TPS25924: TPS259241DRCR questions

add schematic for reference.

Hi Neo,

Are you seeing linear startup during all tries when you are not probing dvdt pin. Probing this pin shouldn't cause this.

Regarding the retry mode, for many faults, TSD mechanism turns off the device. TPS259241 device will wait for 100us after Tj falls below TSD -10C to auto retry the device. 

Best Regards,
Arush

Hi Arush,

Yes, without passive probe on DVDT cap, i can see consistent linear power up waveform with rising time is ~50ms. (the 2nd waveform in previous).

As for auto retry, will the device retry after short circuit in below conditions?

1. Output shorted to GND then hotswap is turned on

2. Output hard shorted during hotswap operation.

We observed below waveform when hotswap start up into short (Green is input voltage, yellow is output voltage and red is the shorted current), is this expected?

Thanks

Neo

Hi Neo,

Figure 29 and Figure 30 shows the test case which you asked for i.e. short circuit test and wake up in short.

Yes, the device will perform auto-retry in these cases. In case of short circuit during operation, the device will perform fast trip and then will regulate the current until it goes into TSD. Time to TSD will depend on the power dissipation on the device. 

After TSD, the device will perform auto-retry.

In case of wake up in short,

Best Regards,
Arush

Regarding the dvdt probing issue, can you please double verify the setup once.

This makes sense. I verified short circuit on my board, similar waveforms can be captured.

Thanks.

For DVDT waveform, I rechecked the setup and use different probe for DVDT measurement, observed similar nonlinear start up on DVDT and Vout.

Can you verify on your EVB board? Looks no DVDT waveform was captured in datasheet.

Thanks

Neo

Hi Neo,

Please give me time till end of week for this testing. If I am able to get the testing done earlier, I will inform you. 

Can you share the exact test conditions like Vin, load current during startup output. 

Best Regards,
Arush

Sure, thanks.

Here is the condition:

Vin=12V, Cout=122uF (100uF poscap+22uF mlcc), Rload=1.2kohm.
A divided voltage from VIN is tied to EN of TPS259241 for UVLO control, please refer the schematic attached earlier for the divider resistance.

Test was performed by turning VIN from OFF to ON.

Thank you for confirmation.

Best Regards,
Arush

Hi Neo,

I got a chance to test it today. Yes, I can also see this behavior. 

This is due to probe taking some current. Internally we have a 220nA current source at dvdt pin. probe is taking some of the current and causing this non-linear behavior.

Best Regards,
Arush