SC1766 Ver la hoja de datos (PDF) - Semtech Corporation
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SC1766 Datasheet PDF : 11 Pages
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BATTERY
CHARGE CONTROLLER
SC1766
Janaury 30, 1998
PRINCIPLES OF OPERATION (cont.)
MODE PIN
The MODE pin determines the mode in which the IC
works:
MODE
Floating
VDD
GND
Mode
NORMAL
TEST
AC
Function
normal operation
1/512 safety timer
-∆V detector reset timer
stops (not reset)
The SC1766 will operate normally when the MODE
pin is left floating (a 0.1µF capacitor is recom-
mended to be tied to the MODE pin if the charge cir-
cuit works in a noisy environment). The SC1766 oth-
erwise works in the following ways if the MODE pin
is biased either to VDD or to GND:
A) AC Mode (MODE pin biased to GND)
In the midst of normal charge operation, where the
VBT pin voltage is in the range from 0.8V to 3.5V
and the preset safety timer has not run out, the
safety timer will stop if the MODE pin is pulled down
to GND level. As long as the MODE pin remains low,
the VOUT pin stays ON and the LED pin OFF re-
gardless of whether the battery pack voltage de-
clines (-∆V present) or not. AC mode can be acti-
vated by pulling the MODE pin to GND to avoid pre-
mature battery charge cutoff due to fluctuating
charge current source. Switching the MODE pin af-
ter the end of the safety timer has no effect on the
SC1766 display outputs, i.e., VOUT pin stays OFF
while LED pin stays ON.
B) TEST Mode (MODE pin biased to VDD)
A unique feature of the SC1766 is that it can be put
into a TEST mode by pulling the MODE pin to VDD,
allowing verification tests for the SC1766 charge cir-
cuit to be performed in a few tens of seconds, ex-
tremely valuable in the final phase of production.
When the SC1766 is in TEST mode, all the internal
timers are reduced by the following factors when
compared to normal operation:
1. Safety timer reduced by a factor of 512 times;
2. Initial timer reduced by a factor of 512 times;
3. Peak timer reduced by a factor of 64 times.
One critical requirement needs to be observed for the
OPERATION CHART OF THE SC1766
POWER ON
VOUTgoes high for
IF
trickle charge.
0.65V<VBT<3.7V
Safety timer and
NO -∆V detector reset.
YES
VOUT goes low for fast
charge.
Safety timer starts
counting.
YES
IF
αNTCL >αNTC
&
αNTC >αNTCH
VOUT goes high for
trickle charge.
NO
-∆V detector reset.
Safety timer stops.
-∆V detector & peak
voltage timer start
working after initial
period ends.
-∆V detector & peak
voltage timer working.
IF
αNTCL >αNTC
&
αNTC >αNTCH
VOUT goes high for
trickle charge.
NO
-∆V detector reset.
Safety timer stops.
YES
IF
0.65<VBT<3.7V
VOUT goes high for
trickle charge.
NO Safety timer and
-∆V detector reset.
YES
IF
Safety timer
period has
finished
YES
NO
IF
IF
0.25% decline
Peak voltage
of VBT is
timer period has
NO
detected
NO
finished
YES
YES
VOUT goes to high, fast charge finished, and trickle charge starts.
© 1997 SEMTECH CORP.
652 MITCHELL ROAD NEWBURY PARK CA 91320
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