AIC1781 データシートの表示（PDF） - Analog Intergrations

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AIC1781

Battery Charge Controller

Analog Intergrations 

AIC1781

VCC-0.3V, the function of ∆T/∆t

detection is disabled.

PIN 7: SEL3-

PIN 8: TMR-

Determine the acceptable

voltage range of VBT pin and

mode of temperature protection

function.

Determine the period of safety

timer with an external resistor

connected to GND.

PIN 9: MODE- Determine the mode of

operation for the AIC1781.

PIN 10: SEL2 &

PIN 11: SEL1- Tri-level inputs, that jointly

control the LED display mode

and the duty of trickle charge

after the completion of fast

charge.

PIN 12: GND- Power ground.

APPLICATION INFORMATIONS

THE AIC1781 OPERATION

Power-on and Battery Pre-qualifying

When power is first applied to the AIC1781, all

internal digital circuit blocks of the AIC1781 are reset

by the internal power-on-reset circuitry and output

LEDs (depending on the setting of SEL1 and SEL2

pins) flash 3 times to indicate the initiation of power-

on. The internal control unit then examines the

battery condition through the VBT and VTS pins.

The acceptable limits of VBT pin is determined by

the input voltage of SEL3 pin and the acceptable

temperature sense voltage window for VTS pin is

0.29 VCC to 0.72 VCC. If the voltage of VBT pin fails

to fall within the predetermined acceptable limits, the

AIC1781 enters a charge-suspending mode, in

which all the internal circuitry remains in reset state.

If the voltage of VTS pin is outside the 0.29 VCC to

0.72 VCC window, action of AIC1781 is determined

by the input voltage of SEL3 pin.

Discharge-Before-Charge

The AIC1781 provides the function of discharge-

before-charge to precondition NiCd batteries which

suffer from memory effect. This function can only be

activated after the pre-qualification of battery voltage

and temperature, yet before the charge completion

is registered for the fast charge cycle.

To trigger this function, DSW pin has to be biased

to GND for over 0.18 second. After discharge

begins, LED1 and LED2 pins are both off, ICON pin

is on, and DIS pin goes high to activate an external

circuit to discharge the battery until the voltage of

VBT pin falls below 0.9V (or 0.69V, depending on

the input voltage of SEL3 pin) or DSW pin is biased

to GND for over 0.18 second again. Fast charge will

automatically start after discharge is finished. The

application circuit is included in TYPICAL

APPLICATION CIRCUIT.

Fast Charge

After the battery passes fault checks and required

discharging of the battery is completed, fast

charging begins while initial timer and safety timer

of the AIC1781 start counting. Functions of -∆V

detection, peak voltage timer, ∆T/∆t detection, and

maximum battery voltage are, however, disabled

temporarily until the initial timer period in the initial

stage of a charge cycle elapses. The initial timer

period is equal to 1/80 of safety timer.

Since the low limit of acceptable VBT voltage is

only about 0.16V during the initial timer period,

even deeply discharged batteries can easily qualify

to be fast charged subsequently.

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