ADR430 datasheet(19/24 Pages) AD

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ADR430/ADR431/ADR433/ADR434/ADR435/ADR439

Rev. B | Page 19 of 24

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.

SERIAL CLOCK

READ (TRANSMIT)

DATA READY

+5V

ANALOG

SUPPLY

SERIAL CLOCK

RANGES

SELECT

CALIBRATE

ANALOG

INPUT

ANALOG

GROUND

–5V

ANALOG

SUPPLY

DVDD

SLEEP

MODE

DRDV

SCLK

SDATA

CLKIN

CLKOUT

SC1

SC2

DGND

DVSS

AVSS

AGND

AIN

CAL

BP/UP

VREF

AVDD

VIN

VOUT

GND

ADR431

AD7701

0.1

µF

0.1

µF

0.1

µF

0.1

µF

0.1

µF

0.1

µF

Figure 40. Voltage Reference for 16-Bit ADC AD7701

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 VO to be equal to VREF by regulating the turn on of

N1. Therefore, the load current is furnished by VIN. In this

configuration, a 50 mA load is achievable at VIN of 5 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–

V+

–

VIN

VOUT

TRIM

GND

2N7002

AD8601

ADR431

RL 25Ω

Figure 41. Precision Boosted Output Regulator

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