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Original question:

TPS2H160-Q1: Current Limit working on TPS2H160-Q1

TPS2H160-Q1: ST1 Fault inconsistent during over-current condition

Rushi Gajjar
Intellectual 765 points
Part Number: TPS2H160-Q1

Hi,

I am using TPS2H160AQPWPRQ1 part on one of the application to drive the 12V, 120mA Cooling FAN.

We have observed that during stall current condition (fan blades blocked scenario) where the fan tries to restart itself, there is a stall current flown through the FAN which is much higher than the operating current 120mA. The current limit Resistor as shown in the below schematics is R570 = 7.5K, 1%.

The waveform shows that it triggers a fault but not consistent. This is observed in multiple boards and with multiple fans. What is the reason for this inconsistency?

  • 0
    TI__Mastermind 34885 points

    Hello Rushi,

    What is the voltage drop over the TPS2H160 in this motor overload condition (VIN - VOUT)? It seems that you might be hitting a "current creep" scenario where the internal sense FET is going into linear mode and not quite hitting the saturation region/setting the current limit. This phenomenon is described in the current creep section of the current limiting application note (http://www.ti.com/lit/an/slva859b/slva859b.pdf). 

    The key point of the datasheet too is the footnote "(2) External current limit accuracy is only applicable to overload conditions greater than 1.5 × the current limit setting". The current limit feature is primarily used to catch fast and sharp current spikes such as short-to-ground and capacitor inrush events. In your scenario you might want to set the current limit around 200mA in order to account for the accuracy hit you will have with only jumping marginally to the current limit trip value.