SE555-SP Datasheet, PDF (15/18 Pages) Texas Instruments – QML CLASS V PRECISION TIMER

SE555-SP
www.ti.com
SGLS401 – FEBRUARY 2010
Sequential Timer
Many applications, such as computers, require signals for initializing conditions during start-up. Other
applications, such as test equipment, require activation of test signals in sequence. These timing circuits can be
connected to provide such sequential control. The timers can be used in various combinations of astable or
monostable circuit connections, with or without modulation, for extremely flexible waveform control. Figure 23
shows a sequencer circuit with possible applications in many systems, and Figure 24 shows the output
waveforms.
VCC
4
8
RA _{33 W}
4
8
RB ^{33 kW}
4
8
RC
RESET VCC ₃
2 _TRIG
OUT
RESET
2
VCC ₃
OUT
TRIG
RESET VCC ₃
2
OUT
TRIG
S
DISCH ⁷
0.001 mF
7
DISCH
0.001 mF
7
DISCH
5 _CONT
THRES ⁶
5
CONT
6
THRES
5
CONT
6
THRES
0.01 mF
GND
1
CA
0.01 mF
GND
1
CB
0.01 mF
GND
1
CC
CA = 10 mF
RA = 100 kW
Output A
CB = 4.7 mF
RB = 100 kW
Output B
CC = 14.7 mF
RC = 100 kW
Output C
NOTE A: S closes momentarily at t = 0.
Figure 23. Sequential Timer Circuit
ÏÏÏÏÏÏÏÏÏÏ _{See Figure 22}
ÏÏÏÏÏÏÏÏÏÏÏÏ ÏÏÏÏÏÏÏÏÏÏ _{OutputA twA}
ÏÏÏÏÏÏÏÏÏÏÏÏÏÏÏÏÏÏ ÏÏÏÏÏÏÏÏÏÏÏÏÏÏÏÏÏÏÏÏ _OutputB
t_wA = 1.1 R_AC_A
t_wB
t_wB = 1.1 R_BC_B
ÏÏÏÏÏÏÏÏÏÏÏÏÏÏÏÏ _{ÏÏÏÏÏÏÏÏÏÏÏÏÏÏÏÏÏÏ ÏÏÏÏÏÏÏÏÏÏÏÏÏÏÏ OutputC}
t_wC
t_wC = 1.1 R_CC_C
t=0
t − Time − 1 s/div
Figure 24. Sequential Timer Waveforms
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