MAX77751 datasheet(22/40 Pages) MAXIM

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MAX77751

3.15A USB-C Autonomous Charger

for 1-Cell Li+ Batteries

www.maximintegrated.com

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Input Voltage Regulation Loop

An input voltage regulation loop allows the charger to be well behaved when it is attached to a poor-quality charge source.

The loop improves performance with relatively high resistance charge sources that exist when long cables are used or

devices are charged with noncompliant USB hub configurations.

The input voltage regulation loop automatically reduces the input current limit in order to keep the input voltage at

VCHGIN_REG. If the input current limit is reduced to ICHGIN_REG_OFF (50mA typ) and the input voltage is below

VCHGIN_REG, then the charger input is turned off.

Input Self-Discharge

When the charge source is removed, the input voltage decays below the UVLO threshold in time (tINSD). The input self-

discharge is implemented with a 44kΩ resistor (RINSD) from the CHGIN input to ground.

Charger States

The MAX77751 utilizes several charging states to safely and quickly charge batteries, as shown in Figure 5 and Figure 6.

Figure 5 shows an exaggerated view of a Li+/Li-Poly battery progressing through the following charge states when there

is no system load and the die and battery are close to room temperature: precharge ➔

trickle ➔ fast-charge ➔ top-off

➔ done.

Figure 5. Li+/Li-Poly Charge Profile

VTRICKLE

VBATTREG

ICHG ISET

ITO

ITRICKLE

VPRECHG

TIME

VRSTRT

IPRECHG

CHARGER

ENABLED

NOT TO SCALE, VCHGIN = 5.0V, ISYS = 0A, TJ = +25°C

MAX77751 Datasheet(PDF) 22 Page - Maxim Integrated Products