TPS40060 maximum output voltage supported

triet tran

Other Parts Discussed in Thread: TPS40060

Hi,

We are designing an application need to step down voltage from 48V input to 12V output with current up to 4A. Whether TPS40060 is a choice? Otherwise, recommend us with some IC met this requirements.

Thanks

Triet Tran

over 13 years ago

0 Peter James Miller over 13 years ago

TI__Guru 51555 points

Triet,

As long as the UVLO level is programmed above 18V, 48V to 12V should not be an issue.

At lower UVLO levels, I would need to check the derating of the max duty cycle at higher input voltages.

0 triet tran over 13 years ago in reply to Peter James Miller

Prodigy 140 points

Thanks Miller,

Could you spend little time to review the schematics that I have done for this device?

Thanks

Triet Tran

5432.page 12.pdf

0 Peter James Miller over 13 years ago in reply to triet tran

TI__Guru 51555 points

Triet,

Applications does not normal do schematic reviews. Normally you should contact your local field associate (TI AFA or distributor FAE) however, I have taken a few minutes to quickly look over your schematic:

1) R451 (806kOhms) should be connected to the KFF pin voltage not to VIN. This resistor feeds a small amount of current from the LDRV peak detector (D22 & C547) into the KFF pin to increase UVLO hysteresis.

2) BPN10 should not have a 2 ohm series resistor. Unlike bootstrap circuits used in N-channel high-side drive, BPN10 is a regulated output and this high resistance could affect the stability of the 8V regulator.

3) R453 (10 Ohms) might be too large for this location. If this slows the rise of the SW node on turn-on of the high-side FET too much, it could affect the current limit accuracy. I would recommend reducing this resistor to3.3 Ohms or less.

4) I calculate a VIN(min) value from the Rkff (R452) of 7V. I would recommend this being a minimum of 211kOhm (which is an 18V minimum input voltage) to support a 12V output.

I did not review: MOSFET parameters, L-C, Compensation or current limit settings.

0 triet tran over 13 years ago in reply to Peter James Miller

Prodigy 140 points

Hi all,

We are bringing the power supply with TPS40060 up and there an issue, that is both the upper and the lower power mosfet SI7415DN and SI7850DP are too hot. We have one board has this mosfet pair burned if not use heatsink and colling fan for them.

these mosfet PN got from reference design from TI with the same 48VDC input, the differences are on reference design, the output voltage/current is +3.3V/5A, in our design, the output voltage and current is +12V/4A.

Appreciated if you Guru could advise us on:

- Is there any way to reduce power lost on these power mosfet? Could we reduce switching frequency to do that? if frequency reduced, which component(s) should be changed along with?

- Is the compensation circuit affect to mosfet power loss (Both switching and conduction losses)?

- Could we reduce the input voltage to reduce the switching loss? in this case, which component(s) should be changed along with?

- In case we must change the mosfet device for next revision, what is the recommendation for our case? Which package is recommended? Current package is PowerP AK SO-8 and PowerPAK 1212-8.

- Is it better in term of reducing power loss on these Mosfet if we step down the input voltage to 24V, then from 24V step it down to +12V?

1362.TPS40060 schematics.pdf

6433.SI7850DP.pdf

6811.SI7415DN.pdf

Thanks and regards

Triet Tran