REF5045 datasheet(23/62 Pages) TI2

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REF

Buffer

ADC

RREF_FLT

CREF_FLT

Voltage

Reference

CBUF_FLT

ADS8881

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SBAS547D – MAY 2013 – REVISED AUGUST 2015

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10.3.2 Reference

The device operates with an external reference voltage and switches binary-weighted capacitors onto the

reference terminal (REF pin) during the conversion process. The switching frequency is proportional to the

internal conversion clock frequency but the dynamic charge requirements are a function of the absolute value of

the input voltage and reference voltage. This dynamic load must be supported by a reference driver circuit

without degrading the noise and linearity performance of the device. During the acquisition process, the device

automatically powers down and does not take any dynamic current from the external reference source. The basic

circuit diagram for such a reference driver circuit for precision ADCs is shown in Figure 48; see the ADC

Reference Driver section for more details on the application circuits.

Figure 48. Reference Driver Schematic

10.3.3 Clock

The device uses an internal clock for conversion. Conversion duration may vary but is bounded by the minimum

and maximum value of tconv, as specified in the Timing Requirements section. An external SCLK is only used for

a serial data read operation. Data are read after a conversion completes and when the device is in acquisition

phase for the next sample.

REF5045 Datasheet(PDF) 23 Page - Texas Instruments