BQ35100: How to set GE pin when using a level shifter that requires pull ups

Mike Tatro

Part Number: BQ35100

Tool/software:

Hi,

I'm using the BQ35100 with the LSF0204RUTR level shifter. The processor operates at 1.8V while the BQ35100 is being operated at VBAT which is 3.6V. When the GE pin isn't being drive high it is pulled low via a 1M resistor has shown in the reference design. Currently, when the GE pin is set high by the processor, the level shifter only outputs 1.8V to the GE pin. I believe the input to the GE pin needs to be higher than 2.65V to enable. In order to bring that pin up to VBAT it would need a pull up resistor to VBAT, however, when switched off I don't believe it would be able to go low. What is the best way to interface the GE pin with the level shifter to ensure operation and minimal current draw when off? See attached image for the schematic. Please let me know if you need any additional details.

3 months ago

0 Alan Frias 3 months ago

TI__Mastermind 25475 points

Hello Mike,

After reviewing your schematic it does appear to be good however if the trave is no able to go low than I would use a pull down resistor in order to help with the floating voltage. Also the voltage level input for GE is 2.65V to be signal as high and 0.8V to be signal as low.

Thank you,
Alan

0 Mike Tatro 3 months ago in reply to Alan Frias

Prodigy 40 points

Hi Alan,

In the current schematic, the GE pin is only going to 1.8V since it doesn't have a pull up. This isn't getting to the 2.65V threshold. Are you recommending adding the pull up and pull down? Please confirm.

0 Alan Frias 3 months ago in reply to Mike Tatro

TI__Mastermind 25475 points

Hello Mike,

Mike Tatro said:
the GE pin is only going to 1.8V since it doesn't have a pull up. This isn't getting to the 2.65V threshold

-If the pin can't go up to 2.65V than the signal won't be registered

Mike Tatro said:
Are you recommending adding the pull up and pull down?

-Understanding that the pin can't be registered as high I would look into different solutions.

Thank you,

Alan

0 Mike Tatro 3 months ago in reply to Alan Frias

Prodigy 40 points

Hi Alan,

Thanks for the response. Can you provide some potential options? What has been used in the past when pairing this device with a level shifter?

0 Alan Frias 3 months ago in reply to Mike Tatro

TI__Mastermind 25475 points

Hello Mike,

This would have to be decided by the user, I haven't seen people use level shifters in this application but I don't see why the a level shifter wouldn't work in this type of application.

Thank you,
Alan

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BQ35100: How to set GE pin when using a level shifter that requires pull ups