LM5143-Q1: Larger pull high resistor for DEMB pin in LM5143

Hello William 

Basically, the DEMB pin voltage should be higher than 2V for FPWM mode and less than 0.8V for DE mode. 

Assuming PR1837 is not populated and the maximum leakage current of PQ1807 is 60uA, the voltage drop across 47 kOhm resistor is 2.82V (47k*60u =2.82).

Which means REG_VDDA voltage should be greater than 4.82V always at the minimum input voltage if you want to use 47kOhm. 

-EL

Hello William 

Assuming the maximum leakage current of PQ1807 is 60uA, I think there is a possibility the DEMB pin voltage is lower than the DEMB rising threshold 2.0V. (4.75 - 47k*60u = 1.93)

-EL

Hello William 

I couldn't find the datasheet previously, so I referred one of random MOSFET datasheets in my laptop. 

I tried to find the datasheet again today, it seems the leakage current is smaller than the previous assumption if they are using this MOSFET bss138lt1-d.

Assuming the maximum leakage current is 1uA, 4.75 - 47k*1u = 4.7, then you are very safe. 

- EL 

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-EL