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

FEATURES

Fast Charge Control of NiMH/NiCd Batteries,
even with a Fluctuating Charging Current.

Fast Charge Termination by:

T / t ,

V ,

0 V

, Safety Timer, Maximum Temperature,

Maximum Voltage.

Linearly Adjustable

T / t Detection Slope and

Safety Timer.

Adjustable Peak Voltage Timer for 0 V

Battery Voltage Protection Range Selectable.

Selectable Battery Temperature Protection
Mode.

Protection against Battery Voltage and Battery
Temperature Faults.

Selectable LED Display Mode for Battery Status.

Five Pulsed Trickle Charge Modes.

Discharge-before-Charge Function Available for
Eliminating Memory Effect.

Quick and Easy Testing for Production.

16-pin DIP or SO Packages.

APPLICATIONS

Battery Fast Chargers for:

Mobile Phones.

Notebook and Laptop Personal Computers.

Portable Power Tools and Toys.

Portable Communication Equipments.

Portable Video & Stereo Equipments.

1.15

1.25

1.35

1.45

1.55

100

Temperature (

)

Temperature

Cell Voltage

Cell Voltage (V)

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

DESCRIPTION

The AIC1781A fast charge controller IC is
designed for intelligent charging of NiMH or NiCd
batteries without the risk of overcharge.

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.

AIC1781A

Discharge-before-charge function is included to
get rid of memory effect of NiCd batteries without
the risk of overdischarging. Test mode is provided
for charger manufactures to dramatically reduce

production test time.

TYPICAL APPLICATION CIRCUIT

PEAK

VBT

DIS

VTS

VCC

ADJ

SEL3

TMR

MODE

SEL2

SEL1

GND

LED1

LED2

ICON

DSW

AIC1781A

300K

91K

R10

100K

4.7

0.1

C10

47nF

R15

680

270

20/5W

SW1

PB SW

R12

100K

R16

680

R17

680

R14

200K

C11

100

R11

100K

0.1

R13

470K

MMBT2222A

50K

LED2

GREEN

LED3

RED

LED1

YELLOW

MPS2222A

220

C12

C13

120/0.5W

BAT1

ATTERY

THERMISTOR

VIN
11~15V

220

470P

0.3/1W

GND

VCC

BOOST

AIC1563

220

390K

IN4148

IN5819

1N5819

VIN

VOUT

GND

78L05

**3~5 NiMH/NiCd cells.
Note: Charge Current=0.3/RS Ampere

Safety Timer: 80min

Battery Charge Circuit for Fluctuating Charging Current Application

AIC1781A

ORDERING INFORMATION

TOP VIEW

PIN CONFIGURATION

PEAK

VBT

DIS

VTS

VCC

ADJ

SEL3

SEL1

SEL2

MODE

LED1

GND

TMR

DSW

ICON

LED2

PACKING TYPE
TR: TAPE & REEL
TB: TUBE

PACKAGE TYPE
N: PLASTIC DIP
S: SMALL OUTLINE

C: COMMERCIAL
P: LEAD FREE COMMERCIAL
(Available for PS only)

Example: AIC1781CSTR

in SO-16 Package & Tape & Reel Packing Type

(CN is not available in TR packing type)

AIC1781PSTR

in SO-16 Lead Free Package & Tape & Reel
Packing Type

AIC1781AXXXX

ABSOLUTE MAXIMUM RATINGS

Supply Voltage

............................................... ... ... ... ........................................ 5.5V

DC Voltage Applied on any pin ......................... ... ... ... ... ...................................... 5.5V
Sink current of ICON pin, LED1 and LED2 pin .......................... ... ... .................. 20mA
Operating Temperature Range ........................................ ... ... ... ... .............. 0

C~ 70

Storage Temperature Range ................................................ ... ... ... ...... -65

C~ 150

TEST CIRCUIT

PEAK

DSW

VBT

ICON

DIS

LED2

VTS

LED1

VCC

GND

ADJ

SEL1

SEL3

SEL2

TMR

MODE

V2 (3V)

V1 (0.95V)

(5V)

GREEN

ORANGE

RED

560

AIC1781A

YELLOW

VOLTAGE

SOURCE

VOLTAGE SOURCE

100K

560

AIC1781A

ELECTRICAL CHARACTERISTICS

=25

C, V

=5V, unless otherwise specified.)

PARAMETER

TEST CONDITIONS

SYMBOL

MIN.

TYP.

MAX. UNIT

Supply Voltage

4.5

5.0

5.5

Supply Current

1.1

Battery Low

During Initial Timer

0.11

0.16

0.21

After Initial Timer

(SEL3>3V)

0.63

0.69

0.75

(SEL3<2V)

1.1

1.2

1.30

Battery High

(SEL3>3V)

2.6

2.7

2.80

Voltage Protection Limit

(SEL3<2V)

1.9

2.0

2.10

Temperature High

1.35

1.45

1.55

Temperature Sense Limit

Temperature Low

3.5

3.6

3.70

Output impedance of DIS Pin

DIS

100

LED1, LED2, ICON pins

Output Impedance

OFF

Source Current Capability

SEL3 pin

DSW pin

SEL3

DSW

5.5

MODE, PEAK, SEL1,
SEL2 pins

300

Input Impedance

VBT, VTS, ADJ pins

Recommended External

Resistor of TMR pin

TMR

100

1000

V Detection Level w.r.t.*

Peak Value

-0.25

* w.r.t.: with respect to

AIC1781A

TYPICAL PERFORMANCE CHARACTERISTICS

=25

C, R2=100K

, V

=5V,

refer to Test Circuit)

4.4

4.6

4.8

5.0

5.2

5.4

0.84

0.90

0.96

1.02

1.08

Supply Current (mA)

(V)

Fig. 2 Supply Current vs. Supply Voltage

Safety Timer (min)

(V)

Fig. 3 Safety Timer vs. Supply Voltage

4.4

4.6

4.8

5.0

5.2

5.4

5.6

78.0

78.5

79.0

79.5

80.0

80.5

81.0

81.5

(V)

Frequency (Hz)

Fig. 4 LED Flashing Frequency vs.

Supply Voltage

4.4

4.6

4.8

5.0

5.2

5.4

5.6

3.6

3.8

4.0

4.2

4.4

Supply Current (mA)

Temperature (

Fig.5 Supply Current vs. Temperature

0.80

0.85

0.90

0.95

1.00

1.05

Temperature (

Safety Timer (min)

Fig. 6 Safety Timer vs. Temperature

Frequency (Hz)

Temperature (

Fig. 7 LED Flashing Frequency vs.

Temperature

-20

3.4

3.6

3.8

4.0

4.2

4.4

4.6

4.8

5.0

AIC1781A

TYPICAL PERFORMANCE CHARACTERISTICS

(Continued)

Temperature (

(V)

Fig. 8 VBT (High) Limit vs. Temperature

(SEL3>3V)

2.60

2.64

2.68

2.72

2.76

2.80

Temperature (

(V)

Fig. 9 VBT (High) Limit vs. Temperature

(SEL3<2V)

1.92

2.04

2.16

2.28

0.12

0.14

0.16

0.18

0.20

Temperature (

(V)

Fig.10 VBT (Low) Limit vs. Temperature

(During Initial Timer)

Temperature (

Output Impedance (O)

Fig.11 Output Impedance vs. Temperature

(LED1, LED2, ICON Pins)

3.2

3.4

3.6

3.8

4.0

Temperature (

(V)

Fig.12 VTS (Low Temp) Limit vs.

Temperature

1.35

1.40

1.45

1.50

1.55

Temperature (

(

)

Fig.13 V

(High Temp) Limit vs.

Temperature

AIC1781A

Temperature (

(V)

Fig. 14 V

(Low) Limit vs. Temperature

(SEL3>3V, After Initial Timer)

0.68

0.8

Temperature (

(

)

Fig.15

VBT (Low) Limit vs. Temperature

(SEL3<2V, After Initial Timer)

1.0

1.1

1.2

1.3

1.4

1.5

BLOCK DIAGRAM

Charge Control

State Machine

SEL1

SEL2

ADJ

SEL3

ICON

LED1

LED2

VTS

VBT

DSW

DIS

Discharge

Control Unit

Battery

Voltage

Protection

13-bit

A/D

Battery Temp.

Protection

Display
Control

Unit

TMR

Oscillator

VCC

GND

Bandgap

Reference &

Voltage

Regulator

PEAK

MODE

Selection

Peak Voltage

Timer Control

Battery Voltage &

Temperature

Portection Setting

LED`s Display

& Trickle Pulse

Duty Setting

t Detection

Setting

Charge

Control Unit

AIC1781A

PIN DESCRIPTIONS

PIN 1: PEAK- Tri-level input, determining the

period of peak voltage timer.
(See 0

V cut-off section in

application informations.)

PIN 2: VBT- Divided battery voltage input to

sense the battery voltage.

PIN 3: DIS-

Push-pull output, used to
control an external transistor to
discharge the battery. DIS is
active high when the
AIC1781A enters discharge
mode.

PIN 4: VTS- The battery cell temperature is

represented as a voltage input
to the AIC1781A at this pin.
The acceptable voltage range
of VTS pin is 0.29V

0.72V

. The battery

temperature is regarded as too
high if the voltage of VTS pin is
lower than 0.29V

, and is

otherwise regarded as too low
if the voltage of VTS pin is
higher than 0.72V

PIN 5: VCC- Power supply input at 5V

10%.

PIN 6: ADJ- For adjusting the slope of

Acceptable voltage range for
this pin is approximately 0.28V
to 3.8V. If voltage higher than
VCC-0.3V, the function of

t detection is disabled.

PIN 7: SEL3-

Determine the acceptable
voltage range of VBT pin and
mode of temperature
protection function.

PIN 8: TMR- Determine the period of safety

timer with an external resistor
connected to GND.

PIN 9: MODE- Determine the mode of

operation for the AIC1781A.

PIN 10: SEL2 - Tri-level inputs, that jointly

control the LED display mode
and the duty of trickle charge
after the completion of fast
charge.

PIN 11: SEL1- The same as Pin 10.

PIN 12: GND- Power ground.

PIN 13: LED1 &
PIN 14: LED2- Open-drained outputs used to

indicate the battery charging
status. Two modes of display
are available, depending on
the setting of SEL1 and SEL2
pins.

PIN 15: ICON- Open-drained output, used to

control the charging current to
the battery.

PIN 16: DSW- Controlling the function of

discharge- before- charge.
(See discharge- before- charge
subsection in application
informations).

AIC1781A

APPLICATION INFORMATIONS

THE AIC1781A OPERATION

Power-on and Battery Pre-qualifying
When power is first applied to the AIC1781A, all
internal digital circuit blocks of the AIC1781A 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 V

to 0.72 V

. If the voltage of VBT pin fails

to fall within the predetermined acceptable limits,
the AIC1781A 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 V

0.72 V

window, action of AIC1781A is determined

by the input voltage of SEL3 pin.

Discharge-Before-Charge
The AIC1781A 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 AIC1781A start counting. Functions of -

detection, peak voltage timer,

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.

In the course of fast charge, the AIC1781A
constantly monitors the voltages at VBT and VTS
pins. The fast charge process is switched to trickle
charge when any one of the following situations is
encountered, which are explained below:

Negative delta voltage (-

Peak voltage timer (0 V

)

Delta temperature/ delta time (

Maximum charge time

Maximum battery voltage

Maximum battery temperature

V Cutoff

The AIC1781A makes a voltage sampling at VBT
pin every 4 seconds when safety timer period is set
equal to 80 minutes. If a negative delta voltage of
0.25% compared to its peak value is detected at
VBT pin, the fast charge cycle is terminated.

V Cutoff

If the battery voltage stays at its peak value or
decreases very slowly for the duration determined

AIC1781A

by the peak voltage timer, which is in turn
determined by PEAK pin voltage, the fast charge
action is terminated.

t Cutoff

The

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

detection can be

disabled if the voltage of ADJ pin is higher than V

- 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, -

sampling rate, and

sampling rate will be

longer if the resistor value is larger. When the value
of the resistor is 100K

, the safety timer period

equals 80 minutes. This can be verified by biasing
MODE pin to V

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)

DESIGN GUIDE

Selecting Peak Voltage Timer (0

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

PEAK VOLTAGE TIMER

1.5% of safety timer

Floating

3.7% of safety timer

GND

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.

BAT

4.7

100K

0.1

AIC1781A

VBT

Fig. 17 Battery Voltage Divider

For SEL3 > (V

/2) + 0.4V, the suggested divider

resistance of RA and RB for the corresponding
number of battery cells are as below:

AIC1781A

TABLE 2

BATTERY

CELLS

RA/RB

RA (K

)

RB (K

)

2~4

240

120

3~6

3.3

300

4~8

4.9

300

5~10

6.4

300

6~12

7.8

310

8~16

10.8

390

For SEL3 < (V

/2) -0.4V, the suggested divider

resistance of RA and RB for the corresponding
number of battery cells are as below:

TABLE 3

BATTERY

CELLS

RA/RB

RA(K

)

RB (K

)

240

120

240

300

360

390

410

Battery Temperature Measurement
The AIC1781A employs a negative temperature
coefficient (NTC) thermistor to measure the
battery's temperature. The thermistor is inherently
nonlinear with respect to temperature. To reduce
the effect of nonlinearity, a resistor-divider network
in parallel with the thermistor is recommended. A
typical application circuit is shown in Fig. 18.

BAT

0.1

VCC

GND

Thermistor

VTS

AIC1781A

Fig. 18 Battery Temperature Sense Circuit

with a Negative Temperature Coefficient
(NTC) Thermistor

AIC1781A

Power ON

LED Flash 3 Times

VBT in Normal

Range

VNTC<0.72 VCC

If VNTC>0.29VCC

Discharge

Enabled

LED's Display Abnormal,

ICON ON,

Safety Timer Reset

SEL3>VCC-0.3V

or VCC/2-0.4V>SEL3

>1.4V

Discharge

Finished

LED's Display Fast Charge, ICON OFF

Safety Timer Counts

Initial Timer

Finished

Peak Timer Period

has Finished

0.25% Decline of VBT

is Detected

has Reached

Safety Timer Period

has Finished

LED's Display

Battery Fulll,
Fast Charge

Finished,

Trickle charge

Starts

t Detector,

V Detector,

Peak timer are all
Disabled

LED's Display,

Abnormal,
ICON ON,

Safety Timer Reset

SEL3>VCC-0.3V

or VCC/2-0.4V>SEL3

>1.4V

Battery Replacement

Yes

t Disabled

Fig. 16 Function Flow Chart of AIC1781A

AIC1781A

The calculation for Rx and Ry in the circuit is as
following.

0.29 V

)

(Ry//

Ry//R

x V

= The resistance of thermistor at upper limit of

temperature protection.

0.72 V

)

(Ry//

Ry//R

x V

= The resistance of thermistor at lower limit of

temperature protection.

Substitution and rearranging the equations yield

Rx= 2.061

Ry =

5. 3

6. 3R

If temperature characteristic of the thermistor is like
that of SEMITEC 103AT-2, the resistance of Rx and
Ry is tabulated for different TL and TH as below.

(Note: TL is lower temperature limit and TH is upper
temperature limit.)

TABLE 4 Values of Rx and Ry at TL = 0

TH (

Rx(K

)

Ry (K

)

10.1

551.1

9.7

300.7

9.4

204.8

9.0

153.9

8.7

122.8

8.4

101.8

8.1

86.5

7.8

75.0

7.5

66.0

7.2

58.7

7.0

52.8

6.8

47.8

6.5

43.6

6.3

39.9

6.1

36.8

5.9

34.0

5.7

31.6

5.5

29.5

5.3

27.5

5.2

25.8

5.0

24.3

TABLE 5 Values of Rx and Ry at TL = -10

TH (

Rx (K

)

Ry (K

)

11.4

95.6

11.0

85.0

10.6

76.2

10.2

68.9

9.8

62.8

9.5

57.5

9.1

52.9

8.8

48.8

8.5

45.3

8.2

42.1

7.9

39.4

7.6

36.8

7.4

34.6

7.1

32.5

6.9

30.7

6.7

29.0

6.4

27.4

6.2

26.0

6.0

24.6

5.8

23.4

5.6

22.2

Setting the ADJ Pin Voltage
The slope of

t detection is determined by ADJ

pin voltage of the AIC1781A.

The calculation of ADJ pin voltage is shown in the
following procedure followed by an example.

AIC1781A

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

BASE

(min

Timer

Safety

(min

56(sec.)

(sec.)

BASE

T / t at

which temperature rises y

C in x seconds and

fast charge is subsequently cut off.

y
x

(d) Calculate the value of V

ADJ

BASE

ADJ

Example

(a) Let TH=50

C, TL=0

C, V

=5V. We have

0.43 5

50 0

0.043V/ C

BASE

which means that V

decreases 43mV as

temperature rises 1

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

BASE

then 56 seconds.

temperature rises 1

C in 60 seconds, then

0.0166

(d) V

ADJ

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

If the temperature range is from 0

C to 50

the voltage of V

ADJ

under different setting

conditions should be set as tabulated below.

TABLE 6 ADJ pin Voltage (TL=0

C, TH=50

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

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 of temperature protection function is
determined by the voltage of SEL3 pin, shown as
the following:

(a) SEL3 > V

- 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.

AIC1781A

(b) V

- 1.4V> SEL3 >

+ 0.4V

Acceptable VBT Range:

Before initial timer: 0.16V~2.7V
After initial timer: 0.69V~2.7V

Temperature Protection Mode:
If temperature is too high, battery charging is
regarded as completed. If temperature is too
low, function of

t detection is disabled, just

as thermistor is not existing.

(c)

- 0.4V>SEL3 >1.4V

Acceptable VBT Range:

Before initial timer: 0.16V~2V
After initial timer: 1.2V~2V

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.

(d) 0.3V> SEL3

Acceptable VBT Range:

Before initial timer: 0.16V~2V
After initial timer: 1.2V~2V

Temperature Protection Mode:
If temperature is too high, battery charging is
regarded as completed. If temperature is too
low, function of

t detection is disabled, just

as thermistor is not existing.

Setting the Period of Safety Timer

The AIC1781A provides a method for linearly
adjusting the period of safety timer with an external
resistor connected from TMR pin to GND. The
relation between safety timer length and the
external resistor (R

TMR

)

is shown in Fig. 19. The

table following shows the resistor values for some

of the commonly chosen safety timer periods. Also
shown in the table are their corresponding
oscillator frequencies.

100

200

300

400

500

200

400

600

800

TMR

)

Safety Timer (min.)

Fig. 19 Safety Timer vs. R

TMR

TABLE 8

TMR

)

OSC.

Freq.(KHz)

Safety timer

(min.)

256

131

65.8

43.1

100

32.8

152

21.6

120

206

16.0

160

314

10.6

250

491

6.89

380

667

5.04

520

Selecting Mode of Operation

The AIC1781A provides three modes of operation:
normal, test, and AC mode determined by the
setting of MODE pin according to TABLE 9. The
AIC1781A will operate normally when the MODE
pin is left floating (a 0.1

F capacitor is

recommended to be tied to MODE pin if the charge
circuit works in a noisy environment). When the
MODE pin is biased to GND, the function of -

detection is disabled. When the MODE pin is
biased to VCC, the AIC1781A enters the test mode.
The test mode can be used to significantly reduce
production test time. For relevant informations
please contact AIC directly.

AIC1781A

TABLE 9 The Operating Mode of AIC1781A

MODE pin

Mode Function

VCC

Test Safety timer period scaled

down to 1/32....etc.

Floating

Normal Normal operation

GND

V detection disabled

The Mode of LED Display and Trickle Charge

The AIC1781A provides two LED display modes
and five-pulsed trickle charge modes. The
tri-level inputs, SEL1 and SEL2 pins, as in the
TABLE 6 determine the modes of LED display
and trickle charge.

TABLE 10 Mode of LED Display and Trickle

Charge

SEL1

SEL2

Trickle Charge

Duty

LED Display

Mode

Floating

GND

N/A

1/32
1/64

Type 1
Type 1
Type 1

Floating

Floating
GND

1/128
1/256

N/A

Type 1
Type 1
Type 2

GND

Floating

GND

1/32
1/64

1/128

Type 2
Type 2
Type 2

Display the Battery Charging Status

The AIC1781A provides two open-drained
outputs, LED1 and LED2, to indicate the battery
charging status. Refer to the table of LED display
mode (TABLE 10), depending on the setting of
SEL1 and SEL2 pins, the outputs of LED1 and
LED2 pins are shown in the following table:

TYPE 1

Power

Fast

Charging

Charge

Completed

Fault

Conditions

LED1

1Hz

OFF

LED2

OFF

TYPE 2

Power

Fast

Charging

Charge

Completed

Fault

Conditions

LED1

1Hz

OFF

4Hz

Flashing

LED2

1Hz

4Hz

Flashing

OFF

Charging Current Control

As shown in the typical application circuit, the
AIC1781A offers an open-drained output pin, ICON
pin, to control the charging current flow in fast
charge state and switch on to inhibit the charging
current flow in fault conditions. When fast charge is
completed, the AIC1781A enters the trickle charge
mode. In trickle charge mode, the ICON pin output
switches with predetermined duty cycle. Refer to
the table of trickle charge mode (TABLE 6), the
duty cycle is determined by the setting of SEL1
and SEL2 pins. The following table summarizes
how ICON pin corresponds to various charging
states.

Power

Fast

Charging

Charge

Completed

Fault

Conditions

ICON

OFF

See pin 10

& 11

Test Mode

Fig. 20 shows the timing diagram for externally
controlled PEAK, ADJ, VBT, VTS, SEL1 and
SEL2 pin voltages of a recommended AIC1781A
test scheme, utilizing TEST mode function.
Output waveforms of LED1, LED2 and ICON of a
properly functioning AIC1781A are also shown in
the figure.

AIC1781A

TIMING DIAGRAM

Floating
Floating

SAFETY TIMER TEST

t TEST

Floating

GND

Init.

GND
GND

GND

Floating

VCC

Floating

Floating
Floating

(-0.15%)

(-2.5%)

OFF

2mV
Step/100mS

1.993V
(-0.35%)

1.95V

1.97V

1.9V

1.997V

1.5V

VCC, SEL3, MODE=5V, (DSW FREQ.=820KHz, 25 TIMES of 32.8K)

(-2.15%)

1.85V

1.12V

OFF

3.2KHz

OFF

t INITIAL TIMER

OFF

PEAK TIMER TEST

V TEST

OFF

2.14

0.4

0.12

0.28

0.12

0.02

0.32

0.7

0.32

0.2

0.24

0.1

0.5

0.12

5.92 6.02 6.04

3.78

3.38

3.14

2.64

1.94

1.62

0.74

0.54

1.5

1.18

0.86

0.26

0.14

ICON

VBT

ADJ

PEAK

LED2

LED1

VTS

TIME

(SEC.)

STAGE

SEL1
SEL2

OFF

<2.1V

Power

0.1

Fig. 20 Timing Diagram of AIC1781A in Test Mode

AIC1781A

PHYSICAL DIMENSIONS

(unit: mm)

16 LEAD PLASTIC SO (300 mil) (CS) (PS)

SYMBOL

MIN

MAX

2.35

2.65

0.10

0.30

0.33

0.51

0.23

0.32

10.10

10.50

7.40

7.60

1.27(TYP)

10.00

10.65

0.40

1.27

16 LEAD PLASTIC DIP (CN)

SYMBOL

MIN

MAX

0.381

2.92

4.96

0.35

0.56

0.20

0.36

18.66

19.69

7.62

8.26

6.09

7.12

2.54(TYP)

10.92

2.92

3.81

Note:

Information provided by AIC is believed to be accurate and reliable. However, we cannot assume responsibility for use of any
circuitry other than circuitry entirely embodied in an AIC product; nor for any infringement of patents or other rights of third
parties that may result from its use. We reserve the right to change the circuitry and specifications without notice.

Life Support Policy: AIC does not authorize any AIC product for use in life support devices and/or systems. Life support devices
or systems are devices or systems which, (I) are intended for surgical implant into the body or (ii) support or sustain life, and
whose failure to perform, when properly used in accordance with instructions for use provided in the labeling, can be reasonably
expected to result in a significant injury to the user.

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