REF5045 datasheet(43/62 Pages) TI2

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1 k

4.7 nF

OPA333

10 nF

10 k

1 k

OPA333

10 nF

10 k

OPA313

1 µF

4.7

1 k

22 µF

10 k

1 µF

AVDD

VCM

VIN+

VIN-

Input Driver

Reference Drive Circuit

Device running at 10 kSPS.

AVDD

AINP

AINM

REF

GND

AVDD

CONVST

Device

AVDD

REF3325

(See Reference Datasheet

for Detailed Pin Configuration)

ADS8881

www.ti.com

SBAS547D – MAY 2013 – REVISED AUGUST 2015

Product Folder Links: ADS8881

Submit Documentation Feedback

11.2.4 Ultralow-Power DAQ Circuit at 10 kSPS

Figure 72. Ultralow-Power DAQ Circuit at 10 kSPS

11.2.4.1 Design Requirements

Portable and battery-powered applications require ultralow-power consumption and do not need very high

throughput from the ADC.

Design a single-supply, data acquisition circuit optimized for using the ADS8881 to achieve

•

ENOB > 16 bits and

•

Ultralow-power consumption of < 1 mW at throughput of 10 kSPS.

11.2.4.2 Detailed Design Procedure

The application circuit in Figure 72 shows the schematic of a complete reference driver circuit that generates a

voltage of 2.5 V dc using a single 3.3-V supply. This ultralow power reference block is suitable to drive the

ADS8881 for power-sensitive applications at a relatively lower throughput. This design uses the high-precision

REF3325 circuit that provides an accurate 2.5-V reference voltage at an extremely low quiescent current of 5 µA.

The output broadband noise of the reference is heavily filtered by a low-pass filter with a 3-dB cutoff frequency of

16 Hz.

The reference buffer is designed with the low-power OPA313 that can operate from a 3.3-V supply at an

extremely low quiescent current of 50 µA. The wideband noise contribution from the amplifier is limited by a

lowpass filter of a cutoff frequency equal to 1.5 kHz, formed by a 4.7-Ω resistor in combination with a 22-μF

capacitor. The 4.7-Ω series resistor creates an additional drop in the reference voltage that is corrected by a

dual-feedback configuration.

REF5045 Datasheet(PDF) 43 Page - Texas Instruments

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