TMCS1101 datasheet(36/48 Pages) TI1

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TMCS1101

SBOS825A – SEPTEMBER 2019 – REVISED MAY 2020

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11 Power Supply Recommendations

The TMCS1101 only requires a power supply (VS) on the low-voltage isolated side, which powers the analog

circuitry independent of the isolated current input. VS determines the full-scale output range of the analog output

VOUT, and can be supplied with any voltage between 3 V and 5.5 V. The TMCS1101 zero-current output voltage

is derived from VS using a resistor divider; therefore, take care to optimize the power supply path for both noise

and stability across temperature to provide the highest precision measurement. To filter noise in the power-

supply path, place a low-ESR decoupling capacitor of 0.1 uF between VS and GND pins as close as possible to

the supply and ground pins of the device. To compensate for noisy or high-impedance power supplies, add more

decoupling capacitance.

The TMCS1101 power supply VS can be sequenced independently of current flowing through the input. However,

there is a typical 25ms delay between VS reaching the recommended operating voltage and the analog output

being valid. Within this delay VOUT transfers from a high impedance state to the active drive state, during which

time the output voltage could transition between GND and VS. If this behavior must be avoided, a stable supply

voltage to VS should be provided for longer than 25ms prior to applying input current.

12 Layout

12.1 Layout Guidelines

The TMCS1101 is specified for a continuous current handling capability on the TMCS1101EVM, which uses 3-oz

copper pour planes. This current capability is fundamentally limited by the maximum device junction temperature

and the thermal environment, primarily the PCB layout and design. To maximize current-handling capability and

thermal stability of the device, take care with PCB layout and construction to optimize the thermal capability.

Efforts to improve the thermal performance beyond the design and construction of the TMCS1101EVM can result

in increased continuous-current capability due to higher heat transfer to the ambient environment. Keys to

improving thermal performance of the PCB include:

•

Use large copper planes for both input current path and isolated power planes and signals.

•

Use heavier copper PCB construction.

•

Place thermal via farms around the isolated current input.

•

Provide airflow across the surface of the PCB.

The TMCS1101 senses external magnetic fields, so make sure to minimize adjacent high-current traces in close

proximity to the device. The input current trace can contribute additional magnetic field to the sensor if the input

current traces are routed parallel to the vertical axis of the package. Figure 48 illustrates the most optimal input

current routing into the TMCS1101. As the angle that the current approaches the device deviates from 0° to the

horizontal axis, the current trace contributes some additional magnetic field to the sensor, increasing the effective

sensitivity of the device. If current must be routed parallel to the package vertical axis, move the routing away

from the package to minimize the impact to the sensitivity of the device. Terminate the input current path directly

underneath the package lead footprint, and use a merged copper input trace for both the IN+ and IN– inputs.

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