AIC1781A

Battery Charge Controller

Analog Integrations Corporation

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

DS-1781AP-01

011604

TEL: 886-3-5772500

FAX: 886-3-5772510

www.analog.com.tw

1

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Fast Charge Control of NiMH/NiCd Batteries,

even with a Fluctuating Charging Current.

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Fast Charge Termination by: ∆

∆

T / t , −∆V ,

0 V

∆ , Safety Timer, Maximum Temperature,

Maximum Voltage.

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Linearly Adjustable ∆

∆

T / t Detection Slope and

Safety Timer.

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Adjustable Peak Voltage Timer for 0 V

∆ .

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Battery Voltage Protection Range Selectable.

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Selectable

Battery

Temperature

Protection

Mode.

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Protection against Battery Voltage and Battery

Temperature Faults.

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Selectable LED Display Mode for Battery Status.

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Five Pulsed Trickle Charge Modes.

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Discharge-before-Charge Function Available for

Eliminating Memory Effect.

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Quick and Easy Testing for Production.

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16-pin DIP or SO Packages.

Battery Fast Chargers for:

l

Mobile Phones.

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Notebook and Laptop Personal Computers.

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Portable Power Tools and Toys.

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Portable Communication Equipments.

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Portable Video & Stereo Equipments.

0

10

20

30

40

50

60

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

AIC1781A-Controlled

Charger

with

a

Fluctuating Charging Current

The

AIC1781A 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 AIC1781A 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 AIC1781A

utilizes the combination of these two methods to

achieve reliable decision of ending fast charge and

prevent misacting 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 AIC1781A 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.