10.2.2 Typical Application: DAC Force and Sense Reference Drive Circuit

Certain DACs require external voltage references to operate properly. There are DACs that only require a

positive voltage for operating in which the basic connection will work. For other DACs there can be a need a

positive and negative reference voltage due to their bipolar output.

The circuit shown in Figure 10-3 shows a DAC force and sense reference drive circuit for the DACx1001 using

the REF70. This circuit takes advantage of the DACx1001 RCM circuit to remove the need of additional external

resistors to make a negative reference due to the integrated precision resistors. This circuit requires additional

buffers due to undesired series resistance on the reference input of the DAC.

REF7050

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GND

OUTS

OUTF

VIN EN

VIN

REFPF

REFPS

ROFS

RCM

RFB

REFNS

REFNF

DACx1001

VREFN

VREFP

Figure 10-3. Basic Force and Sense Reference Drive Circuit Connections with DACx1001

10.2.2.1 Design Requirements

For this design example, use the reference op amp recommendation listed in Table 10-2 for the buffer circuit.

Table 10-2. Reference Op Amp Options

SELECTION PARAMETERS

OP AMPS

Low voltage and current noise

OPA211, OPA827, OPA828

Low offset and drift

OPA189

The REF70 turn-on time is dependent on the output capacitor. In certain applications that require a fast turn-on

can require a smaller output capacitor as shown in Figure 10-4

REF70

SNAS781D – OCTOBER 2020 – REVISED DECEMBER 2021

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