LP5900/momentary power failure test of power supply

Tsukui Yusuke

Guru 21930 points

Other Parts Discussed in Thread: LP5900, LP5907

Hi,

Please let me know about momentary power failure test of LP5900.
When performing the tests in some cases Vout does not start up.
I will attach a waveform and a circuit diagram of the customer.
LP5900.zip
Could you tell me the reason for this?

I found a note at the time of start-up from past posts.
Is this information related to this problem?
https://e2e.ti.com/support/power_management/linear_regulators/f/321/t/277099

Best Regards,
Yusuke/Japan Disty

over 8 years ago

0 Antony Pierre Carvajales over 8 years ago

TI__Intellectual 1900 points

Hi Yusuke,

The schematic looks fine. The scope shot has a 10 ms time division which makes it hard to notice if they are meeting the 500µs power up requirement (mentioned in the appointed E2E comment). I would suggest to remove the voltage divider and tight V_ENdirectly to V_IN,by doing this the V_ENwill reach V_IH(1.2V)faster.

Do you know why the Vin and EN pin has a voltage steps behavior? This could be related to nosie coupling from the 12V to 3.3V Converter.

Best Regards,

Antony C. - TI Apps

0 Tsukui Yusuke over 8 years ago in reply to Antony Pierre Carvajales

Guru 21930 points

Hi Antony,

Thank you for your support.
After a review of the customer,
Vin of the rise time (500μs) was the cause.
Let me ask you one more thing.
Does LP5907 have limitation of Rise time(500μs)?

Best Regards,
Yusuke / Japan Disty

0 Antony Pierre Carvajales over 8 years ago in reply to Tsukui Yusuke

TI__Intellectual 1900 points

Yusuke you are very welcome,

In respect to you question the LP5907 does not have a timing requirement.

The LP5907 and LP5900 have different architectures with strengths in different areas; the LP5907 have a higher maximum output current, faster start up time and lower quiescent current.

Warm regards,

Antony C. / Applications Eng.

0 Tsukui Yusuke over 8 years ago in reply to Antony Pierre Carvajales

Guru 21930 points

Hi Antony,Tank you for your support.I inform a customer of it.Best Regards,
Yusuke / Japan Disty

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LP5900/momentary power failure test of power supply