TPS2493: About over voltage protection

Hi Tsukui,

The overvoltage comparator has a 90mV hysiterisis. If the voltage goes above 1.35V at the OV pin, the gate is pulled low and the FET is shut off. The FET stays off until the voltage goes at and/or below 1.26V at the OV pin. At this voltage (1.26V or below), the FET will start to turn on again.

Vov_h = 1.35V (typical)
Vov_l = 1.26V (typical)

I hope this helps :-)

Best Regards,
Aramis P. Alvarez

Hi Yusuke-san,

Thank you for the waveforms. There is no difference between OV threshold during startup and after startup. The threshold holds the same for both cases. I took a look at the waveforms and the OV seems to be behaving correctly (OV thresholds are within tolerance of EC Table in the datasheet).

The way the OV threshold works is that the device will turn off (gate pulled low) when the voltage goes above 1.31-1.39V (look below for datasheet spec). And the device will stay off until the voltage at the OV pin is lowered by 70mV-110mV. After this happens, the OV threshold goes back up to the 1.31-1.39V threshold. This is the same case for startup and after startup (there should be no difference in behavior of OV pin between both states).

Best Regards,

Aramis P. Alvarez

Hi Yusuke-san,

Look below for my comments/feedback:

1) Is it correct in understanding that the OV threshold during startup and after startup may fluctuate within the range of variation(1.31V to 1.39V)?

This shouldn't fluctuate that much, but the values could be seen through this range. The top of the EC Table in the datasheet (page 3) shows the operating conditions that one might see this voltage range. Typically speaking, one should observe the typical value of 1.35V for the upper OV threshold, and 90mV below (1.26V), for the lower threshold.

2) Could you tell me how to add hysteresis in the following internal circuit?

The hysteresis is already built in the internal circuit. This hysteresis comparator acts like a Schmitt trigger. Look below for a picture of how this hysteresis comparator would work:

I hope this helps :-)

Best Regards,

Aramis P. Alvarez

Hi  Yusuke-san,

I talked to the IC designer and we believe we know the issue here. During startup, the OV pin needs to start at a known state in order for the hysteresis to work properly. Meaning, during startup the voltage should be either at <=1.26V (gate on) or >=1.35V (gate off).

If the voltage is somewhere in the middle, the hysteresis comparator is in an unknown state. This is why the device is off when 1.31V is applied on the OV pin.

Please have the customer apply 1.26V or less at the OV pin in order for the startup event to work properly every time. I hope this helps :-)

Best Regards,

Aramis P. Alvarez