OPAX607 datasheet(25/49 Pages) TI

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9 Application and Implementation

Note

Information in the following applications sections is not part of the TI component specification,

and TI does not warrant its accuracy or completeness. TI’s customers are responsible for

determining suitability of components for their purposes, as well as validating and testing their design

implementation to confirm system functionality.

9.1 Application Information

9.2 Low-Side Current Sensing

Power converters use current-mode feedback control for superior transient response and multi-phase load

sharing. Inverter stages control the phase currents for torque control in motor drives. Due to its simplicity and

low-cost, many of these topologies use difference amplifier based low-side current sensing. Figure 9-1 shows

the use of OPAx863 in a difference amplifier circuit for low-side current sensing.

600Ÿ

12kŸ

RSH

1.65V

GND

Switchi ng

Circuit

ISH

VOUT

3.3V

OPA x863

250Ÿ

ADS705 6

3.3V

TLV320 1

VTH

MCU

Interrupt

Digital I/O

300V

3.3V

220pF

Figure 9-1. Low-Side Current Sensing in Power Converters

9.2.1 Design Requirements

Table 9-1. Design Requirements

PARAMETER

DESIGN REQUIREMENT

Shunt resistor

10 mΩ

Input current

15 APP

Output voltage

3 VPP

Switching frequency

50 kHz

Data acquisition

1 MSPS with 0.1% accuracy

Input voltage due to ground bounce

10 Vpk

In a difference amplifier circuit, the output voltage is given by,

1 =

(

)

5* 45* + 84'(

(2)

For lowest system noise, small values of RF and RG are preferred. The smallest value of RG is limited by the

input transient voltage (10 V here) seen by the circuit, and is given by,

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OPA863, OPA2863, OPA4863

SBOS982H – JUNE 2020 – REVISED AUGUST 2022

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