AIC1781
Battery Charge Controller
FEATURES
Fast Charge Control of NiMH/NiCd Batteries,
even with a Fluctuating Charging Current.
Fast Charge Termination by:
∆
T /
∆
t ,
−∆V
,
0
∆
V , Safety Timer, Maximum Temperature,
Maximum Voltage.
Linearly Adjustable
∆
T /
∆
t Detection Slope and
Safety Timer.
Adjustable Peak Voltage Timer for 0
∆
V .
Battery Voltage Protection Range Selectable.
Selectable Battery Temperature Protection
Mode.
Protection against Battery Voltage and Battery
Temperature Faults.
Selectable LED Display Mode for Battery Status.
Five Pulsed Trickle Charge Modes.
Discharge-before-Charge Function Available for
Eliminating Memory Effect.
Quick and Easy Testing for Production.
16-pin DIP or SO Packages.
DESCRIPTION
The AIC1781 fast charge controller IC is designed
for intelligent charging of NiMH or NiCd batteries
without the risk of overcharge.
−∆V
detection
(-0.25%), 0
∆
V detection (peak voltage timer)
and
∆
T /
∆
t detection are the primary methods
employed by the AIC1781 to terminate fast charge.
The fast charge can also be cut off by maximum
battery voltage and maximum battery temperature
detection along with the safety timer to prevent
charging under fault conditions of the charging
system or the battery itself.
Both
∆
T /
∆
t and
−∆V
detection methods have
been proved powerful in terminating fast charging
for NiMH and NiCd batteries. The AIC1781 utilizes
the combination of these two methods to achieve
reliable decision of ending fast charge and prevent
misaction caused by using
−∆V
detection alone
under certain conditions. Fig. 1 shows an example
of charging curve of a battery charged by a
fluctuating current from a NiMH battery charger
which uses the AIC1781 controller IC to achieve
optimal charging. This technique, in cooperating
with the 0
∆
V detection (peak voltage timer), is
particularly suitable for NiMH batteries, whose
voltage drop is hardly significant yet temperature
rises rapidly. The
∆
T /
∆
t or
−∆V
detection
circuitry may be disabled independently for
different applications, such as system-integrated
chargers, chargers with varying charge current, or
battery packs lack of temperature sensing
thermistor.
The safety timer period, mode of battery
temperature protection, battery voltage protection
range, pulsed trickle charge duty, and LED display
mode are all adjustable or selectable. Discharge-
before-charge function is included to get rid of
memory effect of NiCd batteries without the risk of
overdischarging. Test mode is provided for charger
manufactures to dramatically reduce production
test time.
www.analog.com.tw
APPLICATIONS
Battery Fast Chargers for:
Mobile Phones.
Notebook and Laptop Personal Computers.
Portable Power Tools and Toys.
Portable Communication Equipments.
Portable Video & Stereo Equipments.
1.55
100
Charge Current = 600 mA
Cell Capacity = 550 mA
NiMH Battery
Cell Voltage
1.35
60
1.25
40
Temperature
1.15
0
10
20
30
40
50
60
20
Charge Time (min.)
Fig. 1 Battery Charging Characteristics Resulting
from an AIC1781-Controlled Charger with a
Fluctuating Charging Current
Analog Integrations Corporation
DS-1781-00
4F, 9, Industry E. 9th Rd, Science Based Industrial Park, Hsinchu Taiwan, ROC
TEL: 886-3-5772500
FAX: 886-3-5772510
Temperature (°C)
Cell Voltage (V)
1.45
80
1
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