1 Features

• Wide input voltage operating range: 4.4V to 70V

• Wide battery voltage operating range: up-to 70V

– 6V up-to 48V lead-acid charging profile with

bulk, absorb and float voltage charging phases

– Charge voltage temperature compensation

• Synchronous buck charge controller with NFET

drivers

– Adjustable switching frequency from 200kHz to

600kHz

– Optional synchronization to external clock

– Integrated loop compensation with soft start

– Optional gate driver supply input for optimized

efficiency

• Bidirectional converter operation (Reverse Mode)

supporting USB-PD Extended Power Range (EPR)

– Adjustable input voltage (VAC) regulation from

3.3V to 65V with 20mV/step

– Adjustable input current regulation (RAC_SNS)

from 400mA to 20A with 50mA/step using 2mΩ

resistor

• Direct power path management for highest

efficiency to power system

– System power selection from adapter or battery

– Dynamic power management

– All N-channel FET drivers

• High accuracy

– ±0.5% charge voltage regulation

– ±3% charge current regulation

– ±3% input current regulation

• I2C controlled for optimal system performance with

resistor-programmable option

– Hardware adjustable input and output current

limits

• Integrated 16-bit ADC for voltage, current, and

temperature monitoring

• Low battery quiescent current

• High safety integration

– Adjustable input overvoltage and undervoltage

protection

– Battery Overvoltage and overcurrent protection

– Charging safety timer in CV Mode

– Thermal shutdown

• Status outputs

– Adapter present status (PG)

– Charger Operation status

• Package

– 36-pin 6mm × 5mm QFN

2 Applications

• Fire alarm control panel

• Anesthesia delivery system

• Battery backup unit (BBU)

• Elevator main control panel

• Emergency power supply

• HVAC gateway

• Intrusion control panel

3 Description

The BQ25751 is a wide input voltage, switched-mode

buck-boost battery charge controller with direct power

path control. The device offers high-efficiency battery

charging over a wide voltage range with bulk, float

and absorption charging for lead-acid batteries. The

device integrates all the loop compensation for the

buck-boost converter, thereby providing a high density

solution with ease of use.

Besides the I2C host-controlled charging mode, the

device also supports standalone charging mode via

resistor programmable limits. Input current, charge

current and charge voltage regulation targets can be

set via the ILIM_HIZ, ICHG and FB pins, respectively.