FSTD3125 — 4-Bit Bus Switch with Level Shifting
May 2012
FSTD3125 — 4-Bit Bus Switch with Level Shifting
Features
4Ω Switch Connection between Two Ports
Minimal Propagation Delay through the Switch
Low I
CC
Zero Bounce in Flow-through Mode
Control Inputs Compatible with TTL Level
TruTranslation Voltage Translation from 5.0V Inputs
to 3.3V Outputs
Description
Fairchild switch FSTD3125 provides four high-speed
CMOS TTL-compatible bus switches. The low on
resistance of the switch allows inputs to be connected to
outputs without adding propagation delay or generating
additional ground bounce noise. A diode to V
CC
has
been integrated into the circuit to allow for level shifting
between 5V inputs and 3.3V outputs.
The device is organized as four one-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.
Ordering Information
Part Number
FSTD3125MTCX
Operating
Temperature
Range
-40 to 85°C
Package
14-Lead, Thin Shrink Small Outline Package (TSSOP), JEDEC
MO-153, 4mm Wide
Packing
Method
Tape and Reel
/OE
1
1
1A 2
/OE
2
4
3
1B
2A
5
6
2B
/OE
3
3A
/OE
4
10
9
13
8
3B
4A
12
11 4B
Figure 1. Logic Diagram
© 2001 Fairchild Semiconductor Corporation
FSTD3125 • Rev. 1.0.3
www.fairchildsemi.com
FSTD3125 — 4-Bit Bus Switch with Level Shifting
Pin Configuration
/OE
1
1A
1
14
V
CC
/OE
4
4A
2
13
1B
3
12
/OE
2
2A
4
11
4B
5
10
/OE
3
3A
2B
6
9
GND
7
8
3B
Figure 2. Pin Assignments
Pin Descriptions
Pin #
1, 4, 10, 13
2, 5, 9, 12
3, 6, 8, 11
14
7
Pin Names
/OE
1
, /OE
2
, /OE
3
, /OE
4
1A, 2A, 3A, 4A
1B, 2B, 3B, 4B
V
CC
GND
Description
Bus Switch Enables
Bus A
Bus B
Supply Voltage
Ground
Truth Table
Inputs
/OE
LOW
HIGH
Inputs/Outputs
A, B
A=B
High Impedance
© 2001 Fairchild Semiconductor Corporation
FST3D125 • Rev. 1.0.3
www.fairchildsemi.com
2
FSTD3125 — 4-Bit Bus Switch with Level Shifting
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
DC Switch Voltage
DC Input Voltage
(1)
Parameter
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
DC Input Diode Current, V
IN
<0V
DC Output Sink Current
DC V
CC
/ GND Current
Storage Temperature Range
-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.
4.5
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
(2)
0
0
-40
Operating Temperature, Free Air
Note:
2. Unused control inputs must be held HIGH or LOW. They may not float.
© 2001 Fairchild Semiconductor Corporation
FST3D125 • Rev. 1.0.3
www.fairchildsemi.com
3
FSTD3125 — 4-Bit Bus Switch with Level Shifting
DC Electrical Characteristics
Typical values are at V
CC
= 5.0V and T
A
= 25°C.
Symbol
V
IK
V
IH
V
OH
V
IL
I
IN
I
OZ
R
ON
Parameter
Clamp Diode Voltage
High-Level Input Voltage
High-Level
Low-Level Input Voltage
Input Leakage Current
Condition
I
IN
= -18mA
Figure 5, Figure 6, and
Figure 7
0
≤
V
IN
≤
5.5V
V
IN
=
5.5V
V
IN
= 0V, I
IN
= 64mA
V
CC
(V)
4.5
4.5 to 5.5
4.0 to 5.5
4.5 to 5.5
5.5
0
5.5
4.5
4.5
4.5
T
A
=-40 to +85°C
Min.
2.0
Typ.
Max.
-1.2
Unit
V
V
V
0.8
±1.0
10
±1.0
4
4
35
7
7
50
1.5
V
µA
µA
µA
Ω
Off-state Leakage Current 0
≤
A, B
≤
V
CC
Switch On Resistance
(3)
V
IN
= 0V, I
IN
= 30mA
V
IN
= 2.4V, I
IN
= 15mA
/OE
1
= /OE
2
= GND
V
IN
= V
CC
or GND,
I
OUT
= 0
/OE
1
= /OE
2
= V
CC
V
IN
= V
CC
or GND,
I
OUT
= 0
One Input at 3.4V, Other
Inputs at V
CC
or GND
I
CC
Quiescent Supply Current
5.5
10
5.5
2.5
µA
ΔI
CC
Increase in I
CC
per Input
mA
Note:
3. Measured by the voltage drop between the 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.
AC Electrical Characteristics
T
A
= -40 to +85°C, C
L
= 50pF, and R
U
= R
D
= 500Ω.
Symbol
t
PHL
, t
PLH
Parameter
Propagation Delay, Bus-to-Bus
(4)
Condition
V
IN
= Open
V
IN
= 7V for t
PZL
V
IN
= Open for t
PZH
V
IN
= 7V for t
PLZ
V
IN
= Open for t
PHZ
V
CC
= 4.5 – 5.5V
Min.
Max.
0.25
Unit
ns
Figure
Figure 3
Figure 4
Figure 3
Figure 4
Figure 3
Figure 4
t
PZH
,t
PZL
Output Enable Time
1.0
6.1
ns
t
PHZ
, t
PLZ
Output Disable Time
1.5
6.4
ns
Note:
4. 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
T
A
= +25°C, f = 1MHz. Capacitance is characterized, but not tested.
Symbol
C
IN
C
I/O
Parameter
Control Pin Input Capacitance
Input/Output Capacitance
V
CC
= 5.0V
Condition
V
CC
, /OE = 5.0V
Typ.
3
6
Unit
pF
pF
www.fairchildsemi.com
© 2001 Fairchild Semiconductor Corporation
FST3D125 • Rev. 1.0.3
4
FSTD3125 — 4-Bit Bus Switch with Level Shifting
AC Loadings and Waveforms
Notes:
Input driven by 50Ω source terminated in 50Ω.
C
L
includes load and stray capacitance.
Input PRR = 1.0MHz, t
w
= 500ns.
Figure 3. AC Test Circuit
Figure 4. AC Waveforms
© 2001 Fairchild Semiconductor Corporation
FSTD3125 • Rev. 1.0.3
www.fairchildsemi.com
5
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