Fairchild Semiconductor DM74LS645WMX, DM74LS645WM, DM74LS645N Datasheet

August 1986

Revised March 2000

DM74LS645

Octal Bus Transceiver

General Description

These octal bus transceivers are designed for asynchronous two-way communication between data buses. The devices transmit data from the A bus to the B bus or from the B bus to the A bus depending upon the level at the direction control (DIR) input. The enable input (G) can be used to disable the device so that the buses are effectively isolated.

Features

■Bi-directional bus transceivers in high-density 20-pin packages

■Hysteresis at bus inputs improves noise margins

■3-STATE outputs

Ordering Code:

Order Number	Package Number	Package Description
DM74LS645WM	M20B	20-Lead Small Outline Integrated Circuit (SOIC), JEDEC MS-013, 0.300 Wide
DM74LS645N	N20A	20-Lead Plastic Dual-In-Line Package (PDIP), JEDEC MS-001, 0.300 Wide

Devices also available in Tape and Reel. Specify by appending the suffix letter “X” to the ordering code.

Connection Diagram	Function Table
				Control
				Inputs			DM74LS645
		G				DIR
			L			L	B data to A bus
			L			H	A data to B bus
			H			X	Isolation
	H = HIGH Level
	L = LOW Level
	X = Irrelevant

Transceiver Bus Octal DM74LS645

© 2000 Fairchild Semiconductor Corporation

DS009056

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DM74LS645

Absolute Maximum Ratings(Note 1)

	Supply Voltage	7V	Note 1: The “Absolute Maximum Ratings” are those values beyond which
			the safety of the device cannot be guaranteed. The device should not be
	Input Voltage	7V	operated at these limits. The parametric values defined in the Electrical
			Characteristics tables are not guaranteed at the absolute maximum ratings.
	Operating Free Air Temperature Range	0°C to +70°C
			The “Recommended Operating Conditions” table will define the conditions
	Storage Temperature Range	−55°C to +150°C	for actual device operation.

Recommended Operating Conditions

Symbol	Parameter	Min	Nom	Max	Units
VCC	Supply Voltage (Note 2)	4.75	5	5.25	V
VIH	HIGH Level Input Voltage	2			V
VIL	LOW Level Input Voltage			0.6	V
IOH	HIGH Level Output Current			−15	mA
IOL	LOW Level Output Current			24	mA
TA	Free Air Operating Temperature	0		70	°C

Note 2: Voltage values are with respect to the network ground terminal.

Electrical Characteristics

over recommended operating free air temperature range (unless otherwise noted)

Symbol	Parameter		Conditions (Note 3)			Min	Typ	Max	Units
							(Note 4)
VI	Input Clamp Voltage	VCC = Min, II = 18 mA						−1.5	V
HYS	Hysteresis (VT+ − V−)	VCC = Min				0.2	0.4		V
	A or B Input
VOH	HIGH Level Output Voltage	VCC = Min, VIH = 2V,			IOH = −3 mA	2.4	3.4		V
		VIL = Max			IOH = Max	2
VOL	LOW Level Output Voltage	VCC = Min, VIH = 2V,			IOL = 12 mA		0.25	0.4	V
		VIL = Max			IOL = 24 mA		0.35	0.5
IOZH	Off-State Output Current,	VCC = Max, G at 2V,						20	μA
	HIGH Level Voltage Applied	VO = 2.7V
IOZL	Off-State Output Current,	VCC = Max, G at 2V						−400	μA
	LOW Level Voltage Applied	VO = 0.4V
II	Input Current at	VCC = Max		A or B	VI = 5.5V			0.1	mA
	Maximum Input Voltage			DIR or G	VI = 7V			0.1
IIH	HIGH Level Input Current	VCC = Max, VIH =		2.7				20	μA
IIL	LOW Level Input Current	VCC = Max, VIL = 0.4V						−0.4	mA
IOS	Short Circuit Output Current (Note 5)	VCC = Max				−40		−225	mA
ICC	Total Supply	Outputs HIGH			VCC = Max,		48	70
	Current	Outputs LOW			Outputs Open		62	90	mA
		Outputs at Hi-Z					64	95

Note 3: For conditions shown as Min or Max, use the appropriate value specified under Recommended Operating Conditions.

Note 4: All typicals are at VCC = 5V, TA = 25°C.

Note 5: Not more than one output should be shorted at a time, and the duration should not exceed one second.

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