Complete, High Speed
16-Bit A/D Converters
AD1376/AD1377
Rev. D
Information furnished by Analog Devices is believed to be accurate and reliable.
However, no responsibility is assumed by Analog Devices for its use, nor for any
infringements of patents or other rights of third parties that may result from its use.
Specifications subject to change without notice. No license is granted by implication
or otherwise under any patent or patent rights of Analog Devices. Trademarks and
registered trademarks are the property of their respective owners.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700 www.analog.com
Fax: 781.481.3113 © 2005 Analog Devices, Inc. All rights reserved.
FEATURES
Complete 16-bit converters with reference and clock
±0.003% maximum nonlinearity
No missing codes to 14 bits over temperature
Fast conversion
17 µs to 16 bits (AD1376)
10 µs to 16 bits (AD1377)
Short cycle capability
Adjustable clock rate
Parallel outputs
Low power
645 mW typical (AD1376)
585 mW typical (AD1377)
Industry-standard pinout
GENERAL DESCRIPTION
The AD1376/AD1377 are high resolution, 16-bit analog-to-
digital converters with internal reference, clock, and laser-
trimmed thin-film applications resistors. The AD1376/AD1377
are excellent for use in high resolution applications requiring
moderate speed and high accuracy or stability over commercial
temperature ranges (0°C to 70°C). They are packaged in
compact 32-lead, ceramic seam-sealed (hermetic), dual in-line
packages (DIP). Thin-film scaling resistors provide bipolar
input ranges of ±2.5 V, ±5 V, and ±10 V and unipolar input
ranges of 0 V to +5 V, 0 V to +10 V, and 0 V to +20 V.
Digital output data is provided in parallel form with
corresponding clock and status outputs. All digital inputs and
outputs are TTL-compatible.
For the AD1376, the serial output function is no longer
available after date code 0111. For the AD1377, the serial output
function is no longer available after date code 0210. The option
of applying an external clock on the CONVERT START pin to
slow down the internally set conversion time is no longer
supported for either part.
PRODUCT HIGHLIGHTS
1. The AD1376/AD1377 provide 16-bit resolution with a
maximum linearity error of ±0.003% (1/2 LSB14) at 25°C.
2. The AD1376 conversion time is 14 µs (typical) short cycled
to 14 bits, and 16 µs to 16 bits.
3. The AD1377 conversion time is 8 µs (typical) short cycled
to 14 bits, and 9 µs to 16 bits.
4. Two binary codes are available on the digital output. They
are CSB (complementary straight binary) for unipolar input
voltage ranges and COB (complementary offset binary) for
bipolar input ranges. Complementary twos complement
(CTC) coding may be obtained by inverting Pin 1 (MSB).
5. The AD1376/AD1377 include internal reference and clock
with external clock rate adjust pin, and parallel digital outputs.
FUNCTIONAL BLOCK DIAGRAM
00699-001
(MSB) BIT 1
1
BIT 2
2
BIT 3
3
BIT 4
4
BIT 5
5
BIT 6
6
BIT 7
7
BIT 8
8
BIT 9
9
BIT 10
10
BIT 11
11
BIT 12
12
(LSB FOR 13 BITS) BIT 1
3
13
(LSB FOR 14 BITS) BIT 14
14
BIT 15
15
BIT 16
16
SHORT CYCL E
32
CONVERT START
31
+5V DC SUPPLY V
L
30
GAIN ADJUST
29
+15V DC SUPPLY V
CC
28
CO M PARATOR I N
27
BIPOLAR OFFSET
26
+10V
25
+20V
24
CLK RAT E CTRL
23
ANALO G COMMON
22
–15V DC SUP P LY V
EE
21
CLO CK OUT
20
DIGITAL COMMON
19
STATUS
18
NC
17
16-BI T DAC
16-BIT SAR
CLOCK
REFERENCE
COMPARATOR
7.5kΩ
3.75kΩ3.75kΩ
AD1376/AD1377
Figure 1.
AD1376/AD1377
Rev. D | Page 2 of 12
TABLE OF CONTENTS
Specifications..................................................................................... 3
Absolute Maximum Ratings............................................................ 5
ESD Caution.................................................................................. 5
Description of Operation ................................................................ 6
Gain Adjustment .......................................................................... 6
Zero Offset Adjustment............................................................... 6
Timing............................................................................................ 7
Digital Output Data ..................................................................... 7
Input Scaling ..................................................................................7
Calibration (14-Bit Resolution Examples).................................8
Grounding, Decoupling, and Layout Considerations ..............9
Clock Rate Control........................................................................9
High Resolution Data Acquisition System.............................. 10
Applications..................................................................................... 11
Outline Dimensions ....................................................................... 12
Ordering Guide .......................................................................... 12
REVISION HISTORY
6/05—Rev. C to Rev. D
Updated Format..................................................................Universal
Updated Outline Dimensions....................................................... 12
6/03—Rev. B to Rev. C
Removed Serial Output Function and
Adjustable Clock Rate........................................................Universal
Updated Format..................................................................Universal
Changes to General Description .................................................... 1
Changes to Product Highlights....................................................... 1
Changes to Functional Block Diagram.......................................... 1
Inserted ESD Warning ..................................................................... 3
Change to Ordering Guide.............................................................. 3
Change to Figure 7 ........................................................................... 5
Deleted text from Digital Output Data.......................................... 5
Deleted Figure 9 and Renumbered Remainder of Figures.......... 5
Deleted the ‘Using the AD1376 or AD1377 at
Slower Conversion Times’ Section............................................... 8
Deleted Figure 16.............................................................................. 8
Change to Figure 13 ......................................................................... 9
Change to Figure 14 ......................................................................... 9
Updated Outline Dimensions....................................................... 10
AD1376/AD1377
Rev. D | Page 3 of 12
SPECIFICATIONS
Typical at TA = 25°C, VS = ±15 V, +5 V, unless otherwise noted.
Table 1.
AD1376JD/AD1377JD AD1376KD/AD1377KD
Model Min Typ Max Min Typ Max Unit
RESOLUTION 16 16 Bits
ANALOG INPUTS
Voltage Ranges
Bipolar ±2.5 ±2.5 V
±5 ±5 V
±10 ±10 V
Unipolar 0 to 5 0 to 5 V
0 to 10 0 to 10 V
0 to 20 0 to 20 V
Impedance (Direct Input) V
0 V to +5 V, ±2.5 V 1.88 1.88 kΩ
0 V to +10 V, ±5.0 V 3.75 3.75 kΩ
0 V to +20 V, ±10 V 7.50 7.50 kΩ
DIGITAL INPUTS1
Convert Command Trailing edge of positive 50 ns (min) pulse
Logic Loading 1 1 LS TTL Load
TRANSFER CHARACTERISTICS2
(ACCURACY)
Gain Error ±0.053±0.2 ± 0.053 ± 0.2 %
Offset Error
Unipolar ±0.053 ±0.1 ±0.053 ±0.1 % of FSR4
Bipolar ±0.053 ±0.2 ±0.053 ±0.2 % of FSR
Linearity Error (Max) ±0.006 ±0.003 % of FSR
Inherent Quantization Error ±1/2 ±1/2 LSB
Differential Linearity Error ±0.003 ±0.003 % of FSR
POWER SUPPLY SENSITIVITY
±15 V DC (±0.75 V) 0.0015 0.0015 % of FSR/% ∆VS
+5 V DC (±0.25 V) 0.001 0.001 % of FSR/% ∆VS
CONVERSION TIME5
12 Bits (AD1376) 11.5 13 11.5 13 µs
14 Bits (AD1376) 13.5 15 13.5 15 µs
16 Bits (AD1376) 15.5 17 15.5 17 µs
14 Bits (AD1377) 8.75 8.75 µs
16 Bits (AD1377) 10 10 µs
POWER SUPPLY REQUIREMENTS
Analog Supplies +14.5 +15 +15.5 +14.5 +15 +15.5 V dc
−14.5 −15 −15.5 −14.5 −15 −15.5 V dc
Digital Supply +4.75 +5 +5.25 +4.75 +5 +5.25 V dc
AD1376 Power Consumption 600 800 600 800 mW
+15 V Supply Drain +10 +10 mA
−15 V Supply Drain −23 −23 mA
+5 V Supply Drain +18 +18 mA
AD1377 Power Consumption 600 800 600 800 mW
+15 V Supply Drain +10 +10 mA
−15 V Supply Drain −23 −23 mA
+5 V Supply Drain +18 +18 mA
WARM-UP TIME 1 1 Minutes
AD1376/AD1377
Rev. D | Page 4 of 12
AD1376JD/AD1377JD AD1376KD/AD1377KD
Model Min Typ Max Min Typ Max Unit
DRIFT6
Gain ±15 ±5 ±15 ppm/°C
Offset
Unipolar ±2 ±4 ±2 ±4 ppm of FSR/°C
Bipolar ±10 ±3 ±10 ppm of FSR/°C
Linearity ±2 ±3 ±0.3 ±2 ppm of FSR/°C
Guaranteed No Missing Code
Temperature Range 0 to 70 (13 Bits) 0 to 70 (14 Bits) °C
DIGITAL OUTPUT1
(All Codes Complementary)
Parallel Output Codes7
Unipolar CSB CSB
Bipolar COB, CTC8 COB, CTC8
Output Drive 5 5 LSTTL Loads
Status
Logic 1 During
Conversion
Logic 1 During
Conversion
Status Output Drive 5 5 LSTTL Loads
Internal Clock9
Clock Output Drive 5 5 LSTTL Loads
Frequency 1040/1750 1040/1750 kHz
TEMPERATURE RANGE
Specification 0 to 70 0 to 70 °C
Operating −25 to +85 −25 to +85 °C
Storage −55 to +125 −55 to +125 °C
1 Logic 0 = 0.8 V max; Logic 1 = 2.0 V min for inputs. For digital outputs, Logic 0 = 0.4 V max. Logic 1 = 2.4 V min.
2 Tested on ±10 V and 0 V to +10 V ranges.
3 Adjustable to zero.
4 Full-scale range.
5 Conversion time may be shortened with “short cycle” set for lower resolution.
6 Guaranteed but not 100% production tested.
7 CSB–Complementary Straight Binary. COB–Complementary Offset Binary. CTC–Complementary Twos Complement.
8 CTC coding obtained by inverting MSB (Pin 1).
9 With Pin 23, clock rate controls tied to digital ground.
AD1376/AD1377
Rev. D | Page 5 of 12
ABSOLUTE MAXIMUM RATINGS
Table 2.
Parameter Rating
Supply Voltage ±18 V
Logic Supply Voltage +7 V
Analog Inputs (Pin 24 and Pin 25) ±25 V
Analog Ground to Digital Ground ±0.3 V
Digital Inputs −0.3 V to VDD + 0.3 V
Junction Temperature 175°C
Storage Temperature 150°C
Lead Temperature (10 sec) 300°C
Stresses above those listed under Absolute Maximum Ratings
may cause permanent damage to the device. This is a stress
rating only; functional operation of the device at these or any
other conditions above those listed in the operational sections
of this specification is not implied. Exposure to absolute
maximum rating conditions for extended periods may affect
device reliability.
ESD CAUTION
ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily accumulate on the
human body and test equipment and can discharge without detection. Although this product features
proprietary ESD protection circuitry, permanent damage may occur on devices subjected to high energy
electrostatic discharges. Therefore, proper ESD precautions are recommended to avoid performance
degradation or loss of functionality.
AD1376/AD1377
Rev. D | Page 6 of 12
DESCRIPTION OF OPERATION
0.0135
0.0080
0.0195
0.0120
0
–0.0120
–0.0195
0.0060
0.0030
0
–0.0030
–0.0060
–0.0080
–0.0135
025 70
00699-002
TEMPERATURE (°C)
LINEARITY ERROR (% FSR)
AD1376/AD1377KD
±2ppm/°C,
±0.003%, @ 25°C
AD1376/AD1377JD
±3ppm/°C,
±0.006%, @ 25°C
Figure 2. Linearity Error vs. Temperature
0.100
AD1376
0.001
0.003
0.006
0.010
5 10152
00699-003
CONVERSION TIME (µs)
LINEARITY AND DIFFERENTIAL LINEARITY
ERROR (% OF FSR)
0
SHORT CYCLED TO 12 BITS
1/2LSB 12-BIT
1/2LSB 13-BIT
1/2LSB 14-BIT
SHORT CYCLED TO 13 BITS
SHORT CYCLED TO 14 BITS
Figure 3. AD1376 Nonlinearity vs. Conversion Time
0.100
0.038
–0.038
0
–0.068
0.068
0
–0.100
0605040302010
00699-004
70
GAIN DRIFT ERROR (% FSR)
Figure 4. Gain Drift Error vs. Temperature
On receipt of a CONVERT START command, the AD1376/
AD1377 convert the voltage at the analog input into an
equivalent 16-bit binary number. This conversion is
accomplished as follows: the 16-bit successive approximation
register (SAR) has its 16-bit outputs connected both to the
device bit output pins and to the corresponding bit inputs of the
feedback DAC. The analog input is successively compared to
the feedback DAC output, one hit at a time (MSB first, LSB
last). The decision to keep or reject each bit is then made at the
completion of each bit comparison period, depending on the
state of the comparator at that time.
GAIN ADJUSTMENT
The gain adjustment circuit consists of a 100 ppm/°C poten-
tiometer connected across ±VS with its slider connected
through a 300 kΩ resistor to Pin 29 (GAIN ADJ) as shown in
Figure 5.
If no external trim adjustment is desired, Pin 27
(COMPARATOR IN) and Pin 29 can be left open.
00699-005
AD1376/AD1377
29
0.01µF
300kΩ
+15V
10kΩ
TO
100kΩ
100ppm/°C
–15V
Figure 5. Gain Adjustment Circuit (±0.2% FSR)
ZERO OFFSET ADJUSTMENT
The zero offset adjustment circuit consists of a 100 ppm/°C
potentiometer connected across ±VS with its slider connected
through a 1.8 MΩ resistor to Pin 27 for all ranges. As shown in
Figure 6, the tolerance of this fixed resistor is not critical; a carbon
composition type is generally adequate. Using a carbon compo-
sition resistor having a −1200 ppm/°C temperature coefficient
contributes a worst-case offset temperature coefficient of 32 LSB14
× 61 ppm/LSB14 × 1200 ppm/°C = 2.3 ppm/°C of FSR, if the offset
adjustment potentiometer is set at either end of its adjustment
range. Since the maximum offset adjustment required is typically
no more than ±16 LSB14, use of a carbon composition offset
summing resistor typically contributes no more than 1 ppm/°C of
FSR offset temperature coefficient.
00699-006
AD1376/AD1377
27
1.8MΩ
+15V
10kΩ
TO
100kΩ
–15V
Figure 6. Zero Offset Adjustment Circuit (±0.3% FSR)
An alternate offset adjustment circuit, which contributes a
negligible offset temperature coefficient if metal film resistors
(temperature coefficient <100 ppm/°C) are used, is shown in
Figure 7.
00699-007
AD1376/AD1377
27
22kΩ M.F.
180kΩM.F. 180kΩM.F.
+15V
10kΩ
TO
100kΩ
OFFSET
ADJ
–15V
Figure 7. Low Temperature Coefficient Zero Adjustment Circuit
AD1376/AD1377
Rev. D | Page 7 of 12
In either adjustment circuit, the fixed resistor connected to
Pin 27 should be located close to this pin to keep the pin
connection short. Pin 27 is quite sensitive to external noise
pickup and should be guarded by ANALOG COMMON.
TIMING
The timing diagram is shown in Figure 8. Receipt of a
CONVERT START signal sets the STATUS flag, indicating
conversion in progress. This in turn removes the inhibit applied
to the gated clock, permitting it to run through 17 cycles. All
the SAR parallel bits, the STATUS flip-flops, and the gated clock
inhibit signal are initialized on the trailing edge of the
CONVERT START signal. At time t0, B1 is reset and B2–B16 are
set unconditionally. At t1, the Bit 1 decision is made (keep) and
Bit 2 is reset unconditionally. This sequence continues until the
Bit 16 (LSB) decision (keep) is made at t16. The STATUS flag is
reset, indicating that the conversion is complete and that the
parallel output data is valid. Resetting the STATUS flag restores
the gated clock inhibit signal, forcing the clock output to the
low Logic 0 state. Note that the clock remains low until the next
conversion.
Corresponding parallel data bits become valid on the same
positive-going clock edge.
00699-008
t
0
t
1
t
2
t
3
t
4
t
5
t
6
t
7
t
8
t
9
t
10
t
11
t
12
t
13
t
14
t
15
t
16
t
17
(3)
(2)
(1)
0110011101111010
0
1
100
1
1
10
1
1
110
10
MSB
STATUS
INTERNAL
CLOCK
CONVERT
START
BIT 2
BIT 3
BIT 4
BIT 5
BIT 6
BIT 7
BIT 8
BIT 9
BIT 10
BIT 11
BIT 12
BIT 13
BIT 14
BIT 15
LSB LSBMSB
MAXIMUM THROUGHPUT TIME
CONVERSION TIME (2)
NOTES:
1. THE CONVERT START PULSEWIDTH IS 50ns MIN AND MUST REMAIN LOW DURING A
CONVERSION. THE CONVERSION IS INITIATED BY THE TRAILING EDGE OF THE
CONVERT COMMAND.
2. MSB DECISION.
3. CLOCK REMAINS LOW AFTER LAST BIT DECISION.
Figure 8. Timing Diagram (Binary Code 0110011101111010)
DIGITAL OUTPUT DATA
Parallel data from TTL storage registers is in negative true form
(Logic 1 = 0 V and Logic 0 = 2.4 V). Parallel data output coding
is complementary binary for unipolar ranges and complement-
tary offset binary for bipolar ranges. Parallel data becomes valid
at least 20 ns before the STATUS flag returns to Logic 0,
permitting parallel data transfer to be clocked on the 1 to 0
transition of the STATUS flag (see Figure 9). Parallel data
output changes state on positive going clock edges.
00699-009
BIT 16
VALID
BUSY
(STATUS)
20ns MIN TO 90ns
Figure 9. LSB Valid to Status Low
Short Cycle Input
Pin 32 (SHORT CYCLE) permits the timing cycle shown in
Figure 8 to be terminated after any number of desired bits has
been converted, allowing somewhat shorter conversion times in
applications not requiring full 16-bit resolution. When 10-bit
resolution is desired, Pin 32 is connected to Bit 11 output
Pin 11. The conversion cycle then terminates and the STATUS
flag resets after the Bit 10 decision (Figure 8). Short cycle
connections and associated 8-, 10-, 12-, 13-, 14-, and 15-bit
conversion times are summarized in Table 3 for a 1.6 MHz
clock (AD1377) or 933 kHz clock (AD1376).
Table 3. Short Cycle Connections
Resolution
Maximum
Conversion Time (µs)
Bits
(%
FSR) AD1377 AD1376
Status
Flag
Reset
Connect
Short Cycle
Pin 32 to
16 0.0015 10 17.1 t16 NC (Open)
15 0.003 9.4 16.1 t15 Pin 16
14 0.006 8.7 15.0 t1Pin 15
13 0.012 8.1 13.9 t13 Pin 14
12 0.024 7.5 12.9 t12 Pin 13
10 0.100 6.3 10.7 t10 Pin 11
8 0.390 5.0 8.6 t8Pin 9
INPUT SCALING
The ADC inputs should be scaled as close to the maximum
input signal range as possible to use the maximum signal
resolution of the ADC. Connect the input signal as shown in
Table 4. See Figure 10 for circuit details.
AD1376/AD1377
Rev. D | Page 8 of 12
Table 4. Input Scaling Connections
Input Signal Line Output Code Connect Pin 26 to Connect Pin 24 to Connect Input Signal to
±10 V COB Pin 271Input Signal Pin 24
±5 V COB Pin 271Open Pin 25
±2.5 V COB Pin 271Pin 271Pin 25
0 V to +5 V CSB Pin 22 Pin 271Pin 25
0 V to +10 V CSB Pin 22 Open Pin 25
0 V to +20 V CSB Pin 22 Input Signal Pin 24
1 Pin 27 is extremely sensitive to noise and should be guarded by ANALOG COMMON.
00699-010
22
ANALOG
COMMON
26
BIPOLAR
OFFSET
COMP IN
24
25
27
7.5kΩ
R2
3.75kΩ
10V SPAN
20V SPAN R1
3.75kΩ
FROM DAC
COMPARATOR
TO
SAR
V
REF
Figure 10. Input Scaling Circuit
CALIBRATION (14-BIT RESOLUTION EXAMPLES)
External zero adjustment and gain adjustment potentiometers,
connected as shown in Figure 5 and Figure 6, are used for
device calibration. To prevent interaction of these two
adjustments, zero is always adjusted first and then gain. Zero is
adjusted with the analog input near the most negative end of the
analog range (0 for unipolar and minus full scale for bipolar
input ranges). Gain is adjusted with the analog input near the
most positive end of the analog range.
0 V to 10 V Range
Set analog input to +1 LSB14 = 0.00061 V. Adjust zero for digital
output = 11111111111110. Zero is now calibrated. Set analog
input to +FSR − 2 LSB = 9.99878 V. Adjust gain for
00000000000001 digital output code; full scale (gain) is now
calibrated. Half-scale calibration check: set analog input to
5.00000 V; digital output code should be 01111111111111.
−10 V to +10 V Range
Set analog input to −9.99878 V; adjust zero for 1111111111110
digital output (complementary offset binary) code. Set analog
input to 9.99756 V; adjust gain for 00000000000001 digital
output (complementary offset binary) code. Half-scale
calibration check: set analog input to 0.00000 V; digital output
(complementary offset binary) code should be 01111111111111.
00699-011
–15V
+15V A
16-BIT SUCCESSIVE
APPROMIXATION REGISTER
16-BIT DAC
REF
CONTROL
3.75kΩ3.75kΩ
24262319
29
28
22
21
25
e
IN
(0V TO +10V)
I
IN
KEEP/
REJECT
7.5kΩ
+15V
–15V
ZERO
ADJ
10kΩ
TO
100kΩ
27
I
OS
= 1.3mA
AD1376/
AD1377
1.8MΩ
1µF
+5V +
30
+
1µF
+
1µF
+15V
–15V
GAIN
ADJ
10kΩ
TO
100
k
Ω
300kΩ
0.01µF
NOTE:
A
NALOG ( ) AND DIGITAL ( ) GROUNDS ARE NOT TIED INTERNALLY AND MUST BE CONNECTED EXTERNALLY
.
Figure 11. Analog and Power Connections
for Unipolar 0 V to 10 V Input Range
00699-012
–15V
+15V A
16-BIT SUCCESSIVE
APPROMIXATION REGISTER
16-BIT DAC
REF
CONTROL
3.75kΩ3.75kΩ
24262319
29
28
22
21
25
e
IN
(–10V TO +10V)
I
IN
KEEP/
REJECT
7.5kΩ
+15V
–15V
ZERO
ADJ
10kΩ
TO
100kΩ
27
I
OS
= 1.3mA
AD1376/
AD1377
1.8MΩ
1µF
+5V +
30
+
1µF
+
1µF
+15V
–15V
GAIN
ADJ
10kΩ
TO
100kΩ
300kΩ
0.01µF
NOTE:
A
NALOG ( ) AND DIGITAL ( ) GROUNDS ARE NOT TIED INTERNALLY AND MUST BE CONNECTED EXTERNALL
Y
Figure 12. Analog and Power Connections
for Bipolar −10 V to +10 V Input Range
Other Ranges
Representative digital coding for 0 V to +10 V and −10 V to
+10 V ranges is given in the 0 V to 10 V Range section and
−10 V to +10 V Range section. Coding relationships and
calibration points for 0 V to +5 V, −2.5 V to +2.5 V, and −5 V to
+5 V ranges can be found by halving proportionally the
corresponding code equivalents listed for the 0 V to +10 V and
−10 V to +10 V ranges, respectively, as indicated in Table 5.
AD1376/AD1377
Rev. D | Page 9 of 12
Table 5. Transition Values vs. Calibration Codes
Output Code
MSB LSB1Range ±10 V ±5 V ±2.5 V 0 V to +10 V 0 V to +5 V
000 ………0002+Full Scale +10 V +5 V +2.5 V +10 V +5 V
−3/2 LSB −3/2 LSB −3/2 LSB −3/2 LSB −3/2 LSB
011………111 Midscale 0 V 0 V 0 V +5 V +2.5 V
–1/2 LSB –1/2 LSB –1/2 LSB –1/2 LSB –1/2 LSB
111………110 −Full Scale −10 V −5 V −2.5 V 0 V 0 V
+1/2 LSB +1/2 LSB +1/2 LSB +1/2 LSB +1/2 LSB
1 For LSB value for range and resolution used, see Ta . ble 6
Table 6. Input Voltage Range and LSB Values
2 Voltages given are the nominal value for transition to the code specified.
Analog Input Voltage Range ±10 V ±5 V ±2.5 V 0 V to +10 V 0 V to +5 V
Code Designation COB1 or CTC2COB1 or CTC2 COB1 or CTC2 CSB3CSB3
One Least Significant Bit (LSB) n
2
FSR n
2
V20 n
2
V10 n
2
V5 n
2
V10 n
2
V5
n = 8 78.13 mV 39.06 mV 19.53 mV 39.06 mV 19.53 mV
n = 10 19.53 mV 9.77 mV 4.88 mV 9.77 mV 4.88 mV
n = 12 4.88 mV 2.44 mV 1.22 mV 2.44 mV 1.22 mV
n = 13 2.44 mV 1.22 mV 0.61 mV 1.22 mV 0.61 mV
n = 14 1.22 mV 0.61 mV 0.31 mV 0.61 mV 0.31 mV
n = 15 0.61 mV 0.31 mV 0.15 mV 0.31 mV 0.15 mV
1 COB = complementary offset binary.
2 CTC = complementary twos complement—achieved by using an inverter to complement the most significant bit to produce MSB.
3 CSB = complementary straight binary
Zero- and full-scale calibration can be accomplished to a
precision of approximately ±1/2 LSB using the static adjustment
procedure described previously. By summing a small sine or
triangular wave voltage with the signal applied to the analog
input, the output can be cycled through each of the calibration
codes of interest to more accurately determine the center (or
end points) of each discrete quantization level. A detailed
description of this dynamic calibration technique is presented
in Analog-Digital Conversion Handbook, edited by D. H.
Sheingold, Prentice Hall, Inc., 1986.
GROUNDING, DECOUPLING, AND LAYOUT
CONSIDERATIONS
Many data acquisition components have two or more ground
pins that are not connected together within the device. These
grounds are usually referred to as DIGITAL COMMON (logic
power return), ANALOG COMMON (analog power return), or
analog signal ground. These grounds (Pin 19 and Pin 22) must
be tied together at one point as close as possible to the
converter. Ideally, a single solid analog ground plane under the
converter would be desirable. Current flows through the wires
and etch stripes of the circuit cards, and since these paths have
resistance and inductance, hundreds of millivolts can be
generated between the system analog ground point and the
ground pins of the ADC. Separate wide conductor stripe
ground returns should be provided for high resolution
converters to minimize noise and IR losses from the current
flow in the path from the converter to the system ground point.
In this way, ADC supply currents and other digital logic-gate
return currents are not summed into the same return path as
analog signals where they would cause measurement errors.
Each of the ADC supply terminals should be capacitively
decoupled as close to the ADC as possible. A large value (such
as 1 µF) capacitor in parallel with a 0.1 µF capacitor is usually
sufficient. Analog supplies are to be bypassed to the ANALOG
COMMON (analog power return) Pin 22 and the logic supply is
bypassed to DIGITAL COMMON (logic power return) Pin 19.
The metal cover is internally grounded with respect to the
power supplies, grounds, and electrical signals. Do not
externally ground the cover.
CLOCK RATE CONTROL
The AD1376/AD1377 can be operated at faster conversion
times by connecting the clock rate control (Pin 23) to an
external multiturn trim potentiometer (TCR <100 ppm/°C) as
shown in Figure 13.
00699-013
AD1376/AD1377
23
2.25MHz @ 5V
1750kHz @ DGND
15V DC
5kΩ
Figure 13. Clock Rate Control Circuit
AD1376/AD1377
Rev. D | Page 10 of 12
HIGH RESOLUTION DATA ACQUISITION SYSTEM
The essential details of a high resolution data acquisition system
using a 16-bit sample-and-hold amplifier (SHA) and the
AD1376/AD1377 are shown in Figure 14. Conversion is
initiated by the falling edge of the CONVERT START pulse.
This edge drives the device’s STATUS line high. The inverter
then drives the SHA into hold mode. STATUS remains high
throughout the conversion and returns low once the conversion
is completed. This allows the SHA to re-enter track mode.
This circuit can exhibit nonlinearities arising from transients
produced at the ADC’s input by the falling edge of CONVERT
START. This edge resets the ADC’s internal DAC; the resulting
transient depends on the SHA’s present output voltage and the
ADC’s prior conversion result. In the circuit of Figure 15, the
falling edge of CONVERT START also places the SHA into hold
mode (via the ADC’s STATUS output), causing the reset
transient to occur at the same moment as the SHA’s track-and-
hold transition. Timing skews and capacitive coupling can cause
some of the transient signal to add to the signal being acquired
by the SHA, introducing nonlinearity.
00699-014
SHA
AD1376/
AD1377
30 21 28
22
24
27
26
19
18 31
BITS
1–16
+
CONVERT
START
–10V TO + 10V
+
10µF+
10µF
10µF
+15
V
–15V
+5V
ANALOG
INPUT
–
10V TO + 10
V
Figure 14. Basic Data Acquisition System Interconnections 16-Bit SHA
A much safer approach is to add a flip-flop, as shown in
Figure 15. The rising edge of CONVERT START places the
track-and-hold device into hold mode before the ADC reset
transients begin. The falling edge of STATUS places the SHA
back into track mode. System throughput will be reduced if a
long CONVERT START pulse is used. Throughput can be
calculated from
CSCONVACQ TTT
Throughput ++
=1
where:
TACQ is the track-and-hold acquisition time.
TCONV is the time required for the ADC conversion.
TCS is the duration of CONVERT START.
The combination of the AD1376 and a 16-bit SHA can provide
greater than 50 kHz throughput. No significant track-and-hold
droop error will be introduced, provided the width of
CONVERT START is small compared with the ADC’s
conversion time.
0
0699-015
SHA
AD1376/
AD1377
30 21 28
22
24
27
26
19 18 31
BITS
1–16
+
–10V TO +10V
+
10µF+
10µF
10µF
+15V
–15V
+5V
ANALOG
INPUT
–10V T O +10V
CONVERT
START
HC112
S
R
QJ
QK
+5V
Figure 15. Improved Data Acquisition System
1
AD1376/AD1377
Rev. D | Page 11 of 12
APPLICATIONS
The AD1376/AD1377 are excellent for use in high resolution
applications requiring moderate speed and high accuracy or
stability over commercial (0°C to 70°C) temperature ranges.
Typical applications include medical and analytic instrumen-
tation, precision measurement for industrial robotics, automatic
test equipment (ATE), multichannel data acquisition systems,
servo control systems, or anywhere wide dynamic range is
required. A proprietary monolithic DAC and laser-trimmed
thin-film resistors guarantee a maximum nonlinearity of
±0.003% (1/2 LSB14). The converters may be short cycled to
achieve faster conversion times—15 µs to 14 bits for the
AD1376 or 8 µs to 14 bits for the AD1377.
AD1376/AD1377
Rev. D | Page 12 of 12
OUTLINE DIMENSIONS
NOTES:
1. INDEX AREA IS INDICATED BY A NOTCH OR LEAD ONE
IDENTIFICATION MARK LOCATED ADJACENT TO LEAD ONE.
2. CONTROLLING DIMENSIONS ARE IN INCHES; MILLIMETER DIMENSIONS
(IN PARENTHESES) ARE ROUNDED-OFF INCH EQUIVALENTS FOR
REFERENCE ONLY AND ARE NOT APPROPRIATE FOR USE IN DESIGN.
0.023 (0.58)
0.014 (0.36)
0.910 (23.11)
0.890 (22.61)
116
1732
1.728 (43.89) MAX
0.225 (5.72)
MAX
0.025 (0.64)
0.015 (0.38)
0.015 (0.38)
0.008 (0.20)
1.102 (27.99)
1.079 (27.41)
0.100 (2.54)
BSC 0.070 (1.78)
0.030 (0.76)
0.120 (3.05)
MAX
PIN 1
INDICATOR
(NOTE 1)
0.192 (4.88)
0.152 (3.86) 0.206 (5.23)
0.186 (4.72)
0.025 (0.64)
MIN
Figure 16. 32 Lead Bottom-Brazed Ceramic DIP for Hybrid [BBDIP_H]
(DH-32E)
Dimensions shown in inches and (millimeters)
ORDERING GUIDE
Model Temperature Range Maximum Linearity Error Conversion Time (16 Bits) Package Option1
AD1376JD 0°C to 70°C ±0.006% 17 µs DH-32E
AD1376KD 0°C to 70°C ±0.003% 17 µs DH-32E
AD1377JD 0°C to 70°C ±0.006% 10 µs DH-32E
AD1377KD 0°C to 70°C ±0.003% 10 µs DH-32E
1 DH-32E = Ceramic DIP.
© 2005 Analog Devices, Inc. All rights reserved. Trademarks and
registered trademarks are the property of their respective owners.
C00699–0–6/05(D)
