TS3V556 Ver la hoja de datos (PDF) - STMicroelectronics
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TS3V556 Datasheet PDF : 8 Pages
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TS3V556
TYPICAL CHARACTERISTICS
Figure 1 : Supply Current (each timer)
versus supply voltage.
300
200
100
0
4
8
12
16
SUPPLY VOLTAGE, VCC (V)
APPLICATION INFORMATION
MONOSTABLE OPERATION
In the monostable mode,the timer functions as a
one-shot. Referring to figure 2 the external capaci-
tor is initially held discharged by a transistor inside
the timer.
Figure 2
VC C
Reset
R
Trigger
Out
1/2
TS3V556
C
Control Voltage
0.01 µF
The circuit triggers on a negative-going input signal
when the level reaches 1/3 VCC. Once triggered,the
circuit remains in this state until the set time has
elapsed,even if it is triggered again during this in-
terval. The duration of the output HIGH state is
given by t = 1.1 R x C.
Notice that since the charge rate and the threshold
level of the comparator are both directly propor-
tional to supply voltage, the timing interval is inde-
pendent of supply. Applying a negative pulse
simultaneously to the Reset terminal (pin 4 or 10)
and the Trigger terminal (pin 2 or 8) during the tim-
ing cycle discharges the external capacitor and
causes the cycle to start over. The timing cycle now
starts on the positive edge of the reset pulse. Dur-
ing the time the reset pulse is applied, the output is
driven to its LOW state.
When a negative trigger pulse is applied to the trig-
ger terminal, the flip-flop is set, releasing the short
circuit across the external capacitor and driving the
output HIGH. The voltage across the capacitor in-
creases exponentially with the time constant τ = R x
C.
When the voltage across the capacitor equals 2/3
VCC, the comparator resets the flip-flop which then
discharges the capacitor rapidly and drives the out-
put to its LOW state.
Figure 3 shows the actual waveforms generated in
this mode of operation.
When Reset is not used, it should be tied high to
avoid any possible or false triggering.
Figure 3
t = 0.1 ms / div
INPUT = 2.0V/div
OUTPUT VOLTAGE = 5.0V/div
CAPACITOR VOLTAGE = 2.0V/div
R = 9.1k , C = 0.01 F , RL = 1.0k
5/8
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