74HC4538 PDF даташит
Спецификация 74HC4538 изготовлена «Toshiba» и имеет функцию, называемую «Dual retriggerable precision monostable multivibrator». |
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Детали детали
Номер произв | 74HC4538 |
Описание | Dual retriggerable precision monostable multivibrator |
Производители | Toshiba |
логотип |
14 Pages
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TC74HC4538AP/AF/AFT
TOSHIBA CMOS Digital Integrated Circuit Silicon Monolithic
TC74HC4538AP,TC74HC4538AF,TC74HC4538AFT
Dual Retriggerable Monostable Multivibrator
The TC74HC4538A 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 (positive edge input), and
B input (negative edge input). These inputs are valid for a slow
rise/fall time signal (tr = tf = 1 s) as they are schmitt trigger
inputs.
After triggering, the output stays in a MONOSTABLE state for
the time period determined by the external resistor and capacitor
(RX, CX). A low level at CD input breaks this STABLE STATE.
In the MONOSTABLE state, if a new trigger is applied, it makes
the MONOSTABLE period longer (retrigger mode).
Limitations for CX and RX are as follows:
External capacitor CX ........... No limitation
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.
Features (Note)
• High speed: tpd = 25 ns (typ.) at VCC = 5 V
• Low power dissipation
Stand by state: ICC = 4 μA (max) at Ta = 25°C
Active state: ICC = 300 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 V to 6 V
• Pin and function compatible with 4538B
Note: In the case of using only one circuit, CD should be
tied to GND, T1·T2·Q· Q should be tied to OPEN, the other
inputs should be tied to VCC or GND.
TC74HC4538AP
TC74HC4538AF
TC74HC4538AFT
Weight
DIP16-P-300-2.54A
SOP16-P-300.1.27A
TSSOP16-P-0044-0.65A
: 1.00 g (typ.)
: 0.18 (typ.)
: 0.06 g (typ.
1 2012-02-29
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Pin Assignment
1T1 1
1T2 2
1CD 3
1A 4
1B 5
1Q 6
1Q 7
GND 8
(top view)
16 VCC
15 2T1
14 2T2
13 2CD
12 2A
11 2B
10 2Q
9 2Q
Truth Table
Inputs
A B CD
HH
XLH
HXH
LH
XXL
X: Don’t care
Outputs
QQ
LH
LH
LH
Note
Output Enable
Inhibit
Inhibit
Output Enable
Reset
TC74HC4538AP/AF/AFT
IEC Logic Symbol
1A
1B
1CD
1T1
1T2
(4)
(5)
(3)
(1)
(2)
2A
2B
2CD
2T1
2T2
(12)
(11)
(13)
(15)
(14)
&
R
CX
RX/CX
&
R
CX
RX/CX
(6) 1Q
(7) 1Q
(10) 2Q
(9) 2Q
2 2012-02-29
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Block Diagram (Note 1)(Note 2)
TC74HC4538AP/AF/AFT
A
B
4
5
DX
CX
12
RX
VCC
T1 T2
6Q
7Q
3
CD
A
B
12
11
DX
CX
15 14
RX
VCC
T1 T2
10 Q
13
CD
9Q
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. Supply
voltage is turned off and CX is discharged mainly through the internal (parasitic) diode. If CX is sufficiently
large and VCC drops rapidly, there will be some possibility of damaging the IC by rush current or latch-up. If
the capacitance of the supply voltage filter is large enough and VCC drops slowly, the 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 limitation of fall time of the supply voltage is determined as follows:
tf ≥ (VCC − 0.7) CX/20 mA
(tf is the time from the voltage supply turning off to the level of supply voltage reaching 0.4 VCC.)
In the care of a system that does not satisfy the above condition, an external clamping diode is needed to
protect the IC from rush current.
3 2012-02-29
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