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TMCS1101

SBOS825 – SEPTEMBER 2019

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Copyright © 2019, Texas Instruments Incorporated

10.2 Typical Application

Inline sensing of motor phase current provides significant benefits to the performance of a motor control system,

allowing advanced control algorithms and diagnostics with minimal postprocessing. A primary challenge to inline

sensing for motor drives is that the current sensor is subjected to full HV supply-level PWM transients driving the

motor phase. The inherent isolation of an in-package Hall-effect current sensor topology helps overcome this

challenge, providing high common-mode immunity, as well as isolation between the high-voltage motor drive

levels and the low-voltage control circuitry. Figure 13 illustrates the use of the TMCS1101 in such an application.

Figure 13. Inline Motor Phase Current Sensing

10.2.1 Design Requirements

For current sensing of a three-phase motor application, make sure to provide linear sensing across the expected

current range, and make sure that the device remains within working thermal constraints. A single TMCS1101 for

each phase can be used, or two phases can be measured, and the third phase calculated on the motor-controller

host processor. For this example, consider a nominal supply of 5 V but a minimum of 4.9 V to include for some

supply variation. Maximum output swings are defined according to TMCS1101 specifications, and a full-scale

current measurement of ±20 A is required.

Table 2. Example Application Design Requirements

DESIGN PARAMETER

EXAMPLE VALUE

5 V

4.9 V

±20 A

10.2.2 Detailed Design Procedure

The primary design parameter for using theTMCS1101 is selecting the correct sensitivity variant, and because

positive and negative current must be measured a bidirectional variant should be selected (A1B-A4B). Further

consideration of noise and integration with an ADC can be explored, but is beyond the scope of this application

design example. The TMCS1101AxB transfer function is effectively a transimpedance with a variable offset set

(28)

Design of the sensing solution focuses on maximizing the sensitivity of the device while maintaining linear

measurement over the expected current input range. The TMCS1101 has a slightly smaller linear output range to

the supply than to ground; therefore, the measurable current range is always constrained by the positive swing to

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