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TPS7H5001-SP: Construction of the current-sense circuit into PWM

Part Number: TPS7H5001-SP

Hello,

This might be somewhat of a dumb question, the datasheet provided a design example utilizing high-side current sensing via a current sense XFMR. The current sense resistor was chosen to be 7.5Ohm in the design example, also shown below in the schematic. What do the other current sense components do and how were they calculated?  

1. The 102 Ohm resistor and 10pF capacitor appear to form an RC filter, with a cutoff frequency at 156kHz. Why is this needed and why at that particular frequency?

2. What type of diode does TI recommend using at the output of the current sense XFMR?  

3. What is the purpose of the 10kOhm resistor? Is it to scale the voltage at the secondary side of the XFMR? 

Thanks a lot 

  • Hey Natan,

    The filter is used to help reduce some of the spike from current sensing.
    Its not strictly needed as the controller has LEB, but I used it anyway.

    A low current schottky will do just fine as the diode.

    The 10k resistor is known as something called a burdening resistor and it is needed for the circuit to work with negative currents which can happen at low current values.

    Thanks,
    Daniel