MAX77751

3.15A USB-C Autonomous Charger

for 1-Cell Li+ Batteries

www.maximintegrated.com

Maxim Integrated | 20

operates from a 4.3V to 13.7V source and delivers up to 3.15A to the battery. The battery charge current is programmable

from 500mA to 3.15A with an external resistor.

As a boost converter, the DC-DC uses energy from the battery to boost the voltage at BYP. The boosted BYP voltage

supplies the power to CHGIN as USB OTG voltage, which is fixed to 5.1V.

Maxim’s Smart Power Selector architecture makes the best use of the limited adapter power and the battery power at all

times to supply up to the Buck Current Limit from the buck to the system (supplement mode also provides additional

current from the battery to the system up to B2SOVRC). Adapter power that is not used for the system goes to charging

the battery. All power switches for charging and switching the system load between the battery and adapter power are

included on chip

—no external MOSFETs are required.

Maxim’s proprietary process technology allows for low-RDSON devices in a small solution size. The total dropout

resistance from adapter power input to the battery is 165mΩ (typ) assuming that the inductor has 0.04Ω of ESR. This

165mΩ typical dropout resistance allows for charging a battery up to 3.0A from a 5V supply. The resistance from the

BATT-to-

SYS node is 20mΩ, allowing for low-power dissipation and long battery life.

A multitude of safety features ensures reliable charging. Features include a charge timer, junction thermal regulation,

over/undervoltage protection, and short circuit protection.

The BATT-to-SYS switch has overcurrent protection (see the Battery Overcurrent Protection section for more information).

Smart Power Selector

The Smart Power Selector (SPS) architecture is a network of internal switches and control loops that distributes energy

between CHGIN, BYP, SYS, and BATT.

Figure 1

shows a simplified arrangement for the smart power selector’s power steering switches. Figure 2 shows a more

Switch and Control Loop Descriptions

or completely off. As shown in Figure 2, there are SPS control loops that monitor the current through the input switches

as well as the input voltage.

up). When operating as a buck, energy is moved from BYP to SYS. When operating as a boost, energy is moved from

SYS to BYP. SPS control loops monitor the DC-DC switch current, the SYS voltage, and the BYP voltage.

SYS Regulation Voltage

• When the DC-DC is enabled as a buck and the charger is enabled but in a non-charging state (i.e., Done, thermal

and the battery provides supplemental current.