TPS25910: Enable and current limits (while powered)

Hi Ari,

Can you please share your schematic, test waveforms to look into it.
In which mode you are using DC Electronic load?

Regards,
Rakesh

Hi Rakesh,

I did some more testing and ran a simulation model in TINA. What I found is that if I load the output after the chip is powered on and enabled then I can drive quite a bit of power out of the chip (20V @ 5A in my case). If I keep that load on and then toggle the enable line then the output dies. It looks like, based on the datasheet, that I am really supposed to be driving only 5 watts out of the chip but then in other places in the datasheet and reference design I see 100 watts (20V @ 5A in the development board).

With a 20V output I was able to drive as much as 600 mA when toggling the enable line. This is more than 5 watts stated as nominal in the datasheet (7.5 watts max) but much less than the 100 watts when I load the output in steady state.

Is there something I can do to drive this chip with 100 watts while toggling the enable line?

Thanks,
Ari

Hi,

I am looking for this exact chip except without the current limitation upon enable or startup. Any thoughts on what else I could use?

Hi,
Please look at TPS259271, TPS25942A, TPS25944A devices.

Regards,
Rakesh

Hi. Thank you for the response but we have a 20V requirement. All of those are less than 20V. Also, do they have the same current limitation like the 26910?

Hi Ari,

These devices has different internal architecture and are different in behavior to TPS25910 device

Regards,
Rakesh

Hi Rakesh,

I have tested out the TPS25942A chip using the TPS25942xEVM-635: Evaluation Module for TPS25942x. Setting the limit and OVP resistors I am able to drive 4.6A @ 20V onto my DC Electronic load. When I disable and re-enable the chip under load (using the reset button in the evaluation module) the output never comes back. If I try this at < 0.6A load (similar to the TPS25910 device) then I am able to get the desired output. In the simulation, however, I am seeing that I should be able to enable/disable under load and come back fine. Is the TINA model correct for this device?

Additionally, I must remove the 330uF capacitor (C4 for channel 1) if I want to drive the full load on the board. I was able to verify this in simulation as well. Anything above 200uF seemed to collapse the output voltage. Any thoughts on this as well?

See the attached simulation here:

1680.TPS25942EVM-635 Evaluation Module for TPS25942x - Reworked.TSC

Note: The simulation reflects my rework on the evaluation board.

Hi Ari,

The TPS25942xEVM-635: Evaluation Module comes in power muxing configuration i.e., outputs of two channels are connected together and hence C4&C10 comes in parallel. You can isolate the channels by removing R7.

Both load resistance and output capacitance forms as load for the device during startup. For successful startup, we need to make sure of using appropriate soft-start capacitor at DVDT pin.
Please use design calculator at www.ti.com/.../toolssoftware and let me know if you have any questions.

Best Regards,
Rakesh

OK. I will investigate and report back. In the meantime could you please provide me with a PDF of the EVM schematic? The schematic in the datasheet does not print well.

Hi Ari,

Please find the attached schematic.

Regards,

Rakesh

PWR635A-002_Sch.pdf