SS6781ACSTB datasheet(14/18 Pages) SSC

14 / 18 page

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14 of 18

SS6781A(G)

1/11/2005 Rev.2.10

Procedure

(a) First, determine the temperature protection

limits TH and TL. Then, substitute TH & TL into

the following equation:

0.43V

0.29V

0.72V

BASE

−

∆

(b) Determine the safety timer to obtain the value of

∆t

BASE .

(min

Timer

Safety

(min

56(sec.)

(sec.)

tBASE

∆

T / t at

which temperature rises y

°C in x seconds and

fast charge is subsequently cut off.

∆

(d) Calculate the value of VADJ

BASE

ADJ

∆

Example

(a) Let TH=50

°C, TL=0°C, VCC =5V. We have

∆

0.43

0.043V/ C

BASE

−

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.

temperature rises 1

°C in 60 seconds, then

0.0166

∆

(d) VADJ =30 x 0.043x 0.0166 x 56 = 1.2(V)

If the temperature range is from 0

°C to 50°C,

the voltage of VADJ under different setting

conditions should be set as tabulated below.

TABLE 6

ADJ pin Voltage (TL=0

°C, TH=50°C)

∆

T / t

S.T.

0.75

(

°C/min.)

1.0

(

°C/min.)

1.25

(

°C/min.)

40 min. (2C)

0.45

0.60

0.75

80 min. (1C)

0.90

1.20

1.50

120 min. (0.67C)

1.35

1.80

2.25

160 min. (0.5C)

1.80

2.40

3.01

200 min. (0.4C)

2.25

3.01

3.76

240 min. (0.33C)

2.70

3.61

4.51

A similar table for temperature range from 0

°C to

°C is as below.

TABLE 7

ADJ Pin Voltage (TL=0

°C, TH=60°C)

∆

T / t

S.T.

0.75

(

°C/min.)

1.0

(

°C/min.)

1.25

(

°C/min.)

40 min. (2C)

0.37

0.50

0.62

80 min. (1C)

0.75

1.00

1.25

120 min. (0.67C)

1.12

1.50

1.88

160 min. (0.5C)

1.50

2.00

2.50

200 min. (0.4C)

1.88

2.50

3.13

240 min. (0.33C)

2.25

3.01

3.76

VBT Range and Temperature Protection

The acceptable voltage range of VBT pin and

mode

temperature

protection

function

determined by the voltage of SEL3 pin, shown as

the following:

(a)

SEL3 > VCC - 0.3V

Acceptable VBT Range:

Before initial timer: 0.16V~2.7V

After initial timer: 0.69V~2.7V

Temperature Protection Mode:

Entering

charge-suspending

mode

when

temperature is either too low or too high,

same as abnormal battery voltage. Latch for

charge-suspending function is provided for

high temperature protection, but not for low

temperature protection.

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