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AIC1782

Dual-Battery Charge Controller

Analog Intergrations 

∆VTS

∆TBASE

=

0.72VCC − 0.29VCC

TH − TL

=

0 . 4 3 V CC

TH − TL

(b) Determine the safety timer to obtain the

value of ∆tBASE .

∆t ( BASE sec. )

=

56(sec. )

80(min. )

×

Safety

Timer

(min. )

(c) Determine the expected slope of ∆T / ∆t at

which temperature rises y°C in x seconds

and fast charge is subsequently cut off.

∆T

∆t

=

y

x

(d) Calculate the value of VADJ

V ADJ

=

25

×

∆V TS

∆TBASE

×

∆T

∆t

×

∆t BASE

Example

(a) Let TH=50°C, TL=0°C, VCC =5V. We have

∆VTS 0. 43 × 5

=

= 0. 043 V / ° C

∆TBASE

50 − 0

which means that VTS decreases 43mV

as temperature rises 1°C.

(b) If safety timer is equal to 80 minutes, ∆tBASE

is then 56 seconds.

(c) If fast charge should be terminated when

temperature rises 1°C in 60 seconds, then

∆T / ∆t =

1

60

=

0. 0166

(d) VADJ =25 x 0.043 x 0.0166 x 56 = 1(V)

If the temperature range is from 0°C to

50°C, the voltage of VADJ under different

setting conditions should be set as tabulat-

ed below.

AIC1782

TABLE. 3 ADJ Pin Voltage (TL=0°C, TH=50°C)

∆T / ∆t 0.75

1.0

1.25

S.T.

(°C/min.) (°C/min.) (°C/min.)

40 min. (2C)

0.37

0.5

0.63

80 min. (1C)

0.75

1.0

1.25

120 min. (0.67C) 1.12

1.5

1.87

160 min. (0.5C)

1.5

2.0

2.5

200 min. (0.4C)

1.87

2.5

3.12

240 min. (0.33C) 2.25

3.0

3.75

A similar table for temperature range from 0°C

to 60°C is as below.

TABLE. 4

TH=60°C)

ADJ Pin Voltage (TL=0°C,

∆T / ∆t 0.75

1.0

1.25

S.T.

(°C/min.) (°C/min.) (°C/min.)

40 min. (2C)

0.31

0.42

0.52

80 min. (1C)

0.62

0.84

1.05

120 min. (0.67C) 0.94

1.25

1.56

160 min. (0.5C) 1.25

1.67

2.08

200 min. (0.4C) 1.56

2.08

2.60

240 min. (0.33C) 1.87

2.5

3.12

Setting the Period of Safety Timer

The AIC1782 provides a method for linearly

adjusting the period of safety timer with an ex-

ternal resistor connected from TMR pin to GND.

The relation between safety timer length and

the external resistor (RTMR) is shown in Fig. 4.

The table following shows the resistor values for

some of the commonly chosen safety timer pe-

riods. Also shown in the table is their corre-

sponding oscillator frequencies.

18

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