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?