TPS2116: Current is drawn from VIN1 even if VIN2 is active

Michael Bengtsson

Part Number: TPS2116

Tool/software:

In my design I'm using the TPS2116 to switch between two voltage sources (A DC/DC 24V --> 5VDC) Voout is connected to a DC/DC 5V ->3.3V

VIN1 = +5.3V

VIN2 = +5.0V

The TPS is set to run in Priority mode (MODE pin is connected to Vin1)
The PR1 pin is connected to a resistor divider 17,8k /5,6k

Scenario

50mA load connected to +3.3V
Both supply is active
Current is drawn from VIN1 (0 from VIN2)
Supply1 (VIN1) is deactivated
Current is drawn from supply 2 (0 from VIN1)
Supply1 (VIN1) is activated
Current is drawn from VIN1 (0 from VIN2)

Everything works as expected, repeating the same scenario but increasing the load to 250mA, causes the VIN1 to draw a small current when its activated again (Step6 & 7), VIN2 still draws the major of the current

Reseting VIN2 (deactivate and then activate) "resets" the issue -> VIN1 draws all the current.

Any ideas what causing this?

10 months ago

0 Kunal Goel 10 months ago

TI__Guru* 79181 points

Hi Michael,

We have national holidays going on. I will get back by early next week.

Regards

Kunal Goel

0 Michael Bengtsson 10 months ago in reply to Kunal Goel

Prodigy 10 points

Some more information...
The voltage level at the PR1 pin is approx 1.27V (Same in both scenarios)
At scenario 1 (Load 50mA) the ST pin behaves as expected (High when VIN1 active, Low when VIN1 inactive)
At scenario 2 (Load 250mA) the ST pin behaves different....
When VIN1 is deactivated ST goes Low (as expected), when VIN1 is activated again ST pin tries to go high but then go low again repeats with a freq approx 11.5kHz, short puls on ST 10us)

0 Kunal Goel 10 months ago in reply to Michael Bengtsson

TI__Guru* 79181 points

Hi Michael,

Please refer this thread. I think something like this is happening.

(+) TPS2121: Seamless Switchover and power ON issues - Power management forum - Power management - TI E2E support forums

Regards

Kunal Goel

+1 Michael Bengtsson 10 months ago in reply to Kunal Goel

Prodigy 10 points

Hi,
I didn't manage so get the scope to trigger on any undervoltage scenario so I don't know if this happens, however I changed the resistor divider (PR1 pin) to 17,8K // 10k, lowering the switch over voltage level, this seems to solve the issue, I will try to do this change on a couple of more samples to verify that the behavior is the same.