AIC1781

Battery Charge Controller

Analog Integrations Corporation

4F, 9, Industry E. 9th Rd, Science Based Industrial Park, Hsinchu Taiwan, ROC

www.analog.com.tw

DS-1781-00

TEL: 886-3-5772500

FAX: 886-3-5772510

1

FEATURES

Fast Charge Control of NiMH/NiCd Batteries,

even with a Fluctuating Charging Current.

Fast Charge Termination by:

∆∆

T / t ,

−∆V,

0V

∆ , Safety Timer, Maximum Temperature,

Maximum Voltage.

Linearly Adjustable

∆∆

T / t Detection Slope and

Safety Timer.

Adjustable Peak Voltage Timer for 0V

∆ .

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.

APPLICATIONS

Battery Fast Chargers for:

Mobile Phones.

Notebook and Laptop Personal Computers.

Portable Power Tools and Toys.

Portable Communication Equipments.

Portable Video & Stereo Equipments.

0

10

2030405060

1.15

1.25

1.35

1.45

1.55

100

80

60

40

20

Temperature

Cell Voltage

Charge Time (min.)

Charge Current = 600 mA

Cell Capacity = 550 mA

NiMH Battery

Fig. 1 Battery Charging Characteristics Resulting

from an AIC1781-Controlled Charger with a

Fluctuating Charging Current

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%), 0V

∆

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 0V

∆

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.