Time (Ps)

0

10

20

30

40

0

0.5

1

1.5

2

2.5

3

1

2

3

4

5

6

0

D014

Time (s)

0

-5

0.5

-4

1

-3

1.5

-2

2

-1

2.5

0

3

1

3.5

2

4

3

4.5

4

5

5

5.5

6

0

.00005

.0001

.00015

.0002

.00025

D005

Output Voltage

Input Current

14

TMCS1100

SBOS820 – SEPTEMBER 2019

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Product Folder Links: TMCS1100

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Copyright © 2019, Texas Instruments Incorporated

Feature Description (continued)

9.3.3.2 Transient Response

The TMCS1100 signal chain is a discrete time-sampled system with a typical sampling frequency of 250 kHz.

Any variation in the input current signal over this sampling period is averaged. As such, the device has an

effective Nyquist frequency of 125 kHz. At the end of each integration cycle, the signal propagates through the

remainder of the signal chain to the output. Depending on the alignment of a change in input current relative to

the sampling window, the output might not settle to the final signal until the second integration cycle. Figure 5

shows a typical output waveform response to ramp and step input currents. For a slowly varying input current

signal, the output is a discrete time representation with a phase delay of the integration sampling window.

Figure 5. Precision Signal-Chain Response Behavior

Transient response to an input current step is critical for overcurrent of fault-condition detection. As a result of the

TMCS1100 discrete time signal chain, the transient response to step input events varies depending on the

relative timing of the event to the sampling window. Figure 6 shows two transient waveforms to an input-current

step event, but occurring at different times during the sampling interval. With Vout1, the event occurs near the

beginning of the 4-µs sampling interval, so more of the high-current signal is averaged into the first 4-µs output

value. If the event occurs closer to the end of the sampling interval, as with Vout2, the initial output response is

smaller, but occurs closer to the input current step. In both cases, the full transition of the output takes two

sampling intervals to reach the final output value. The timing of the current event relative to the sampling window

determines the proportional amplitude of the first and second sampling intervals.

Figure 6. Transient Response to Input-Current Step Sufficient for 1-V Output Swing