LTC3643 bottom switch is broken

Hi There,

I have a question regarding a charge process in LTC3643.

Is there any situation that a bottom switch of LTC3643 is broken during charge process?

It is described in the datasheet that maximum charge current is limited up to 2A, therefor internal MOSFET should be protected in the charge process.

If we use a current limit resistor of 0.01ohm (charge current could be 2A), bottom switch is broken. However we use the current limit resistor of 0.1ohm(charge current could be 0.4A), charge process is completed correctly. Load current of LTC3643 is 100mA for PMIC. Our LTC3643 schematic is as attached.

When we tested boost/buck mode operation in the DC2220A demo board same as our configuration, that is worked correctly.

Input voltage = 5.5V

Vcap = 39.5V

Output volgate = 5.5V

PFI Rising voltage = 5.029V / Falling voltage = 4.571V

Best Regards,

Kumac