SN54221, SN54LS221, SN74221, SN74LS221

DUAL MONOSTABLE MULTIVIBRATORS

WITH SCHMITT-TRIGGER INPUTS
SDLS213A – DECEMBER 1983 – REVISED FEBRUARY 1998

D Dual Versions of Highly Stable SN54121 SN54221, SN54LS221 . . . J OR W PACKAGE

and SN74121 One Shots SN74221 . . . N PACKAGE
SN74LS221 . . . D, DB, OR N PACKAGE
D SN54221 and SN74221 Demonstrate (TOP VIEW)
Electrical and Switching Characteristics
That Are Virtually Identical to the SN54121 1A 1 16 VCC
and SN74121 One Shots 1B 2 15 1Rext/Cext
D Pinout Is Identical to the SN54123, 1CLR 3 14 1Cext
SN74123, SN54LS123, and SN74LS123 1Q 4 13 1Q
D Overriding Clear Terminates Output Pulse 2Q 5 12 2Q

D Package Options Include Plastic

2Cext
2Rext/Cext
6
7
11
10
2CLR
2B
Small-Outline (D), Shrink Small-Outline
GND 8 9 2A
(DB) Packages, Ceramic Chip Carriers (FK)
and Flat Packs (W), and Standard Plastic
(N) and Ceramic (J) 300-mil DIPs SN54LS221 . . . FK PACKAGE
(TOP VIEW)
MAXIMUM

1R ext /Cext
OUTPUT
PULSE
TYPE LENGTH(S)

VCC
NC
1B
1A
SN54221 21
SN74221 28
3 2 1 20 19
SN54LS221 49 1CLR 4 18 1Cext
1Q 5 17 1Q
SN74LS221 70
NC 6 16 NC
2Q 7 15 2Q
description 2Cext 8 14 2CLR
9 10 11 12 13
The ’221 and ’LS221 devices are monolithic dual
multivibrators with performance characteristics

2A
2B
NC
GND
virtually identical to those of the ’121 devices. 2R ext/Cext
Each multivibrator features a negative-transition-
triggered input and a positive-transition-triggered
input, either of which can be used as an inhibit NC – No internal connection
input.
Pulse triggering occurs at a particular voltage level and is not directly related to the transition time of the input
pulse. Schmitt-trigger input circuitry (TTL hysteresis) for B input allows jitter-free triggering from inputs with
transition rates as slow as 1 V/s, providing the circuit with excellent noise immunity, typically of 1.2 V. A high
immunity to VCC noise, typically of 1.5 V, is also provided by internal latching circuitry.
Once fired, the outputs are independent of further transitions of the A and B inputs and are a function of the timing
components, or the output pulses can be terminated by the overriding clear. Input pulses can be of any duration
relative to the output pulse. Output pulse length can be varied from 35 ns to the maximums shown in the above
table by choosing appropriate timing components. With Rext = 2 kΩ and Cext = 0, an output pulse typically of
30 ns is achieved, which can be used as a dc-triggered reset signal. Output rise and fall times are TTL
compatible and independent of pulse length. Typical triggering and clearing sequences are shown as a part of
the switching characteristics waveforms.
Pulse-width stability is achieved through internal compensation and is virtually independent of VCC and
temperature. In most applications, pulse stability is limited only by the accuracy of external timing components.

Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of
Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.

PRODUCTION DATA information is current as of publication date. Copyright  1998, Texas Instruments Incorporated
Products conform to specifications per the terms of Texas Instruments On products compliant to MIL-PRF-38535, all parameters are tested
standard warranty. Production processing does not necessarily include unless otherwise noted. On all other products, production
testing of all parameters. processing does not necessarily include testing of all parameters.

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 1

SN54221, SN54LS221, SN74221, SN74LS221
DUAL MONOSTABLE MULTIVIBRATORS
WITH SCHMITT-TRIGGER INPUTS
SDLS213A – DECEMBER 1983 – REVISED FEBRUARY 1998

description (continued)
Jitter-free operation is maintained over the full temperature and VCC ranges for more than six decades of timing
capacitance (10 pF to 10 µF) and more than one decade of timing resistance (2 kΩ to 30 kΩ for the SN54221,
2 kΩ to 40 kΩ for the SN74221, 2 kΩ to 70 kΩ for the SN54LS221, and 2 kΩ to 100 kΩ for the SN74LS221).
Throughout these ranges, pulse width is defined by the relationship: tw(out) = CextRext In2 ≈ 0.7 CextRext. In
circuits where pulse cutoff is not critical, timing capacitance up to 1000 µF and timing resistance as low as 1.4 kΩ
can be used. Also, the range of jitter-free output pulse widths is extended if VCC is held to 5 V and free-air
temperature is 25°C. Duty cycles as high as 90% are achieved when using maximum recommended RT. Higher
duty cycles are available if a certain amount of pulse-width jitter is allowed.
The variance in output pulse width from device to device typically is less than ±0.5% for given external timing
components. An example of this distribution for the ’221 is shown in Figure 3. Variations in output pulse width
versus supply voltage and temperature for the ’221 are shown in Figures 4 and 5, respectively.
Pin assignments for these devices are identical to those of the SN54123/SN74123 or SN54LS123/SN74LS123
so that the ’221 or ’LS221 devices can be substituted for those products in systems not using the retrigger by
merely changing the value of Rext and/or Cext; however, the polarity of the capacitor must be changed.
The SN54221 and SN54LS221 are characterized for operation over the full military temperature range of –55°C
to 125°C. The SN74221 and SN74LS221 are characterized for operation from 0°C to 70°C.

FUNCTION TABLE
(each monostable multivibrator)
INPUTS OUTPUTS
CLR A B Q Q
L X X L H
X H X L H
X X L L H
H L ↑ † †
H ↓ H † †
↑‡ L H † †
† Pulsed-output patterns are tested during
AC switching at 25°C with Rext = 2 kΩ, and
Cext = 80 pF.
‡ This condition is true only if the output of
the latch formed by the two NAND gates
has been conditioned to the logic 1 state
prior to CLR going high. This latch is
conditioned by taking either A high or
B low while CLR is inactive (high).

2 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

 SN54221, SN54LS221, SN74221, SN74LS221
DUAL MONOSTABLE MULTIVIBRATORS
WITH SCHMITT-TRIGGER INPUTS
SDLS213A – DECEMBER 1983 – REVISED FEBRUARY 1998

logic symbol†

1 &
1A 1
2
1B 13
1Q

3
1CLR R 4
14 1Q
1Cext CX
15
1Rext/Cext RX/CX
9
2A & 1
10
2B 5
2Q
11
2CLR R
12
6 2Q
2Cext CX
7
2Rext/Cext RX/CX

† This symbol is in accordance with ANSI/IEEE Std 91-1984 and IEC Publication 617-12.
Pin numbers shown are for the D, DB, J, N, and W packages.

timing component connections

VCC

Rext

To Cext To Rext/Cext
Terminal Terminal

NOTE: Due to the internal circuit, the Rext/Cext terminal is never more positive than the Cext terminal.

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 3

SN54221, SN54LS221, SN74221, SN74LS221
DUAL MONOSTABLE MULTIVIBRATORS
WITH SCHMITT-TRIGGER INPUTS
SDLS213A – DECEMBER 1983 – REVISED FEBRUARY 1998

schematics of inputs and outputs

SN54/74221

EQUIVALENT OF EACH INPUT TYPICAL OF ALL OUTPUTS

VCC VCC
Req 100 Ω NOM

Input

Output

A Input: Req = 4 kΩ NOM

B, CLR Input: Req = 2 kΩ NOM

SN54/74LS221

EQUIVALENT OF EACH INPUT TYPICAL OF ALL OUTPUTS

VCC VCC
Req 120 Ω NOM

Input

Output

A Input: Req = 25 kΩ NOM

B Input: Req = 15.4 kΩ NOM
CLR: Req = 12.5 kΩ NOM

4 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

 SN54221, SN54LS221, SN74221, SN74LS221
DUAL MONOSTABLE MULTIVIBRATORS
WITH SCHMITT-TRIGGER INPUTS
SDLS213A – DECEMBER 1983 – REVISED FEBRUARY 1998

absolute maximum ratings over operating free-air temperature range (unless otherwise noted)†
Supply voltage range, VCC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 V
Input voltage range, VI (see Note 1): ’LS221 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 V
’221 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.5 V
Package thermal impedance, θJA (see Note 2): D package . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113°C/W
DB package . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131°C/W
N package . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78°C/W
Storage temperature range, Tstg . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . –65°C to 150°C
† Stresses beyond those listed under “absolute maximum ratings” may cause permanent damage to the device. These are stress ratings only, and
functional operation of the device at these or any other conditions beyond those indicated under “recommended operating conditions” is not
implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
NOTES: 1. The input and output negative-voltage ratings may be exceeded if the input and output clamp-current ratings are observed.
2. The package thermal impedance is calculated in accordance with JESD 51, except for through-hole packages, which use a trace
length of zero

recommended operating conditions

SN54221 SN74221
UNIT
MIN NOM MAX MIN NOM MAX
VCC Supply voltage 4.5 5 5.5 4.75 5 5.25 V
VIH High-level input voltage A input 2 2 V
VIL Low-level input voltage A input 0.8 0.8 V
IOH High-level output current –800 –800 µA
IOL Low-level output current 16 16 mA
B input 1* 1 V/s
∆v/∆t Rise or fall of input pulse rate
A input 1* 1 V/µs
TA Operating free-air temperature –55 125 0 70 °C
∗ On products compliant to MIL-PRF-38535, this parameter is not production tested.

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 5

SN54221, SN54LS221, SN74221, SN74LS221
DUAL MONOSTABLE MULTIVIBRATORS
WITH SCHMITT-TRIGGER INPUTS
SDLS213A – DECEMBER 1983 – REVISED FEBRUARY 1998

electrical characteristics over recommended operating free-air temperature range (unless

otherwise noted)
SN54221 SN74221
PARAMETER TEST CONDITIONS† UNIT
MIN TYP‡ MAX MIN TYP‡ MAX
Positive-going threshold voltage,
VT+ VCC = MIN 1.55 2* 1.55 2 V
B input
Negative-going threshold voltage,
VT– VCC = MIN 0.8* 1.35 0.8 1.35 V
B input
VIK VCC = MIN, II = –12 mA –1.5 –1.5 V
VOH VCC = MIN, IOH = –800 µA 2.4 3.4 2.4 3.4 V
VOL VCC = MIN, IOL = 16 mA 0.2 0.4 0.2 0.4 V
II VCC = MAX, VI = 5.5 V 1 1 mA
A input 40 40
IIH VCC = MAX
MAX, VI = 2
2.4
4V µA
CLR, B input 80 80
A input –1.6 –1.6
IIL VCC = MAX
MAX, VI = 0
0.4
4V mA
CLR, B input –3.2 –3.2
IOS§ VCC = MAX –20 –55 –18 –55 mA
Quiescent 26 50* 26 50
ICC VCC = MAX mA
Triggered 46 80* 46 80
∗ On products compliant to MIL-PRF-38535, this parameter is not production tested.
† For conditions shown as MIN or MAX, use the appropriate value specified under recommended operating conditions.
‡ All typical values are at VCC = 5 V, TA = 25°C.
§ Not more than one output should be shorted at a time and the duration of the short circuit should not exceed one second.

timing requirements over recommended ranges of supply voltage and operating free-air
temperature
SN54221 SN74221
UNIT
MIN MAX MIN MAX
A or B input 50 50
tw Pulse duration ns
CLR 20 20
tsu Setup time, inactive-state¶ CLR 15 15 ns
Rext External timing resistance 1.4* 30* 1.4 40 kΩ
Cext External timing capacitance 0* 1000* 0 1000 µF
Rext = 2 kΩ 67% 67%
Output duty cycle
Rext = MAX Rext 90% 90%
∗ On products compliant to MIL-PRF-38535, this parameter is not production tested.
¶ Inactive-state setup time is also referred to as recovery time.

6 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

 SN54221, SN54LS221, SN74221, SN74LS221
DUAL MONOSTABLE MULTIVIBRATORS
WITH SCHMITT-TRIGGER INPUTS
SDLS213A – DECEMBER 1983 – REVISED FEBRUARY 1998

switching characteristics VCC = 5 V, RL = 400 Ω, TA = 25_C (see Figures 1 and 2)

FROM TO SN54221 SN74221
PARAMETER TEST CONDITIONS UNIT
(INPUT) (OUTPUT) MIN TYP MAX MIN TYP MAX
A 45 70 45 70
tPLH Q
B 35 55 35 55
Cext = 80 pF
pF, Rext = 2 kΩ ns
A 50 80 50 80
tPHL Q
B 40 65 40 65
tPHL Q 27 27
CLR Cext = 80 pF
pF, Rext = 2 kΩ ns
tPLH Q 40 40
Cext = 80 pF, Rext = 2 kΩ 70 110 150 70 110 150
Cext = 0, Rext = 2 kΩ 17 30 50 17 30 50 ns
tw A or B Q or Q
Cext = 100 pF, Rext = 10 kΩ 650 700 750 650 700 750
Cext = 1 µF, Rext = 10 kΩ 6.5* 7 7.5* 6.5 7 7.5 ms
∗ On products compliant to MIL-PRF-38535, this parameter is not production tested.

recommended operating conditions

SN54LS221 SN74LS221
UNIT
MIN NOM MAX MIN NOM MAX
VCC Supply voltage 4.5 5 5.5 4.75 5 5.25 V
VIH High-level input voltage A input 2 2 V
VIL Low-level input voltage A input 0.7 0.8 V
IOH High-level output current –400 –400 µA
IOL Low-level output current 4 8 mA
B input 1* 1 V/s
∆v/∆t Rise or fall of input pulse rate
A input 1* 1 V/µs
TA Operating free-air temperature –55 125 0 70 °C
∗ On products compliant to MIL-PRF-38535, this parameter is not production tested.

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 7

SN54221, SN54LS221, SN74221, SN74LS221
DUAL MONOSTABLE MULTIVIBRATORS
WITH SCHMITT-TRIGGER INPUTS
SDLS213A – DECEMBER 1983 – REVISED FEBRUARY 1998

electrical characteristics over recommended operating free-air temperature range (unless

otherwise noted)
SN54LS221 SN74LS221
PARAMETER TEST CONDITIONS† UNIT
MIN TYP‡ MAX MIN TYP‡ MAX
Positive-going threshold voltage,
VT+ VCC = MIN 1 2* 1 2 V
B input
Negative-going threshold voltage,
VT– VCC = MIN 0.7* 0.9 0.8 0.9 V
B input
VIK VCC = MIN, II = –18 mA –1.5 –1.5 V
VOH VCC = MIN, IOH = –400 µA 2.5 3.4 2.7 3.4 V
IOL = 4 mA 0.25 0.4 0.25 0.4
VOL VCC = MIN V
IOL = 8 mA 0.35 0.5
II VCC = MAX, VI = 7 V 0.1 0.1 mA
IIH VCC = MAX, VI = 2.7 V 20 20 µA
A input –0.4 –0.4
IIL VCC = MAX
MAX, VI = 0
0.4
4V mA
CLR, B input –0.8 –0.8
IOS§ VCC = MAX –20 –100 –20 –100 mA
Quiescent 4.7 11 4.7 11
ICC VCC = MAX mA
Triggered 19 27* 19 27
∗ On products compliant to MIL-PRF-38535, this parameter is not production tested.
† For conditions shown as MIN or MAX, use the appropriate value specified under recommended operating conditions.
‡ All typical values are at VCC = 5 V, TA = 25°C.
§ Not more than one output should be shorted at a time and the duration of the short circuit should not exceed one second.

timing requirements over recommended ranges of supply voltage and operating free-air
temperature
SN54LS221 SN74LS221
UNIT
MIN MAX MIN MAX
A or B 50 50
tw Pulse duration ns
CLR 40 40
tsu Setup time, inactive state¶ CLR 15 15 ns
Rext External timing resistance 1.4* 70* 1.4 100 kΩ
Cext External timing capacitance 0* 1000* 0 1000 µF
RT = 2 kΩ 50% 50%
Output duty cycle
RT = MAX Rext 90% 90%
∗ On products compliant to MIL-PRF-38535, this parameter is not production tested.
¶ Inactive-state setup time is also referred to as recovery time.

8 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

 SN54221, SN54LS221, SN74221, SN74LS221
DUAL MONOSTABLE MULTIVIBRATORS
WITH SCHMITT-TRIGGER INPUTS
SDLS213A – DECEMBER 1983 – REVISED FEBRUARY 1998

switching characteristics VCC = 5 V, RL = 2 kΩ, TA = 25_C (see Figures 1 and 2)

FROM TO SN54LS221 SN74LS221
PARAMETER TEST CONDITIONS UNIT
(INPUT) (OUTPUT) MIN TYP MAX MIN TYP MAX
A 45 70 45 70
tPLH Q
B 35 55 35 55
Cext = 80 pF
pF, Rext = 2 kΩ ns
A 50 80 50 80
tPHL Q
B 40 65 40 65
tPHL Q 35 55 35 55
CLR Cext = 80 pF
pF, Rext = 2 kΩ ns
tPLH Q 44 65 44 65
Cext = 80 pF, Rext = 2 kΩ 70 120 150 70 120 150
Cext = 0, Rext = 2 kΩ 20 47 70 20 47 70 ns
tw A or B Q or Q
Cext = 100 pF, Rext = 10 kΩ 670 740 810 670 740 810
Cext = 1 µF, Rext = 10 kΩ 6* 6.9 7.5* 6 6.9 7.5 ms
∗ On products compliant to MIL-PRF-38535, this parameter is not production tested.

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 9

SN54221, SN54LS221, SN74221, SN74LS221
DUAL MONOSTABLE MULTIVIBRATORS
WITH SCHMITT-TRIGGER INPUTS
SDLS213A – DECEMBER 1983 – REVISED FEBRUARY 1998

PARAMETER MEASUREMENT INFORMATION

tw
3V
B†
0V
≥ 60 ns
3V
CLR
0V
tPLH tPHL
VOH
Q
VOL
tPHL tPLH
VOH
Q
VOL

CONDITION 1: TRIGGER FROM B, THEN CLR

3V
B†
0V
≥ 60 ns
3V
CLR
0V

VOH
Q
VOL

CONDITION 2: TRIGGER FROM B, THEN CLR

3V
B†
0V
≥ 50 ns tsu
≥0
3V
CLR
0V
tw
Triggered
VOH
Q
VOL
Not Triggered
CONDITION 3: CLR OVERRIDING B, THEN TRIGGER FROM B

† A is low.

Figure 1. Switching Characteristics

10 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

 SN54221, SN54LS221, SN74221, SN74LS221
DUAL MONOSTABLE MULTIVIBRATORS
WITH SCHMITT-TRIGGER INPUTS
SDLS213A – DECEMBER 1983 – REVISED FEBRUARY 1998

PARAMETER MEASUREMENT INFORMATION

3V
B†
0V
≥ 50 ns ≥ 50 ns
3V
CLR
0V

VOH
Q
VOL

CONDITION 4: TRIGGERING FROM POSITIVE TRANSITION OF CLR

tw
3V
A‡
0V
≥ 60 ns
3V
CLR
0V
tPLH tPHL
VOH
Q
VOL
tPHL tPLH
VOH
Q
VOL

CONDITION 5: TRIGGER FROM A, THEN CLR

3V
A‡
0V
tw
VOH
Q
VOL

tw
VOH
Q
VOL

CONDITION 6: TRIGGER FROM A

† A is low.
‡ B and CLR are high.
NOTES: A. Input pulses are supplied by generators having the following characteristics: PRR ≤ 1 MHz, ZO ≈ 50Ω; for SN54/74221, tr ≤ 7 ns,
tf ≤ 7 ns, for SN54/74LS221, tr ≤ 15 ns, tf ≤ 6 ns.
B. All measurements are made between the 1.5-V points of the indicated transitions for the SN54/74221 or between the 1.3-V points
for the SN54/74LS221.

Figure 1. Switching Characteristics (Continued)

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 11

SN54221, SN54LS221, SN74221, SN74LS221
DUAL MONOSTABLE MULTIVIBRATORS
WITH SCHMITT-TRIGGER INPUTS
SDLS213A – DECEMBER 1983 – REVISED FEBRUARY 1998

PARAMETER MEASUREMENT INFORMATION

VCC
Test
Point

RL

From Output
(see Note B)
Under Test High-Level
CL = 15 pF
Pulse
(see Note A)

tw

Low-Level
Pulse
LOAD CIRCUIT FOR
BI-STATE VOLTAGE WAVEFORMS
TOTEM-POLE OUTPUTS PULSE DURATIONS

3V
Input
0V
tPLH tPHL

Timing 3V In-Phase VOH

Input Output
0V VOL
th tPLH
tsu tPHL
3V VOH
Data
Out-of-Phase
Input
Output
0V VOL
VOLTAGE WAVEFORMS VOLTAGE WAVEFORMS
SETUP AND HOLD TIMES PROPAGATION DELAY TIMES

NOTES: A. CL includes probe and jig capacitance.

B. All diodes are 1N3064 or equivalent.
C. In the examples above, the phase relationships between inputs and outputs have been chosen arbitrarily.
D. All input pulses are supplied by generators having the following characteristics: PRR ≤ 1 MHz, ZO ≈ 50 Ω and, for SN54/74221,
tr ≤ 7 ns, tf ≤ 7 ns, for SN54/74LS221, tr ≤ 15 ns, tf ≤ 6 ns.
E. All measurements are made between the 1.5-V points of the indicated transitions for the SN54/74221 or between the 1.3-V points
for the SN54/74LS221.

Figure 2. Load Circuits and Voltage Waveforms

12 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

 SN54221, SN54LS221, SN74221, SN74LS221
DUAL MONOSTABLE MULTIVIBRATORS
WITH SCHMITT-TRIGGER INPUTS
SDLS213A – DECEMBER 1983 – REVISED FEBRUARY 1998

TYPICAL CHARACTERISTICS (SN54/74221 ONLY)†

VARIATION IN OUTPUT PULSE

DISTRIBUTION OF UNITS
vs
FOR
SUPPLY VOLTAGE
OUTPUT PULSE
1
Cext = 60 pF
VCC = 5 V
Rext = 10 kΩ
TA = 25°C
TA = 25°C

∆ t w – Variation in Output Pulse – %

Relative Frequency of Occurrence

0.5

tw ≈ 420 ns
0 at VCC = 5 V

– 0.5

Median Median
+0.5% +0.5%
–1
4.5 4.75 5 5.25 5.5
Median
VCC – Supply Voltage – V
tw – Output Pulse
Figure 3 Figure 4

VARIATION IN OUTPUT PULSE OUTPUT PULSE

vs vs
FREE-AIR TEMPERATURE TIMING RESISTOR VALUE
1 10 ms
VCC = 5 V Cext = 1 µ F
Cext = 60 pF
Rext = 10 kΩ 1 ms
∆ t w – Variation in Output Pulse – %

Cext = 0.1 µ F
0.5

100 µs
t w – Output Pulse

Cext = 0.01 µ F
tw ≈ 420 ns
0 at TA = 25°C 10 µs
Cext = 1000 pF

1 µs
– 0.5 Cext = 100 pF

100 ns Cext = 10 pF
VCC = 5 V See Note A
TA = 25°C
–1 10 ns
–75 –50 –25 0 25 50 75 100 125 1 2 4 7 10 20 40 70 100
TA – Free-Air Temperature – °C Rext – Timing Resistor Value – kΩ

Figure 5 Figure 6
† Data for temperatures below 0°C and above 70°C, and for supply voltages below 4.75 V and above 5.25 V are applicable for the SN54221 only.
NOTE A: These values of resistance exceed the maximum recommended for use over the full military temperature range of the SN54221.

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 13

 IMPORTANT NOTICE

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Copyright  1998, Texas Instruments Incorporated