SAA1501T Datasheet, PDF (8/20 Pages) NXP Semiconductors – Battery charge level indicator

Philips Semiconductors
Battery charge level indicator
Objective specification
SAA1501T
Display decoder driver
The counters are used to output the battery charge
amount via a decoder and driver stage to the display
outputs L100, L80, L60, L40 and L20 to drive an LCD
screen or an LED bargraph. A 64 Hz (based on
f_osc = 4 kHz) block signal at output BP (back plane) must
be connected to the back plane of the LCD bar. If pin BP
is connected to ground, the display outputs L20 to L100
will produce signals for an LED bargraph. Output signal
POL (power-on LED) indicates when the batteries are in
the charge mode. When the counter is not at its maximum
state, POL is on and flickers at 2 Hz (based on
f_osc = 4 kHz) when the counter is at its maximum. The
waveforms illustrated in Fig.4 depict operation of the
monitor display. The outputs BLI (battery low indication),
BUZ (buzzer) and FULL indicate the extreme status
(empty or full) of the counters and the batteries. The
waveforms of the signals BLI and BUZ if one switches over
from BATLD to standby when BLI is active, are given in
Fig.4.
The BLI sequence is as follows. If during discharge the
charge state falls below 0%, the red BLI LED is turned on.
Changing mode from discharge to standby means that the
BLI LED and the buzzer (BUZ) are activated as indicated
in Fig.4. If after a 0% passing recharge is activated, the red
BLI LED is turned on again for as long as the counter
remains below 10%. Switch-over in the 0 to 10% range to
standby will activate BLI and BUZ again.
The LEDs of the LED bargraph are activated as a result of
each operational mode change, starting with a step-up
pattern. Step-up means that LEDs are activated
successively one after the other, in accordance with the
charge status each ¹â„₈ s (based on f_osc = 4 kHz). After the
step-up, the LEDs will be on for 8 s (based on
f_osc = 4 kHz), except for the POCH mode, where the LEDs
will be on continuously to inform the user about the charge
state of the batteries. The LCD display is, apart from the
LED mode, always visible.
Figure 5 shows the legend for Fig.6. Figure 6 shows the
operation of the monitor display.
BUZ
Fig.4 BLI and buzzer timing.
December 1994
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