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1999 Fairchild Semiconductor Corporation
DS500022
www.fairchildsemi.com
June 1997
Revised December 1999
FST6
800 1
0
-Bi
t
Bus Swit
ch
w
i
th
Pre
-
Charg
e
d Out
puts
FST6800
10-Bit Bus Switch with Pre-Charged Outputs
General Description
The Fairchild Switch FST6800 provides 10-bits of high-
speed CMOS TTL-compatible bus switching. The low on
resistance of the switch allows inputs to be connected to
outputs without adding propagation delay or generating
additional ground bounce noise. The device precharges
the B Port to a selectable bias voltage (BiasV) to minimize
live insertion noise.
The device is organized as a 10-bit switch with a bus
enable (OE) signal. 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 the B Port is precharged to BiasV
through an equivalent 10-k
resistor.
Features
s
4
switch connection between two ports.
s
Minimal propagation delay through the switch.
s
Low l
CC
.
s
Zero bounce in flow-through mode.
s
Output precharge to minimize live insertion noise.
s
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
FST6800WM
M24B
24-Lead Small Outline Integrated Circuit (SOIC), JEDEC MS-013, 0.300 Wide
FST6800QSC
MQA24
24-Lead Quarter Size Outline Package (QSOP), JEDEC MO-137, 0.150 Wide
FST6800MTC
MTC24
24-Lead Thin Shrink Small Outline Package (TSSOP), JEDEC MO-153, 4.4mm Wide
Pin Name
Description
OE
Bus Switch Enable
A
Bus A
B
Bus B
OE
B
0
B
9
Function
L
A
0
A
9
Connect
H
BiasV
Precharge
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2
FST6800
Absolute Maximum Ratings
(Note 1)
Recommended Operating
Conditions
(Note 3)
Note 1: The Absolute Maximum Ratings are those values beyond which
the safety of the device cannot be guaranteed. The device should not be
operated at these limits. The parametric values defined in the Electrical
Characteristics tables are not guaranteed at the absolute maximum ratings.
The Recommended Operating Conditions tables will define the conditions
for actual device operation.
Note 2: The input and output negative voltage ratings may be exceeded if
the input and output diode current ratings are observed.
Note 3: Unused control inputs must be held HIGH or LOW. They may not
float.
DC Electrical Characteristics
Note 4: Typical values are at V
CC
=
5.0V and T
A
=
+
25
C
Note 5: 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 (V
CC
)
-
0.5V to
+
7.0V
DC Switch Voltage (V
S
)
-
0.5V to
+
7.0V
Bias V Voltage Range
-
0.5V to
+
6.0V
DC Input Voltage (V
IN
) (Note 2)
-
0.5V to
+
7.0V
DC Input Diode Current (l
IK
) V
IN
<
0V
-
50mA
DC Output (I
OUT
) Sink Current
128mA
DC V
CC
/GND Current (I
CC
/I
GND
)
+
/
-
100mA
Storage Temperature Range (T
STG
)
-
65
C to
+
150
C
Power Supply Operating (V
CC
)
4.0V to 5.5V
Precharge Supply (BiasV)
1.5V to V
CC
Input Voltage (V
IN
)
0V to 5.5V
Output Voltage (V
OUT
)
0V to 5.5V
Input Rise and Fall Time (t
r
, t
f
)
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
(V)
T
A
=
-
40
C to
+
85
C
Units
Conditions
Min
Typ
(Note 4)
Max
V
IK
Clamp Diode Voltage
4.5
-
1.2
V
I
IN
=
-
18mA
V
IH
HIGH Level Input Voltage
4.05.5
2.0
V
V
IL
LOW Level Input Voltage
4.05.5
0.8
V
I
I
Input Leakage Current
5.5
1.0
A
0
V
IN
5.5V
I
O
Output Current
4.5
0.25
mA
BiasV
=
2.4V, B
=
0
I
OZ
OFF-STATE Leakage Current
5.5
1.0
A
0
A
V
CC
R
ON
Switch On Resistance
4.5
4
7
V
IN
=
0V, I
IN
=
64mA
(Note 5)
4.5
4
7
V
IN
=
0V, I
IN
=
30mA
4.5
8
15
V
IN
=
2.4V, I
IN
=
15mA
4.0
11
20
V
IN
=
2.4V, I
IN
=
15mA
I
CC
Quiescent Supply Current
5.5
3
A
V
IN
=
V
CC
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
3
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FST6
800
AC Electrical Characteristics
Note 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 the source (zero output impedance).
Capacitance
(Note 7)
Note 7: T
A
=
+
25
C, f
=
1 MHz, Capacitance is characterized but not tested.
AC Loading and Waveforms
Note: Input driven by 50
source terminated in 50
Note: C
L
includes load and stray capacitance
Note: Input PRR
=
1.0 MHz, t
W
=
500 ns
FIGURE 1. AC Test Circuit
FIGURE 2. AC Waveforms
Symbol
Parameter
T
A
=
-
40
C to
+
85
C,
C
L
=
50pF, RU
=
RD
=
500
Units
Conditions
Figure No.
V
CC
=
4.5 5.5V
V
CC
=
4.0V
Min
Max
Min
Max
t
PHL
,t
PLH
Prop Delay Bus to Bus (Note 6)
0.25
0.25
ns
V
I
=
OPEN
Figures 1,
2
t
PZH
Output Enable Time
1.5
6.2
6.5
ns
V
I
=
OPEN, BiasV
=
GND
Figure 1
Figure 2
t
PZL
1.5
6.2
6.5
ns
V
I
=
7V, BiasV
=
3V
t
PHZ
Output Disable Time
1.5
6.1
6.5
ns
V
I
=
OPEN, BiasV
=
GND
Figure 1
Figure 2
t
PLZ
1.5
7.3
6.8
ns
V
I
=
7V, BiasV
=
3V
Symbol
Parameter
Typ
Max
Units
Conditions
C
IN
Control Pin Input Capacitance
3
pF
V
CC
=
5.0V
C
I/O
Input/Output Capacitance
5
pF
V
CC
, OE
=
5.0V
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4
FST6800
Physical Dimensions
inches (millimeters) unless otherwise noted
24-Lead Small Outline Integrated Circuit (SOIC), JEDEC MS-013, 0.300 Wide
Package Number M24B
24-Lead Quarter Size Outline Package (QSOP), JEDEC MO-137, 0.150 Wide
Package Number MQA24
5
www.fairchildsemi.com
FST6
800 1
0
-Bi
t
Bus Swit
ch
w
i
th
Pre
-
Charg
e
d Out
puts
Physical Dimensions
inches (millimeters) unless otherwise noted (Continued)
24-Lead Thin Shrink Small Outline Package (TSSOP), JEDEC MO-153, 4.4mm Wide
Package Number MTC24
Technology Description
The Fairchild Switch family derives from and embodies Fairchild's proven switch technology used for several years in its
74LVX3L384 (FST3384) bus switch product.
Fairchild does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and
Fairchild reserves the right at any time without notice to change said circuitry and specifications.
LIFE SUPPORT POLICY
FAIRCHILD'S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT
DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT OF FAIRCHILD
SEMICONDUCTOR CORPORATION. As used herein:
1. Life support devices or systems are devices or systems
which, (a) are intended for surgical implant into the
body, or (b) support or sustain life, and (c) whose failure
to perform when properly used in accordance with
instructions for use provided in the labeling, can be rea-
sonably expected to result in a significant injury to the
user.
2. A critical component in any component of a life support
device or system whose failure to perform can be rea-
sonably expected to cause the failure of the life support
device or system, or to affect its safety or effectiveness.
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