AIC1781
Battery Charge Controller
Analog Integrations Corporation 4F, 9, Industry E. 9th Rd, Science Based Industrial Park, Hsinchu Taiwan, ROC www.analog.com.tw
DS-1781-00 TEL: 886-3-5772500 FAX: 886-3-5772510 1
FEATURES
Fast Charge Control of NiMH/NiCd Batteries,
even with a Fluctuating Charging Current.
Fast Charge Termination by: ∆∆T
/
t, −∆V,
0V∆, Safety Timer, Maximum Temperature,
Maximum Voltage.
Linearly Adjustable ∆∆T
/
t Detection Slope and
Safety Timer.
Adjustable Peak Voltage Timer for 0V∆.
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.
0 102030405060
1.15
1.25
1.35
1.45
1.55 100
80
60
40
20
Temperature (°C)
Temperature
Cell Voltage
Cell Volta
g
e
(
V
)
Charge Time (min.)
Charge Current = 600 mA
Cell Capacity = 550 mA
NiMH Battery
Fig. 1 Battery Charging Characteristics Resulting
from an AIC1781-Controlled Charger with a
Fluctuating Charging Current
DESCRIPTION
The AIC1781 fast charge controller IC is designed
for intelligent charging of NiMH or NiCd batteries
without the risk of overcharge. −∆V detection
(-0.25%), 0V∆ detection (peak voltage timer)
and ∆∆T
/
t detection are the primary methods
employed by the AIC1781 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 AIC1781 utilizes
the combination of these two methods to achieve
reliable decision of ending fast charge and prevent
misaction 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 AIC1781 controller IC to achieve
optimal charging. This technique, in cooperating
with the 0V∆ 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. 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.
AIC1781
2
TYPICAL APPLICATION CIRCUIT
PEAK
1
VBT
2
DIS
3
VTS
4
VCC
5
ADJ
6
SEL3
7
TMR
8MODE 9
SEL2 10
SEL1 11
GND 12
LED1 13
LED2 14
ICON 15
DSW 16
U2
AIC1781
R9
240K
R8
120K
R10
100K
+
C9
4.7µF
C7
0.1µF
C10
47nF
R15
680
R3
270
R2
20/5W
SW1
SW PB
R12
100K
R16
680 R17
680
R14
200K
C8
0.1µF
+
C11
100
µ
F
RX1
100K
R11
100K
RY1
100K
C6
0.1
µ
F
R13
470K
Q2
2N3904
R18
50K
LED2
GREEN
LED3
RED
LED1
YELLOW
Q1
2N3904
+
C4
220µF
C5
0.1µF
+
C12
1uF
+
C13
10µF
R5 120/0.5W
R1
1K
BAT1
BATTERY
R7
THERMISTOR
VIN
L1
220µH
C2 1µF
C1
1000P
R6 0.3/1W
1
2
3
GND
4
FB
5
VCC
DC
DE
CF 6
IS
7
BOOST
8
U1
AIC1563
+C3
220µF
R4
390K
D3
IN4148
D1
IN4148 D2 IN4148
D4
1N5819
VIN
1VOUT
3
2GND
U3 7805
Battery Charge Circuit for Fluctuating Charging Current Application
ORDERING INFORMATION
PACKAGE TYPE
N: PLASTIC DIP
S: SMALL OUTLINE
TEMPERATURE RANGE
C= 0°C~70°C
ORDER NUMBER
A
IC1781CN
(PLASTIC DIP)
PIN CONFIGURATION
A
IC1781XX
A
IC1781CS
(
PLASTIC SO
)
1
3
2
16
14
15
5
7
6
10
12
11
4
8
13
9
PEAK
VBT
DIS
VTS
VCC
A
DJ
SEL3
SEL1
SEL2
MODE
LED1
GND
TMR
DSW
ICON
LED2
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°C
Storage Temperature Range .............................................…………...... -65°C~ 150°C
AIC1781
3
TEST CIRCUIT
PEAK DSW
VBT ICON
DIS LED2
VTS LED1
VCC GND
A
DJ SEL1
SEL3 SEL2
TMR MODE
V2 (3V)
V1 (0.95V)
VCC
VCC (5V)
VCC
GREEN
ORANGE
RED
560
AIC1781
R2
-+
-+
YELLOW
VOLTAGE
SOURCE
VOLTAGE SOURCE
VCC
VCC
VCC
VCC
100K
R1
560
560
R3
R4
560
R5
ELECTRICAL CHARACTERISTICS (Ta=25°
°°
°C, VCC=5V, unless otherwise specified.)
PARAMETER TEST CONDITIONS SYMBOL MIN. TYP. MAX. UNIT
Supply Voltage VCC 4.5 5.0 5.5 V
Supply Current ICC 1.1 mA
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)
VBT
1.9 2.0 2.10
V
AIC1781
4
ELECTRICAL CHARACTERISTICS (Ta=25°
°°
°C, VCC=5V, unless otherwise specified.)
PARAMETER TEST CONDITIONS SYMBOL MIN. TYP. MAX. UNIT
Temperature High 1.35 1.45 1.55
Temperature Sense Limit Temperature Low VTS 3.5 3.6 3.70
V
Output impedance of DIS Pin ZDIS 140 250 Ω
LED1, LED2, ICON Pins
Output Impedance ON
OFF 1
25 50 Ω
MΩ
Source Current
Capability
SEL3 pin
DSW pin
ISEL3
IDSW
5.5
16 µA
MODE, PEAK, SEL1,
SEL2 pins 300 KΩ
Input Impedance
VBT, VTS, ADJ pins 1 MΩ
Recommended
External Resistor of TMR pin
RTMR 2 100 1000 KΩ
-∆V Detection Level w.r.t.*
Peak Value
-0.25 %
TYPICAL PERFORMANCE CHARACTERISTICS (Ta=25°
°°
°C, R2=100KΩ
ΩΩ
Ω,
VCC=5V, refer to Test Circuit)
Supply Current vs Supply Voltage
4.4 4.6 4.8 5.0 5.2 5.4
1.00
1.06
1.12
1.18
1.21
Supply Current (mA)
V
CC (V)
4.4 4.6 4.8 5.0 5.2 5.4
79.0
79.5
80.0
80.5
81.0
Safety Timer vs Supply Volatge
Safety Timer (min.)
VCC (V)
AIC1781
5
TYPICAL PERFORMANCE CHARACTERISTICS (Continued)
4.44.64.85.05.25.4
3.8
4.0
4.2
4.4
4.6
4.8
LED Flashing Frequency vs Supply Voltage
Frequency (Hz)
V
CC (V)
020406080
0.9
1.02
1.14
1.26
Supply Current vs Temperature
Supply Current (mA)
Temperature (°C)
020 40 60 80
79.0
80.0
81.0
82.0
Safety Timer vs Temperature
Safety Timer (min.)
Temperature(°C)
020406080
LED Flashing Frequency vs Temperature
3.4
3.8
4.2
4.6
5.0
Frequency (Hz)
Temperature(°C)
0 20406080
2.62
2.66
2.70
2.74
VBT (high) Limit vs Temperature
(SEL3>3V)
V
BT
(V)
Temperature (°C)
020 40 60 80
1.98
1.99
2.01
2.03
VBT (high) Limit vs Temperature
(SEL3<2V)
V
BT
(V)
Temperature (°C)
AIC1781
6
TYPICAL PERFORMANCE CHARACTERISTICS (Continued)
Temperature (°C)
0 20406080
0.158
0.159
0.160
0.161
0.162
0.163
VBT (low) Limit vs Temperature (During Initial Timer)
V
BT
(V)
Output Impedance vs Temperature
(LED1,LED2,ICON pins)
Output Impedance(Ω)
Temperature (°C)
0 20406080
23
25
27
29
Temperature (°C)
0 20406080
3.58
3.59
3.60
3.61
3.62
VTS (high) Limit vs Temperature
V
TS
(V)
Temperature (°C)
020 40 60 80
1.42
1.44
1.46
1.48
VTS (low) Limit vs Temperature
V
TS
(V)
02040 60 80
0.685
0.690
0.695
0.700
VBT(LOW) Limits vs Temperature
(SEL3>3V, After Initial Timer)
V
BT
(V)
Temperature (°C)
VBT(LOW) Limits vs Temperature
(SEL3<3V, After Initial Timer)
0 20406080
1.18
1.20
1.22
1.24
V
BT
(
V
)
Temperature (°C)
AIC1781
7
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
Charge
Control Unit
TMR
Oscillator
VCCGND
Bandgap
Reference &
Voltage
Regulator
PEAK MODE
MODE
Selection
Peak Voltage
Timer Control
Battery Voltage &
Temperature
Portection Setting
LED‘s Display &
Trickle Pulse Duty
Setting
∆T/∆t Detection
Setting
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 AIC1781
enters discharge mode.
PIN 4: VTS- The battery cell temperature is
represented as a voltage input
to the AIC1781 at this pin. The
acceptable voltage range of
VTS pin is 0.29 VCC to 0.72
VCC. The battery temperature
is regarded as too high if the
voltage of VTS pin is lower than
0.29 VCC, and is otherwise
regarded as too low if the
voltage of VTS pin is higher
than 0.72 VCC.
PIN 5: VCC- Power supply input at 5V±10%.
PIN 6: ADJ- For adjusting the slope of ∆T/∆t.
Acceptable voltage range for
this pin is approximately 0.28V
to 3.8V. If voltage higher than
AIC1781
8
VCC-0.3V, the function of ∆T/∆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 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, tT/∆∆ 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.
AIC1781
9
In the course of fast charge, the AIC1781 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 (-∆V)
Peak voltage timer (0 V∆)
Delta temperature/ delta time (∆T/∆t)
Maximum charge time
Maximum battery voltage
Maximum battery temperature
-∆
∆∆
∆V Cutoff
The AIC1781 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.
0∆
∆∆
∆V Cutoff
If the battery voltage stays at its peak value or
decreases very slowly for the duration determined
by the peak voltage timer, which is in turn
determined by PEAK pin voltage, the fast charge
action is terminated.
∆
∆∆
∆T/∆
∆∆
∆t Cutoff
The tT/∆∆ detection of the AIC1781 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 tT/∆∆ 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 tT/∆∆ 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 AIC1781 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 AIC1781 (Fig. 2)
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:
PEAK PIN PEAK VOLTAGE TIMER
VCC 1.5% of safety timer
Floating 3.7% of safety timer
GND 6% of safety timer
AIC1781
10
Battery Voltage Measurement
The AIC1781 measures the battery voltage through
VBT pin, which is connected to battery positive
terminal through a resistor-divider network, as
shown in Fig. 3. The input voltage of SEL3 pin
determines the acceptable limit of divided battery
voltage.
VBAT
RA
RB C5
4.7µF
2
R5
100K
C6
0.1µF
AIC1781
VBT
+
Fig. 3 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:
BATTERY
CELLS RA/RB RA (KΩ)RB (KΩ)
2~4 2 240 120
3~6 3.3 300 91
4~8 4.9 300 62
5~10 6.4 300 47
6~12 7.8 310 39
8~16 10.8 390 36
For SEL3 < (VCC/2) – 0.4V, the suggested divider
resistance of RA and RB for the corresponding
number of battery cells are as below:
BATTERY
CELLS
RA/RB RA(KΩ
ΩΩ
Ω) RB (KΩ
ΩΩ
Ω)
21 240 240
32 240 120
43 240 80
54 300 75
65 300 60
87 360 51
10 9 360 40
12 11 390 36
16 15 410 27
Battery Temperature Measurement
The AIC1781 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. 4.
VBAT
4
Rx
C7
0.1µF
VCC
Ry
5
VCC
GND
12
Thermistor
VTS
AIC1781
Fig. 4 Battery Temperature Sense Circuit with
a Negative Temperature Coefficient
(NTC) Thermistor
AIC1781
11
Power ON
LED Flash 3 Times
If
VBT in Normal
Range
If
VNTC<0.72 VCC
If VNTC>0.29VCC
If
Discharge
Enabled
LED's Display Abnormal,
ICON ON,
Safety Timer Reset
If
SEL3>VCC-0.3V
or VCC/2-0.4V>SEL3
>1.4V
If
Discharge
Finished
LED's Display Fast Charge, ICON OFF
Safety Timer Counts
If
Initial Timer
Finished
If
Peak Timer Period
has Finished
If
0.25% Decline of VBT
is Detected
If ∆T/ ∆=t
has Reached
If
Safety Timer Period
has Finished
LED's Display
Battery Fulll,
Fast Charge
Finished,
Trickle charge
Starts
∆
T/
∆
t Detector,
-∆V Detector,
Peak timer are all
Disabled
LED's Display,
Abnormal,
ICON ON,
Safety Timer Reset
If
SEL3>VCC-0.3V
or VCC/2-0.4V>SEL3
>1.4V
Battery Replacement
Battery Replacement
No
No
Yes
Yes
No
Yes
Yes
Yes
No
No
Yes
No
Yes
No
No
Yes
Yes
Yes
Yes
Yes
No
No
No Yes
Yes
No
No
No
∆
T/
∆
t Disabled
Fig. 2 Function Flow Chart of AIC1781
AIC1781
12
The calculation for Rx and Ry in the circuit is as
following.
0.29 VCC = )R(Ry// Rx
Ry//R
TH
TH
+ x VCC
RTH= The resistance of thermistor at upper limit of
temperature protection.
0.72 VCC = )R(Ry// Rx
Ry//R
TL
TL
+ x VCC
RTL= The resistance of thermistor at lower limit of
temperature protection.
Substitution and rearranging the equations yield
Rx= 2.061 ××
−
RR
RR
TL TH
TL TH
Ry = 5. 3 R R
R6.3R
TL TH
TL TH
××
−
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. 1 Values of Rx and Ry at TL = 0°
°°
°C
TH (°C) Rx(KΩ)Ry (KΩ)
50 10.1 551.1
51 9.7 300.7
52 9.4 204.8
53 9.0 153.9
54 8.7 122.8
55 8.4 101.8
56 8.1 86.5
57 7.8 75.0
58 7.5 66.0
59 7.2 58.7
60 7.0 52.8
61 6.8 47.8
62 6.5 43.6
63 6.3 39.9
64 6.1 36.8
65 5.9 34.0
66 5.7 31.6
67 5.5 29.5
68 5.3 27.5
69 5.2 25.8
70 5.0 24.3
TABLE. 2 Values of Rx and Ry at TL = -10°
°°
°C
TH (°C) Rx (KΩ)Ry (KΩ)
45 11.4 95.6
46 11.0 85.0
47 10.6 76.2
48 10.2 68.9
49 9.8 62.8
50 9.5 57.5
51 9.1 52.9
52 8.8 48.8
53 8.5 45.3
54 8.2 42.1
55 7.9 39.4
56 7.6 36.8
57 7.4 34.6
58 7.1 32.5
59 6.9 30.7
60 6.7 29.0
61 6.4 27.4
62 6.2 26.0
63 6.0 24.6
64 5.8 23.4
65 5.6 22.2
Setting the ADJ Pin Voltage
The slope of ∆T/∆t detection is determined by ADJ
pin voltage of the AIC1781.
The calculation of ADJ pin voltage is shown in the
following procedure followed by an example.
AIC1781
13
Procedure
(a) First, determine the temperature protection limits
TH and TL. Then, substitute TH & TL into the
following equation:
∆
∆
V
T
0.72 V 0.29 V
TH TL
0.43 V
TH TL
TS
BASE
CC CC CC
=−
−=−
(b) Determine the safety timer to obtain the value of
∆tBASE .
∆t (sec.) = 56(sec.) Safety TimerBASE 80(min. ) (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
V25V
T
T
ttADJ
TS
BASE
BASE=× × ×
∆
∆
∆
∆∆
Example
(a) Let TH=50°C, TL=0°C, VCC =5V. We have
∆
∆
V
T
0.43 5
50 0 0.043V/ C
TS
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.
(c) If fast charge should be terminated when
temperature rises 1°C in 60 seconds, then
0.0166
60
1
=tT/ =∆∆
(d) VADJ =25 x 0.043x 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 tabulated below.
TABLE. 3 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) 0.37 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 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) 0.31 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
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 > 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
AIC1781
14
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.
(b) VCC - 1.4V> SEL3 > V
2
cc - 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/∆t detection is disabled, just as
thermistor is not existing.
(c) V
2
cc - 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/∆t detection is disabled, just as
thermistor is not existing.
Setting the Period of Safety Timer
The AIC1781 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 (RTMR) is shown in Fig. 5. 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.
0 100 200 300 400 500
0
200
400
600
800
RTMR (KΩ)
Safety Timer (min.)
Fig. 5 Safety Timer vs RTMR
RTMR (KΩ)OSC.
Freq.(KHz)
Safety timer
(min.)
11 262.4 10
23 131.2 20
48 65.6 40
74 43.7 60
100 32.8 80
152 21.9 120
206 16.4 160
314 10.9 240
491 7.3 360
667 5.5 480
Selecting Mode of Operation
The AIC1781 provides three modes of operation:
normal, test, and AC mode determined by the
setting of MODE pin according to TABLE 5. The
AIC1781 will operate normally when the MODE pin
is left floating (a 0.1µF capacitor is recommended
AIC1781
15
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 -∆V detection is
disabled. When the MODE pin is biased to VCC,
the AIC1781 enters the test mode. The test mode
can be used to significantly reduce production test
time. For relevant informations please contact AIC
directly.
TABLE. 5 The Operating Mode of AIC1781
MODE pin Mode Function
VCC Test Safety timer period scaled
down to 1/32....etc.
Floating Normal Normal operation
GND AC –∆V detection disabled
The Mode of LED Display and Trickle Charge
The AIC1781 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. 6 Mode of LED Display and Trickle
Charge
SEL1 SEL2 Trickle Charge
Duty
LED Display
Mode
VCC VCC
Floating
GND
N/A
1/32
1/64
Type 1
Type 1
Type 1
Floating VCC
Floating
GND
1/128
1/256
N/A
Type 1
Type 1
Type 2
GND VCC
Floating
GND
1/32
1/64
1/128
Type 2
Type 2
Type 2
Display the Battery Charging Status
The AIC1781 provides two open-drained outputs,
LED1 and LED2, to indicate the battery charging
status. Refer to the table of LED display mode
(TABLE 6), 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
ON
Fast
Charging
Charge
Completed
Fault
Conditions
LED1 1Hz ON OFF OFF
LED2 OFF OFF ON OFF
TYPE 2
Power
ON
Fast
Charging
Charge
Completed
Fault
Conditions
LED1 1Hz ON OFF 4Hz
Flashing
LED2 1Hz 4Hz
Flashing ON OFF
Charging Current Control
As shown in the typical application circuit, the
AIC1781 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 AIC1781 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
ON
Fast
Charging
Charge
Completed
Fault
Conditions
ICON ON OFF See pin 10
& 11
ON
Test Mode
Fig. 6 shows the timing diagram for externally
controlled PEAK, ADJ, VBT, VTS, SEL1 and
SEL2 pin voltages of a recommended AIC1781
test scheme, utilizing TEST mode function.
Output waveforms of LED1, LED2 and ICON of a
properly functioning AIC1781 are also shown in
the figure.
AIC1781
16
TIMING DIAGRAM
Floating
Floating
SAFETY TIMER TEST
∆T/∆t TEST
Floating
GND
Init.
GND
GND
GND
Floating
VCC
Floating
Floating
Floating
4V
(-0.15%)
(-0.15%)
(-2.5%)
4V
ON
OFF
4V
2mV
Step/100mS
2mV
Step/100mS
2V
1.993V
(-0.35%)
2V2V
1.95V
ON
1.96V
2V
4V
2V
1.9V
1.997V
1.997V
1.997V
1.5V
VCC, SEL3, MODE=5V, (DSW FREQ.=820KHz, 25 TIMES of 32.8K)
(-2.15%)
0V
1.85V
5V
5V
1.12V
ON
ON
OFF
3.2KHz
ON
OFF
ON
-∆V DISALBE TEST
OFF
OFF
PEAK TIMER TEST -∆V TEST
OFF
OFF
ON
2.14
9
0.4
8
0.12
4
0.280.12
2
0.02
10
0.32
5
0.32 0.7
0.320.2
3
0.24 0.10.5
7
0.12
6
5.92 6.02 6.043.783.383.142.641.941.620.740.54 1.51.180.860.260.14
0.14
1
ICON
VBT
ADJ
PEAK
LED2
LED1
VTS
TIME
(SEC.)
STAGE
SEL1
SEL2
OFF
ON
<2.1V
2V
Power
ON
3V
0V
0.1
0
2V
2V
Fig. 6 Timing Diagram of AIC1781 in Test Mode
AIC1781
17
PHYSICAL DIMENSIONS
16 LEAD PLASTIC DIP (unit: mm)
SYMBOL MIN MAX
A1 0.381 —
A2 2.92 4.96
b 0.35 0.56
C 0.20 0.36
D 18.66 19.69
E 7.62 8.26
E1 6.09 7.12
e 2.54(TYP)
eB — 10.92
be
L
A2
A1
eB
E
C
E1
D
L 2.92 3.81
16 LEAD PLASTIC SO (300 mil) (unit: mm)
SYMBOL MIN MAX
A 2.35 2.65
A1 0.10 0.30
B 0.33 0.51
C 0.23 0.32
D 10.10 10.50
E 7.40 7.60
e 1.27(TYP)
H 10.00 10.65
HE
e
Bc
A
A1
D
LL 0.40 1.27
