ICM7249 Datasheet, PDF (8/9 Pages) Intersil Corporation – 51/2 Digit LCD, Micro-Power Event/Hour Meter

ICM7249
turns off at the end of the 16th BP cycle and turns back on at
the end of the 32nd BP cycle, giving a half-second wink. If
the counting occurs more frequently than once a second, the
wink output will continue to flash at the constant rate of 1Hz.
a
fb
g
ec
d
FIGURE 7. DIGITS SEGMENT ASSIGNMENT
Display Test and Reset
The display may be tested at any time without disturbing
operation by pulsing DT high, as seen in Figure 6. On the
next positive transition of BP, all the segments turn on and
remain on until the end of the 16th BP cycle. This takes a
half-second or less. All the segments then turn off for an
additional 48 BP cycles (the end of the 64th cycle), after
which valid data returns to the display. As long as DT is held
high, the segments will remain on.
Additional display testing is provided by using mode 12. In this
mode each displayed decade is incremented on each positive
transition of S/S. Modes 13 and 14 are manufacturer testing only.
Mode 15 resets all the decades and internal counters to zero,
essentially bringing everything back to power-up status.
Applications
A typical use of the ICM7249 is seen in Figure 8, the Motor
Hour Meter. In this application the ICM7249 is configured as
an hours-in-use meter and shows how many whole hours of
line voltage have been applied. The resistor network and
high-pass filtering allow AC line activation of the S/S input.
This configuration, which is powered by a 3V lithium cell, will
operate continuously for 2¹/₂ years. Without the display,
which only needs to be connected when a reading is
required, the span of operation is extended to 10 years.
When the ICM7249 is configured as an attendance counter,
as shown in Figure 9, the display shows each increment. By
using mode 2, external debouncing of the gate switch is
unnecessary, provided the switch bounce is less than 10ms.
The 3V lithium battery can be replaced without disturbing
operation if a suitable capacitor is connected in parallel with
it. The display should be disconnected, if possible, during the
procedure to minimize current drain. The capacitor should
be large enough to store charge for the amount of time
needed to physically replace the battery (∆t = ∆VC/I). A
100µF capacitor initially charged to 3V will supply a current
of 1.0µA for 50 seconds before its voltage drops to 2.5V,
which is the minimum operating voltage for the ICM7249.
Before the battery is removed, the capacitor should be
placed in parallel, across the V_DD and GND terminals. After
the battery is replaced, the capacitor can be removed and
the display reconnected.
LCD
120VAC
60Hz
10M
M ^{AC MOTOR}
100K
10M
W BP
36
A1
B6/C6
32.768kHz
CRYSTAL
OSC₁
ICM7249
S/S
OSC₀
V_DD
V_SS C0 C1 C2 C3
DT
+
+3V Li
FIGURE 8. MOTOR HOUR METER
DISPLAY
TEST
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