Hello,
There are a couple of resistors (R3 & R4) connected to the EN pin by default, if I want to use the EN pin in a normal fashion such as connecting to an MCU or ON/OFF controller IC, should I remove these resistors from the board? Or would just connecting up to EN still be OK with these resistors in place?
Referring to this board:
Many thanks.
I could not find any more specific info on the AP63357 EN function on the Datasheet or EVM guide for the IC; but to be safe I would either pull the AP63357 EN pin to GND (via MCU pin) to disable or make MCU pin input to “pull” up the AP63357 EN pin via resistor pull-up. That is just so you are not driving external voltage to the AP63357 EN pin without voltage being applied to the AP63357 Vin pin (just to be safe) - though there is nothing on the datasheet or EVM about any danger in doing so.
I took the resistors off, it works OK just driven from the ON/OFF controller LTC2955.
Adjusting Undervoltage Lockout (UVLO) Undervoltage lockout is implemented to prevent the IC from insufficient input voltages. The AP63356/AP63357 device has a UVLO comparator that monitors the input voltage and the internal bandgap reference. The AP63356/AP63357 disables if the input voltage falls below 3.08V. In this UVLO event, both the high-side and low-side power MOSFETs turn off. Some applications may desire higher VIN UVLO threshold voltages than is provided by the default setup. A 4µA hysteresis pull-up current source on the EN pin along with an external resistive divider (R3 and R4) configures the VIN UVLO threshold voltages as shown in Figure 37.