74VHC221AMTCX Fairchild Semiconductor, 74VHC221AMTCX Datasheet - Page 4
![no-image](/images/manufacturer_photos/0/2/252/fairchild_semiconductor_sml.jpg)
74VHC221AMTCX
Manufacturer Part Number
74VHC221AMTCX
Description
MULTIVIBRATOR DUAL MONO 16TSSOP
Manufacturer
Fairchild Semiconductor
Series
74VHCr
Datasheet
1.74VHC221AMTCX.pdf
(12 pages)
Specifications of 74VHC221AMTCX
Logic Type
Monostable
Independent Circuits
2
Schmitt Trigger Input
No
Propagation Delay
8.1ns
Current - Output High, Low
8mA, 8mA
Voltage - Supply
2 V ~ 5.5 V
Operating Temperature
-40°C ~ 85°C
Mounting Type
Surface Mount
Package / Case
16-TSSOP
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
Available stocks
Company
Part Number
Manufacturer
Quantity
Price
Company:
Part Number:
74VHC221AMTCX
Manufacturer:
ABOV
Quantity:
26
Company:
Part Number:
74VHC221AMTCX
Manufacturer:
FSC
Quantity:
8 300
©1994 Fairchild Semiconductor Corporation
74VHC221A Rev. 1.2
Functional Description
1. Stand-by State
2. Trigger Operation
The external capacitor (Cx) is fully charged to V
the Stand-by State. That means, before triggering,
the Q
Rx/Cx node are in the off state. Two comparators that
relate to the timing of the output pulse, and two refer-
ence voltage supplies turn off. The total supply cur-
rent is only leakage current.
Trigger operation is effective in any of the following
three cases. First, the condition where the A input is
LOW, and B input has a rising signal; second, where
the B input is HIGH, and the A input has a falling sig-
nal; and third, where the A input is LOW and the B
input is HIGH, and the CLR input has a rising signal.
After a trigger becomes effective, comparators C1
and C2 start operating, and Q
external capacitor discharges through Q
age level at the Rx/Cx node drops. If the Rx/Cx volt-
age level falls to the internal reference voltage V
the output of C1 becomes LOW. The flip-flop is then
reset and Q
C2 continues operating.
After Q
starts rising at a rate determined by the time constant
of external capacitor Cx and resistor Rx.
P
and Q
N
turns off, the voltage at the Rx/Cx node
N
N
turns off. At that moment C1 stops but
transistors which are connected to the
N
is turned on. The
N
. The volt-
CC
ref
L,
in
4
3. Reset Operation
Upon triggering, output Q becomes HIGH, following
some delay time of the internal F/F and gates. It stays
HIGH even if the voltage of Rx/Cx changes from fall-
ing to rising. When Rx/Cx reaches the internal refer-
ence voltage V
the output Q goes LOW and C2 stops its operation.
That means, after triggering, when the voltage level
of the Rx/Cx node reaches V
MONOSTABLE state.
With large values of Cx and Rx, and ignoring the dis-
charge time of the capacitor and internal delays of
the IC, the width of the output pulse, t
follows:
t
In normal operation, the CLR input is held HIGH. If
CLR is LOW, a trigger has no affect because the Q
output is held LOW and the trigger control F/F is
reset. Also, Q
V
This means if CLR is set LOW, the IC goes into a wait
state.
W
CC
(OUT)
.
1.0 Cx Rx
p
ref
turns on and Cx is charged rapidly to
H, the output of C2 becomes LOW,
ref
H, the IC returns to its
W
www.fairchildsemi.com
(OUT), is as