MAX77751

3.15A USB-C Autonomous Charger

for 1-Cell Li+ Batteries

www.maximintegrated.com

Maxim Integrated | 24

INIT State

From any state shown in Figure 6 except thermal shutdown, the INIT state is entered whenever the charger inputs that

CHGIN is invalid or the charger timer is suspended.

While in the INIT state, the charger current is 0mA, the charge timer is forced to 0, and the power to the system is provided

by the battery.

To exit the INIT state, the charger input must be valid.

Buck State

The chip has a state where battery charging is disabled while the charger input CHGIN is valid. The state is called buck

state. Entering or leaving buck state is controlled by the voltage of the ITOPOFF pin. If the voltage of this pin is pulled

only when CHGIN is valid, charging can be enabled or disabled. Therefore, the external device (i.e., MCU) should check

using the INOKB signal if CHGIN is valid before trying to enable or disable charging.

Precharge State

The following events cause the state machine to exit this state:

state.

The precharge state works with battery voltages down to 0V. The low 0V operation typically allows this battery charger to

recover batteries that have an “open” internal pack protector. Typically, an internal pack protection circuit opens if the

b

attery has seen an overcurrent, undervoltage, or overvoltage. When a battery with an “open” internal pack protector is

used with this charger, the precharge state current flows into the 0V battery

—this current raises the pack’s terminal voltage

to the voltage level where the internal pack protection switch closes.

Note that a normal battery typically stays in the precharge state for several minutes or less. Therefore, a battery that stays

Trickle Charge State

• The charger input current is lower than the input current limit

• The charger input voltage is low

• The charger is in thermal foldback

• The system load is consuming adapter current. Note that the system load always gets priority over the battery charge

current.

The following events cause the state machine to exit this state:

charge constant current state.

state.

Note that a normal battery typically stays in the trickle charge state for several minutes or less. Therefore, a battery that