TPS23751: Phase Margin

Seishin

Part Number: TPS23751

Hi,

I have a question.(Customer inquiries)

【Question】
We measured the phase margin of POE+ circuit (prototype board) with TPS 23751 using Frequency Response Analyzer.
The phase margin is 45 ° or more, but the crossover frequency is about 1 kHz.
Is everything OK?
In the transient response test, the output voltage is within the acceptable range (24 V ± 5%).

【Test Conditions】
●Vin=42V
●Vo=24V
●Io=0.02A

【Result】
●Phase Margin ：　49.59°
●Gain Margin ：　-54.5dB
●Crossover frequency ：　801Hz
I have attached a screenshot.

Best regards,
Seishin

over 7 years ago

0 Darwin Fernandez over 7 years ago

TI__Mastermind 41760 points

Hi Seishin,

Since the output is 24V, is this a diode rectified output flyback? I say this because you must make sure the converter is not pulse skipping at light loads when you take this measurement so hopefully 20mA was enough.

Under the test conditions, yes, it is expected that the BW drops at light loads and we expect it to be typically less than 3kHz and still want phase margin greater than 50 deg.

Regards,

Darwin

0 Seishin over 7 years ago in reply to Darwin Fernandez

Genius 4135 points

Hi Darwin,

Thanks for the prompt response.

I understand your comments.

Best regards,
Seishin

Power management

Power management forum

TPS23751: Phase Margin