REG71055: Start up problem

Zita

Part Number: REG71055

Hi TI experts,

we are using the charge pump REG71055 in several projects. At about 1 percent of the components we observe a maltfunction related to the turnig on the input voltage and the enable signal.

1) If the Enable is activated shortly after the supply voltage is applied, the components function correctly.

2) If only some time (e.g. 30s) after turning on the supply voltage the enable is activated, the conspicuous components do not work. There is no output voltage. If you wait in this condition for some time (about 60 s), the IC still generates the output voltage.

3) If the enable is removed and reactivated, the behavior is similar. With a short interruption (few seconds) of the enable signal, the IC can be activated again. If the enable signal was interrupted for a longer time (about 30 seconds), the above mentioned malfunction occurs.

At low temperatures the problem is more pronounced, that is, the time to start the IC is longer.

Has anyone ever observed this behavior or any idea what the problem might be?

Thanks and Regards

over 5 years ago

0 Julian Hagedorn over 5 years ago

TI__Mastermind 20900 points

Hello,

this is a strange behavior.

Could you check whether there are abnormal input/output currents?

Does the failure follow the device, in case you solder it on a new board?

regards,

Julian

0 Zita over 5 years ago in reply to Julian Hagedorn

Prodigy 60 points

Hello Julian,

yes, the failure follows the device when it is soldered on a new board.

On an inconspicuous device, the input current after applying the enable is approx. 70uA (no load at the output). This value corresponds to the datasheet specification.

On a conspicuous device, the input current after applying the enable slowly rises form 0 to 150uA and then slowly drops back again to about 70uA. Then the device start working. It is also noticeable that no switching action can be recognized on the Cpump-Pins until the device starts after a delay of approx. 60s.