Fairchild Semiconductor FSTU3257QSCX, FSTU3257QSC, FSTU3257MX, FSTU3257MTCX, FSTU3257MTC Datasheet
© 2000 Fairchild Semiconductor Corporation DS500302 www.fairchildsemi.com
August 1999
Revised April 2000
FSTU3257 Quad 2:1 Multiplexer/Demultiplexer Bus Switch with −2V Undershoot Protection
FSTU3257
Quad 2:1 Multiplexer/Demultiplexer Bus Switch
with −2V Undershoot Protection
General Description
The Fairchild Swit ch FSTU3257 is a quad 2:1 h igh-speed
CMOS TTL-compatible multiplexer/demultiplexer bus
switch. The low on resistance of the switch allows inputs to
be connected to outputs wi thout a dding pr opagation delay
or generating additional ground bounce noise.
When OE
is LOW, the select pin connects the A Port to the
selected B Port output. The A and B Ports are “undershoot
hardened” with UHC pro tection to support an extended
range of 2.0V below groun d. Fairchild’s integrated Undershoot Hardened Circuit UHC senses undershoot at the I/O
and responds by preventing voltage differentials from
developing and turning on the switch. When OE
is HIGH,
the switch is OPEN and a high-impedance state exists
between the two ports.
Features
■ Undershoot hardened to −2V (A and B Ports)
■ Soft enable turn-on to minimize bus to bus charge
sharing during enable
■ 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.
■ See Applications Note AN-5008 for details
Ordering Code:
Device also available in Tape and Reel. Specify by appending suffix letter “X” to the ordering code.
UHC is a trademark of Fairchild Semiconductor Corporation.
Order Number Package Number Package Description
FSTU3257M M16A 16-Lead Small Outline Integrated Circuit (SOIC), JEDEC MS-012, 0.150 Narrow
FSTU3257QSC MQA16 16-Lead Quarter Size Outline Package (QSOP), JEDEC MO-137, 0.150 Wide
FSTU3257MTC MTC16 16-Lead Thin Shrink Small Outline Package (TSSOP), JEDEC MO-153, 4.4mm Wide
www.fairchildsemi.com 2
FSTU3257
Logic Diagram
Pin Descriptions
Connection Diagram
Tr uth Table
Pin Name Description
OE
Bus Switch Enable
S Select Input
ABus A
B
1–B2
Bus B
SOE Function
X H Disconnect
LL A = B
1
HL A = B
2
3 www.fairchildsemi.com
FSTU3257
Absolute Maximum Ratings(Note 1) Recommended Operating
Conditions
(Note 4)
Note 1: The Absolute Maxi mum Ratings are those v alues beyond which
the safety of the dev ice cannot b e guaranteed . The device sh ould not be
operated at these limit s. The parametric values defi ned in the Electrical
Characteristics tables are not guaranteed at the absolute maximum rating.
The Recommend ed Oper ating Condi tions ta bles will de fine the conditions
for actual device operation.
Note 2: V
S
is the volt age observed/applied at either t he A or B Por t s across
the switch.
Note 3: The input and output negative voltage ratings may be exceeded if
the input and ou t put diode curr ent ratings ar e observed.
Note 4: Unused control inputs must be held HIGH or LOW. They may not
float.
DC Electrical Characteristics
Note 5: Typical values are at VCC = 5.0V and TA = +25°C
Note 6: 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 two (A or B) pins.
Supply Voltage (VCC) −0.5V to +7.0V
DC Switch Voltage (V
S
) (Note 2) −2.0V to +7.0V
DC Input Control Pin Voltage (V
IN
)(Note 3) −0.5V to +7.0V
DC Input Diode Current (l
IK
) VIN<0V −50mA
DC Output (I
OUT
)128mA
DC V
CC
/GND Current (ICC/I
GND
) +/− 100mA
Storage Temperature Range (T
STG
) −65°C to +150 °C
Power Supply Operating (V
CC
) 4.0V to 5.5V
Input Voltage (V
IN
) 0V to 5.5V
Output Voltage (V
OUT
) 0V to 5.5V
Input Rise and Fall Time (t
r
, tf)
Switch Control Input 0nS/V to 5nS/V
Switch I/O 0nS/V to DC
Free Air Operating Temperature (T
A
) −40 °C to +85 °C
Symbol Parameter
V
CC
TA = −40 °C to +85 °C
Units Conditions
(V) Min
Typ
(Note 5)
Max
V
IK
Clamp Diode Voltage 4.5 −1.2 V IIN = −18mA
V
IH
HIGH Level Input Voltage 4.0–5.5 2.0 V
V
IL
LOW Level Input Voltage 4.0–5.5 0.8 V
I
I
Input Leakage Current 5.5 ±1.0 µA0≤ VIN ≤5.5V
I
OZ
OFF-STATE Leakage Current 5.5 ±1.0 µA0 ≤A, B ≤V
CC
R
ON
Switch On Resistance 4.5 4 7 Ω VIN = 0V, IIN = 64mA
(Note 6) 4.5 4 7 Ω VIN = 0V, IIN = 30mA
4.5 8 15 Ω V
IN
= 2.4V, IIN = 15mA
4.0 11 20 Ω V
IN
= 2.4V, IIN = 15mA
I
CC
Quiescent Supply Current 5.5 3 µAVIN = VCC or GND, I
OUT
= 0
∆ I
CC
Increase in I
CC
per Input 5.5 2.5 mA One input at 3.4V
Other inputs at V
CC
or GND
V
IKU
Voltage Undershoot 5.5 −2.0 V 0.0 mA ≥ IIN ≥ −50 mA
OE
= 5.5V
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