TPS7A37: Turn off Vout waveform with bump symptom

Jim Tsai

Expert 4470 points

Part Number: TPS7A37

Hi,

We measure Vout waveform when turn off with full load condition and get the waveform with bump as below.

CH1:Vin CH2:EN CH3:Vout

After install 2.2uF cap on PC54 for EN, the symptom is gone. Please see below:

Can we add cap on EN?

Why there's bump voltage after EN low? Looks like it related to Vin voltage?

over 3 years ago

0 Juliette over 3 years ago

TI__Mastermind 18466 points

Hi Jim,

Sections 7.3.2 Enable Pin and Shutdown and 7.3.3 Reverse Current of the datasheet talk about what happens when enable is tied to Vin during shutdown.

The capacitor you add to enable, helps create a delay for your operation. This means that with the delay, the VOUT is no longer tracking VIN on the falling edge - it simply turns off once Vin crosses a specific threshold.

This App not belongs to a different product line, but it may help you in choosing your capacitor value.

Precise Start-Up Delay Using Enable Pin with Precise Voltage Threshold

Best,

Juliette

Power management

Power management forum

TPS7A37: Turn off Vout waveform with bump symptom