19-3923; Rev 0; 1/06
SMBus Level 2 Battery Charger with
The MAX8731 is an SMBus™ programmable multichem-
istry battery charger. The MAX8731 uses a minimal
command set to easily program the charge voltage,
charge current, and adapter current limit.
The MAX8731 charges one to four Li+ series cells and
delivers up to 8A charge current. The MAX8731 drives
n-channel MOSFETs for improved efficiency and
reduced cost. Low-offset current-sense amplifiers pro-
vide high accuracy with 10mΩ sense resistors.
The MAX8731 current-sense amplifiers provide high
accuracy (3% at 3.5A) and also provide fast cycle-by-
cycle current-mode control to protect against battery
short circuit and system load transients.
The charger employs dual remote-sense, which reduces
charge time by measuring the feedback voltage directly
at the battery, improving accuracy of initial transition into
constant-voltage mode. The MAX8731 provides 0.5%
battery voltage accuracy directly at the battery terminal.
The MAX8731 provides a digital output that indicates the
presence of the AC adapter, as well as an analog output
that indicates the adapter current within 4% accuracy.
The MAX8731 is available in a small 5mm x 5mm,
28-pin, thin (0.8mm) QFN package. An evaluation kit is
available to reduce design time. The MAX8731 is avail-
able in lead-free packages.
SMBus is a trademark of Intel Corp.
Portable Equipment with Rechargeable Batteries
21 20 19 18 17 16 15
5mm x 5mm
♦ 0.5% Battery Voltage Accuracy
♦ 3% Input Current-Limit Accuracy
♦ 3% Charge-Current Accuracy
♦ SMBus 2-Wire Serial Interface
♦ Cycle-by-Cycle Current Limit
Battery Short-Circuit Protection
Fast Response for Pulse Charging
Fast System-Load-Transient Response
♦ Dual-Remote-Sense Inputs
♦ Monitor Outputs for
Adapter Current (4% Accuracy)
AC Adapter Detection
♦ 11-Bit Battery Voltage Setting
♦ 6-Bit Charge-Current/Input-Current Setting
♦ 8A (max) Battery Charger Current
♦ 11A (max) Input Current
♦ +8V to +26V Input Voltage Range
♦ Charges Li+, NiMH, and NiCd Battery Chemistries
MAX8731ETI+ -40°C to +85°C
+Indicates lead-free packaging.
28 Thin QFN (5mm x 5mm)
Typical Operating Circuit
DAC CCS CCI
________________________________________________________________ Maxim Integrated Products 1
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.