 5V/16384 = 305.2µV.  
common mode voltage. The common mode rejection  
holds up to extremely high frequencies (see Figure 10a).  
Theonlyrequirementisthatbothinputscannotexceedthe  
AVDD orAVSS powersupplyvoltages. Integralnonlinearity  
errors (INL) and differential nonlinearity errors (DNL) are  
independent of the common mode voltage, however, the  
bipolar zero error (BZE) will vary. The change in BZE is  
typically less than 0.1% of the common mode voltage.  
Dynamic performance is also affected by the common  
mode voltage. THD will degrade as the inputs approach  
either power supply rail, from 90dB with a common mode  
of 0V to 79dB with a common mode of 2.5V or 2.5V.  
In applications where absolute accuracy is important,  
offset and full-scale errors can be adjusted to zero. Offset  
error must be adjusted before full-scale error. Figure 11b  
shows the extra components required for full-scale error  
adjustment. Zero offset is achieved by adjusting the offset  
applied to the AIN input. For zero offset error, apply  
152µV (i.e., 0.5LSB) at AIN+ and adjust the offset at the  
Differential inputs allow greater flexibility for accepting  
different input ranges. Figure 10b shows a circuit that  
AIN input until the output code flickers between 0000  
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applications, however, do not have a –5V supply readily  
available and most ADCs have inadequate PSRR to suffi-  
ciently attenuate the noise created by a switching or  
charge pump supply. The LTC1416’s excellent PSRR  
makesitpossibletoachievegoodperformance, evenat14  
bits, using a switch based regulator for a –5V supply.  
Figure 12a shows a circuit using an LT1373 configured as  
a Cuk converter creating –5V from a 5V supply. The circuit  
shown in Figure 12b uses an LT1054 regulated charge  
pump to provide –5V. This circuit has the advantage of  
reduced board space and fewer passive components. (For  
further details refer to Linear Technology Magazine, June  
1997, Page 29.)  
0000 0000 00 and 1111 1111 1111 11. For full-scale  
adjustment,aninputvoltageof2.499544V(FS/21.5LSB)  
is applied to AIN and R2 is adjusted until the output code  
flickers between 0111 1111 1111 10 and 0111 1111  
1111 11.  
011...111  
011...110  
000...001  
000...000  
111...111  
111...110  
100...001  
100...000  
BOARD LAYOUT AND BYPASSING  
Wire wrap boards are not recommended for high resolu-  
tion or high speed A/D converters. To obtain the best  
performance from the LTC1416, a printed circuit board  
with ground plane is required. Layout for the printed  
circuit board should ensure that 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.  
(FS – 1LSB)  
INPUT VOLTAGE (A – A  
FS – 1LSB  
+
)
IN  
IN  
1416 F11a  
Figure 11a. LTC1416 Transfer Characteristics  
–5V  
ANALOG  
INPUT  
R3  
24k  
1
2
+
A
A
IN  
IN  
R1  
50k  
R4  
100Ω  
LTC1416  
An analog ground plane separate from the logic system  
ground should be established under and around the ADC  
(see Figure 13). Pin 5 (AGND), Pins 14 and 19 (ADC’s  
DGND) and all other analog grounds should be connected  
to this single analog ground point. The REFCOMP bypass  
capacitor and the DVDD bypass capacitor should also be  
connected to this analog ground plane. No other digital  
groundsshouldbeconnectedtothisanaloggroundplane.  
Low impedance analog and digital power supply common  
returnsareessentialtolownoiseoperationoftheADCand  
the foil width for these tracks should be as wide as  
possible. In applications where the ADC data outputs and  
control signals are connected to a continuously active  
microprocessor bus, it is possible to get errors in the  
conversion results. These errors are due to feedthrough  
fromthemicroprocessortothesuccessiveapproximation  
comparator. The problem can be eliminated by forcing the  
microprocessor into a Wait state during conversion or by  
using three-state buffers to isolate the ADC data bus. The  
3
4
R5 R2  
47k 50k  
V
REF  
R6  
24k  
REFCOMP  
AGND  
5
22µF  
1416 F11b  
Figure 11b. Offset and Full-Scale Adjust Circuit  
Generating a 5V Supply  
There are several advantages to using±5V supplies rather  
than a single 5V supply. A larger signal magnitude is  
possible which increases the dynamic range and  
improves the signal-to-noise ratio. Operating on ±5V  
supplies also offers increased headroom which eases the  
requirements for signal conditioning circuitry, avoids the  
limitations of rail-to-rail operation and widens the selec-  
tion of high performance operational amplifiers. Some  
13  
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5V  
–5V  
L1  
2
1
3
4
C6  
1
2
28  
27  
26  
25  
24  
23  
22  
21  
20  
19  
18  
17  
16  
15  
+
A
A
V
AV  
DV  
IN  
DD  
DD  
ANALOG  
INPUT  
+
IN  
C7  
C11  
100µF  
10V  
1µF CER  
3
V
CUK*  
REF  
SS  
C10  
10µF  
CER  
CONVERTER  
4
TANT  
COMP  
AGND  
D13 (MSB)  
D12  
BUSY  
CS  
C5  
5
5
4
7
6
8
V
V
SW  
R4  
4.99k  
1%  
IN  
C8  
22µF  
10V  
6
+
C12  
0.1µF  
CONVST  
RD  
MICROPROCESSOR/  
MICROCONTROLLER  
INTERFACE  
S/S  
U2  
LT1373  
7
3
1
TANT  
GND  
NFB  
D1  
8
D11  
SHDN  
D0  
GND S  
V
C
9
R5  
4.99k  
1%  
R6  
R3  
4.99k  
D10  
LTC1416  
499Ω  
10  
11  
12  
13  
14  
1%  
D9  
D1  
C9  
0.01µF  
D8  
D2  
1416 F12a  
D7  
D3  
C5 = µ2F2 CERAMIC  
C6, C7 = µ1F0 CERAMIC  
D6  
D4  
L1 = OCTAPAC CTX-100-1  
D1 = 1N5818  
DGND  
D5  
Figure 12a. Using the LT1373 to Generate a 5V Supply  
5V  
–5V  
C6  
C4  
1
28  
27  
26  
25  
24  
23  
22  
21  
20  
19  
18  
17  
16  
15  
+
C2  
A
A
V
AV  
100µF  
IN  
DD  
DD  
ANALOG  
INPUT  
2µF  
TANT  
2
3
1
8
DV  
IN  
C7  
+
FB/SHDN  
V
+
1µF CER  
2
3
4
7
6
5
V
REF  
SS  
+
CAP  
OSC  
U1  
LT1054  
4
R1, 30.1k  
R2, 120k  
C1  
10µF  
TANT  
C3  
0.002µF  
+
COMP  
AGND  
D13 (MSB)  
D12  
BUSY  
CS  
GND  
V
REF  
C5  
5
CAP  
V
OUT  
6
CONVST  
RD  
MICROPROCESSOR/  
MICROCONTROLLER  
INTERFACE  
1416 F12b  
7
8
D11  
SHDN  
D0  
9
D10  
LTC1416  
10  
11  
12  
13  
14  
D9  
D1  
D8  
D2  
D7  
D3  
C5 = 2µ2F CERAMIC  
D6  
D4  
C6, C7 = 1µ0F CERAMIC  
DGND  
D5  
Figure 12b. Using the LT1054 to Generate a 5V Supply  
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1
+
A
A
IN  
DIGITAL  
SYSTEM  
LTC1416  
AV  
IN  
REFCOMP AGND  
V
DV  
DGND  
14  
SS  
DD  
27  
2
DD  
ANALOG  
INPUT  
CIRCUITRY  
+
5
4
28  
26  
22µF  
10µF  
10µF  
1416 F13  
Figure 13. Power Supply Grounding Practice.  
traces connecting the pins and bypass capacitors must be  
kept short and should be made as wide as possible.  
DIGITAL INTERFACE  
The A/D converter is designed to interface with micropro-  
cessors as a memory mapped device. The CS and RD  
control inputs are common to all peripheral memory  
interfacing. A separate CONVST is used to initiate a con-  
version.  
The LTC1416 has differential inputs to minimize noise  
coupling. CommonmodenoiseontheAIN+ andAINleads  
will be rejected by the input CMRR. The AINinput can be  
+
used as a ground sense for the AIN input; the LTC1416  
+
will hold and convert the difference voltage between AIN  
and AIN. The leads to AIN+ (Pin 1) and AIN(Pin 2) should  
be kept as short as possible. In applications where this is  
not possible, the AIN and AIN traces should be run side  
by side to equalize coupling.  
Internal Clock  
The A/D converter has an internal clock that eliminates the  
need for synchronization between the external clock and  
the CS and RD signals found in other ADCs. The internal  
clock is factory trimmed to achieve a typical conversion  
time of 1.8µs, and a maximum conversion time over the  
full operating temperature range of 2.2µs. No external  
adjustments are required. The guaranteed maximum  
acquisition time is 400ns. In addition, a throughput time  
of 2.5µs and a minimum sampling rate of 400ksps is  
guaranteed.  
+
Supply Bypassing  
High quality, low series resistance ceramic, bypass  
capacitorsshouldbeusedattheVDD (10µF)andREFCOMP  
(22µF)pinsasshownintheTypicalApplicationonthefirst  
page of this data sheet. Surface mount ceramic capacitors  
such as Murata GRM235Y5V106Z016 provide excellent  
bypassing in a small board space. Alternatively tantalum  
capacitorsinparallelwith0.1µFceramiccapacitorscanbe  
used. Bypass capacitors must be located as close to the  
pins as possible. The traces connecting the pins and the  
bypass capacitors must be kept short and should be made  
as wide as possible.  
Power Shutdown  
TheLTC1416providestwopowershutdownmodes—nap  
mode and sleep mode to save power during inactive  
periods. The nap mode reduces the power by 95% and  
leavesonlythedigitallogicandreferencepoweredup. The  
wake-up time from nap to active is 200ns. In sleep mode  
the reference is shut down and only a small current of  
120µA remains. Wake-up time from sleep mode is much  
slower since the reference circuit must power up and  
settle to 0.005% for full 14-bit accuracy. Sleep mode  
wake-up time is dependent on the value of the capacitor  
connected to the REFCOMP (Pin 4). The wake-up time is  
20ms with the recommended 22µF capacitor.  
Example Layout  
Figures 14a, 14b, 14c and 14d show the schematic and  
layoutofanevaluationboard.Thelayoutdemonstratesthe  
proper use of decoupling capacitors and ground plane  
with a 2-layer printed circuit board.  
15  
LTC1416  
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APPLICATIONS INFORMATION  
16  
LTC1416  
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APPLICATIONS INFORMATION  
Figure 14b. Suggested Evaluation Circuit Board—  
Component Side Silkscreen  
Figure 14c. Suggested Evaluation Circuit Board—  
Component Side Layout  
CS  
t
3
SHDN  
1416 F15a  
Figure 15a. CS to SHDN Timing  
SHDN  
t
3
CONVST  
1416 F15b  
Figure 15b. SHDN to CONVST Wake-Up Timing  
Figure 14d. Suggested Evaluation Circuit Board—  
Solder Side Layout  
17  
LTC1416  
U
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APPLICATIONS INFORMATION  
Shutdown is controlled by Pin 21 (SHDN), the ADC is in  
shutdown when it is low. The shutdown mode is selected  
with Pin 20 (CS), low selects nap.  
starts the conversion and reads the output with the RD  
signal. Conversions are started by the MPU or DSP (no  
external sample clock).  
In slow memory mode the processor applies a logic low to  
RD (=CONVST), starting the conversion. BUSY goes low,  
forcing the processor into a Wait state. The previous  
conversion result appears on the data outputs. When the  
conversion is complete, the new conversion results  
appear on the data outputs; BUSY goes high releasing the  
processor, and the processor takes RD (=CONVST) back  
high and reads the new conversion data.  
Timing and Control  
Conversion start and data read operations are controlled  
by three digital inputs: CONVST, CS and RD. A logic “0”  
applied to the CONVST pin will start a conversion after the  
ADC has been selected (i.e., CS is low). Once initiated, it  
cannot be restarted until the conversion is complete.  
Converter status is indicated by the BUSY output. BUSY is  
low during a conversion.  
In ROM mode, the processor takes RD (=CONVST) low,  
startingaconversionandreadingthepreviousconversion  
result. Aftertheconversioniscomplete, theprocessorcan  
read the new result and initiate another conversion.  
Figures 16 through 21 show several different modes of  
operation. In modes 1a and 1b (Figures 17 and 18) CS and  
RDarebothtiedlow.ThefallingedgeofCONVSTstartsthe  
conversion. The data outputs are always enabled and data  
can be latched with the BUSY rising edge. Mode 1a shows  
operationwithanarrowlogiclowCONVSTpulse. Mode1b  
shows a narrow logic high CONVST pulse.  
CS  
t
2
In mode 2 (Figure 19) CS is tied low. The falling edge of  
CONVST signal again starts the conversion. Data outputs  
are in three-state until read by the MPU with the RD signal.  
Mode 2 can be used for operation with a shared MPU data  
bus.  
CONVST  
RD  
t
1
1416 F16  
In slow memory and ROM modes (Figures 20 and 21), CS  
istiedlowandCONVSTandRDaretiedtogether. TheMPU  
Figure 16. CS to CONVST Setup Timing  
t
CONV  
CS = RD = 0  
CONVST  
(SAMPLE N)  
t
5
t
t
8
6
BUSY  
DATA  
t
7
DATA (N – 1)  
DB13 TO DB0  
DATA N  
DB13 TO DB0  
DATA (N + 1)  
DB13 TO DB0  
1416 F17  
Figure 17. Mode 1a. CONVST Starts a Conversion. Data Outputs Always Enabled  
(CONVST =  
)
18  
LTC1416  
U
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APPLICATIONS INFORMATION  
t
CS = RD = 0  
t
8
CONV  
t
13  
t
5
CONVST  
t
t
6
t
6
6
BUSY  
DATA  
t
7
DATA (N – 1)  
DB13 TO DB0  
DATA N  
DB13 TO DB0  
DATA (N + 1)  
DB13 TO DB0  
1416 F18  
Figure 18. Mode 1b. CONVST Starts a Conversion. Data Outputs Always Enabled  
(CONVST =  
)
t
13  
(SAMPLE N)  
t
t
8
CS = 0  
CONV  
t
5
CONVST  
t
6
BUSY  
RD  
t
t
11  
9
t
12  
t
10  
DATA N  
DB13 TO DB0  
DATA  
1416 F19  
Figure 19. Mode 2. CONVST Starts a Conversion. Data Is Read by RD  
t
t
8
CS = 0  
CONV  
(SAMPLE N)  
RD = CONVST  
t
t
11  
6
BUSY  
t
t
7
10  
DATA (N – 1)  
DB13 TO DB0  
DATA N  
DB13 TO DB0  
DATA N  
DB13 TO DB0  
DATA (N + 1)  
DB13 TO DB0  
DATA  
1416 F20  
Figure 20. Slow Memory Mode Timing  
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.  
19  
LTC1416  
APPLICATIONS INFORMATION  
U
W U U  
t
t
8
CONV  
CS = 0  
(SAMPLE N)  
RD = CONVST  
t
t
11  
6
BUSY  
DATA  
t
10  
DATA (N – 1)  
DB13 TO DB0  
DATA N  
DB13 TO DB0  
1416 F21  
Figure 21. ROM Mode Timing  
U
PACKAGE DESCRIPTIO  
Dimensions in inches (millimeters) unless otherwise noted.  
G Package  
28-Lead Plastic SSOP (0.209)  
(LTC DWG # 05-08-1640)  
0.397 – 0.407*  
(10.07 – 10.33)  
0.205 – 0.212**  
(5.20 – 5.38)  
0.068 – 0.078  
(1.73 – 1.99)  
28 27 26 25 24 23 22 21 20 19 18  
16 15  
17  
0° – 8°  
0.301 – 0.311  
(7.65 – 7.90)  
0.0256  
(0.65)  
BSC  
0.005 – 0.009  
(0.13 – 0.22)  
0.022 – 0.037  
(0.55 – 0.95)  
0.002 – 0.008  
(0.05 – 0.21)  
0.010 – 0.015  
(0.25 – 0.38)  
*DIMENSIONS DO NOT INCLUDE MOLD FLASH. MOLD FLASH  
SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE  
**DIMENSIONS DO NOT INCLUDE INTERLEAD FLASH. INTERLEAD  
FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE  
5
7
8
1
2
3
4
6
9
10 11 12 13 14  
G28 SSOP 0694  
RELATED PARTS  
PART NUMBER  
LTC1278/LTC1279  
LTC1400  
DESCRIPTION  
COMMENTS  
Single Supply, 12-Bit, 500ksps/600ksps ADCs  
High Speed Serial 12-Bit ADC  
Low Power, 5V or ±5V Supply  
400ksps, Complete with V , CLK, Sample-and-Hold in SO-8  
REF  
LTC1409  
Low Power, 12-Bit, 800ksps Sampling ADC  
12-Bit, 1.25Msps Sampling ADC with Shutdown  
12-Bit, 3Msps Sampling ADC  
Best Dynamic Performance, f  
800ksps, 80mW Dissipation  
SAMPLE  
LTC1410  
Best Dynamic Performance, THD = 84dB and SINAD = 71dB at Nyquist  
Best Dynamic Performance, SINAD = 72dB at Nyquist  
Single Supply, 55mW Dissipation  
LTC1412  
LTC1415  
Single 5V, 12-Bit, 1.25Msps ADC  
LTC1418  
14-Bit, 200ksps Sampling ADC  
16mW Dissipation, Serial and Parallel Outputs  
81.5dB SINAD, 150mW from ±5V Supplies  
±2.5V Input, SINAD = 90dB, THD = 100dB  
Low Power, ±10V Inputs  
LTC1419  
14-Bit, 800ksps Sampling ADC with Shutdown  
16-Bit, 333ksps Sampling ADC  
LTC1604  
LTC1605  
Single 5V, 16-Bit, 100ksps ADC  
1416f LT/TP 0598 4K • PRINTED IN USA  
LinearTechnology Corporation  
1630 McCarthy Blvd., Milpitas, CA 95035-7417  
20  
LINEAR TECHNOLOGY CORPORATION 1997  
(408)432-1900 FAX:(408)434-0507 www.linear-tech.com  

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