TPS62745: About Discharge function.

Kengo.Y

Part Number: TPS62745
Other Parts Discussed in Thread: TPS62125, TPS62170

Hi team,

When does the Discharge function work after UVLO?

When the Discharge function is activated, the voltage of the output drops sharply. Is there a way to smooth this out?

Sincerely.
Kengo.

over 4 years ago

0 Matthew Murdock over 4 years ago

TI__Intellectual 1610 points

Kengo,

The TPS62745's output discharge (25 Ohms - typical) is activated as soon as Vin drops below the 2.9V (typ) UVLO threshold.

The most direct way to slowdown the discharge rate would be to use a larger output capacitor.

Alternatively, we do offer other regulators (TPS62125, TPS62170, & TPS6215xA-Q1) that can use the PG pin to discharge Vout through an external pull up resistor which can be sized to adjust the discharge rate.

Sincerely,

-Matt

0 Kengo.Y over 4 years ago in reply to Matthew Murdock

Guru 11285 points

Hi Matt,

Thank you for your reply.

Is there a maximum output capacity?

Sincerely.
Kengo.

0 Vincent Zhang(BSR) over 4 years ago in reply to Kengo.Y

TI__Expert 4795 points

Hi Kengo,

I think the maximum capacitor allowed depends on the Vout and load condition. Once the vout could be built after soft start finished, it should be fine. Thanks.

0 Matthew Murdock over 4 years ago in reply to Vincent Zhang(BSR)

TI__Intellectual 1610 points

Kengo

The datasheet specified a 22uF maximum recommended effective output capacitance, but you should be able to use a slightly larger Cout value (possibly upwards of 100uF). However, bench testing and/or simulation will be required to ensure the stability and load transient behavior is maintained within acceptable limits.

Although not specific to the TPS62745 device, the SLVA463 & SLVA519 application notes provide more information how the output filter may be resized for a few of our other DCS regulator devices.

0 Kengo.Y over 4 years ago in reply to Matthew Murdock

Guru 11285 points

Hi Matt,

I'd like to talk about my customer schematic.
I'll send a message on a private message.

Sincerely.
Kengo.

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TPS62745: About Discharge function.