MAX77751

3.15A USB-C Autonomous Charger

for 1-Cell Li+ Batteries

www.maximintegrated.com

Maxim Integrated | 21

Input Validation

The charger input is compared with several voltage thresholds to determine if it is valid. A charger input must meet the

following three characteristics to be valid:

Once CHGIN is above the UVLO threshold, the information (together with LIN2SYS, as shown in Figure 3) is latched

and can only be reset when the charger is in the adaptive input current loop (AICL) and the input current is lower than

Figure 3. CHGIN Valid Signal Generation Logic

finishes USB detection, the switcher in the chip starts. The system can detect that a valid charger is present by the INOKB

output signal, which is issued when the switcher starts and the VCHGIN_VLD signal is valid, as shown in Figure 4.

Figure 4. INOKB Signal Generation Logic

Input Current Limit

After the charger-type detection is done, the MAX77751 automatically configures the input current limit to the highest

settings that the source can provide. If the input source is not a standard power source described by BC1.2 or USB Type-

C or is not a proprietary charger type that the MAX77751 can detect, the MAX77751 sets the input current limit to 3A.

USB_CHGR_EN

INPUT IS NOT

UNDERVOLTAGE

INPUT IS NOT

OVERVOLTAGE

LOW INPUT TO

SYS HEADROOM

LIN2SYS

ADAPTIVE INPUT

CURRENT LOOP

I_IULO

INPUT CURRENT

LOW

S

R

Q