TC74HC123AP/AF
TOSHIBA CMOS Digital Integrated Circuit
Silicon Monolithic
TC74HC123AP, TC74HC123AF
Dual Retriggerable Monostable Multivibrator
The TC74HC123A is a high speed CMOS MONOSTABLE
MULTIVIBRATOR fabricated with silicon gate C2MOS
technology.
It achieves the high speed operation similar to equivalent
LSTTL while maintaining the CMOS low power dissipation.
There are two trigger inputs, A input (negative edge), and B
input (positive edge). These inputs are valid for a slow rise/fall
time signal (tr = tf = 1 s) as they are schmitt trigger inputs. This
device may also be triggered by using CLR input (positive
edge).
After triggering, the output stays in a MONOSTABLE state for
a time period determined by the external resistor and capacitor
(Rx, Cx ). A low level at the CLR input breaks this state. In the
MONOSTABLE state, if a new trigger is applied, it extends the
MONOSTABLE period (retrigger mode).
Limits for Cx and Rx are:
External capacitor, Cx: No limit
External resistor, Rx: VCC = 2.0 V more than 5 kΩ
VCC ≥ 3.0 V more than 1 kΩ
All inputs are equipped with protection circuits against static
discharge or transient excess voltage.
TC74HC123AP
TC74HC123AF
Weight
DIP16-P-300-2.54A
SOP16-P-300-1.27A
Features (Note)
•
High speed: tpd = 25 ns (typ.) at VCC = 5 V
•
Low power dissipation
Standby state: ICC = 4 μA (max) at Ta = 25°C
Active state: ICC = 700 μA (max) at Ta = 25°C
•
High noise immunity: VNIH = VNIL = 28% VCC (min)
•
Output drive capability: 10 LSTTL loads
•
•
Symmetrical output impedance: |IOH| = IOL = 4 mA (min)
∼
Balanced propagation delays: tpLH − tpHL
•
Wide operating voltage range: VCC (opr) = 2 to 6 V
•
: 1.00 g (typ.)
: 0.18 g (typ.)
Pin and function compatible with 74LS123
Note: In the case of using only one circuit, CLR should be tied to GND, Rx/Cx･Cx･Q･ Q should be tied to OPEN,
the other inputs should be tied to VCC or GND.
Start of commercial production
1988-05
1
2014-03-01
TC74HC123AP/AF
Block Diagram (Note 1)(Note 2)
Note 1: Cx, Rx, Dx are external
capacitor, resistor, and diode, respectively.
Note 2: External clamping diode, Dx;
The external capacitor is charged to VCC level in the wait state, i.e. when no trigger is applied.
If the supply voltage is turned off, Cx is discharges mainly through the internal (parasitic) diode. If Cx is
sufficiently large and VCC drops rapidly, there will be some possibility of damaging the IC through in rush
current or latch-up. If the capacitance of the supply voltage filter is large enough and VCC drops slowly, the
in rush current is automatically limited and damage to the IC is avoided.
The maximum value of forward current through the parasitic diode is ±20 mA.
In the case of a large Cx, the limit of fall time of the supply voltage is determined as follows:
tf ≥ (VCC − 0.7) Cx/20 mA
(tf is the time between the supply voltage turn off and the supply voltage reaching 0.4 VCC.)
In the event a system does not satisfy the above condition, an external clamping diode (Dx) is needed to
protect the IC from in rush current.
Truth Table
Inputs
Outputs
CLR
H
H
X
L
H
L
H
Inhibit
H
X
H
L
H
Inhibit
L
Q
Function
B
A
Q
Output Enable
H
L
H
X
X
Output Enable
Output Enable
L
L
H
Inhibit
X: Don’t care
3
2014-03-01
