1. The AD694 is a complete voltage in to 4–20 mA out current
transmitter.
2. Pin programmable input ranges are precalibrated at 0 V to
2 V and 0 V to 10 V.
3. The input amplifier may be configured to buffer and scale the
input voltage, or to serve as an output amplifier for current
output DACs.
4. The output voltage compliance extends to within 2 V of the
positive supply and below common. When operated with a
5 V supply, the output voltage compliance extends 30 V be-
low common.
5. The AD694 interfaces directly to 8-, 10-, and 12-bit single
supply CMOS and bipolar DACs.
6. The 4 mA zero current may be switched on and off with a
TTL control pin, allowing 0–20 mA operation.
7. An open collector alarm warns of loop failure due to open
wires or noncompliance of the output stage.
8. A monitored output is provided to drive an external pass
transistor. The feature off-loads power dissipation to extend
the temperature range of operation and minimize self-heating
error.
AD694–SPECIFICATIONS
Model AD694JN/AQ/AR AD694BQ/BR
MinTypMaxMinTypMaxUnit
INPUT CHARACTERISTICS
Input Voltage Range–0.2V
S
–2.0 VV
S
–2.5 V–0.2V
S
–2.0 VV
S
–2.5 VV
Input Bias Current
Either Input, T
MIN
to T
MAX
1.551.55nA
Offset Current, T
MIN
to T
MAX
±0.1ⴞ1±0.1ⴞ1nA
Offset Current Drift±1.0±5.0±1.0±5.0pA/°C
Input Impedance55MΩ
OUTPUT CHARACTERISTICS
Operating Current Range023023mA
Specified Performance420420mA
Output Voltage ComplianceV
S
–36 VV
S
–2 VV
S
–36 VV
S
2 VV
Output Impedance, 4–20 mA40.050.040.050.0MΩ
Current Limit (@ 2 ×FS Overdrive24442444mA
Slew Rate1.31.3mA/µs
SPAN AND ZERO ACCURACY
1
4 mA Offset Error @ 0 V Input
2
Error from 4.000 mA, 4 mA On±10ⴞ20±5ⴞ10µA
Error from 0.000 mA, 4 mA Off0+10+200+5+10µA
T
MIN
to T
MAX
±10ⴞ40±5ⴞ20µA
vs. Supply (2 V Span/10 V Span)0.3/0.050.8/0.40.3/0.050.8/0.4µA/V
Trim Range, 4 mA Zero2.04.82.04.8mA
Span
Nominal Transfer Function
Input FS = 2 V8.08.0mA/V
Input FS = 10 V1.61.6mA/V
Transfer Function Error from Nom,
Input FS = 2 V, 10 V±0.1ⴞ0.3±0.05ⴞ0.15% of Span
T
MIN
to T
MAX
±0.002±0.005±0.001ⴞ0.0025% of Span/°C
vs. Supply±0.001ⴞ0.005±0.001ⴞ0.005% of Span/V
Nonlinearity
3
±0.005ⴞ0.015±0.001ⴞ0.005% of Span
4 mA On: Max Pin 9 Voltage0.80.8V
4 mA Off: Min Pin 9 Voltage3.02.53.02.5V
VOLTAGE REFERENCE
Output Voltage: 10 V Reference9.96010.00010.0409.98010.00010.020V
Output Voltage: 2 V Reference1.9922.0002.0081.9962.0002.004V
T
MIN
to T
MAX
4
30502030ppm/°C
vs. Load, V
REF
= 2 V, 10 V0.150.500.150.50mV/mA
vs. Supply, V
REF
= 2 V, 10 V±0.001ⴞ0.005±0.001ⴞ0.005%/V
Output Current
Source55mA
Sink0.20.2mA
ALARM CHARACTERISTICS
V
CE(SAT)
@ 2.5 mA0.350.35V
Leakage Currentⴞ1ⴞ1µA
Alarm Pin Current (Pin 10)2020mA
POWER REQUIREMENTS
Specified Performance2424V
Operating Range
2 V FS, V
REF
= 2 V4.5364.536V
2 V, 10 V FS, V
REF
= 2 V, 10 V12.53612.536V
Quiescent Current, 4 mA Off1.52.01.52.0mA
TEMPERATURE RANGE
Specified Performance
5
AD694AQ/BQ/AR/BR–40+85–40+85°C
AD694JN0+700+70°C
Operating AD694AQ/BQ/AR/BR–55+125–55+125°C
AD694JN–40+85–40+85°C
(@ +25ⴗC, R
L
= 250 ⍀, and V
S
= +24 V, unless otherwise noted.)
REV. B
–2–
Model AD694JN/AQ/AR AD694BQ/BR
MinTypMaxMinTypMaxUnit
BUFFER AMPLIFIER
6
Input Offset Voltage
Initial Offset±150ⴞ500±50ⴞ500µV
T
MIN
to T
MAX
±2±3±2±3µV/°C
vs. Supply80908090dB
vs. Common Mode80908090dB
Trim Rangeⴞ2.5±4.0ⴞ2.5±4.0mV
Frequency Response
Unity Gain, Small Signal300300kHz
Input Voltage Noise (0.1 Hz to 10 Hz)22µV p-p
Open-Loop Gain
V
O
= +10 V, R
L
≥10 kΩ5050V/mV
Output Voltage @ Pin 1, FB
1
Minimum Output Voltage1.0101.010mV
Maximum Output VoltageV
S
–2.5 V V
S
–2 VV
S
–2.5 VV
S
–2 VV
NOTES
1
The single supply op amps of the AD694, lacking pull down current, may not reach 0.000 V at their outputs. For this reason, span, offset, and nonlinearity are
specified with the input amplifiers operating in their linear range. The input voltage used for the tests is 5 mV to 2 V and 5 mV to 10 V for the two precalibrated
input ranges. Span and zero accuracy are tested with the buffer amplifier configured as a follower.
2
Offset at 4 mA out and 0 mA out are extrapolated to 0.000 V input from measurements made at 5 mV and at full scale. See Note 1.
3
Nonlinearity is specified as the maximum deviation of the output, as a % of span, from a straight line drawn through the endpoints of the transfer function.
4
Voltage reference drift guaranteed by the Box Method. The voltage reference output over temperature will fall inside of a box whose length is determined by the
temperature range and whose height is determined by the maximum temperature coefficient multiplied by the temperature span in degrees C.
5
Devices tested at these temperatures with a pass transistor. Allowable temperature range of operation is dependent upon internal power dissipation. Absolute
maximum junction and case temperature should not be exceeded. See section: “Power Dissipation Considerations.”
6
Buffer amplifier specs for reference. Buffer amplifier offset and drift already included in Span and Zero accuracy specs above.
Specifications subject to change without notice.
Specifications shown in boldfaceare tested on all production units at final electrical test. Results from those tests are used to calculate outgoing quality levels.
All min and max specifications are guaranteed, although only those shown in boldface are tested on all production units.