TPS53681EVM-002: About helper and indicators circuits

user4811888

Intellectual 530 points

Part Number: TPS53681EVM-002
Other Parts Discussed in Thread: TPS53681, TPS536C7

Hi TI expert,

I'm confused about below circuits you used in EVM:

1. Sometimes you're using a comparator to drive the N-MOS, sometimes direct drive is used. Why are there differences?

2. Why is there a pull-up resistor to 3.3V of VREN signal?

That means by default the indicator LED diode is conducting. Assume we don't have a pull-up resistor, although if VREN is floating, it's possible that N-MOS is on or off, LED is on or off.

This also makes sense because we should only ensure LED diode is on when VREN is high level. That's enough, right?

over 4 years ago

+1 Rama Pamidi over 4 years ago

TI__Intellectual 1790 points

Hi,

Comparator is used for EN_VOUT_A,EN_VOUT_B and VR_HOT# signal. The assumption is, these pins can be pull-up to 1V supply also. but this schematic is using only 3.3V pull-up. so we can remove comparator also. It also possible to apply 1V at these pins with comparator. The other pins are always pull-up to 3.3V so direct is ok.
I don't see this circuit in TPS53681 EVM. But it is ok to use 3.3V pull-up instead of comparator.
yes. we can ensure LED diode is on when VREN is high level.

Thanks.

Regards,

Rama.

0 user4811888 over 4 years ago in reply to Rama Pamidi

Intellectual 530 points

Hi Rama,

thanks for your kind reply, the first image is from TPS536C7 EVM and the second image is from TPS53681 EVM.

0 user4811888 over 4 years ago in reply to Rama Pamidi

Intellectual 530 points

Hi Rama,

would like to know how you test output current waveform from TPS53681-EVM? Differential isolated probe across resistors?

0 Rama Pamidi over 4 years ago in reply to user4811888

TI__Intellectual 1790 points

Hi,

Yes. We have measured current as differential voltage across resistors.

R = 0.3/15 = 0.02, Peak-Voltage at one Bank= 0.75V, Per-bank current = 0.75/0.02 = 37.5A.

so Total current for all 4 banks = 37.5A*4 = 150A.

Thanks.

Regards,

Rama.

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TPS53681EVM-002: About helper and indicators circuits