ADR430 Analog Devices, Inc., ADR430 Datasheet - Page 19

• Manufacturer Part Number: ADR430
• Description: Ultralow Noise Xfet Voltage References With Current Sink And Source Capability
• Manufacturer: Analog Devices, Inc.

ANALOG
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 an 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-Δ ADC, a calibration
microcontroller with on-chip static RAM, a clock oscillator,
and a serial communications port.
SUPPLY
CALIBRATE
GROUND
ANALOG
RANGES
ANALOG
ANALOG
+5V
SELECT
SUPPLY
INPUT
–5V
0.1µF
Figure 40. Voltage Reference for the AD7701 16-Bit ADC
0.1µF
0.1µF
10µF
ADR431
10µF
GND
V
0.1µF
V
2
4
IN
OUT
6
CAL
AGND
AV
V
BP/UP
A
AV
IN
REF
DD
SS
AD7701
CLKOUT
SDATA
SLEEP
CLKIN
MODE
DGND
DRDY
SCLK
DV
DV
SC1
SC2
CS
DD
SS
DATA READY
0.1µF
READ (TRANSMIT)
SERIAL CLOCK
SERIAL CLOCK
0.1µF
ADR430/ADR431/ADR433/ADR434/ADR435/ADR439
Rev. D | 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
ate 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 can be
added at the output to enhance the transient response.
V
IN
ADR431
GND
V
U1
2
4
IN
V
TRIM
O
OUT
Figure 41. Precision Boosted Output Regulator
to be equal to V
6
5
+
–
U2
AD8601
5V
V+
V–
REF
2N7002
by regulating the turn-on of
N1
IN
of 5 V. Moder-
IN
25Ω
. In this
R
L
V
O