ADR431B AD [Analog Devices], ADR431B Datasheet - Page 19

• Manufacturer Part Number: ADR431B
• Description: Ultralow Noise XFET Voltage References with Current Sink and Source Capability
• Manufacturer: AD [Analog Devices]

PRECISION VOLTAGE REFERENCE FOR
DATA CONVERTERS
The ADR43x family has a number of features that make it ideal
for use with ADCs and DACs. The exceptional low noise, tight
temperature coefficient, and high accuracy characteristics make
the ADR43x ideal for low noise applications such as cellular
base station applications.
Another example of ADC for which the ADR431 is well suited
is the AD7701. Figure 40 shows the ADR431 used as the
precision reference for this converter. The AD7701 is a 16-bit
ADC with on-chip digital filtering intended for the
measurement of wide dynamic range and low frequency signals
such as those representing chemical, physical, or biological
processes. It contains a charge-balancing (Σ-∆) ADC, a
calibration microcontroller with on-chip static RAM, a clock
oscillator, and a serial communications port.
ANALOG
SUPPLY
CALIBRATE
GROUND
ANALOG
RANGES
ANALOG
ANALOG
+5V
SELECT
SUPPLY
INPUT
–5V
0.1µF
0.1µF
Figure 40. Voltage Reference for 16-Bit ADC AD7701
0.1µF
10µF
ADR431
10µF
GND
0.1µF
V
IN
V
OUT
CAL
AGND
AV
V
BP/UP
A
AV
REF
IN
DD
SS
AD7701
CLKOUT
SDATA
SLEEP
CLKIN
MODE
DRDV
DGND
SCLK
DV
DV
SC1
SC2
CS
DD
SS
DATA READY
0.1µF
READ (TRANSMIT)
SERIAL CLOCK
SERIAL CLOCK
ADR430/ADR431/ADR433/ADR434/ADR435/ADR439
0.1µF
Rev. B | Page 19 of 24
PRECISION BOOSTED OUTPUT REGULATOR
A precision voltage output with boosted current capability can
be realized with the circuit shown in Figure 41. In this circuit,
U2 forces V
N1. Therefore, the load current is furnished by V
configuration, a 50 mA load is achievable at V
Moderate heat is generated on the MOSFET, and higher current
can be achieved with a replacement of the larger device. In
addition, for a heavy capacitive load with step input, a buffer
may be added at the output to enhance the transient response.
V
IN
GND
2
4
V
IN
U1
O
TRIM
V
ADR431
Figure 41. Precision Boosted Output Regulator
OUT
to be equal to V
6
5
+
–
AD8601
REF
5V
V+
V–
by regulating the turn on of
2N7002
U2
N1
IN
of 5 V.
IN
. In this
R
L
25Ω
V
O