August 1997
Revised December 1999
FST3126
Quad Bus Switch
General Description
The Fairchild Switch FST3126 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.
The device is organized as four 1-bit switches with separate OE inputs. When OE is HIGH, the switch is ON and Port A is connected to Port B. When OE is LOW, the switch is OPEN and a high-impedance state exists between the two ports.
Features
■4Ω switch connection between two ports.
■Minimal propagation delay through the switch.
■Low lCC.
■Zero bounce in flow-through mode.
■Control inputs compatible with TTL level.
Ordering Code:
Order Number |
Package Number |
Package Description |
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FST3126M |
M14A |
14-Lead Small Outline Integrated Circuit (SOIC), JEDEC MS-120, 0.150 Narrow |
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FST3126QSC |
MQA16 |
16-Lead Quarter Size Outline Package (QSOP), JEDEC MO-137, 0.150 Wide |
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FST3126MTC |
MTC14 |
14-Lead Thin Shrink Small Outline Package (TSSOP), JEDEC MO-153, 4.4mm Wide |
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Devices also available in Tape and Reel. Specify by appending the suffix letter “X” to the ordering code.
Logic Diagram |
Connection Diagrams |
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Pin Assignment for SOIC and TSSOP |
Pin Assignment for QSOP
Pin Descriptions
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Truth Table |
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Pin Name |
Description |
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Inputs |
Inputs/Outputs |
OE1, OE2, OE3, OE4 |
Bus Switch Enables |
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OE |
A,B |
1A, 2A, 3A, 4A |
Bus A |
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L |
Z |
1B, 2B, 3B, 4B |
Bus B |
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H |
A = B |
NC |
Not Connected |
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Switch Bus Quad FST3126
© 1999 Fairchild Semiconductor Corporation |
DS500044 |
www.fairchildsemi.com |
FST3126
Absolute Maximum Ratings(Note 1)
Supply Voltage (VCC) |
− 0.5V to + 7.0V |
DC Switch Voltage (VS) |
− 0.5V to + 7.0V |
DC Input Voltage (VIN) (Note 2) |
− 0.5V to + 7.0V |
DC Input Diode Current (lIK) VIN< 0V |
− 50mA |
DC Output (IOUT) Sink Current |
128mA |
DC VCC/GND Current (ICC/IGND) |
+ /− 100mA |
Storage Temperature Range (TSTG) |
− 65° C to + 150 ° C |
Recommended Operating
Conditions (Note 3)
Power Supply Operating (VCC) |
4.0V to 5.5V |
Input Voltage (VIN) |
0V to 5.5V |
Output Voltage (VOUT) |
0V to 5.5V |
Input Rise and Fall Time (tr, tf) |
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Switch Control Input |
0nS/V to 5nS/V |
Switch I/O |
0nS/V to DC |
Free Air Operating Temperature (TA) |
− 40 ° C to + 85 ° 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: 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
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VCC |
TA = − 40 ° C to + 85 ° C |
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Symbol |
Parameter |
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Units |
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Conditions |
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(V) |
Min |
Typ |
Max |
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(Note 4) |
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VIK |
Clamp Diode Voltage |
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4.5 |
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− 1.2 |
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V |
IIN = |
− 18mA |
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VIH |
HIGH Level Input Voltage |
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4.0–5.5 |
2.0 |
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V |
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VIL |
LOW Level Input Voltage |
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4.0–5.5 |
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0.8 |
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V |
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II |
Input Leakage Current |
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5.5 |
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± 1.0 |
µ |
A |
0≤ VIN ≤ 5.5V |
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IOZ |
OFF-STATE Leakage Current |
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5.5 |
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± 1.0 |
µ |
A |
0 ≤ A, B ≤ VCC |
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RON |
Switch On Resistance |
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4.5 |
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4 |
7 |
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Ω |
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VIN = |
0V, IIN = |
64mA |
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(Note 5) |
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4.5 |
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4 |
7 |
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Ω |
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VIN = |
0V, IIN = |
30mA |
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4.5 |
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8 |
15 |
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Ω |
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VIN = |
2.4V, IIN = |
15mA |
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4.0 |
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11 |
20 |
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Ω |
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VIN = |
2.4V, IIN = |
15mA |
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ICC |
Quiescent Supply Current |
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5.5 |
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3 |
µ |
A |
VIN = |
VCC or GND, |
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IOUT = 0 |
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∆ ICC |
Increase in ICC per Input |
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5.5 |
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2.5 |
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mA |
One input at 3.4V. |
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Other inputs at VCC or GND |
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Note 4: Typical values are at VCC = 5.0V and TA = |
+ 25° C |
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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.
www.fairchildsemi.com |
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