LPC1788: High current consumption at VBAT pin.

[robertmolnar]

I use LPC1788FBD208 chip, firmware use RTC with backup battery (3 V lithium), MCI (SD card), SPI, 2 UART modules. Sometime I find that the I(VBAT) goes to 55 mA and stay constant even power off state and deep power-down state too. At first time I think it is a chip hard fault (ESD), I replace them. But tomorrow I found a chip, which first time worked I(VBAT) = 1uA, then fault I(VBAT) = 55 mA, then again worked I(VBAT) = 1 uA.

Someone had seen this phenomenon? This may be a firmware problem?

[Carlos_Mendoza]

Hi Robert,

There is an IBAT errata for these devices that mentions that IBAT current could go as high as about 10 uA when only VBAT is applied, but it is not near the 55mA you mention:

http://www.nxp.com/documents/errata_sheet/ES_LPC177X_8X.pdf 

So I believe there is a hardware problem, make sure there are no damaged diodes or a short circuit somewhere in your design.

Hope it helps!

Best Regards,
Carlos Mendoza
Technical Support Engineer

[robertmolnar]

Hi Carlos,

Thank you for your suggestion!

Yes I read this errata, and try it. It doesn't resolve the problem.

Now it seems to hardware problem, but I don't know what can cause it.

Best regards,

Robert Molnar