aic1761 Analog Devices, Inc., aic1761 Datasheet - Page 6

• Manufacturer Part Number: aic1761
• Description: Battery Charge Controller
• Manufacturer: Analog Devices, Inc.

ANALOG INTEGRATIONS CORPORATION
4F, 9 Industry E. 9th Road, Science-based Industrial Park , Hsinchu, Taiwan, R.O.C.
Fig. 1
1.7
1.6
1.5
1.4
1.3
1.2
1.1
PIN DESCRIPTIONS
APPLICATION INFORMATIONS
VDD PIN
GND PIN
VBT PIN
MODE PIN -
TIMER PIN -
VREF PIN
BATTERY PROPERTIES
The basic principle of rechargeable battery sys-
tems, including NiMH and NiCd cells, is that the
processes of charge and discharge are reversible.
The charge characteristics of NiMH and NiCd
cells look similar in that (1) the cell voltage at the
end of charge drops and (2) the cell temperature
increases rapidly near the end of charge. Fig. 1
shows the charge voltage and charge tempera-
ture characteristics of NiMH and NiCd cells. No-
tice that the cell voltage decline of NiMH cells at
the end of charge is less pronounced than for
NiCd cells.
Fast-charge batteries are available where re-
charging takes for only 1 hour or less with a sim-
ple control circuit. One main purpose of the con-
trol circuit is to terminate the fast-charge process
to prevent the temperature and internal pressure
of the battery cell from building up to a damaging
level which degrades or even destroys the battery
cell.
0
Charge Current=1C
Voltage
Temperature
Typical
NiMH/NiCd Battery
20
-
-
-
-
Supply voltage input.
Ground.
Input, to sense battery voltage.
Input, to set IC operation mode.
Input, for safety timer control.
Voltage reference output.
NiCd
Time (min.)
40
Charge
60
NiMH
Characteristics
NiMH
80
NiCd
100
80
70
60
50
40
30
20
of
LED PIN
VOUT PIN - Output, for LED indicator.
FLASH PIN - Output, for LED indicator.
VNTC PIN - Input, for temperature protection.
TEL: [phone] FAX:[phone]
www.analog.com.tw
The AIC1761/1766 is a battery fast charge con-
troller IC that utilizes the following methods to
terminate the fast charge process for NiMH or
NiCd battery cells:
The principle of operation of the AIC1761/1766 is
described in the following section.
THE AIC1761/1766 OPERATION
When power is first applied to the charge system,
consisting of rechargeable battery cells, charge cur-
rent source, the AIC1761/1766 and its associated
external circuit, all internal digital circuit blocks of
the AIC1761/1766 are reset by internal power-on-
reset circuitry. The internal control unit then checks
the battery condition to prevent fast charge from
taking place under battery fault conditions, i.e. cell
voltage fault (V
perature fault ( NTC> NTCL or NTC< NTCH, for
the 14-pin version). Temperature fault limits corre-
sponding to NTCL and NTCH are determined by
an external thermistor divider circuit as included in
the Application Examples, Fig. 10. After the battery
passes condition fault checks, VOUT pin goes to
low to start fast charge while initial timer and safety
timer of the AIC1761/1766 start counting. Both the
negative delta voltage detector and the peak voltage
timer, however, are disabled until the initial timer
period in the initial stage of a charge circle elapses.
Negative delta voltage cutoff (- V).
Peak voltage timer cutoff (0 V).
Maximum temperature cutoff (TCO).
Maximum voltage cutoff (VCO).
Safety timer cutoff.
BATTERY CHARGE CONTROLLER
- Output, for LED indicator.
(Available for 14-pin version only.)
(Available for 14-pin version only.)
BT
<0.65V or V
AIC1761/1766
SPEC NO: DS-1761-02
BT
>3.7V) or cell tem-
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