IN74HC221A Datasheet, PDF (1/7 Pages) Integral Corp. – DUAL MONOSTABLE MULTIVIBRATOR

IN74HC221A
DUAL MONOSTABLE MULTIVIBRATOR
The IN74HC221A is identical in pinout to the LS/ALS221. The
device inputs are compatible with standard CMOS outputs; with
pullup resistors, they are compatible with LS/ALSTTL outputs.
There are two trigger inputs, A INPUT (negative edge) and
B INPUT (positive edge). These inputs are valid for rising/falling
signals
The device may also be triggered by using the RESET input
(positive-edge) because of the Schmitt-trigger input; after
triggering the output maintains the MONOSTABLE state for the
time period determined by the external resistor R_EXT and
capacitor C_EXT. Taking RESET low breaks this MONOSTABLE
STATE. If the next trigger pulse occurs during the
MONOSTABLE period it makes the MONOSTABLE period
longer.
• Outputs Directly Interface to CMOS, NMOS, and TTL
• Operating Voltage Range: 3.0 to 6.0 V
• Low Input Current: 1.0 µA
• High Noise Immunity Characteristic of CMOS Devices
N SUFFIX
PLASTIC
16
1
D SUFFIX
16
SOIC
1
ORDERING INFORMATION
IN74HC221AN Plastic
IN74HC221AD SOIC
IZ74HC221AZ Chip
T_A = -55° to 125° C for all
packages
LOGIC DIAGRAM
C_EXT
D_EXT
R_EXT
PIN 16 =V_CC
PIN 8 = GND
C_EXT
D_EXT
R_EXT
PIN ASSIGNMENT
1A 1
1B 2
1RESET 3
1Q 4
2Q 5
2C_EXT
6
2R_EXT/C_EXT 7
GND 8
16 VCC
15 1R_EXT/C_EXT
14 1C_EXT
13 1Q
12 2Q
11 2RESET
10 _2B
9 2A
FUNCTION TABLE
Inputs
Outputs Note
A B RESET Q Q
HH
Output
Note
(1) C_EXT, R_EXT, D_EXT are external components.
(2) D_EXT is a clamping diode.
The external capacitor is charged to V_CC in the stand-by
X
H
L
L
X
state, i.e. no trigger. When the supply voltage is turned off
C_X is discharged mainly through an internal parasitic
L
H
H
H
H
Enable
L ^* H ^* Inhibit
L ^* H ^* Inhibit
Output
Enable
Output
Enable
diode. If C_X is sufficiently large and V_CC decreases rapidy, _{X X}
L
L H Inhibit
there will be some possibility of damaging the I.C. with a _{X = don’t care}
surge current or latch-up. If the voltage supply filter * _{- except for monostable period}
capacitor is large enough and V_CC decrease slowly, the
surge current is automatically limited and damage the I.C.
is avoided. The maximum forward current of the parasitic
diode is approximately 20 mA.
1