TS556I STMicroelectronics, TS556I Datasheet - Page 8

• Manufacturer Part Number: TS556I
• Description: LOW POWER DUAL CMOS TIMERS
• Manufacturer: STMicroelectronics

TS556C,I,M
TYPICAL CHARACTERISTICS
Figure 1 : Supply Current (each timer) versus
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
8/11
Trigger
V
Out
CC
300
200
100
0
Supply Voltage
Reset
SUPPLY VOLTAGE, V
4
TS556
1/2
8
CC
12
(V)
Control Voltage
R
0.01 F
C
16
The circuit triggers on a negative-goinginput signal
when the level reaches 1/3 V
circuit remains in this state until the set time has
elapsed,even if it is triggered again during this
interval. 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
timing 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.
During the time the reset pulse is applied, the
output is driven to its LOW state.
When a negative trigger pulse is applied to the
trigger terminal, the flip-flop is set, releasing the
short circuit across the external capacitor and driv-
ing the output HIGH. The voltage across the ca-
pacitor increases exponentially with the time
constant = R x C.
When the voltage across the capacitor equals 2/3
V
discharges the capacitor rapidly and drives the
output 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
CC
, the comparator resets the flip-flop which then
R = 9.1k , C = 0.01 F , R = 1.0k
t = 0.1 ms / div
OUTPUT VOLTAGE = 5.0V/div
CAPACITOR VOLTAGE = 2.0V/div
INPUT = 2.0V/div
CC
. Oncetriggered,the
L