TMCS1100 datasheet(36/50 Pages) TI1

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OUT,max

OUT,min

B,MAX

A x

2 S

OUT,max

OUT,min

U,MAX

A x

OUT,min

GND

Swing

OUT,max

S,min

Swing

OUT

REF

TMCS1100

SBOS820A – SEPTEMBER 2019 – REVISED JUNE 2020

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10.2.2 Detailed Design Procedure

The TMCS1100 application design procedure has two key design parameters: the sensitivity version chosen (A1-

A4) and the reference voltage input. Further consideration of noise and integration with an ADC can be explored,

but is beyond the scope of this application design example. The TMCS1100 transfer function is effectively a

transimpedance with a variable offset set by VREF, defined by Equation 28.

(28)

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

measurement over the expected current input range. The linear output voltage range is constrained by the

TMCS1100 linear swing to ground, SwingGND, and swing to supply, SwingVS. With the previous parameters, the

maximum linear output voltage range is the range between VOUT,max and VOUT,min, as defined by Equation 29 and

Equation 30.

(29)

(30)

For a bidirectional current-sensing application, a sufficient linear output voltage range is required from VREF to

both ground and the power supply. Design parameters for this example application are shown in Table 4 along

with the calculated output range.

Table 4. Example Application Design Parameters

DESIGN PARAMETER

EXAMPLE VALUE

SwingVS

0.2 V

SwingGND

0.05 V

VOUT,max

4.7 V

VOUT,min

0.05 V

VOUT,max - VOUT,min

4.65 V

These design parameters result in a maximum linear output voltage swing of 4.65 V. To determine which

sensitivity variant of the TMCS1100 most fully uses this linear range, calculate the maximum current range by

Equation 31 for a unidirectional current (IU,MAX), and Equation 32 for a bidirectional current (IB,MAX).

(31)

where

•

SA<x> is the sensitivity of the relevant A1-A4 variant.

(32)

Table 5 shows such calculation for each gain variant of the TMCS1100 with the appropriate sensitivities.

Table 5. Maximum Full-Scale Current Ranges With 4.65-V Output Range

SENSITIVITY VARIANT

SENSITIVITY

IU,MAX

IB,MAX

TMCS1100A1

50 mV/A

93 A

±46.5 A

TMCS1100A2

100 mV/A

46.5 A

±23.2A

TMCS1100A3

200 mV/A

23.2 A

±11.6A

TMCS1100A4

400 mV/A

11.6 A

±5.8 A

In general, select the highest sensitivity variant that provides for the desired full-scale current range. For the

design parameters in this example, the TMCS1100A2 with a sensitivity of 0.1 V/A is the proper selection because

the maximum-calculated ±23.2 A linear measurable range is sufficient for the desired ±20-A full-scale current.

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