SGS-THOMSON M54HC4538, M74HC4538 Technical data

M54HC4538

M54HC4538

M74HC4538

DUAL RETRIGGERABLE MONOSTABLE MULTIVIBRATOR

.HIGH SPEED

.tPD = 25 ns (TYP.) AT VCC = 5 V LOW POWER DISSIPATION

STANDBY STATEICC =4 μA (MAX.) AT TA = 25 °C

.ACTIVE STATE ICC = 200 μA (TYP.) AT VCC = 5 V HIGH NOISE IMMUNITY

.VNIH = VNIL = 28 % VCC (MIN.) OUTPUT DRIVE CAPABILITY

.10 LSTTL LOADS

BALANCED PROPAGATION DELAYS

.tPLH = tPHL

WIDE OUTPUT PULSE WIDTH RANGE

.tWOUT = 120 ns ~ 60 s OVER AT VCC = 4.5 V OUTPUT PULSE WIDTH INDEPENDENT

.FROM TRIGGER INPUT PULSE WIDTH

PIN AND FUNCTION COMPATIBLE WITH 4538B

B1R	F1R
(Plastic Package)	(Ceramic Package)

M1R	C1R
(Micro Package)	(Chip Carrier)

ORDER CODES :

M54HC4538F1R M74HC4538M1R M74HC4538B1R M74HC4538C1R

PIN CONNECTIONS (top view)

DESCRIPTION

The M54/74HC4538 is a high speed CMOS DUAL MONOSTABLEMULTIVIBRATOR fabricated in silicon gate C2MOS technology. It has the same high speed performance of LSTTL combined with true CMOS low power consumption. Each multivibrator features both a negative, A, and a positive, B, edge triggered input, either of which can be used as an inhibit input. Also included is a clear input that when taken low resets the one shot. The monostable multivibrators are retriggerable. That is, they may be triggered reapeatedly while their outputs are generating a pulse and the pulse will be extended. Pulse width stability over a wide range of temperature and supply is achieved using linear CMOS techniques. The output pulse equation is simply : PW = 0.7 (R)(C) where PW is in seconds, R in Ohms, and C is in Farads.

All inputs are equipped with protection circuits against static discharge and transient excess voltage.

NC =

No Internal

Connection

October 1993

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M54/M74HC4538

SYSTEM DIAGRAM

TIMING CHART

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M54/ M74HC4538

BLOCK DIAGRAM

Notes : 1. Cx, Rx, Dx are external components.

2.Dx is a clamping diode.

3.The external capacitor is charged to VCC in the stand-by state, i.e. no trigger. When the supply voltage is turned off Cx is discharged mainlythrough an internal parasitic diode (see figures). IfCx is sufficiently largeandVCC decreases rapidy, there willbesome possibility of damaging the I.C. with a surge current or latch-up. If the voltage supply filter capacitor is large enough and VCC 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. In cases where Cx is large the time taken for the supply voltage to fall to 0.4 VCC can be calculated as follows : tf ≥ (VCC ± 0.7) Cx/20 mA

In cases where tf is too short an external champing diode is required to protect the I.C. from the surge current.

FUNCTIONAL DESCRIPTION

STAND-BY STATE

The external capacitor, Cx, is fully charged to VCC in the stand-by state. Hence, before triggering, transistor Qp and Qn (connected to the Rx/Cx node) are both turned off. The two comparators that control the timing and the two reference voltage sources stop operating. The total supply current is therefore only leakage current.

TRIGGER OPERATION

Triggering occurs when :

1 st) A is ºlowº and B has a falling edge ;

2 nd) B is ºhighº and A has a rising edge ;

After the multivibrator has been retriggered comparator C1 and C2 start operating and Qn is turned on. Cx then discharges through Qn. The voltage at the node Rx/Cx external falls.

When it reaches VREFL the output of comparator C1 becomes low. This in turn resets the flip-flop and Qn is turned off.

At this point C1 stops functioning but C2 continues to operate. The voltage at R/C external begins to rise with a time constant set by the external components Rx, Cx.

Triggering the multivibrator causes Q to go high after internal delay due to the flip-flop and the gate. Q remains high until the voltage at R/C external rises again to VREFH. At this point C2 output goes low and G goes low. C2 stops operating. That means that after triggering when the voltage at R/C external returns to VREFH the multivibrator has returned to its MONOSTABLE STATE. In the case where Rx •Cx are large enough and the discharge time of the capacitor and the delay time in the I.C. can be ignored, the width of the output pulse tw (out) is as follows :

tW(OUT) = 0.72 Cx •Rx

RE-TRIGGER OPERATION

When a second trigger pulse follows the first its effect will depend on the state of the multivibrator. If the capacitor Cx is being charged the voltage level of Rx/Cx external falls to VREFL again and Q remains high i.e. the retrigger pulse arrives in a time shorter than the period Rx • Cx seconds, the capacitor charging time constant. If the second trigger pulse is very close to the initial trigger pulse it is ineffective ; i.e., the second trigger must arrive in the capacitor discharge cycle to be ineffective.

Hence the minimum time for a second trigger to be effective, trr (Min.) depends on VCC and Cx.

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M54/M74HC4538

FUNCTIONAL DESCRIPTION (continued)

RESET OPERATION

CD is normally high. If CD is low, the trigger is not effective because Q output goes low and trigger control flip-flop is reset.

TRUTH TABLE

Also transistor Op is turned on and Cx is charged quicky to VCC. This means if CD input goes low, the IC becomes waiting state both in operating and non operating state.

		INPUTS			OUTPUTS	NOTE
	A	B	CD	Q	Q
		H	H			OUTPUT ENABLE
	X	L	H	L	H	INHIBIT
	H	X	H	L	H	INHIBIT
	L		H			OUTPUT ENABLE
	X	X	L	L	H	INHIBIT

INPUT AND OUTPUT EQUIVALENT CIRCUIT

PIN DESCRIPTION			IEC LOGIC SYMBOL
PIN No	SYMBOL		NAME AND FUNCTION
1, 15	1T1,	2T1	External Capacitor
			Connections
2, 14	1T2,	2T2	External Resistor/Capacitor
			Connections
3, 13	1CD, 2CD		Direct Reset Inputs (Active
			LOW)
4, 12	1A,	2A	Trigger Inputs (LOW to
			HIGH, Edge-Triggered)
5, 11	1B,	2B	Trigger Inputs (HIGH to
			LOW, Edge-Triggered)
6, 10	Q1,	Q2	Pulse Outputs
7, 9	Q1, Q2		Complementary Pulse Outputs
8	GND		Ground (0V)
16	VCC		Positive Supply Voltage

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M54/ M74HC4538

ABSOLUTE MAXIMUM RATINGS

Symbol	Parameter	Value	Unit
VCC	Supply Voltage	-0.5 to +7	V
VI	DC Input Voltage	-0.5 to VCC + 0.5	V
VO	DC Output Voltage	-0.5 to VCC + 0.5	V
IIK	DC Input Diode Current	± 20	mA
IOK	DC Output Diode Current	± 20	mA
IO	DC Output Source Sink Current Per Output Pin	± 25	mA
ICC or IGND	DC VCC or Ground Current	± 50	mA
PD	Power Dissipation	500 (*)	mW
Tstg	Storage Temperature	-65 to +150	oC
TL	Lead Temperature (10 sec)	300	oC

Absolute Maximum Ratings are those values beyond which damage to the device may occur. Functional operation under these condition isnotimplied.

(*) 500 mW: 65 oC derate to 300 mW by 10mW/oC: 65 oC to 85 oC

RECOMMENDED OPERATING CONDITIONS

Symbol	Parameter		Value		Unit
VCC	Supply Voltage		2 to 6		V
VI	Input Voltage		0 to VCC		V
VO	Output Voltage		0 to VCC		V
Top	Operating Temperature: M54HC Series		-55 to +125		oC
	M74HC Series		-40 to +85		oC
tr, tf	Input Rise and Fall Time (CLR only)	VCC = 2 V	0 to 1000
		VCC = 4.5 V	0 to 500		ns
		VCC = 6 V	0 to 400
CX	External Capacitor		NO LIMITATION (*)
RX	External Resistor	VCC ≤ 3 V	5K to 1M	(*)	Ω
		VCC > 3 V	1K to 1M	(*)

(*) The maximum allowable values of Cx and Rx are a function of leakage of capacitor Cx, the leakage of device and leakage due to the board layout and surface resistance. Susceptibility to externally induced noise may occur for Rx > 1MΩ

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