Secondary Side, Off-Line
Battery Charger Controllers
a
ADP3810/ADP3811
FEATURES
off-line applications, the output directly drives the diode side of
an optocoupler to give isolated feedback control of a primary
side PWM. The circuitry includes two gain (gm) stages, a preci-
sion 2.0 V reference, a control input buffer, an Undervoltage
Lock Out (UVLO) comparator, an output buffer and an over-
voltage comparator.
Programmable Charge Current
High Precision Battery Voltage Limit
Precision 2.000 V Reference
Low Voltage Drop Current Sense: 300 mV Full Scale
Full Operation in Shorted and Open Battery Conditions
Drives Diode-Side of Optocoupler
Wide Operating Supply Range: 2.7 V to 16 V
Undervoltage Lockout
SO-8 Package
ADP3810
Internal Precision Voltage Divider for Battery Sense
Four Final Battery Voltage Options Available: 4.2 V,
8.4 V, 12.6 V, 16.8 V
The current limit amplifier senses the voltage drop across an
external sense resistor to control the average current for charg-
ing a battery. The voltage drop can be adjusted from 25 mV
to 300 mV, giving a charging current limit from 100 mA to
1.2 amps with a 0.25 Ω sense resistor. An external dc voltage
on the VCTRL input sets the voltage drop. Because this input
is high impedance, a filtered PWM output can be used to set
the voltage.
ADP3811
As the battery voltage approaches its voltage limit, the voltage
sense amplifier takes over to maintain a constant battery volt-
age. The two amplifiers essentially operate in an “OR” fash-
ion. Either the current is limited, or the voltage is limited.
Adjustable Final Battery Voltage
APPLICATIONS
Battery Charger Controller for:
LiIon Batteries (ADP3810)
NiCad, NiMH Batteries (ADP3811)
The ADP3810 has internal thin-film resistors that are trimmed
to provide a precise final voltage for LiIon batteries. Four volt-
age options are available, corresponding to 1-4 LiIon cells as
follows: 4.2 V, 8.4 V, 12.6 V and 16.8 V.
GENERAL DESCRIPTION
The ADP3810 and ADP3811 combine a programmable current
limit with a battery voltage limit to provide a constant current,
constant voltage battery charger controller. In secondary side,
The ADP3811 omits these resistors allowing any battery volt-
age to be programmed with external resistors.
FUNCTIONAL BLOCK DIAGRAM
V
V
V
V
CC
REF
SENSE
R1
GND
CS
ADP3810
ONLY
UVLO
UVLO
1.5MΩ
80kΩ
V
REF
V
REF
R2
V
CTRL
ADP3810/
ADP3811
GM1
GM2
UVLO
GM
COMP
OUT
REV. 0
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© Analog Devices, Inc., 1996