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© 1999 Fairchild Semiconductor Corporation DS500021 www.fairchildsemi.com
June 1997
Revised December 1999
FST3244 Octal Bus Switch
FST3244
Octal Bus Switch
General Description
The Fairchild Switch FST3244 provides 8-bits of high-
speed CMOS TTL-compatible bus switching in a standard
’244 pin-out. The low on resistance of the switch allows
inputs to be connected to outputs without adding propaga-
tion delay or generating additional ground bounce noise.
The device is organized as two 4-bit switches with separate
OE
inputs. When OE is LOW, the switch is ON and Port A
is connected to Port B. When OE
is HIGH, the switch is
OPEN and a high-impedance state exists between the two
ports.
Features
■ 4Ω switch connection between two ports.
■ Minimal propagation delay through the switch.
■ Low l
CC
.
■ Zero bounce in flow-through mode.
■ Control inputs compatible with TTL level.
Ordering Code:
Devices also available in Tape and Reel. Specify by appending the suffix letter “X” to the ordering code.
Logic Diagram
Pin Descriptions
Connection Diagram
Truth Table
Order Number Package Number Package Description
FST3244WM M20B 20-Lead Small Outline Integrated Circuit (SOIC), JEDEC MS-013, 0.300 Wide
FST3244QSC MQA20 20-Lead Quarter Size Outline Package (QSOP), JEDEC MO-137, 0.150 Wide
FST3244MTC MTC20 20-Lead Thin Shrink Small Outline Package (TSSOP), JEDEC MO-153, 4.4mm Wide
Pin Name Description
OE
1
, OE
2
Bus Switch Enable
1A, 2A Bus A
1B, 2B Bus B
Inputs Inputs/Outputs
OE
1
OE
2
1A, 1B 2A, 2B
LL1A = 1B 2A = 2B
LH1A = 1B Z
HLZ2A = 2B
HHZZ
