The M74HC221 is an high speed CMOS
MONOSTABLE MULTIVIBRATOR fabricated with
silicon gate C
There are two trigger inputs, A
2
MOS technology.
INPUT (negative
edge) and B INPUT (positive edge).
Triggering on the B input occurs at a particular
voltage threshold and is not related to rise and fall
time of the applied pulse. The device may also be
trigger by using the CLR
input (positive edge)
because of the Schimtt-trigger input; after
TSSOPDIPSOP
ORDER CODES
PACKAGETUBET & R
DIPM74HC221B1R
SOPM74HC221M1RM74HC221RM13TR
TSSOPM74HC221TTR
triggering the output maintains the
MONOSTABLE STATE for the time period
determined by the external resistor Rx and
capacitor Cx. Taking CLR
low breaks this
MONOSTABLE STATE. If the next trigger pulse
occurs during the MONOSTABL E period it makes
the MONOSTABLE period longer.
Limit for values of Cx and Rx :
Cx : NO LIMIT
Rx : V
V
K
< 3.0V 5KΩ to 1MΩ
cc
> 3.0V 1KΩ to 1MΩ
cc
≅ 0.7
All inputs are equipped with protection circuits
against static discharge and transient excess
voltage.
PIN CONNECTION AND IEC LOGIC SYMBOLS
1/14July 2001
M74HC221
INPUT AND OUTPUT EQUIVALENT CIRCUIT PIN DESCRIPTION
PIN NoSYMBOLNAME AND FUNCTION
1,91A
2, 101B, 2B
3, 11
4, 121Q
7
13, 51Q, 2QOutputs (Active High)
14, 6
15
8GNDGround (0V)
16VccPositive Supply Voltage
TRUTH TABLE
, 2A
1 CLR
2 CLR
, 2QOutputs (Active Low)
2R
X/CX
1C
X
2C
X
1R
X/CX
Trigger Inputs (Negative
Edge Triggered)
Trigger Inputs (Positive
Edge Triggered)
Direct Reset LOW and
trigger Action at Positive
Edge
External Resistor
Capacitor Connection
External Capacitor
Connection
External Resistor
Capacitor Connection
INPUTSOUTPUTS
A
BCLRQQ
HHOUTPUT ENABLE
XLHL(*)H(*)INHIBIT
HXHL(*)H(*)INHIBIT
LHOUTPUT ENABLE
LHOUTPUT ENABLE
XXLLHINHIBIT
X : Don’t Care
(*) : Exce pt for monostable period
NOTE
2/14
SYSTEM DIAGRAM
M74HC221
This log i c diagram has not be used to estim at e propagation delays
TIMING CHART
3/14
M74HC221
BLOCK DIAGRAM
(1) Cx, Rx , Dx are extern al components.
(2) Dx is a clamping diode.
The external capacitor is charged to Vcc in the stand-by-stat e, i.e. no trigger. When the supply vol tage is turned off Cx is discharged mainly
trough an internal parasitic diode(see figures). If Cx is sufficiently large and Vcc decreases rapidly, there will be some possibility of damaging
the I.C. with a surge current or latch-up. If the volta ge supply filter capacitor is la rge enough and Vcc decrease s l owly, the surge cu rr ent is
automatically limited and damage to the I.C. is avoided. The maximum forward current of the parasitic diode is approximately 20 mA. In cases
where Cx is large the time taken for the supply voltage to fall to 0.4 Vcc can be calculated as follows :
t
> (Vcc - 0.7) x Cx/20mA
f
In cases where t
is too short an ext ernal clamping diode is required to prot ect the I.C. from t he surge current.
f
FUNCTIONAL DESCRIPTION
STAND-BY STATE
The external capacit or,Cx, is f ully charged t o Vcc
in the stand-by state. Hence, before triggering,
transistor Qp and Qn (connected to the Rx/Cx
node) are both turned-off. The two comparators
that control the timing and the two reference
voltage sources stop operating. The t otal supply
current is therefore only leakage current.
TRIGGER OPERATION
Triggering occurs when :
1 st) A is "LOW" and B has a falling edge;
2 nd) B is "HIGH" and A has a rising edge;
3 rd) A is "LOW" and B is HIGH and C1 has a
rising edge;
After the multivibrator has been retriggered
comparator C1 and C2 start operating and Q n is
turned on. Cx then discharges through Qn. The
voltage at the node R/C external falls.
When it reaches V
the output of comparat or
REFL
C1 becomes low. This in turn reset the flip-flop
and Qn is turned off.
At this point C1 stops functioning but C2 continues
to operate.
The voltage at R/C external begins to rise with a
time constant set by the external com ponents Rx,
Cx.
Triggering the multivibrator causes Q to go high
after internal delay due to the flip-flop and the
gate. Q remains high until the voltage at R/C
external rises again to V
. At this point C2
REFH
output goes low and O goes low. C2 stop
operating. That means that a fter triggering when
the voltage R/C external returns to V
REFH
the
multivibrator has returned to its MONOSTABLE
STATE. In the case where Rx · Cx are large
enough and the discharge time of the capacitor
and the delay time in the I.C. can be ignored, t he
width of the output pulse tw (out) is as follows :
tW(OUT) = 0.70 Cx · Rx
RESET OPERATION
CL is normally high. If CL is low, the trigger is not
effective because Q output goes low and trigger
control f lip -f lo p is res et .
Also transistor Op is turned on and Cx is charged
quickly to Vcc. This means if CL input goes low the
IC becomes waiting state both in operating and
non operating state.
4/14
M74HC221
ABSOLUTE MAXIMUM RATINGS
SymbolParameterValueUnit
V
V
V
I
I
OK
I
I
or I
CC
P
T
T
Absolute Maximum Ratings are those values beyond which damage to the device may occur. Functional operation under these conditions is
not implied
(*) 500mW at 65
RECOMMENDED OPERATING CONDITIONS
SymbolParameterValueUnit
V
V
V
T
t
r
CxExternal Capacitor> 100 (*)pF
Rx
(*) The Maximum allowable values of Cx and Rx are a function of leakage of capacitor Cx, the leakage of device and leakage due to the board
layout and surface resistance. Susceptibility to externally induced noise may occur for Rx > 1MΩ
Supply Voltage
CC
DC Input Voltage-0.5 to VCC + 0.5
I
DC Output Voltage-0.5 to VCC + 0.5
O
DC Input Diode Current
IK
DC Output Diode Current
DC Output Current
O
DC VCC or Ground Current
GND
Power Dissipation
D
Storage Temperature
stg
Lead Temperature (10 sec)
L
°C; derate to 300mW by 10 m W/°C from 65 °C to 85°C
Supply Voltage
CC
Input Voltage0 to V
I
Output Voltage0 to V
O
Operating Temperature
op
Input Rise and Fall Time (CLR and A only)VCC = 2.0V
WAVEFORM 3 : REMOVAL TIME (CLR TO A-B) (f=1MHz; 50% duty cycle)
WAVEFORM 4 : REMOVAL TIME (CLR
TO A-B) (f=1MHz; 50% duty cycle)
10/14
M74HC221
Plastic DIP-16 (0.25) MECHANICAL DATA
mm.inch
DIM.
MIN.TYPMAX.MIN.TYP.MAX.
a10.510.020
B0.771.650.0300.065
b0.50.020
b10.250.010
D200.787
E8.50.335
e2.540.100
e317.780.700
F7.10.280
I5.10.201
L3.30.130
Z1.270.050
P001C
11/14
M74HC221
SO-16 MECHANICAL DATA
DIM.
A1.750.068
a10.10.20.0030.007
a21.650.064
b0.350.460.0130.018
b10.190.250.0070.010
C0.50.019
c145° (typ.)
D9.8100.3850.393
E5.86.20.2280.244
e1.270.050
e38.890.350
F3.84.00.1490.157
G4.65.30.1810.208
L0.51.270.0190.050
M0.620.024
S8° (max.)
MIN.TYPMAX.MIN.TYP.MAX.
mm.inch
12/14
PO13H
M74HC221
TSSOP16 MECHANICAL DATA
mm.inch
DIM.
MIN.TYPMAX.MIN.TYP.MAX.
A1.20.047
A10.050.150.0020.0040.006
A20.811.050.0310.0390.041
b0.190.300.0070.012
c0.090.200.0040.0089
D4.955.10.1930.1970.201
E6.26.46.60.2440.2520.260
E14.34.44.480.1690.1730.176
e0.65 BSC0.0256 BSC
K0°8°0°8°
L0.450.600.750.0180.0240.030
A2
A
A1
b
e
c
K
L
E
D
E1
PIN 1 IDENTIFICATION
1
0080338D
13/14
M74HC221
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