‡

‡

‡

OUT

SHUNT

BIAS

LOAD

SHUNT

BIAS

V

G

V

V

G

I

R

V

r

r

RSHUNT

±ILOAD

VBUS

+

IN+

IN-

REF

OUT

+

Bandgap

V+

VCC

VREF

VBIAS

VIN

EN

GND

GND

VOUT

REF19xx

INA213B

+

±

+

±

± VSHUNT

18

REF1925, REF1930, REF1933, REF1941

SBOS697A – SEPTEMBER 2014 – REVISED JANUARY 2017

www.ti.com

Product Folder Links: REF1925 REF1930 REF1933 REF1941

Submit Documentation Feedback

Copyright © 2014–2017, Texas Instruments Incorporated

Typical Application (continued)

10.2.1 Design Requirements

The design requirements are as follows:

1. Supply voltage: 5.0 V

2. Load current: ±2.5 A

3. Output: 250 mV to 2.75 V

4. Maximum shunt voltage: ±25 mV

10.2.2 Detailed Design Procedure

Low-side current sensing is desirable because the common-mode voltage is near ground. Therefore, the current-

sensing solution is independent of the bus voltage, VBUS. When sensing bidirectional currents, use a differential

amplifier with a reference pin. This procedure allows for the differentiation between positive and negative

currents by biasing the output stage such that it can respond to negative input voltages. There are a variety of

methods for supplying power (V+) and the reference voltage (VREF, or VBIAS) to the differential amplifier. For a

low-drift solution, use a monolithic reference that supplies both power and the reference voltage. Figure 46

shows the general circuit topology for a low-drift, low-side, bidirectional, current-sensing solution. This topology is

particularly useful when interfacing with an ADC; see Figure 45. Not only do VREF and VBIAS track over

temperature, but their matching is much better than alternate topologies. For a more detailed version of the

design procedure, refer to TIDU357.

Figure 46. Low-Drift, Low-side, Bidirectional, Current-Sensing Circuit Topology

The transfer function for the circuit given in Figure 46 is as shown in Equation 5:

(5)