RES11A10DDFR datasheet(39/56 Pages) TI2

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8.2 Typical Application

8.2.1 Common-Mode Shifting Input Stage

The RES11A can be used to implement a common-mode attenuator at the high-impedance inputs of an

instrumentation amplifier (INA). This configuration extends the usable signal range, so long as the maximum

differential voltage limitation of each resistor divider is respected.

Figure 8-16 shows an example of a high-side current-sense circuit where a differential voltage, VSHUNT, develops

across a sense resistor with an undesirably high common-mode voltage VCM. VREF is used to shift input

common-mode voltages VMID1 and VMID2 to levels within the specified input common-mode range of the INA.

The amplifier output, VOUT, is a scaled function of VSHUNT, such that nominally:

VOUT=VSHUNT× RIN

RG+RIN+REQUIV

(73)

VOUT can be gained up further by the INA stage, to make maximal use of the effective resolution of a

downstream ADC. In practice REQUIV is optional; however, if REQUIV = RSHUNT, this resistance equalizes

the nominal impedance between VCM and each of the INA high-impedance inputs, thus improving CMRR

performance. Select an INA with input bias currents IB1 and IB2 << ISTATIC1 and ISTATIC2, such as the INA333 or

INA823. Select a RES11A device with a sufficiently high divider series resistance so that ISTATIC1 and ISTATIC2 <<

ILOAD.

SHUNT

BUS

GND

–

EQUIV

IN1

REF

GND

–

IN2

GND

STATIC1

STATIC2

LOAD

LOAD + ISTATIC2

LOAD + ISTATIC1 + ISTATIC2

INA

MID1

MID2

OUT

LOAD

SHUNT

–

Figure 8-16. RES11A Common-Mode Shifting Circuit

To achieve a desired nominal input common-mode voltage, VMID1TARGET, set VREF as follows:

VREF=VMID1TARGET× RG+RIN+REQUIV

RG+REQUIV −VCM× RG+RIN+REQUIV

RG+REQUIV −1

(74)

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RES11A

SLPS785A – DECEMBER 2023 – REVISED OCTOBER 2025

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