Fairchild FST3125 service manual
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FST3125
Quad Bus Switch
FST3125 Quad Bus Switch
August 1997
Revised December 1999
General Description
The Fairchild Switch FST3125 provides four high-speed
CMOS TTL-compatible bus switches. The low on resistance of the switch allows inputs to be connect ed to outputs without adding propagation delay or generating
additional ground bounce noise.
The device is organized as four 1- bit switches with separate OE
inputs. When OE is LOW, the switch is ON and
Port A is connected to Port B. When OE
switch is OPEN and a high-impedance state exists
between the two ports.
is HIGH, the
Features
■ 4Ω switch connection between two ports.
■ Minimal propagation delay through the switch.
■ Low l
■ Zero bounce in flow-through mode.
■ Control inputs compatible with TTL level.
.
CC
Ordering Code:
Order Number Package Number Package Description
FST3125M M14A 14-Lead Small Outline Integrated Circuit (SOIC), JEDEC MS-120, 0.150 Narrow
FST3125QSC MQA16 16-Lead Quarter Size Outline Package (QSOP), JEDEC MO-137, 0.150 Wide
FST3125MTC MTC14 14-Lead Thin Shrink Small Outline Package (TSSOP), JEDEC MO-153, 4.4mm Wide
Devices also availab le in Tape and Reel. Specify by appending the suffix letter “X” to the o rdering code.
Logic Diagram
Connection Diagrams
Pin Assignment for SOIC and TSSOP
Pin Assignment for QSOP
Pin Descriptions
Pin Name Description
OE
, OE2, OE3, OE
1
1A, 2A, 3A, 4A Bus A
1B, 2B, 3B, 4B Bus B
NC Not Connected
© 1999 Fairchild Semiconductor Corporation DS500043 www.fairchildsemi.com
Bus Switch Enables
4
Truth Table
Inputs Inputs/Outputs
OE
LA = B
HZ
A,B
Absolute Maximum Ratings(Note 1) Recommended Operating
Supply Voltage (VCC) −0.5V to +7.0V
DC Switch Voltage (V
FST3125
DC Input Voltage (V
DC Input Diode Current (l
DC Output (I
DC V
OUT
/GND Current (ICC/I
CC
Storage Temperature Range (T
) −0.5V to +7.0V
S
)(Note 2) −0.5V to +7.0V
IN
) VIN<0V −50mA
IK
) Sink Current 128mA
) +/− 100mA
GND
) −65°C to +150 °C
STG
Conditions
Power Supply Operating (V
Input Voltage (V
Output Voltage (V
Input Rise and Fall Time (t
Switch Control Input 0ns/V to 5ns/V
Switch I/O 0ns/V to DC
Free Air Operating Temperature (T
Note 1: The “Absolute Maximum Ratings” are those values bey ond which
the safety of the d evice cannot be guaranteed. The device sh ould not be
operated at these limit s. The parametric values defin ed in the Electrical
Characteristics tables are not guaranteed at the absolute maximum rating.
The “Recomme nded O peratin g Cond itions ” table will defin e the condition s
for actual device operation.
Note 2: The input and output ne gative vo ltage ra tings may be excee ded 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.
(Note 3)
) 4.0V to 5.5V
CC
)0V to 5.5V
IN
)0V to 5.5V
OUT
, tf)
r
DC Electrical Characteristics
) −40 °C to +85 °C
A
V
Symbol Parameter
V
IK
V
IH
V
IL
I
I
I
OZ
R
ON
I
CC
∆I
CC
Note 4: Typi c al values are at VCC = 5.0V and TA = +25°C
Note 5: Measured by the volta ge drop between A an d B pins at the indicated c urrent through the switch. On resistance is determined by the lower of the
voltages on the two (A or B) pins.
Clamp Diode Voltage 4.5 −1.2 V IIN = −18mA
High Level Input Voltage 4.0–5.5 2.0 V
Low Level Input Voltage 4.0–5.5 0.8 V
Input Leakage Current 5.5 ±1.0 µA0≤ VIN ≤5.5V
OFF-STATE Leakage Current 5.5 ±1.0 µA0 ≤A, B ≤V
Switch On Resistance 4.5 4 7 Ω VIN = 0V, IIN = 64mA
(Note 5) 4.5 4 7 Ω V
Quiescent Supply Current 5.5 3 µAVIN = VCC or GND,
Increase in I
per Input 5.5 2.5 mA One input at 3.4V.
CC
CC
(V)
4.5 8 15 Ω V
4.0 11 20 Ω VIN = 2.4V, IIN = 15mA
TA = −40 °C to +85 °C
Min Typ
(Note 4)
Max
Units Conditions
CC
= 0V, IIN = 30mA
IN
= 2.4V, IIN = 15mA
IN
= 0
I
OUT
Other inputs at V
CC
or GND
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