ADP2291_15 Datasheet, PDF (14/20 Pages) Analog Devices – Compact, 1.5 A Linear Charger for Single-Cell Li Battery

ADP2291
TYPICAL APPLICATION CIRCUIT
A typical application circuit is shown in Figure 22. The circuit is
capable of a 750 mA charge current for an input voltage of 4.5 V
to 6 V. Higher input voltages can be used, but the increased power
dissipation of the pass device must be taken into account.
INPUT
4.6V–12V
D1
BAT1000
CIN
2.2µF
RS
200mΩ
Q1
FZT549
CS
DRV
IN
BAT
ADP2291
CHG
GND
TIMER
ADJ
CTIMER
100nF
+
COUT
10µF
Figure 22. Typical Application Circuit
CHARGE TERMINATION
In some applications, the charger is required to terminate charg-
ing when the EOC threshold is reached. Automatic charger
restart is not desired. Adding components R1, C1, and Q2
terminates charging when the CHG pin opens and prevents
further charging until the adapter is removed and reasserted.
D1
BAT1000
INPUT
4.6V–12V
CIN
2.2µF
R1
500kΩ
RS
200mΩ
Q1
FZT549
CS
DRV
IN
BAT
ADP2291
CHG
GND
TIMER
ADJ
CTIMER
100nF
C1
100nF
Q2
2N7002
COUT
10µF
+
LI-ION
CELL
Figure 23. Self-Termination Circuit
SELECTABLE CHARGE CURRENT
In applications where the charge current needs to be selectable,
use the circuit shown in Figure 24. This circuit allows a proces-
sor to determine if the charge current needs to be reduced due
to an input source limitation or a different battery capacity
option or simply to reduce the stress on the pass transistor.
R2 and Q2 allow the charge current to be selected between
high, which results in a charge current of 750 mA; and low,
which results in a charge current of 250 mA.
INPUT
4.6V–12V
D1
BAT1000
CIN
2.2µF
LOW/HIGH
RS
200mΩ
Q1
FZT549
CS
DRV
IN
CHG
ADP2291
BAT
GND
TIMER
ADJ
CTIMER
100nF
R2
100kΩ
Q2
2N7002
COUT
10µF
+
LI-ION
CELL
Figure 24. Selectable Charge Current Circuit
THERMAL PROTECTION
In applications where the overall size must be small or the input
voltage range is wide, adding thermal regulation is suggested.
This allows the charger to monitor the temperature of the pass
device and decrease the charge current as the temperature
increases. By adding an NTC thermistor to the ADJ pin, it is
possible to accomplish this; however, care is still required to
ensure that the power dissipation of the pass device is not
exceeded.
INPUT
4.6V–12V
D1
BAT1000
CIN
2.2µF
RS
200mΩ
Q1
FZT549
CS
DRV
COUT
10µF
IN
CHG
ADP2291
BAT
GND
TIMER
CTIMER
100nF
ADJ
R1
470k
NTC LOCATED
NEAR Q1
R2
100k
+
LI-ION
CELL
Figure 25. Thermal Regulation Circuit
Some suggested NTC thermistor suppliers are listed in Table 6.
Table 6. NTC Thermistor Manufacturers
Vendor
Part Number
Website
BetaTHERM SMD2500KJ435J
www.betatherm.com
Murata
NCP18WM474J
www.murata .com
Panasonic ERTJ0EV474J
www.panasonic.com
Vishay
2322 615 1.474
www.vishay.com
Rev. A | Page 14 of 20