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FST16861 20-Bit Bus Switch
March 2000
Revised June 2005
FST16861
20-Bit Bus Switch
General Description
The Fairchild Switch FST16861 provides 20-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 is organized as a 10-bit or 20-bit bus switch.
When OE
1
is LOW, the switch is ON and Port 1A is con-
nected to Port 1B. When OE
2
is LOW, Port 2A is connected
to Port 2B. When OE
X
is HIGH, a high impedance state
exists between the A and B Ports.
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
Control inputs compatible with TTL level
Ordering Code:
Order Number
FST16861MTD
Package Number
MTD48
Package Description
48-Lead Thin Shrink Small Outline Package (TSSOP), JEDEC MO-153, 6.1mm Wide
Devices also available in Tape and Reel. Specify by appending the suffix letter “X” to the ordering code.
Logic Diagram
Connection Diagram
Truth Table
Inputs
OE
1
L
L
H
H
OE
2
L
H
L
H
Inputs/Outputs
1A, 1B
1A
1A
Z
Z
1B
1B
2A
Z
2A, 2B
2A
Z
2B
2B
Pin Descriptions
Pin Name
OE
1
, OE
2
1A, 2A
1B, 2B
Description
Bus Switch Enables
Bus A
Bus B
© 2005 Fairchild Semiconductor Corporation
DS500318
www.fairchildsemi.com
FST16861
Absolute Maximum Ratings
(Note 1)
Supply Voltage (V
CC
)
DC Switch Voltage (V
S
) (Note 2)
DC Input Voltage (V
IN
) (Note 3)
DC Input Diode Current (l
IK
) V
IN
0V
DC Output (I
OUT
) Current
DC V
CC
/GND Current (I
CC
/I
GND
)
Storage Temperature Range (T
STG
)
0.5V to
7.0V
Recommended Operating
Conditions
(Note 4)
Power Supply Operating (V
CC)
Input Voltage (V
IN
)
Output Voltage (V
OUT
)
Input Rise and Fall Time (t
r
, t
f
)
Switch Control Input
Switch I/O
Free Air Operating Temperature (T
A
)
0 ns/V to 5 ns/V
0 ns/V to DC
-40
q
C to
85
q
C
4.0V to 5.5V
0V to 5.5V
0V to 5.5V
0.5V to
7.0V
0.5V to
7.0V
50 mA
128 mA
r
100 mA
65
q
C to
150
q
C
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 rating.
The “Recommended Operating Conditions” table will define the conditions
for actual device operation.
Note 2:
V
S
is the voltage observed/applied at either the A or B Ports across
the switch.
Note 3:
The input and output negative voltage ratings may be exceeded if
the input and output diode current ratings are observed.
Note 4:
Unused control inputs must be held HIGH or LOW. They may not
float.
DC Electrical Characteristics
Symbol
V
IK
V
IH
V
IL
I
I
I
OZ
R
ON
Parameter
Clamp Diode Voltage
HIGH Level Input Voltage
LOW Level Input Voltage
Input Leakage Current
OFF-STATE Leakage Current
Switch On Resistance
(Note 6)
V
CC
(V)
4.5
4.0–5.5
4.0–5.5
5.5
0
5.5
4.5
4.5
4.5
4.0
I
CC
Quiescent Supply Current
Increase in I
CC
per Input
5.0V and T
A
T
A
Min
40
q
C to
85
q
C
Typ
(Note 5)
Max
Units
V
V
0.8
V
I
IN
Conditions
1.2
2.0
18 mA
r
1.0
10
10
4
4
7
11
7
7
12
20
3
2.5
P
A
P
A
P
A
:
:
:
:
P
A
mA
0
d
V
IN
d
5.5V
V
IN
V
IN
V
IN
V
IN
V
IN
V
IN
5.5V
0V, I
IN
0V, I
IN
2.4V, I
IN
2.4V, I
IN
64 mA
30 mA
15 mA
15 mA
0
0
d
A, B
d
V
CC
5.5
5.5
25
q
C
V
CC
or GND, I
OUT
'
I
CC
One Input at 3.4V
Other Inputs at V
CC
or GND
Note 5:
Typical values are at V
CC
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.
www.fairchildsemi.com
2
FST16861
AC Electrical Characteristics
C
L
Symbol
Parameter
V
CC
Min
t
PHL
, t
PLH
t
PZH
, t
PZL
t
PHZ
, t
PLZ
Propagation Delay Bus-to-Bus
(Note 7)
Output Enable Time
Output Disable Time
1.0
1.0
T
A
40
q
C to
85
q
C,
50pF, RU RD 500
:
V
CC
Min
4.0V
Max
0.25
5.3
6.3
ns
ns
ns
V
I
V
I
V
I
6.0
V
I
V
I
OPEN
7V for t
PZL
OPEN for t
PZH
7V for t
PLZ
OPEN for t
PHZ
Figures
1, 2
Figures
1, 2
Figures
1, 2
Units
Conditions
Figure
Number
4.5 – 5.5V
Max
0.25
5.0
Note 7:
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).
Capacitance
Symbol
C
IN
C
I/O
Note 8:
T
A
(Note 8)
Parameter
Typ
3
6
Max
Units
pF
pF
V
CC
Conditions
5.0V, V
IN
0V
0V
Control Pin Input Capacitance
Input/Output Capacitance “OFF State”
25
q
C, f
V
CC
, OE
5.0V, V
IN
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
3
www.fairchildsemi.com
FST16861 20-Bit Bus Switch
Physical Dimensions
inches (millimeters) unless otherwise noted
48-Lead Thin Shrink Small Outline Package (TSSOP), JEDEC MO-153, 6.1mm Wide
Package Number MTD48
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.
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4
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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PCB Design
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