Philips 74HCT221N, 74HCT221DB, 74HCT221D, 74HC221N, 74HC221DB Datasheet
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DATA SH EET
Product specification
Supersedes data of April 1988
File under Integrated Circuits, IC06
December 1990
INTEGRATED CIRCUITS
74HC/HCT221
Dual non-retriggerable monostable
multivibrator with reset
For a complete data sheet, please also download:
•The IC06 74HC/HCT/HCU/HCMOS Logic Family Specifications
•The IC06 74HC/HCT/HCU/HCMOS Logic Package Information
•The IC06 74HC/HCT/HCU/HCMOS Logic Package Outlines
December 1990 2
Philips Semiconductors Product specification
Dual non-retriggerable monostable
multivibrator with reset
74HC/HCT221
FEATURES
• Pulse width variance is typically less than ±5%
• Pin-out identical to “123”
• Overriding reset terminates output pulse
• nB inputs have hysteresis for improved noise immunity
• Output capability: standard (except for nR
EXT/CEXT
)
• ICC category: MSI
GENERAL DESCRIPTION
The 74HC/HCT221 are high-speed Si-gate CMOS devices
and are pin compatible with low power Schottky TTL
(LSTTL). They are specified in compliance with JEDEC
standard no. 7A.
The 74HC/HCT221 are dual non-retriggerable monostable
multivibrators. Each multivibrator features an active
LOW-going edge input (n
A) and an active HIGH-going
edge input (nB), either of which can be used as an enable
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 for the nB inputs allow
jitter-free triggering from inputs with slow transition rates,
providing the circuit with excellent noise immunity.
Once triggered, the outputs (nQ, nQ) are independent of
further transitions of nA and nB inputs and are a function
of the timing components. The output pulses can be
terminated by the overriding active LOW reset inputs
(nRD). Input pulses may be of any duration relative to the
output pulse.
Pulse width stability is achieved through internal
compensation and is virtually independent of VCC and
temperature. In most applications pulse stability will only
be limited by the accuracy of the external timing
components.
The output pulse width is defined by the following
relationship:
tW=C
EXTREXTIn2
tW= 0.7C
EXTREXT
Pin assignments for the “221” are identical to those of the
“123” so that the “221” can be substituted for those
products in systems not using the retrigger by merely
changing the value of R
EXT
and/or C
EXT
.
QUICK REFERENCE DATA
GND = 0 V; T
amb
=25°C; tr=tf= 6 ns
Notes
1. C
PD
is used to determine the dynamic power dissipation (PD in µW):
PD=CPD× V
CC
2
× fi+∑(CL× V
CC
2
× fo) + 0.33 × C
EXT
× V
CC
2
× fo+ D × 28 × VCCwhere:
fi= input frequency in MHz; fo= output frequency in MHz
∑ (CL× V
CC
2
× fo) = sum of outputs
C
EXT
= timing capacitance in pF; CL= output load capacitance in pF
VCC= supply voltage in V; D = duty factor in %
2. For HC the condition is VI= GND to V
CC
For HCT the condition is VI= GND to VCC− 1.5 V
SYMBOL PARAMETER CONDITIONS
TYPICAL
UNIT
HC HCT
propagation delay C
L
= 15 pF; VCC=5 V;
R
EXT
=5 kΩ; C
EXT
= 0 pF
t
PHL
nA, nB, nRD to nQ, nQ 2932ns
t
PLH
nA, nB, nRD to nQ, nQ 3536ns
C
I
input capacitance 3.5 3.5 pF
C
PD
power dissipation capacitance per package notes 1 and 2 90 96 pF
December 1990 3
Philips Semiconductors Product specification
Dual non-retriggerable monostable
multivibrator with reset
74HC/HCT221
ORDERING INFORMATION
See
“74HC/HCT/HCU/HCMOS Logic Package Information”
.
PIN DESCRIPTION
PIN NO. SYMBOL NAME AND FUNCTION
1, 9 1
A, 2A trigger inputs (negative-edge triggered)
2, 10 1B, 2B trigger inputs (positive-edge triggered)
3, 11 1
RD, 2R
D
direct reset inputs (active LOW)
4, 12 1
Q, 2Q outputs (active LOW)
72R
EXT/CEXT
external resistor/capacitor connection
8 GND ground (0 V)
13, 5 1Q, 2Q outputs (active HIGH)
14, 6 1C
EXT
, 2C
EXT
external capacitor connection
15 1R
EXT/CEXT
external resistor/capacitor connection
16 V
CC
positive supply voltage
Fig.1 Pin configuration. Fig.2 Logic symbol. Fig.3 IEC logic symbol.
December 1990 4
Philips Semiconductors Product specification
Dual non-retriggerable monostable
multivibrator with reset
74HC/HCT221
Fig.4 Functional diagram.
FUNCTION TABLE
Notes
1. H = HIGH voltage level
L = LOW voltage level
X = don’t care
↑ = LOW-to-HIGH level
↓ = HIGH-to-LOW level
= one HIGH-level output pulse
= one LOW-level output pulse
2. If the monostable was triggered before this condition
was established the pulse will continue as
programmed.
3. For this combination the reset input must be LOW and
the following sequence must be used:
pin 1 (or 9) must be set HIGH or pin 2 (or 10) set LOW;
then pin 1 (or 9) must be LOW and pin 2 (or 10) set
HIGH. Now the reset input goes from LOW-to-HIGH
and the device will be triggered.
INPUTS OUTPUTS
nR
D
nAnBnQnQ
LXXLH
XHXL
(2)
H
(2)
XXLL
(2)
H
(2)
HL↑
H↓H
↑LH
(3) (3)
December 1990 5
Philips Semiconductors Product specification
Dual non-retriggerable monostable
multivibrator with reset
74HC/HCT221
Note
It is recommended to ground pins 6 (2C
EXT
) and 14 (1C
EXT
) externally to pin 8 (GND).
Fig.5 Logic diagram.
Fig.6 Timing component connections.
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