TPS22954: Sequence requirements of IN, BIAS and EN pin

Tamio Yokokura

Part Number: TPS22954

Hi, Support team

The customer circuit is designed as below. EN is controlled by CPU.

The voltage on EN pin is always kept to more than VIH(0.7V), but the voltage on IN pin and BIAS pin is suddenly shutdown and is recovered.

In that case, is the output voltage appeared correctly? I would like to know if there are any sequence requirement of IN, BIAS and EN pin.

Thanks

Tamio

over 3 years ago

0 Tamio Yokokura over 3 years ago

TI__Expert 3630 points

0 Shreyas Dmello over 3 years ago in reply to Tamio Yokokura

TI__Mastermind 32650 points

Hi Tamio,

This method of operation is acceptable but you will see variation from the expected datasheet numbers. This is because the device will turn on as soon as the voltage on the IN and BIAS pin become valid.

At this moment in time, the device will perform its soft start. If the voltage ramps up faster than the soft start, you will see some variation in the rise time as the voltage and internal biases change. If the soft start is faster than the voltage ramp, the the turn on will be limited by the rising voltage of the power source.

0 Tamio Yokokura over 3 years ago in reply to Shreyas Dmello

TI__Expert 3630 points

Hi, Shreyas

Thank you for your quick response.

I was relieved to hear that the customer sequence was accepted. I understand that the rise time changes depending on the relationship between the rise of the input voltage and Soft Start.

By the way, have you ever seen the output turned off even though IN, BIAS and EN are valid?

Thanks

Tamio

0 Shreyas Dmello over 3 years ago in reply to Tamio Yokokura

TI__Mastermind 32650 points

Hi Tamio,

This device has a few internal protection features like thermal shutdown and voltage monitoring by the SNS pin which could cause the device to turn off even though the inputs are valid.

Power management

Power management forum

TPS22954: Sequence requirements of IN, BIAS and EN pin