a
High-Frequency Switch Mode
Li-Ion Battery Charger
ADP3806
FEATURES
Li-Ion Battery Charger
Three Battery Voltage Options
Selectable 12.525 V/16.700 V
Selectable 12.600 V/16.800 V
Adjustable
High End-of-Charge Voltage Accuracy
؎0.4% @ 25؇C
؎0.6% @ 5؇C to 55ЊC
؎0.7% @ 0؇C to 85؇C
Programmable Charge Current with Rail-to-Rail
Sensing
System Current Sense with Reverse Input Protection
Softstart Charge Current
Undervoltage Lockout
Bootstrapped Synchronous Drive for External NMOS
Programmable Oscillator Frequency
Oscillator SYNC Pin
Low Current Flag
Trickle Charge
GENERAL DESCRIPTION
The ADP3806 is a complete Li-Ion battery-charging IC. The
device combines high output voltage accuracy with constant
current control to simplify the implementation of ConstantCurrent, Constant-Voltage (CCCV) chargers. The ADP3806 is
available in three options. The ADP3806-12.6 guarantees the
final battery voltage be selected to 12.6 V or 16.8 V ± 0.6%, the
ADP3806-12.5 guarantees 12.525 V/16.7 V ± 0.6% and the
ADP3806 is adjustable using two external resistors to set the
battery voltage. The current sense amplifier has rail-to-rail
inputs to accurately operate under low drop out and short circuit
conditions. The charge current is programmable with a dc
voltage on ISET. A second differential amplifier senses the system
current across an external sense resistor and outputs a linear
voltage on the ISYS pin. The bootstrapped synchronous driver
allows the use of two NMOS transistors for lower system cost.
APPLICATIONS
Portable Computers
Fast Chargers
FUNCTIONAL BLOCK DIAGRAM
VCC
BST
DRVH SW
DRVL
CS+
PGND
BOOTSTRAPPED
SYNCHRONOUS
DRIVER
ISYS
–
+
AMP2
IN DRVLSD DRVLSD
–
+
VREF
+
BSTREG
VREF + VREG
UVLO
BIAS
+
–
AMP1
SYS+ SYS–
–
SD
CS–
–
LIMIT
2.5V
VTH
–
gm1
+
+
ISET
–
SD
+
BAT
LOGIC
CONTROL
LC
–
gm2
+
OSCILLATOR
VREF
ADP3806
AGND
SELECT
12.6/16.8
REG
REF
SYNC
CT
COMP
BATSEL
REV. 0
Information furnished by Analog Devices is believed to be accurate and
reliable. However, no responsibility is assumed by Analog Devices for its
use, nor for any infringements of patents or other rights of third parties that
may result from its use. No license is granted by implication or otherwise
under any patent or patent rights of Analog Devices.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781/329-4700
www.analog.com
Fax: 781/326-8703
© Analog Devices, Inc., 2001
