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ADR06AR-REEL7 View Datasheet(PDF) - Analog Devices

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ADR06AR-REEL7 Datasheet PDF : 24 Pages
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0.80
VIN = 15V
0.75 SAMPLE SIZE = 5
0.70
0.65
0.60
ΔVTEMP/ΔT 1.96mV/°C
0.55
0.50
0.45
0.40
–50 –25
0
25
50
75
TEMPERATURE (°C)
100 125
Figure 36. Voltage at TEMP Pin vs. Temperature
The TEMP function is provided as a convenience rather than a
precise feature. Because the voltage at the TEMP node is
acquired from the band gap core, current pulling from this pin
has a significant effect on VOUT. Care must be taken to buffer the
TEMP output with a suitable low bias current op amp, such as
the AD8601, AD820, or OP1177, all of which result in less than
a 100 μV change in ΔVOUT (see Figure 37). Without buffering,
even tens of microamps drawn from the TEMP pin can cause
VOUT to fall out of specification.
15V
VIN
U1
ADR01/
ADR02/
ADR03/
ADR06
VIN VOUT
VO
VTEMP
1.9mV/°C
V+
OP1177
U2 V–
TEMP TRIM
GND
Figure 37. Temperature Monitoring
NEGATIVE REFERENCE
Without using any matching resistors, a negative reference can
be configured, as shown in Figure 38. For the ADR01, the
voltage difference between VOUT and GND is 10.0 V. Because
VOUT is at virtual ground, U2 closes the loop by forcing the
GND pin to be the negative reference node. U2 should be a
precision op amp with a low offset voltage characteristic.
LOW COST CURRENT SOURCE
Unlike most references, the ADR01/ADR02/ADR03/ADR06
employ an NPN Darlington in which the quiescent current
remains constant with respect to the load current, as shown in
Figure 23. As a result, a current source can be configured as
shown in Figure 39 where ISET = (VOUT − VL)/RSET. IL is simply
the sum of ISET and IQ. Although simple, IQ varies typically from
0.55 mA to 0.65 mA, limiting this circuit to general-purpose
applications.
ADR01/ADR02/ADR03/ADR06
+5V TO +15V
U1
ADR01/
ADR02/
ADR03/
ADR06
VIN VOUT
TEMP TRIM
GND
+15V
–VREF
U2
V+
OP1177
V–
–15V
Figure 38. Negative Reference
VIN
IIN
ADR01/
ADR02/ VOUT
ADR03/
ADR06
RSET
GND
ISET = (VOUT – VL)/RSET
IQ 0.6mA
RL
VL
IL = ISET + IQ
Figure 39. Low Cost Current Source
PRECISION CURRENT SOURCE WITH
ADJUSTABLE OUTPUT
Alternatively, a precision current source can be implemented
with the circuit shown in Figure 40. By adding a mechanical or
digital potentiometer, this circuit becomes an adjustable current
source. If a digital potentiometer is used, the load current is
simply the voltage across Terminal B to Terminal W of the
digital potentiometer divided by RSET.
IL
= VREF × D
R SET
(1)
where D is the decimal equivalent of the digital potentiometer
input code.
+12V
U1
ADR01/
ADR02/
ADR03/
ADR06
VIN VOUT
TEMP TRIM
GND
0V TO (5V + VL)
B
AD5201 W
100k
A
+12V
U2
V+
OP1177
–5V TO VL V–
RSET
1k
VL
–12V
RL 1kIL
Figure 40. Programmable 0 mA to 5 mA Current Source
Rev. L | Page 15 of 24
 

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