FST3257 — Quad 2:1 Multiplexer / Demultiplexer Bus Switch
May 2009
FST3257
Quad 2:1 Multiplexer / Demultiplexer Bus Switch
Features
4Ω Switch Connection Between Two Ports
Minimal Propagation Delay Through the Switch
Low I
CC
Zero Bounce in Flow-Through Node
Control Inputs Compatible with TTL Level
Description
The Fairchild Switch FST3257 is a quad 2:1 high-speed
CMOS TTL-compatible multiplexer / demultiplexer bus
switch. The low on resistance of the switch allows
inputs to be connected to outputs without adding
propagation delay or generating additional ground
bounce noise.
When /OE is LOW, the select pin connects the A port to
the selected B port output. When /OE is HIGH, the
switch is OPEN and a high-impedance state exists
between the two ports.
Ordering Information
Operating
Part Number Temperature
Range
FST3257M
FST3257MX
FST3257QSC
FST3257QSCX
FST3257MTC
FST3257MTCX
-40 to 85°C
-40 to 85°C
-40 to 85°C
-40 to 85°C
-40 to 85°C
-40 to 85°C
Eco Status
Package
16-Lead Small Outline Integrated Circuit
(SOIC) JEDEC MS-012,0.150 Narrow
16-Lead Quarter Size Outline Package
(QSOP) JEDEC MO-137 0.150 Inch Wide
16-Lead Thin Shrink Small Outline Package
(TSSOP) JEDEC MO-153, 4mm Wide
Packing
Method
Tubes
Tape and Reel
Tubes
Tape and Reel
Tubes
Tape and Reel
RoHS
Green
RoHS
For Fairchild’s definition of Eco Status, please visit:
http://www.fairchildsemi.com/company/green/rohs_green.html.
© 1997 Fairchild Semiconductor Corporation
FST3257 • Rev. 1.0.3
www.fairchildsemi.com
FST3257 — Quad 2:1 Multiplexer / Demultiplexer Bus Switch
Pin Assignments
Figure 1. Logic Diagram
Figure 2. Connection Diagram
Pin Descriptions
Pin #
1
2, 3, 5, 6, 10, 11, 13, 14
4, 7, 9, 12
8
15
16
Names
S
1B
1
, 1B
2 ,
2B
1
, 2B
2
, 3B
1
, 3B
2
, 4B
1
, 4B
2
1A, 2A, 3A, 4A
GND
/OE
VCC
Description
Select Input
Bus B
Bus A
Ground
Bus Switch Enables
Supply Voltage
Truth Table
Select Inputs
S
Logic Level LOW
Logic Level HIGH
Bus Switch Enabled
Logic Level HIGH
Logic Level LOW
Logic Level LOW
Function
Disconnected
A=B
1
A=B
2
© 1997 Fairchild Semiconductor Corporation
FST3257 • Rev. 1.0.3
www.fairchildsemi.com
2
FST3257 — Quad 2:1 Multiplexer / Demultiplexer Bus Switch
Absolute Maximum Ratings
Stresses exceeding the absolute maximum ratings may damage the device. The device may not function or be
operable above the recommended operating conditions and stressing the parts to these levels is not recommended.
In addition, extended exposure to stresses above the recommended operating conditions may affect device
reliability. The absolute maximum ratings are stress ratings only.
Symbol
V
CC
V
S
V
IN
I
IK
I
OUT
I
CC
/I
GND
T
STG
Supply Voltage
Parameter
DC Switch Voltage
DC Input Voltage
DC Input Current
DC Output Sink Current
DC V
CC
/GND Current
Storage Temperature Range
(1)
Min.
-0.5
-0.5
-0.5
Max.
+7.0
+7.0
+7.0
-50
128
±100
Unit
V
V
V
mA
mA
mA
°C
-65
+150
Note:
1. The input and output negative voltage ratings may be exceeded if the input and output diode current ratings are
observed.
Recommended Operating Conditions
The Recommended Operating Conditions table defines the conditions for actual device operation. Recommended
operating conditions are specified to ensure optimal performance to the datasheet specifications. Fairchild does not
recommend exceeding them or designing to Absolute Maximum Ratings.
Symbol
V
CC
V
IN
V
OUT
t
r
,t
f
T
A
Input Voltage
Output Voltage
Parameter
Power Supply Operating
Min.
3.0
0
0
Max.
5.5
5.5
5.5
5
DC
+85
Unit
V
V
V
ns/V
°C
Input Rise and Fall Time
Switch Control Input
Switch I/O
0
0
-40
Free Air Operating Temperature
Note:
2. Unused control inputs must be held HIGH or LOW. They may not float.
© 1997 Fairchild Semiconductor Corporation
FST3257 • Rev. 1.0.3
www.fairchildsemi.com
3
FST3257 — Quad 2:1 Multiplexer / Demultiplexer Bus Switch
DC Electrical Characteristics
Symbol
V
IK
V
IH
V
IL
I
IN
I
OZ
Parameter
Clamp Diode Voltage
High-Level Input Voltage
Low-Level Input Voltage
Input Leakage Current
Off-state Leakage Current
Conditions
I
IN
=-18mA
V
CC
(V)
4.5
3.0 to 3.6
3.0 to 3.6
(5)
T
A
=-40 to +85°C
Min.
1.8
2.0
0.7
0.8
±1.0
±1.0
13
28
200
210
4
4
8
11
20
40
230
250
7
7
15
20
3
2.5
Typ.
(3)
Units
V
V
V
µA
µA
Max.
-1.2
4.0 to 5.5
(5)
4.0 to 5.5
0
≤
V
IN
≤
5.5
0
≤
A, B
≤
V
CC
V
IN
=0V, I
IN
=64mA
V
IN
=0V, I
IN
=30mA
V
IN
=2.4V, I
IN
=15mA
V
IN
=2.4V, I
IN
=15mA
V
IN
=0V, I
IN
=64mA
V
IN
=0V, I
IN
=30mA
V
IN
=2.4V, I
IN
=15mA
V
IN
=2.4V, I
IN
=15mA
V
IN
=V
CC
or GND,
I
OUT
=0,
One Input at 3.4V, Other
inputs at V
CC
or GND
5.5
5.5
3.3
3.3
3.3
3.0
(5)
(5)
(5)
(5)
R
ON
Switch On Resistance
(4)
4.5
4.5
4.5
4.0
5.5
5.5
Ω
I
CC
ΔI
CC
Quiescent Supply Current
Increase in I
CC
per input
µA
mA
Notes:
3. Typical values are at nominal V
CC
for the V
CC
range and T
A
=25°C.
4. Measured by the voltage drop between A and B pins at the indicated current through the switch. On resistance
is determined by the lower of the voltages on the A or B pins.
5. This parameter is guaranteed by design, but is not tested.
© 1997 Fairchild Semiconductor Corporation
FST3257 • Rev. 1.0.3
www.fairchildsemi.com
4
FST3257 — Quad 2:1 Multiplexer / Demultiplexer Bus Switch
AC Electrical Characteristics
T
A
=-40 to +85°C, C
L
= 50pF,
RU=RD=500Ω
Symbol
Parameter
Conditions
V
CC
= 4.5
to 5.5V
Min.
Propagation Delay
(6)
Bus to Bus
Propagation Delay
(6)
Select to Bus A
Output Enable
Time, Select to
Bus B
Output Enable
Time, Select to
Bus /OE
Output Disable
Time, Select to
Bus B
Output Disable
Time, Select to
Bus /OE
Max.
V
CC
=4.0V
Min.
Max.
V
CC
=3.0
(7)
to 3.6V
Min.
Max.
0.25
V
IN=
Open
0.25
0.25
1.0
1.0
1.0
5.0
5.5
1.0
8.5
6.8
7.9
ns
Figure 3
Figure 4
ns
Figure 3
Figure 4
Units
Figure
t
PHL
,t
PLH
t
PZH
,t
PZL
V
IN
=7V for t
PZL
V
IN
=Open for
t
PZH
t
PHZ
,t
PLZ
V
IN
=7V for t
PLZ
V
IN
=Open for
t
PHZ
1.0
1.5
5.3
5.6
1.5
9.9
ns
Figure 3
Figure 4
9.9
Notes:
6. This parameter is guaranteed by design but is not tested. The bus switch contributes no propagation delay other
than the RC delay of the typical on resistance of the switch and the 50pF load capacitance, when driven by an
ideal voltage source (zero output impedance).
7. These parameters are guaranteed by design, but not tested.
Capacitance
T
A
=+25°C, f=1MHz. Capacitance is characterized by not tested.
Symbol
C
IN
Parameter
Control Pin Input Capacitance
A Port
C
I/O
Input/Output Capacitance
B Port
A Port
B Port
Conditions
V
CC
=5.0V
V
CC
/OE=5.0V
V
CC
/OE=3.3V
Typ.
3.0
7.0
5.0
3.0
3.5
Max.
Units
pF
pF
pF
© 1997 Fairchild Semiconductor Corporation
FST3257 • Rev. 1.0.3
www.fairchildsemi.com
5
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