AIC1781A 查看數據表（PDF） - Analog Intergrations

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AIC1781A

Battery Charge Controller

Analog Intergrations 

AIC1781A

by the peak voltage timer, which is in turn

determined by PEAK pin voltage, the fast charge

action is terminated.

∆T/∆t Cutoff

The ∆T/∆t detection of the AIC1781A is performed

by sensing the decrease of VTS pin voltage in a

specific timer interval dictated by the safety timer.

The fast charging terminates when the decrease of

VTS pin voltage in 56 seconds exceeds the

predetermined value set by ADJ pin input. This time

interval of 56 seconds is based on the assumption

that voltage of VTS pin is sampled once for every 8

seconds, which is also determined by safety timer.

Functioning of -∆V detection and peak voltage timer

(0∆V ) can be disabled if the MODE pin is biased to

GND. Functioning of ∆T/∆t detection can be

disabled if the voltage of ADJ pin is higher than VCC

- 0.3V.

Maximum Safety Timer Cutoff

The maximum fast charge period is determined by

the safety timer, which is set by a resistor

connected from TMR pin to GND. Safety timer, -∆V

sampling rate, and ∆T/∆t sampling rate will be

longer if the resistor value is larger. When the value

of the resistor is 100KΩ, the safety timer period

equals 80 minutes. This can be verified by biasing

MODE pin to VCC and the measured frequency on

DSW pin should be around 32.8 KHz. After the

safety timer period is finished, the fast charge

action is terminated.

Maximum Voltage and Temperature Cutoff

The AIC1781A guards against the maximum limits

for battery voltage and temperature during fast

charging. If either of these limits is exceeded, fast

charge action is terminated.

Trickle Charge

There are five different selectable duty cycles for

trickle charge after the fast charge to prevent the

loss of charge due to battery self-discharging. The

duty cycle is controlled by the setting of SEL1 and

SEL2 pins.

The functions and charging states control

mentioned above are illustrated in the function flow

chart of AIC1781A (Fig. 16)

l DESIGN GUIDE

Selecting Peak Voltage Timer (0∆V)

The voltage of PEAK pin along with safety timer

determines the period of peak voltage timer. It can

be selected according to the following table:

TABLE 1

PEAK PIN

VCC

Floating

GND

PEAK VOLTAGE TIMER

1.5% of safety timer

3.7% of safety timer

6% of safety timer

Battery Voltage Measurement

The AIC1781A measures the battery voltage

through VBT pin, which is connected to battery

positive terminal through a resistor-divider network,

as shown in Fig. 17. The input voltage of SEL3 pin

determines the acceptable limit of divided battery

voltage.

VBAT

RA

R5

2

VBT

+ 100K

RB

C5

C6

AIC1781A

Fig. 17 Battery Voltage Divider

For SEL3 > (VCC/2) + 0.4V, the suggested divider

resistance of RA and RB for the corresponding

number of battery cells are as below:

10

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