DATA SH EET
Product specification
File under Integrated Circuits, IC06 September 1993
INTEGRATED CIRCUITS
74HC/HCT4538
Dual retriggerable precision
monostable multivibrator
For a complete data sheet, please also download:
•The IC06 74HC/HCT/HCU/HCMOS Logic Family Specifications
•The IC06 74HC/HCT/HCU/HCMOS Logic Package Information
•The IC06 74HC/HCT/HCU/HCMOS Logic Package Outlines
September 1993 2
Philips Semiconductors Product specification
Dual retriggerable precision monostable
multivibrator 74HC/HCT4538
FEATURES
•Separate reset inputs
•Triggering from leading or trailing edge
•Output capability: standard
•ICC category: MSI
•Power-on reset on-chip
GENERAL DESCRIPTION
The 74HC/HCT4538 are high-speed Si-gate CMOS
devices and are pin compatible with “4538” of the “4000B”
series. They are specified in compliance with JEDEC
standard no. 7A.
The 74HC/HCT4538 are dual retriggerable-resettable
monostable multivibrators. Each multivibrator has an
active LOW trigger/retrigger input (nA0), an active HIGH
trigger/retrigger input (nA1) , an overriding active LOW
direct reset input (nRD), an output (nQ) and its complement
(nQ), and two pins (nCTC and nRCTC) for connecting the
external timing components Ctand Rt. Typical pulse width
variation over temperature range is ±0.2%.
The “4538” may be triggered by either the positive or the
negative edges of the input pulse. The duration and
accuracy of the output pulse are determined by the
external timing components Ctand Rt. The output pulse
width (T) is equal to 0.7 ×Rt×Ct. The linear design
techniques guarantee precise control of the output pulse
width.
A LOW level at nRDterminates the output pulse
immediately.
Schmitt-trigger action in the trigger inputs makes the circuit
highly tolerant to slower rise and fall times.
QUICK REFERENCE DATA
GND = 0 V; Tamb = 25 °C; tr= tf= 6 ns
Notes
1. CPD is used to determine the dynamic power dissipation (PDin µW):
PD= CPD ×VCC2×fi+∑(CL×VCC2×fo)+
+0.48 ×CEXT ×VCC2×fo+D×0.8 ×VCC where:
fi= input frequency in MHz
fo= output frequency in MHz
∑(CL×VCC2×fo) = sum of outputs
CL= output load capacitance in pF
VCC = supply voltage in V
D = duty factor in %
CEXT = timing capacitance in pF
2. For HC the condition is VI= GND to VCC
For HCT the condition is VI= GND to VCC −1.5 V
ORDERING INFORMATION
See
“74HC/HCT/HCU/HCMOS Logic Package Information”
.
SYMBOL PARAMETER CONDITIONS TYPICAL UNIT
HC HCT
tPHL/ tPLH propagation delay nA0,nA
1to nQ, nQC
L
= 15 pF; VCC = 5 V 27 30 ns
CIinput capacitance 3.5 3.5 pF
CPD power dissipation capacitance per multivibrator notes 1 and 2 136 138 pF
September 1993 3
Philips Semiconductors Product specification
Dual retriggerable precision monostable
multivibrator 74HC/HCT4538
PIN DESCRIPTION
PIN NO. SYMBOL NAME AND FUNCTION
1, 15 1CTC,2C
TC external capacitor connections
2, 14 1RCTC, 2RCTC external resistor/capacitor connections
3, 13 1RD,2R
Ddirect reset inputs (active LOW)
4, 12 1A1,2A
1trigger inputs (LOW-to-HIGH, edge-triggered)
5, 11 1A0,2A
0trigger inputs (HIGH-to-LOW, edge-triggered)
6, 10 1Q, 2Q pulse outputs
7, 9 1Q, 2Q complementary pulse outputs
8 GND ground (0 V)
16 VCC positive supply voltage
Fig.1 Pin configuration. Fig.2 Logic symbol. Fig.3 IEC logic symbol.
September 1993 4
Philips Semiconductors Product specification
Dual retriggerable precision monostable
multivibrator 74HC/HCT4538
Fig.4 Functional diagram.
Fig.5 Connection of the external timing
components Rtand Ct.
(1) Connect CTC (pins 1 and 15) to GND (pin 8).
FUNCTION TABLE
Notes
1. H = HIGH voltage level
L = LOW voltage level
X = don’t care
↑= LOW-to-HIGH transition
↓= HIGH-to-LOW transition
= one HIGH level output pulse
= one LOW level output pulse
INPUTS OUTPUTS
nA0nA1nRDnQ nQ
↓LH
H↑H
XXL LH
Fig.6 Timing diagram.
(1) Positive edge triggering.
(2) Positive edge retriggering (pulse
lengthening).
(3) Negative edge triggering.
(4) Reset (pulse shortening).
(5) Vref1 and Vref2 are internal reference voltages.
(6) T = 0.7 ×Rt×Ct(see also Fig.5).
September 1993 5
Philips Semiconductors Product specification
Dual retriggerable precision monostable
multivibrator 74HC/HCT4538
handbook, full pagewidth
MBA338
Vref2
ref1
V
GND
nCTC
nRCTC
enable
enable
VCC
power - on reset VCC
nRD
nA1
nA0
nQ
nQ
Fig.7 Logic diagram (Vref1 and Vref2 are internal reference voltages).
September 1993 6
Philips Semiconductors Product specification
Dual retriggerable precision monostable
multivibrator 74HC/HCT4538
DC CHARACTERISTICS FOR 74HC
For the DC characteristics see
“74HC/HCT/HCU/HCMOS Logic Family Specifications”
.
Output capability: standard
ICC category: MSI
AC CHARACTERISTICS FOR 74HC
GND = 0 V; tr= tf= 6 ns; CL= 50 pF
SYMBOL PARAMETER
Tamb (°C)
UNIT
TEST CONDITIONS
74HC VCC
(V) OTHER+25 −40 to +85 −40 to +125
min. typ. max. min. max. min. max.
tPLH propagation delay
nA0,nA
1to nQ 85
31
25
265
53
45
330
66
56
400
80
68
ns 2.0
4.5
6.0
Fig.8
tPHL propagation delay
nA0,nA
1to nQ 83
30
24
265
53
45
330
66
56
400
80
68
ns 2.0
4.5
6.0
Fig.8
tPHL propagation delay
nRDto nQ 80
29
23
265
53
45
330
66
56
400
80
68
ns 2.0
4.5
6.0
Fig.8
tPLH propagation delay
nRDto nQ 83
30
24
265
53
45
340
68
58
400
80
68
ns 2.0
4.5
6.0
Fig.8
tTHL/ tTLH output transition
time 19
7
6
75
15
13
95
19
16
110
22
19
ns 2.0
4.5
6.0
Fig.8
tWnA0pulse width
LOW 80
16
14
17
6
5
100
20
17
120
24
20
ns 2.0
4.5
6.0
Fig.8
tWnA1pulse width
HIGH 80
16
14
17
6
5
100
20
17
120
24
20
ns 2.0
4.5
6.0
Fig.8
tWnRDpulse width
LOW 80
16
14
19
7
6
100
20
17
120
24
20
ns 2.0
4.5
6.0
Fig.8
tWnQ, nQ pulse width
HIGH or LOW 0.63 0.70 0.77 0.602 0.798 0.595 0.805 ms 5.0 Fig.8;
Rt= 10 kΩ;
Ct= 0.1 µF
trem removal time
RDto nA0,nA
1
35
7
6
6
2
2
45
9
8
55
11
9
ns 2.0
4.5
6.0
Fig.8
September 1993 7
Philips Semiconductors Product specification
Dual retriggerable precision monostable
multivibrator 74HC/HCT4538
NON-STANDARD DC CHARACTERISTICS FOR 74HC
Voltages are referenced to GND (ground = 0 V)
Note
1. This measurement can only be carried out after a trigger pulse is applied.
trt retrigger time
nA0,nA
1
−
−
−
455+X
80+X
55+X
−
−
−
−
−
−
ns 2.0
4.5
6.0
Fig.8
X=C
EXT /
(4.5 ×VCC)
REXT external timing
resistor 10
21000
1000 kΩ2.0
5.0
CEXT external timing
capacitor no limits pF 5.0
SYMBOL PARAMETER
Tamb (°C)
UNIT
TEST CONDITIONS
74HC VCC
(V) VI
(V) OTHER
+25 −40 to +85 −40 to +125
min. typ max. min. max. min. max.
±IIinput leakage current
nRCEXT
0.5 5.0 10.0 µA 6.0 2.0
or
GND
VCC or GND;
note 1
SYMBOL PARAMETER
Tamb (°C)
UNIT
TEST CONDITIONS
74HC VCC
(V) OTHER+25 −40 to +85 −40 to +125
min. typ. max. min. max. min. max.
September 1993 8
Philips Semiconductors Product specification
Dual retriggerable precision monostable
multivibrator 74HC/HCT4538
DC CHARACTERISTICS FOR 74HCT
For the DC characteristics see
“74HC/HCT/HCU/HCMOS Logic Family Specifications”
.
Output capability: standard
ICC category: MSI
Note to HCT types
The value of additional quiescent supply current (∆ICC) for a unit load of 1 is given in the family specifications.
To determine ∆ICC per input, multiply this value by the unit load coefficient shown in the table below.
AC CHARACTERISTICS FOR 74HCT
GND = 0 V; tr= tf= 6 ns; CL= 50 pF
INPUT UNIT LOAD COEFFICIENT
nA0,nA
1
nR
D
0.50
0.65
SYMBOL PARAMETER
Tamb (°C)
UNIT
TEST CONDITIONS
74HCT VCC
(V) OTHER
+25 −40 to +85 −40 to +125
min. typ. max. min. max. min. max.
tPLH propagation delay
nA0,nA
1to nQ 35 60 75 90 ns 4.5 Fig.8
tPHL propagation delay
nA0,nA
1to nQ 35 60 75 90 ns 4.5 Fig.8
tPHL propagation delay
nRDto nQ 35 60 75 90 ns 4.5 Fig.8
tPLH propagation delay
nRDto nQ 35 60 75 90 ns 4.5 Fig.8
tTHL/ tTLH output transition time 7 15 19 21 ns 4.5 Fig.8
tWnA0pulse width
LOW 20 11 25 30 ns 4.5 Fig.8
tWnA1pulse width
HIGH 16 5 20 24 ns 4.5 Fig.8
tWnRDpulse width
LOW 20 11 25 30 ns 4.5 Fig.8
tWnQ, nQ pulse width
HIGH or LOW 0.63 0.70 0.77 0.602 0.798 0.595 0.805 ms 5.0 Fig.8; Rt= 10 kΩ;
Ct= 0.1 µF
trem removal time
RDto nA0, nA1 7 2 9 11 ns 4.5 Fig.8
trt retrigger time
nA0,nA
1
−80+X −−ns 4.5 Fig.8
X=C
EXT /
(4.5 ×VCC)
REXT external timing
resistor 2 1000 kΩ5.0
CEXT external timing
capacitor no limits pF 5.0
September 1993 9
Philips Semiconductors Product specification
Dual retriggerable precision monostable
multivibrator 74HC/HCT4538
NON-STANDARD DC CHARACTERISTICS FOR 74HCT
Voltages are referenced to GND (ground = 0 V)
Note
1. This measurement can only be carried out after a trigger pulse is applied.
AC WAVEFORMS
SYMBOL PARAMETER
Tamb (°C)
UNIT
TEST CONDITIONS
74HCT VCC
(V) VI
(V) OTHER
+25 −40 to +85 −40 to +125
min. typ max. min. max. min. max.
±IIinput leakage current
nRCEXT
0.5 5.0 10.0 µA 5.5 2.0
or
GND
VCC or GND;
note 1
Fig.8 Waveforms showing the input (nA1,nA
0
,nR
D
) to output (nQ, nQ) propagation delays, the output transition
times, the input and output pulse widths, the removal time from direct reset (nRD) to input (nA1,nA
0
), and
the input retrigger time.
(1) HC : VM= 50%; VI= GND to VCC.
HCT: VM= 1.3 V; VI= GND to 3 V.
September 1993 10
Philips Semiconductors Product specification
Dual retriggerable precision monostable
multivibrator 74HC/HCT4538
APPLICATION INFORMATION
Fig.9 Retriggerable monostable circuitry.
(a) rising-edge triggered; (b) falling-edge triggered.
(a) (b)
Fig.10 Non-retriggerable monostable circuitry.
(a) rising-edge triggered; (b) falling-edge triggered.
(a) (b)
September 1993 11
Philips Semiconductors Product specification
Dual retriggerable precision monostable
multivibrator 74HC/HCT4538
Fig.11 Power-down protection circuit.
Power-down considerations
A large capacitor (CX) may cause problems when
powering-down the monostable due to the energy stored
in this capacitor. When a system containing this device is
powered-down or a rapid decrease of VCC to zero occurs,
the monostable may sustain damage, due to the capacitor
discharging through the input protection diodes. To avoid
this possibility, use a damping diode (DX) preferably a
germanium or Schottky type diode able to withstand large
current surges and connect as shown in Fig.11.
Fig.12 Typical pulse width accuracy versus external capacitance; VCC = 4.5 V; Tamb = 25 °C.
Fig.13 Typical pulse width accuracy versus external resistance; VCC = 4.5 V; Tamb = 25 °C.
September 1993 12
Philips Semiconductors Product specification
Dual retriggerable precision monostable
multivibrator 74HC/HCT4538
Fig.14 Typical pulse width accuracy versus external capacitance; REXT = 10 kΩ;V
CC = 4.5 V; Tamb = 25 °C.
Fig.15 Typical pulse width accuracy versus power supply; CEXT = 1 nF; Tamb = 25 °C.
Fig.16 Typical pulse width accuracy versus power supply; CEXT = 100 nF; Tamb = 25 °C.
September 1993 13
Philips Semiconductors Product specification
Dual retriggerable precision monostable
multivibrator 74HC/HCT4538
PACKAGE OUTLINES
See
“74HC/HCT/HCU/HCMOS Logic Package Outlines”
.
Fig.17 Typical pulse width accuracy versus temperature; CEXT = 1 nF; VCC = 4.5 V.
Fig.18 Typical pulse width accuracy versus temperature; CEXT =1µF; VCC = 4.5 V.
