TPS22933: What is the absolute maximum ratting for TPS22933 CAP pin, pin 6?

Why do I ask this? Because I killed one in my design while probing around, and I want to understand in what way I abused the poor beast. So I don't do it again. JCC

Hi JCC,

CAP is an output, so there are no max voltage or current ratings for this pin. If a voltage or current is applied, then there will likely be damage on the pin.

In general though, the highest voltage on this pin will be the highest input voltage used. In the case of this device, this can be 12V.

Thanks,

Alek Kaknevicius

Hi Alek,
Thanks for your quick reply, but I still think there should be an additional specification. Even though this pin is an output, it is not unusual for outputs to have maximum current or voltage specifications. For example the TI TPS62300 series of step down regulators has an SW pin, its output. It is listed with an absolute maximum voltage of -0.3 to +7.0 volts in the data sheet.
For the TPS22933, given it is a MOSFET switch I'd expect a maximum output something like not more than a fraction of a volt higher than the highest of BAT, USB, and DC_IN. But what amount might that be?
The TPS22933 does specify maximum and operational currents for the BAT, USB, and DC_IN inputs (100mA pulse, 85 max DC, 50 mA operational). Given that current has to go somewhere, there is an implied maximum CAP current as well. But that may be overly ambitious for the CAP pin given the other outputs VOUT aned LOUT.

I think the specification problem for this TPS22933 is that most of the data sheet is cast in terms of using the 3.6 Volt LDO output.
In my application, I'm not using the LDO output, and I'm not doing dynamic switching across the three possible input voltages.
The data sheet seems to assume dynamic switching, and the 50 mA in the data sheet is at the 3.6V output. The TPS22933AEVM-005 evaluation card data sheet reinterprets the LDO output maximum current as a maximum input current. For the LDO use case that is fine. But for the EVM reconfigured to use CAP pin output, I believe that is overly restrictive.

And if you aren't dynamically switching inputs, is the 75 mA maximum switch current a real number? In my application, I statically set up input voltages, then start to draw current, using the CAP pin as my output. The TPS22933 seems to be very comfortable with 85 mA input current into BAT pin, coming out CAP, operating at 5 to 5.5 Volts. Voltage drop BAT to CAP is 0.22 volts, power dissipation is 19 mW, temperature rise assuming 27.4 degC/Watt is less than 0.6 deg C above PCB temperature. Is that not an acceptable operating point, even though it exceeds the 75 mA maximum continuous switch current? What current damage mechanism would come into play with a junction temperature rise of less than 1 deg C?

This TPS22933 seems like a great part, but it's hard to know that from the data sheet. Please help me understand and interpret the data sheet for my particular application. Thanks, John C.