TPS53353: EN Pin Strange Behaviour

Hi Eren,

    We will take a look at this on our board and get back to you.

regards,

Gerold

Eren,

While the TPS53353 does not have an intentional current source forcing current out of the EN pin, a small amount of current can be sourced by the EN-pin.

The datasheet specification is a maximum of 1uA of current into the EN pin at EN = 5V, a 2uA current source out of the pin would be -2uA.

Peter,

We intend to use the TPS53353 in a high reliability application that cannot be maintained during lifetime. Therefore we have to design carefully.

Isn’t sourcing current of any digital pin strange? Can you give more information about this issue?

I'm also disappointed that you don’t see any problems with the TPS53353 EN pin, which has a 1uA maximum current, delivers 2 times the maximum current unexpectedly.

With your sense, if EN pin deliver 1mA, would you consider it normal?

Can you please also explain why EN pin deliver large amount of current?

Regards,

Eren

Eren,

Yes, I would find that 1mA of leakage current into or out of the EN pin of a device to be unusual and a sign that the pin had been damaged.  In this case, we're not looking at 1mA of current, we're looking at 2uA of current, 3 orders of magnitude less.

The EN pin, like most pins on TI power ICs includes ESD protection devices that shut sudden voltage spikes from ESD events away from the gate oxide of sensitive components, like the comparators on EN.  These ESD structures include MOS devices that are connected between the pins and other internal supply rails, such as BP and VDD.  Those MOS devices can leak current into or out of pins, including digital input pins.

The TPS53353 datasheet specifies that the maximum leakage current into the IC pin at 5V is 1uA, it does not specify a minimum current, which could include a negative current flowing into the pin (positive current out of the pin), as you have measured here.  I will try to find an expected minimum level based on test data.  Generally, a small, negative source current out of the EN pin when the part is enabled is not considered problematic as it holds the IC in the ON state, reducing its potential for noise sensitivity.  In fact, a number of device include circuits that deliberately drive current into the EN pin to force it into the ON state if floating, or to provide hysteresis to the turn-on function by forcing the EN voltage higher as the device enables.