Dose Lm5067 turn off mosfet when current flows in the reverse direction?

Hi Yishan,

I would not expect that behavior. Additionally unless there is a second blocking FET, the LM5067 cannot stop reverse current flow as current would conduct through the body diode of the MOSFET.

Do you have a waveform of the behavior? Note that the LM5067 has an ABS_MAX of +/- 0.3V for SENSE to VEE pins. If the reverse current exceeds an amount such that a >0.3V differential voltage occurs between SENSE and VEE, then the device may be damaged (and could cause misbehavior such as shutting off).

Thanks!
Alex

Hello, Alex:

    Thank you for your reply.

     The peak voltage is -1V for SENSE to VEE pins. Does any document have the information?

Best Regards

Li Yishan 

Hi Yishan,

 

In the LM5067 datasheet, page 3 shows the Absolute Maximum Ratings. The SENSE to VEE has a +/- 0.3V rating.

 

In a typical application, the LM5067 is meant to protect an overcurrent condition from the source to the load. Once current increases such that SENSE - VEE reaches 100mV typical (Vcb = Circuit Breaker Threshold Voltage), then the IC will shut off the MOSFET very quickly (responds within ~1-2us, then pulls down on the GATE with 110mA).

 

Thus SENSE - VEE should not exceed 0.3V

 

But in the reverse current condition, there is nothing which turns off the current. So if reverse current causes a large voltage differential, then it will exceed this ABS_MAX rating and could damage the IC.

 

The 0.3V rating comes from anti-parallel diodes within the IC (block diagram, page 10). Because they're diodes, the current draw through them will vary exponentially depending on the voltage. Thus 0.3V may be a little conservative of a rating, but certainly after going above 0.7V, then the diodes should be past their Vth and may damage the IC.

 

We do not have documentation regarding reverse current testing with hot swaps. The closest topic would be a document which discusses stopping reverse current flow for a positive voltage hot swap controller:

But it does not go into detail about the SENSE pin ratings.

 

Thanks,

Alex