Input Current (A)

-25 -20 -15 -10

-5

0

5

10

15

20

25

30

35

40

45

50

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

D002

Time (Ps)

0

5

10

15

20

0

5

10

15

20

25

30

6

5

4

3

2

1

0

D013

15

TMCS1100

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SBOS820 – SEPTEMBER 2019

Product Folder Links: TMCS1100

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Copyright © 2019, Texas Instruments Incorporated

Feature Description (continued)

The output value is effectively an average over the sampling window; therefore, a large-enough current transient

can drive the output voltage to the full range in the first sample response. This condition is likely to be true in the

case of a short-circuit or fault event. Figure 7 shows an input-current step of 100 A, and the output response of

an TMCS1100A3B. In the case of Vout1, the event occurs near the beginning of a sampling window, and so the

output transitions to full scale in the first integrator output sample. In the case of Vout2, the event occurs near the

end of an integration cycle, so there are two distinct output transitions. The relative timing and size of the input

current transition determines whether the output transitions to full scale in a single cycle. In either case, the total

response time is approximately one integration period.

Figure 7. Transient Response to a Large Input Current Step

9.3.4 External Reference Voltage Input

The reference voltage provided externally to the TMCS1100 on the VREF pin determines the zero current output

range of the device, and allows for unidirectional or bidirectional sensing, as described in the Absolute Maximum

1.25 V, and 2.5 V. By shifting the zero current output voltage of the device, the dynamic range of measurable

input current can be modified.

Figure 8. Output Voltage Relationship to Input Current With Varying VREF Voltages

The input voltage on this pin can be provided by any external voltage source or potential, such as a discrete

precision reference, a voltage divider, ADC reference, or ground. The VREF pin is sampled by the internal

circuitry at approximately 1 MHz, then buffered and provided to the signal chain of the device. An apparent dc

load of approximately 1 µA will be observed by the external reference. In order to prevent errors due to sampling

settling, keep the source impedance below the level specified in Electrical Characteristics.