19-1182; Rev 2; 12/98
N KIT M EET
Charges 1 to 4 Lithium-Ion Battery Cells
±0.75% Voltage-Regulation Accuracy
Using 1% Resistors
Provides up to 4A without Excessive Heating
Uses Low-Cost Set Resistors and
Up to 24V Input
Up to 18V Maximum Battery Voltage
300kHz PWM Operation: Low-Noise,
Stand-Alone Operation; No Microcontroller
The MAX745 provides all functions necessary for
charging lithium-ion battery packs. It provides a regu-
lated charging current of up to 4A without getting hot,
and a regulated voltage with only ±0.75% total error at
the battery terminals. It uses low-cost, 1% resistors to
set the output voltage, and a low-cost N-channel MOS-
FET as the power switch.
The MAX745 regulates the voltage set point and charg-
ing current using two loops that work together to transi-
tion smoothly between voltage and current regulation.
The per-cell battery voltage regulation limit is set
between 4.0V and 4.4V using standard 1% resistors,
and then the number of cells is set from 1 to 4 by pin-
strapping. Total output voltage error is less than ±0.75%.
For a similar device with an SMBus™ microcontroller
interface and the ability to charge NiCd and NiMH cells,
refer to the MAX1647 and MAX1648. For a low-cost
lithium-ion charger using a linear-regulator control
scheme, refer to the MAX846A.
Lithium-Ion Battery Packs
Desktop Cradle Chargers
Pin Configuration appears on last page.
0°C to +70°C
-40°C to +85°C
are tested at T
___________________________________________________Typical Operating Circuit
(UP TO 24V)
WITH 1% RESISTORS
1–4 Li+ CELLS
(UP TO 18V)
SMBus is a trademark of Intel Corp.
Maxim Integrated Products
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800.
For small orders, phone 1-800-835-8769.