TPS24742: Maximum Load Current in Transient Simulation for TPS24740EVM-596 Evaluation Module

hirano

Part Number: TPS24742
Other Parts Discussed in Thread: TPS24740EVM-596, PSPICE-FOR-TI,

Tool/software:

Hi there,

I tried transient simulation for TPS24740EVM-596 Evaluation Module (actually half of it), but I could not get expected result for maximum load current.
What I did is;
# Downloaded TPS24742 Unencrypted PSpice Transient Model Package (Rev. A) SLVMAP4A.ZIP and PSPICE-for-TI.
# Modified the schematics of it to match TPS24740EVM-596 Evaluation Module, except for TPS24742, while referring to TPS24740EVM-596 datasheet Figure 3. TPS24740EVM-596 OR Then Hotswap Schematic A.
# Ran some transient simulations by changing RLOAD value.

I tried RLOAD value 1, 0.9. 0.8 0.7 ohms. Down to RLOAD 0.8-ohm, HS FET is ON, but at RLOAD 0.7-ohm, HS FET is OFF.
TPS24740EVM-596 Evaluation Module should be able to supply 30A to load by design, but maximum load current in simulation is around 17A (12/0.7).

Please let me know the reason for this discrepancy.

Thanks in advance.
Toru

over 1 year ago

0 Kunal Goel over 1 year ago

TI__Guru* 79181 points

Hi Toru,

I will check and get back to you.

Regards

Kunal Goel

0 Kunal Goel over 1 year ago in reply to Kunal Goel

TI__Guru* 79181 points

Hi Toru,

Are you applying load after VOUT=VIN or before when hotswap is turning on FET?

Regards

Kunal Goel

0 hirano over 1 year ago in reply to Kunal Goel

Prodigy 90 points

Hi Kunal,

Thank you for your comments.

In my first try, I just changed RLOAD value of TPS24742 Unencrypted PSpice Transient Model Package (Rev. A) from "{12/1}" to "1" or "0.7", and RLOAD1 value from 0.12 to 0.12Meg (to make transient current negligible).

And here is new information. When I changed my load from simple 0.7-ohm to (0.8-ohm + PWL current source starts drawing current after HS FET ON), the load current goes up to about 41A as expected.

I am attaching my schematics after load change.

Regards,
Toru

0 Kunal Goel over 1 year ago in reply to hirano

TI__Guru* 79181 points

Let me check on this.

Regards

Kunal Goel

0 hirano over 1 year ago

Prodigy 90 points

Hi Kunal,

Is there any update for this?

Regards,
Toru

0 Kunal Goel over 1 year ago in reply to hirano

TI__Guru* 79181 points

Hi Toru,

I think the difference is in one case load current is very high during startup so we are seeing failed startup, VOUT not rising. To check maximum load capability load should be applied after VOUT=VIN.

Regards

Kunal Goel

Power management

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TPS24742: Maximum Load Current in Transient Simulation for TPS24740EVM-596 Evaluation Module