AIC1781A AIC [Analog Intergrations Corporation], AIC1781A Datasheet - Page 10

• Manufacturer Part Number: AIC1781A
• Description: Battery Charge Controller
• Manufacturer: AIC [Analog Intergrations Corporation]

by the peak voltage timer, which is in turn
determined by PEAK pin voltage, the fast charge
action is terminated.
The
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
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, - V
sampling rate, and
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
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
T/ t Cutoff
T/
t
detection of the AIC1781A is performed
CC
and the measured frequency on
T/
t
T/
sampling rate will be
t
detection can be
CC
duty cycle is controlled by the setting of SEL1 and
SEL2 pins.
The
mentioned above are illustrated in the function flow
chart of AIC1781A (Fig. 16)
l 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:
TABLE 1
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.
For SEL3 > (V
resistance of RA and RB for the corresponding
number of battery cells are as below:
V
BAT
PEAK PIN
V
Floating
GND
functions
CC
Fig. 17 Battery Voltage Divider
RB
RA
CC
C5
+
/2) + 0.4V, the suggested divider
and
PEAK VOLTAGE TIMER
1.5% of safety timer
3.7% of safety timer
6% of safety timer
100K
R5
charging
C6
AIC1781A
states
2
VBT
AIC1781A
control
10