In some application cases, the
charge current needs to be controlled by a MCU. In those cases, the GPIOs of the MCU can
be used for on/off control of the charge current setting resistors R
ICHG1 and
R
ICHG2 as shown in
Figure 9-7. With GPIO1 and GPIO2 on/off control, three levels of charge current
can be programmed. If the charge current needs to be controlled smoothly in a wide
range, a PWM output of the MCU can be used to generate an average DC voltage output to
program the charge current as shown in the
Figure 9-7. The charge current can be calculated as: (1V - V
PWM) / (R
ICHG1
+ R
ICHG2). V
PWM is the averaged DC voltage of the PWM output and
it must be lower than 1 V. The regulated voltage at the ICHG pin is 1 V.