TI NE555

NE555, NE555Y, SA555, SE555, SE555C
PRECISION TIMERS
SLFS022 – SEPTEMBER 1973 – REVISED FEBRUARY 1992
D
D
D
D
D
Timing From Microseconds to Hours
Astable or Monostable Operation
Adjustable Duty Cycle
TTL-Compatible Output Can Sink or
Source up to 200 mA
Functionally Interchangeable With the
Signetics NE555, SA555, SE555, SE555C;
Have Same Pinout
D, JG, OR P PACKAGE
(TOP VIEW)
GND
TRIG
OUT
RESET
1
8
2
7
3
6
4
5
VCC
DISCH
THRES
CONT
FK PACKAGE
(TOP VIEW)
NC
GND
NC
VCC
NC
SE555C FROM TI IS NOT RECOMMENDED
FOR NEW DESIGNS
description
NC
TRIG
NC
OUT
NC
3 2 1 20 19
18
5
17
6
16
7
15
8
14
9 10 11 12 13
NC
DISCH
NC
THRES
NC
NC
RESET
NC
CONT
NC
These devices are precision monolithic timing
circuits capable of producing accurate time delays
or oscillation. In the time-delay or monostable
mode of operation, the timed interval is controlled
by a single external resistor and capacitor
network. In the astable mode of operation, the
frequency and duty cycle may be independently
controlled with two external resistors and a single
external capacitor.
4
NC–No internal connection
The threshold and trigger levels are normally two-thirds and one-third, respectively, of VCC. These levels can
be altered by use of the control voltage terminal. When the trigger input falls below the trigger level, the flip-flop
is set and the output goes high. If the trigger input is above the trigger level and the threshold input is above
the threshold level, the flip-flop is reset and the output is low. RESET can override all other inputs and can be
used to initiate a new timing cycle. When RESET goes low, the flip-flop is reset and the output goes low.
Whenever the output is low, a low-impedance path is provided between DISCH and ground.
The output circuit is capable of sinking or sourcing current up to 200 mA. Operation is specified for supplies of
5 V to 15 V. With a 5-V supply, output levels are compatible with TTL inputs.
The NE555 is characterized for operation from 0°C to 70°C. The SA555 is characterized for operation from
– 40°C to 85°C. The SE555 and SE555C are characterized for operation over the full military range of – 55°C
to 125°C.
AVAILABLE OPTIONS
PACKAGE
TA
VTHRES max
VCC = 15 V
0°C to 70°C
11.2 V
NE555D
– 40°C to 85°C
11.2 V
SA555D
– 55°C to 125°C
10.6 V
11.2 V
SE555D
SE555CD
SMALL OUTLINE
(D)
CHIP CARRIER
(FK)
CERAMIC DIP
(J)
PLASTIC DIP
(P)
CHIP FORM
(Y)
NE555P
SA555P
SE555FK
SE555CFK
SE555JG
SE555CJG
NE555Y
SE555P
SE555CP
The D package is available taped and reeled. Add the suffix R to the device type (e.g., NE555DR).
Copyright  1992, Texas Instruments Incorporated
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of Texas Instruments
standard warranty. Production processing does not necessarily include
testing of all parameters.
POST OFFICE BOX 655303
• DALLAS, TEXAS 75265
1
NE555, NE555Y, SA555, SE555, SE555C
PRECISION TIMERS
SLFS022 – SEPTEMBER 1973 – REVISED FEBRUARY 1992
RESET
TRIGGER VOLTAGE†
FUNCTION TABLE
THRESHOLD VOLTAGE†
OUTPUT
DISCHARGE SWITCH
Low
Irrelevant
Irrelevant
Low
On
High
< 1/3 VDD
Irrelevant
High
Off
High
> 1/3 VDD
> 2/3 VDD
Low
On
High
> 1/3 VDD
† Voltage levels shown are nominal.
< 2/3 VDD
As previously established
functional block diagram
VCC
8
CONT
5
R
RESET
4
Î Î Î
R1
6
THRES
Î
R
1
3
OUT
S
R
2
TRIG
R
ÎÎ
ÎÎ
7
1
GND
RESET can override TRIG, which can override THRES.
Pin numbers shown are for the D, JG, and P packages only.
2
POST OFFICE BOX 655303
• DALLAS, TEXAS 75265
DISCH
NE555, NE555Y, SA555, SE555, SE555C
PRECISION TIMERS
SLFS022 – SEPTEMBER 1973 – REVISED FEBRUARY 1992
chip information
These chips, properly assembled, display characteristics similar to the NE555 (see electrical table for NE555Y).
Thermal compression or ultrasonic bonding may be used on the doped aluminum bonding pads. Chips may be
mounted with conductive epoxy or a gold-silicon preform.
BONDING PAD ASSIGNMENTS
VCC
(8)
(2)
THRES
(6)
CONT
(5)
R
RESET
(4)
R1
R
(3)
(3)
1
OUT
S
(4)
R
TRIG
(2)
R
(7)
41
(5)
DISCH
(1)
GND
(1)
(8)
CHIP THICKNESS: 15 TYPICAL
BONDING PADS: 4 × 4 MINIMUM
TJ max = 150° C
(7)
(6)
TOLERANCES ARE ± 10%
ALL DIMENSIONS ARE IN MILS
42
PIN (1) INTERNALLY CONNECTED
TO BACKSIDE OF CHIP
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• DALLAS, TEXAS 75265
3
NE555, NE555Y, SA555, SE555, SE555C
PRECISION TIMERS
SLFS022 – SEPTEMBER 1973 – REVISED FEBRUARY 1992
absolute maximum ratings over operating free-air temperature range (unless otherwise noted)
Supply voltage, VCC (See Note 1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 V
Input voltage (CONT, RESET, THRES, and TRIG) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . VCC
Output current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ± 225 mA
Continuous total dissipation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . See Dissipation Rating Table
Operating free-air temperature range: NE555 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0°C to 70°C
SA555 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . – 40°C to 85°C
SE555, SE555C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . – 55°C to 125°C
Storage temperature range . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . – 65°C to 150°C
Case temperature for 60 seconds: FK package . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 260°C
Lead temperature 1,6 mm (1/16 inch) from case for 10 seconds: D or P package . . . . . . . . . . . . . . . . . 260°C
Lead temperature 1,6 mm (1/16 inch) from case for 60 seconds: JG package . . . . . . . . . . . . . . . . . . . . 300°C
NOTE 1: All voltage values are with respect to network ground terminal.
DISSIPATION RATING TABLE
PACKAGE
TA ≤ 25°C
POWER RATING
DERATING FACTOR
ABOVE TA = 25°C
TA = 70°C
POWER RATING
TA = 85°C
POWER RATING
TA = 125°C
POWER RATING
D
725 mW
5.8 mW/°C
464 mW
377 mW
N/A
FK
1375 mW
11.0 mW/°C
880 mW
715 mW
275 mW
210 mW
JG (SE555, SE555C)
1050 mW
8.4 mW/°C
672 mW
546 mW
JG (SA555, NE555C)
825 mW
6.6 mW/°C
528 mW
429 mW
N/A
P
1000 mW
8.0 mW/°C
640 mW
520 mW
N/A
recommended operating conditions
NE555
Supply voltage, VCC
SE555
SE555C
MAX
MIN
MAX
MIN
MAX
MIN
MAX
4.5
16
4.5
16
4.5
18
4.5
16
Input voltage (CONT, RESET, THRES, and TRIG)
VCC
± 200
Output current
Operating free-air temperature, TA
4
SA555
MIN
0
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70
VCC
± 200
– 40
• DALLAS, TEXAS 75265
85
VCC
± 200
– 55
125
– 55
UNIT
V
VCC
± 200
mA
V
125
°C
NE555, NE555Y, SA555, SE555, SE555C
PRECISION TIMERS
SLFS022 – SEPTEMBER 1973 – REVISED FEBRUARY 1992
electrical characteristics, VCC = 5 V to 15 V, TA = 25°C (unless otherwise noted)
PARAMETER
NE555, SA555,
SE555C
SE555
TEST CONDITIONS
MIN
TYP
MAX
MIN
UNIT
TYP
MAX
VCC = 15 V
VCC = 5 V
9.4
10
10.6
8.8
10
11.2
2.7
3.3
4
2.4
3.3
4.2
30
250
30
250
TRIG voltage level
VCC = 15 V
VCC = 5 V
4.8
5
5.2
4.5
5
5.6
1.45
1.67
1.9
1.1
1.67
2.2
TRIG current
TRIG at 0 V
0.5
0.9
0.5
2
µA
0.7
1
0.7
1
V
THRES voltage level
THRES current (see Note 2)
RESET voltage level
0.3
RESET at VCC
RESET current
0.1
0.4
0.1
0.4
– 0.4
–1
– 0.4
– 1.5
20
100
20
100
9.6
10
10.4
9
10
11
2.9
3.3
3.8
2.6
3.3
4
0.1
0.15
0.1
0.25
0.4
0.5
0.4
0.75
2
2.2
2
2.5
RESET at 0 V
DISCH switch off-state current
VCC = 15 V
VCC = 5 V
CONT voltage (open circuit)
IOL = 10 mA
IOL = 50 mA
VCC = 15 V
IOL = 100 mA
IOL = 200 mA
Low level output voltage
Low-level
High-level output voltage
2.5
VCC = 5 V
IOL = 5 mA
IOL = 8 mA
VCC = 15 V
IOH = – 100 mA
IOH = – 200 mA
13
IOH = – 100 mA
VCC = 15 V
3
VCC = 5 V
Output low,
low
No load
Supply current
Output high,
high
No load
0.3
2.5
0.1
0.2
0.1
0.35
0.15
0.25
0.15
0.4
13.3
12.75
12.5
VCC = 5 V
VCC = 15 V
2.75
nA
V
mA
nA
V
V
13.3
12.5
3.3
V
V
3.3
10
12
10
3
5
3
15
6
9
10
9
13
mA
VCC = 5 V
2
4
2
5
NOTE 2: This parameter influences the maximum value of the timing resistors RA and RB in the circuit of Figure 12. For example, when
VCC = 5 V, the maximum value is R = RA + RB ≈ 3.4 MΩ, and for VCC = 15 V, the maximum value is 10 MΩ.
operating characteristics, VCC = 5 V and 15 V
TEST
CONDITIONS†
PARAMETER
Initial error of timing interval‡
Each timer, monostable§
Each timer, astable¶
Temperature coefficient
of timing interval
Each timer, monostable§
Supply
y voltage
g sensitivity
y
of timing interval
Each timer, monostable§
Output pulse rise time
Each timer, astable¶
Each timer, astable¶
NE555, SA555,
SE555C
SE555
MIN
TA = 25°C
TYP
MAX
0.5%
1.5%
1.5%
TA = MIN to MAX
30
100
100
MAX
1%
3%
50
ppm/°C
150
0.2
0.15
CL = 15 pF,,
TA = 25°C
UNIT
TYP
2.25%
90
0.05
TA = 25°C
MIN
0.1
0.5
0.3
200
100
%/V
300
ns
Output pulse fall time
100
200
100
300
† For conditions shown as MIN or MAX, use the appropriate value specified under recommended operating conditions.
‡ Timing interval error is defined as the difference between the measured value and the average value of a random sample from each process
run.
§ Values specified are for a device in a monostable circuit similar to Figure 9, with component values as follow: RA = 2 kΩ to 100 kΩ, C = 0.1 µF.
¶ Values specified are for a device in an astable circuit similar to Figure 12, with component values as follow: RA = 1 kΩ to 100 kΩ, C = 0.1 µF.
POST OFFICE BOX 655303
• DALLAS, TEXAS 75265
5
NE555, NE555Y, SA555, SE555, SE555C
PRECISION TIMERS
SLFS022 – SEPTEMBER 1973 – REVISED FEBRUARY 1992
electrical characteristics, VCC = 5 V to 15 V, TA = 25°C (unless otherwise noted)
PARAMETER
TEST CONDITIONS
VCC = 15 V
VCC = 5 V
THRES voltage level
MIN
TYP
MAX
8.8
10
11.2
2.4
3.3
4.2
30
250
4.5
5
5.6
1.1
1.67
2.2
0.5
2
µA
0.7
1
V
0.1
0.4
– 0.4
– 1.5
THRES current (see Note 2)
TRIG voltage level
VCC = 15 V
VCC = 5 V
TRIG current
TRIG at 0 V
RESET voltage level
0.3
RESET at VCC
RESET current
RESET at 0 V
DISCH switch off-state current
VCC = 15 V
VCC = 5 V
CONT voltage (open circuit)
VCC = 15 V
Low level output voltage
Low-level
High-level output voltage
20
100
9
10
11
2.6
3.3
4
0.1
0.25
0.4
0.75
2
2.5
IOL = 10 mA
IOL = 50 mA
IOL = 100 mA
IOL = 200 mA
2.5
VCC = 5 V
IOL = 5 mA
IOL = 8 mA
VCC = 15 V
IOH = – 100 mA
IOH = – 200 mA
12.75
IOH = – 100 mA
VCC = 15 V
2.75
VCC = 5 V
low No load
Output low,
Supply current
Output high,
high No load
0.1
0.35
0.15
0.4
UNIT
V
nA
V
mA
nA
V
V
13.3
V
12.5
3.3
10
15
3
6
9
13
VCC = 5 V
VCC = 15 V
mA
VCC = 5 V
2
5
NOTE 2: This parameter influences the maximum value of the timing resistors RA and RB in the circuit of Figure 12. For example, when
VCC = 5 V, the maximum value is R = RA + RB ≈ 3.4 MΩ, and for VCC = 15 V, the maximum value is 10 MΩ
operating characteristics, VCC = 5 V and 15 V, TA = 25°C (unless otherwise noted)
TEST
CONDITIONS
PARAMETER
Initial error of timing interval†
Each timer, monostable‡
Each timer, astable§
Supply voltage sensitivity of timing interval
Each timer, monostable‡
Each timer, astable§
Output pulse rise time
MIN
TYP
MAX
1%
3%
UNIT
2.25%
0.1
0.3
0.5
%/V
100
300
CL = 15 pF
ns
Output pulse fall time
100
300
† Timing interval error is defined as the difference between the measured value and the average value of a random sample from each process
run.
‡ Values specified are for a device in a monostable circuit similar to Figure 9, with component values as follow: RA = 2 kΩ to 100 kΩ, C = 0.1 µF.
§ Values specified are for a device in an astable circuit similar to Figure 12, with component values as follow: RA = 1 kΩ to 100 kΩ, C = 0.1 µF.
6
POST OFFICE BOX 655303
• DALLAS, TEXAS 75265
NE555, NE555Y, SA555, SE555, SE555C
PRECISION TIMERS
SLFS022 – SEPTEMBER 1973 – REVISED FEBRUARY 1992
TYPICAL CHARACTERISTICS†
LOW-LEVEL OUTPUT VOLTAGE
vs
LOW-LEVEL OUTPUT CURRENT
4
2
1
0.7
0.4
ÏÏÏÏ
ÏÏÏÏ
ÏÏÏÏÏ
ÏÏÏÏÏ
ÏÏÏ
ÏÏÏÏÏ
ÏÏÏÏÏ
ÏÏÏÏ
ÏÏÏÏ
ÏÏÏÏ
ÏÏÏÏ
ÏÏÏÏ
10
7
VCC = 5 V
TA = – 55°C
TA = 25°C
ÏÏÏÏ
TA = 125°C
0.2
0.1
0.07
0.04
VOL – Low-Level Output Voltage – V
VOL – Low-Level Output Voltage – V
10
7
LOW-LEVEL OUTPUT VOLTAGE
vs
LOW-LEVEL OUTPUT CURRENT
0.02
VCC = 10 V
4
2
TA = 25°C
1
0.7
TA= – 55°C
TA = 125°C
0.4
0.2
0.1
0.07
0.04
0.02
0.01
0.01
1
2
4
7
10
20
40
70 100
1
IOL – Low-Level Output Current – mA
2
Figure 1
TA = – 55°C
1
0.7
TA = 25°C
TA = 125°C
0.1
0.07
0.04
1.6
1.2
0.8
0.6
0.4
0.01
0
4
7
10
20
40
70 100
TA = 125°C
1
0.2
2
70 100
TA = 25°C
1.4
0.02
1
40
TA = – 55°C
1.8
2
0.2
20
ÏÏÏÏ
ÏÏÏÏ
ÏÏÏÏ
ÏÏÏÏ
2.0
VCC = 15 V
0.4
10
DROP BETWEEN SUPPLY VOLTAGE AND OUTPUT
vs
HIGH-LEVEL OUTPUT CURRENT
VCC – VOH – Voltage Drop – V
VOL – Low-Level Output Voltage – V
4
ÏÏÏÏÏ
ÏÏÏÏÏ
7
Figure 2
LOW-LEVEL OUTPUT VOLTAGE
vs
LOW-LEVEL OUTPUT CURRENT
10
7
4
IOL – Low-Level Output Current – mA
ÏÏÏÏÏÏ
VCC = 5 V to 15 V
1
IOL – Low-Level Output Current – mA
2
4
7 10
20
40
70 100
IOH – High-Level Output Current – mA
Figure 3
Figure 4
† Data for temperatures below 0°C and above 70°C are applicable for SE555 circuits only.
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NE555, NE555Y, SA555, SE555, SE555C
PRECISION TIMERS
SLFS022 – SEPTEMBER 1973 – REVISED FEBRUARY 1992
TYPICAL CHARACTERISTICS†
NORMALIZED OUTPUT PULSE DURATION
(MONOSTABLE OPERATION)
vs
SUPPLY VOLTAGE
SUPPLY CURRENT
vs
SUPPLY VOLTAGE
Pulse Duration Relative to Value at VCC = 10 V
10
Output Low,
No Load
9
I CC – Supply Current – mA
8
TA = 25°C
7
6
5
TA = –55°C
4
TA = 125°C
3
2
1
0
1.015
1.010
1.005
1
0.995
0.990
0.985
5
6
7
8
9
10
12
11
13
14
15
0
5
VCC – Supply Voltage – V
Figure 5
PROPAGATION DELAY TIME
vs
LOWEST VOLTAGE LEVEL
OF TRIGGER PULSE
1.015
300
VCC = 10 V
tPD – Propagation Delay Time – ns
Pulse Duration Relative to Value at TA = 25 °
C
20
Figure 6
NORMALIZED OUTPUT PULSE DURATION
(MONOSTABLE OPERATION)
vs
FREE-AIR TEMPERATURE
1.010
1.005
1
0.995
0.990
250
TA = –55°C
200
TA = 0°C
150
100
TA = 25°C
TA = 70°C
50
TA = 125°C
0.985
–75
0
–50
–25
0
25
50
75
100 125
0
TA – Free-Air Temperature – °C
0.1 x VCC 0.2 x VCC 0.3 x VCC 0.4 x VCC
Lowest Voltage Level of Trigger Pulse
Figure 7
Figure 8
† Data for temperatures below 0°C and above 70°C are applicable for SE555 circuits only.
8
15
10
VCC – Supply Voltage – V
POST OFFICE BOX 655303
• DALLAS, TEXAS 75265
NE555, NE555Y, SA555, SE555, SE555C
PRECISION TIMERS
SLFS022 – SEPTEMBER 1973 – REVISED FEBRUARY 1992
APPLICATION INFORMATION
monostable operation
For monostable operation, any of these timers may be connected as shown in Figure 9. If the output is low,
application of a negative-going pulse to TRIG sets the flip-flop (Q goes low), drives the output high, and turns
off Q1. Capacitor C is then charged through RA until the voltage across the capacitor reaches the threshold
voltage of THRES input. If TRIG has returned to a high level, the output of the threshold comparator will reset
the flip-flop (Q goes high), drive the output low, and discharge C through Q1.
ÏÏÏÏÏ
ÏÏÏÏÏ
ÏÏÏÏÏ
ÏÏÏÏÏ
RA = 9.1 kΩ
CL = 0.01 µF
RL = 1 kΩ
See Figure 9
RA
5
ÎÎ
4
7
6
Input
2
8
CONT
VCC
RESET
RL
DISCH
OUT
3
Input Voltage
Voltage – 2 V/div
VCC
(5 V to 15 V)
Output
Output Voltage
THRES
TRIG
ÏÏÏÏÏÏ
GND
1
Capacitor Voltage
Pin numbers shown are for the D, JG, and P packages.
Time – 0.1 ms/div
Figure 9. Circuit for Monostable Operation
RA = 10 MΩ
1
– Output Pulse Duration – s
Applying a negative-going trigger pulse simultaneously to RESET and TRIG during the timing
interval discharges C and re-initiates the cycle,
commencing on the positive edge of the reset
pulse. The output is held low as long as the reset
pulse is low. To prevent false triggering, when
RESET is not used, it should be connected to VCC.
10
tw
Monostable operation is initiated when TRIG
voltage falls below the trigger threshold. Once
initiated, the sequence ends only if TRIG is high
at the end of the timing interval. Because of the
threshold level and saturation voltage of Q1,
the output pulse duration is approximately
tw = 1.1 RAC. Figure 11 is a plot of the time
constant for various values of RA and C. The
threshold levels and charge rates are both directly
proportional to the supply voltage, VCC. The timing
interval is therefore independent of the supply
voltage, so long as the supply voltage is constant
during the time interval.
Figure 10. Typical Monostable Waveforms
RA = 1 MΩ
10–1
10–2
10–3
RA = 100 kΩ
RA = 10 kΩ
10–4
RA = 1 kΩ
10–5
0.001
0.01
0.1
1
10
100
C – Capacitance – µF
Figure 11. Output Pulse Duration vs Capacitance
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9
NE555, NE555Y, SA555, SE555, SE555C
PRECISION TIMERS
SLFS022 – SEPTEMBER 1973 – REVISED FEBRUARY 1992
APPLICATION INFORMATION
astable operation
As shown in Figure 12, adding a second resistor, RB, to the circuit of Figure 9 and connecting the trigger input
to the threshold input causes the timer to self-trigger and run as a multivibrator. The capacitor C will charge
through RA and RB and then discharge through RB only. The duty cycle may be controlled, therefore, by the
values of RA and RB.
This astable connection results in capacitor C charging and discharging between the threshold-voltage level
(≈ 0.67•VCC) and the trigger-voltage level (≈ 0.33•VCC). As in the monostable circuit, charge and discharge
times (and therefore the frequency and duty cycle) are independent of the supply voltage.
ÏÏÏÏÏÏÏÏÏ
ÏÏÏÏÏÏÏÏÏ
ÏÏÏÏÏÏÏÏÏ
VCC
(5 V to 15 V)
RA = 5 k Ω
RB = 3 k Ω
C = 0.15 µF
RA
RB
Open
(see Note A) 5
CONT
4
RESET
7
DISCH
8
VCC
Î
6
2
RL
3
OUT
Output
THRES
tH
TRIG
Output Voltage
tL
GND
C
Voltage – 1 V/div
0.01 µF
1
Pin numbrs shown are for the D, JG, and P packages.
Capacitor Voltage
NOTE A: Decoupling CONT voltage to ground with a
capacitor may improve operation. This should be
evaluated for individual applications.
Figure 12. Circuit for Astable Operation
10
RL = 1 kΩ
See Figure 12
POST OFFICE BOX 655303
Time – 0.5 ms/div
Figure 13. Typical Astable Waveforms
• DALLAS, TEXAS 75265
NE555, NE555Y, SA555, SE555, SE555C
PRECISION TIMERS
SLFS022 – SEPTEMBER 1973 – REVISED FEBRUARY 1992
APPLICATION INFORMATION
Figure 13 shows typical waveforms generated during astable operation. The output high-level duration tH and
low-level duration tL may be calculated as follows:
100 k
+ 0.693 (RA ) RB) C
H
t + 0.693 (R C
L
B)
RA + 2 RB = 1 kΩ
f – Free-Running Frequency – Hz
t
Other useful relationships are shown below.
+ tH ) tL + 0.693 (RA ) 2RB) C
1.44
frequency [
(R ) 2R ) C
period
A
B
Output driver duty cycle
+ t t)L t + R )RB2R
H
L
A
B
RA + 2 RB = 100 kΩ
1k
100
10
1
Output waveform duty cycle
R
t
B
H
1–
t
t
R
2R
H
L
A
B
t
R
L
B
Low- t o-high ratio
t
R
R
H
A
B
+ ) +
)
+ + )
RA + 2 RB = 10 kΩ
10 k
RA + 2 RB = 1 MΩ
RA + 2 RB = 10 MΩ
0.1
0.001
0.01
0.1
1
10
100
C – Capacitance – µF
Figure 14. Free-Running Frequency
missing-pulse detector
The circuit shown in Figure 15 may be used to detect a missing pulse or abnormally long spacing between
consecutive pulses in a train of pulses. The timing interval of the monostable circuit is continuously retriggered
by the input pulse train as long as the pulse spacing is less than the timing interval. A longer pulse spacing,
missing pulse, or terminated pulse train permits the timing interval to be completed, thereby generating an
output pulse as illustrated in Figure 16.
ÏÏÏÏÏ
ÏÏÏÏÏ
ÏÏÏÏÏ
VCC (5 V to 15 V)
Input
2
8
VCC
OUT
0.01 µF
3
TRIG
DISCH
5
RL
CONT
THRES
GND
7
ÏÏÏ
ÏÏÏ
RA
Output
6
Voltage – 2 V/div
4
RESET
VCC = 5 V
RA = 1 kΩ
C = 0.1 µF
See Figure 15
Input Voltage
ÏÏÏÏÏÏ
ÏÏÏÏÏÏ
Output Voltage
C
1
A5T3644
Capacitor Voltage
Time – 0.1 ms/div
Pin numbers shown are shown for the D, JG, and P packages.
Figure 15. Circuit for Missing Pulse Detector
POST OFFICE BOX 655303
Figure 16. Circuit for Missing Pulse Detector
• DALLAS, TEXAS 75265
11
NE555, NE555Y, SA555, SE555, SE555C
PRECISION TIMERS
SLFS022 – SEPTEMBER 1973 – REVISED FEBRUARY 1992
APPLICATION INFORMATION
frequency divider
By adjusting the length of the timing cycle, the basic circuit of Figure 9 can be made to operate as a frequency
divider. Figure 17 illustrates a divide-by-three circuit that makes use of the fact that retriggering cannot occur
during the timing cycle.
ÏÏÏÏÏ
ÏÏÏÏÏ
ÏÏÏÏÏ
ÏÏÏÏÏ
Voltage – 2 V/div
VCC = 5 V
RA = 1250 Ω
C = 0.02 µF
See Figure 9
Input Voltage
Output Voltage
Capacitor Voltage
Time – 0.1 ms/div
Figure 17. Divide-By-Three Circuit Waveforms
pulse-width modulation
The operation of the timer may be modified by modulating the internal threshold and trigger voltages, which is
accomplished by applying an external voltage (or current) to CONT. Figure 18 shows a circuit for pulse-width
modulation. A continuous input pulse train triggers the monostable circuit, and a control signal modulates the
threshold voltage. Figure 19 illustrates the resulting output pulse-width modulation. While a sine-wave
modulation signal is illustrated, any wave shape could be used.
12
POST OFFICE BOX 655303
• DALLAS, TEXAS 75265
NE555, NE555Y, SA555, SE555, SE555C
PRECISION TIMERS
SLFS022 – SEPTEMBER 1973 – REVISED FEBRUARY 1992
APPLICATION INFORMATION
VCC (5 V to 15 V)
2
Clock
Input
RL
8
RESET
VCC
OUT
TRIG
5
CONT
RA
Modulation Input Voltage
3
Output
7
DISCH
Modulation
Input
(see Note A)
RA = 3 kΩ
C = 0.02 µF
RL = 1 kΩ
See Figure 18
Voltage – 2 V/div
4
THRES
ÏÏÏÏÏ
ÏÏÏÏÏ
ÏÏÏÏÏ
ÏÏÏÏÏÏÏ
ÏÏÏÏÏÏÏ
ÏÏÏÏÏÏÏ
ÏÏÏÏÏÏÏ
ÏÏÏÏÏ
ÏÏÏÏÏ
ÏÏÏÏÏÏ
6
GND
C
1
Clock Input Voltage
Output Voltage
Pin numbers shown are for the D, JG, and P packages only.
NOTE A: The modulating signal may be direct or capacitively
coupled to CONT. For direct coupling, the effects of
modulation source voltage and impedance on the bias of
the timer should be considered.
Capacitor Voltage
Time – 0.5 ms/div
Figure 19. Pulse-Width Modulation Waveforms
Figure 18. Circuit for Pulse-Width Modulation
pulse-position modulation
As shown in Figure 20, any of these timers may be used as a pulse-position modulator. This application
modulates the threshold voltage, and thereby the time delay, of a free-running oscillator. Figure 21 illustrates
a triangular-wave modulation signal for such a circuit; however, any wave shape could be used.
VCC (5 V to 15 V)
8
RESET
2
Modulation 5
Input
(see Note A)
VCC
OUT
RL
RA
3
Output
TRIG
CONT
RA = 3 kΩ
RB = 500 Ω
RL = 1 kΩ
See Figure 20
DISCH
7
THRES
6
RB
GND
C
Pin numbers shown are for the D, JG, and P packages only.
NOTE A: The modulating signal may be direct or capacitively
coupled to CONT. For direct coupling, the effects of
modulation source voltage and impedance on the bias of
the timer should be considered.
Figure 20. Circuit for Pulse-Position Modulation
POST OFFICE BOX 655303
Voltage – 2 V/div
4
ÏÏÏÏÏÏ
ÏÏÏÏÏÏ
ÏÏÏÏÏÏ
ÏÏÏÏÏÏ
ÏÏÏÏÏÏÏÏ
ÏÏÏÏÏÏÏÏ
Modulation Input Voltage
ÏÏÏÏÏÏ
ÏÏÏÏÏÏ
ÏÏÏÏÏÏ
ÏÏÏÏÏÏ
Output Voltage
Capacitor Voltage
Time – 0.1 ms/div
Figure 21. Pulse-Position-Modulation Waveforms
• DALLAS, TEXAS 75265
13
NE555, NE555Y, SA555, SE555, SE555C
PRECISION TIMERS
SLFS022 – SEPTEMBER 1973 – REVISED FEBRUARY 1992
APPLICATION INFORMATION
sequential timer
VCC
4
RESET
2
8
VCC
OUT
TRIG
S
DISCH
5
0.01
µF
CONT
4
RESET
RA 33 kΩ
3
2
0.001
µF
7
1
6
TRIG
CONT
0.01
µF
CA
CA = 10 µF
RA = 100 kΩ
Output A
RB
THRES
GND
1
CB
4
RESET
33 kΩ
3
2
0.001
µF
DISCH 7
5
THRES
GND
8
VCC
OUT
0.01
µF
Output B
CB = 4.7 µF
RB = 100 kΩ
TRIG
DISCH
5
6
8
VCC
OUT
CONT
THRES
GND
1
RC
3
7
6
CC
CC = 14.7 µF
RC = 100 kΩ
Output C
S closes momentarily at t = 0.
Pin numbers shown are for the D, JG, and P packages only.
Figure 22. Sequential Timer Circuit
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 may
be connected to provide such sequential control. The timers may be used in various combinations of astable
or monostable circuit connections, with or without modulation, for extremely flexible waveform control. Figure 22
illustrates a sequencer circuit with possible applications in many systems, and Figure 23 shows the output
waveforms.
ÏÏÏÏÏ
ÏÏ
ÏÏÏÏÏ ÏÏÏÏÏÏ
ÏÏÏ
ÏÏÏ
ÏÏÏ
ÏÏÏÏÏ
ÏÏÏ
ÏÏÏ
ÏÏ ÏÏÏÏÏ
ÏÏÏ
ÏÏÏ
See Figure 22
Voltage – 5 V/div
Output A
tw A
twA = 1.1 RACA
tw B
Output B
twB = 1.1 RBCB
Output C
tw C
twC = 1.1 RCCC
t=0
t – Time – 1 s/div
Figure 23. Sequential Timer Waveforms
14
POST OFFICE BOX 655303
• DALLAS, TEXAS 75265
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