1 Features

• Input voltage up to 30-V tolerant

• Automatic Sleep Mode for low power consumption

– 350-nA battery leakage current

– 85-μA input leakage current when charge

disabled

• Supports 1- to 6-cell NiMH with intermittentcharging

• External resistor programmable operation

– VSET to set NiMH series cell-count from 1s to

6s

– ISET to set charge current from 10 mA to 800

mA

– TMR to set charge safety timer duration from

4 hr to 22 hr

• High accuracy

– ±0.5 charge voltage accuracy

– ±10 charge current accuracy

• Charging features

– NTC thermistor input to monitor battery

temperature

– Cold and hot temperature charging disabled

– VOUT_OVP reduced at cool temperatures

– TS pin for charging function control

– Open-drain output for status and fault indication

• Integrated fault protection

– 18-V IN overvoltage protection

– VSET based OUT overvoltage protection

– 1000-mA overcurrent protection

– 125°C thermal regulation; 150°C thermal

shutdown protection

– OUT short-circuit protection

– VSET, ISET, TMR pins short/open protection

2 Applications

• Fleet management, asset tracking

• Gas detector

• Electronic point of sales (ePOS)

• Beauty and grooming

• Electric toothbrush

• Pulse oximeter

• Blood glucose monitor

• Infrared thermometer

3 Description

The BQ25172 is an integrated 800-mA linear charger

for 1-cell to 6-cell NiMH batteries targeted at industrial

and medical applications. The device has a single

power output that charges the battery. The system

load can be placed in parallel with the battery, as

long as the average system load does not prevent the

battery from being charged fully within the safety timer

duration. When the system load is placed in parallel

with the battery, the charge current is shared between

the system and the battery.

The device charges NiMH cells in constant current

mode only and terminates the charge cycle when

the programmable timer expires or the battery

voltage exceeds the VOUT_OVP threshold. In all

charge phases, an internal control loop monitors

the IC junction temperature and reduces the charge

current if an internal temperature threshold TREG, is

exceeded.

The charger power stage and charge current sense

functions are fully integrated. The charger function

has high accuracy current, charge status display, and

timer-based charge termination. The series cell-count,

charge current, and charge timer are programmable

through external resistors. Intermittent charging allows

a NiMH battery to automatically recharge for a

reduced timer duration once its voltage falls below the

recharge threshold.