ADR510
Rev. B | Page 8 of 12
APPLICATIONS INFORMATION
The ADR510 is a 1.0 V precision shunt voltage reference
designed to operate without an external output capacitor
between the positive terminal and the negative terminal for
stability. An external capacitor can be used for additional
filtering of the supply.
As with all shunt voltage references, an external bias resistor
(R
BIAS
) is required between the supply voltage and the ADR510
(see
Figure 2). R
BIAS
sets the current that is required to pass
through the load (I
L
) and the ADR510 (I
Q
). The load and the
supply voltage can vary, thus R
BIAS
is chosen based on the
following conditions:
• R
BIAS
must be small enough to supply the minimum I
Q
current to the ADR510 even when the supply voltage is at
minimum value and the load current is at maximum value.
• R
BIAS
also needs to be large enough so that I
Q
does not
exceed 10 mA when the supply voltage is at its maximum
value and the load current is at its minimum value.
Given these conditions, R
BIAS
is determined by the supply
voltage (V
S
), the load and operating current (I
L
and I
Q
) of the
ADR510, and the ADR510 output voltage.
Q
L
OUT
S
BIAS
II
VV
R
+
−
=
(3)
ADJUSTABLE PRECISION VOLTAGE SOURCE
The ADR510, combined with a precision low input bias op amp
such as the AD860x, can be used to output a precise adjustable
voltage.
Figure 11 illustrates implementation of this application
using the ADR510.
Output of the op amp, V
OUT
, is determined by the gain of
the circuit, which is completely dependent on the R2 and R1
resistors.
R1
R2
V
OUT
+= 1
(4)
An additional capacitor in parallel with R2 can be added to
filter out high frequency noise. The value of C2 is dependent on
the value of R2.
CC
V
OUT
= (1 + R2/R1)
R
BIAS
DR510
1.0V
AD860x
R2
R1
C2
(OPTIONAL)
03270-011
Figure 11. Adjustable Precision Voltage Source
OUTPUT VOLTAGE TRIM
Using a mechanical or digital potentiometer, the output voltage
of the ADR510 can be trimmed ±0.5%. The circuit in
Figure 12
illustrates how the output voltage can be trimmed using a
10 kΩ potentiometer. Note that trimming using other resistor
values may not produce an accurate output from the ADR510.
CC
V
OUT
R
BIAS
ADR510
POT
10kΩ
R1
470kΩ
03270-012
1
2
3
Figure 12. Output Voltage Trim
USING THE ADR510 WITH PRECISION DATA
CONVERTERS
The compact ADR510 and its low minimum operating current
requirement make it ideal for use in battery-powered portable
instruments, such as the
AD7533 CMOS multiplying DAC, that
use precision data converters.
Figure 13 shows the ADR510 serving as an external reference to
the
AD7533, a CMOS multiplying DAC. Such a DAC requires a
negative voltage input in order to provide a positive output
range. In this application, the ADR510 is supplying a −1.0 V
reference to the REF input of the
AD7533.
0
1
V
DD
MSB
G
N
9
LSB
V
OUT
= 0V TO 1.0V
+
–
AD7533
–V
DD
R2
ADR510
+
–
1
32 1 15
3270-013
Figure 13. ADR510 as a Reference for a 10-Bit CMOS DAC (AD7533)
