74HC_HCT221_CNV_15 Datasheet, PDF (2/15 Pages) NXP Semiconductors – Dual non-retriggerable monostable multivibrator with reset

Philips Semiconductors
Dual non-retriggerable monostable
multivibrator with reset
Product specification
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/C_EXT)
• I_CC 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 (nA) 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
(nR_D). 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 V_CC 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:
t_W = C_EXTR_EXTIn₂
t_W = 0.7C_EXTR_EXT
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; t_r = t_f = 6 ns
SYMBOL PARAMETER
CONDITIONS
propagation delay
t_PHL
nA, nB, nR_D to nQ, nQ
C_L = 15 pF; V_CC = 5 V;
R_EXT = 5 kΩ; C_EXT = 0 pF
t_PLH
nA, nB, nR_D to nQ, nQ
C_I
input capacitance
C_PD
power dissipation capacitance per package notes 1 and 2
TYPICAL
HC HCT
29
32
35
36
3.5
3.5
90
96
Notes
1. C_PD is used to determine the dynamic power dissipation (P_D in µW):
P_D = C_PD × V_CC2 × f_i + ∑ (C_L × V_CC2 × f_o) + 0.33 × C_EXT × V_CC2 × f_o + D × 28 × V_CC where:
f_i = input frequency in MHz; f_o = output frequency in MHz
∑ (C_L × V_CC2 × f_o) = sum of outputs
C_EXT = timing capacitance in pF; C_L = output load capacitance in pF
V_CC = supply voltage in V; D = duty factor in %
2. For HC the condition is V_I = GND to V_CC
For HCT the condition is V_I = GND to V_CC − 1.5 V
UNIT
ns
ns
pF
pF
December 1990
2