MDSL-00044-02 QUALITY SEMICONDUCTOR, INC. 1
JULY 31, 1997
QS35257 ADVANCE INFORMATION
Now an Company
FEATURES/BENEFITS
• Enhanced N channel FET with no inherent
diode to VCC
• Bidirectional switches connect inputs
to outputs
• Pin compatible with the 74F257, 74FCT257,
and 74FCT257T
• Zero propagation delay, zero ground bounce
• TTL-compatible control inputs
• Undershoot clamp diodes on all switch and
control pins
• Available in SOIC (S1), QSOP
APPLICATIONS
• Logic replacement
• Video, audio, graphics switching, muxing
• Hot-swapping, hot-docking
(Application Note AN-13)
• Voltage translation
(5V to 3.3V; Application Note AN-11)
• Bus funneling
Figure 1. Functional Block Diagram
DESCRIPTION
The QS35257 is a high-speed CMOS LVTTL-com-
patible Quad 2:1 multiplexer/demultiplexer. The
QS35257 is a function and pinout compatible
QuickSwitch version of the 74F257, 74FCT257, and
the 74ALS/AS/LS257 Quad 2:1 multiplexers. The
QS35257 has 50Ω series resistors to reduce ground
bounce noise. The series resistor minimizes charge-
sharing effect and is ideal for series termination of
unterminated PCB/transmission lines.
Mux/Demux devices provide an order of magnitude
faster speed than equivalent logic devices.
S
E
Y
A
I0
A
I1
A
I0
B
I1
B
I0
C
I1
C
I0
D
I1
D
Y
B
Y
C
Y
D
QS35257
ADVANCE
INFORMATION
QuickSwitch® Products
High-Speed CMOS QuickSwitch
Quad 2:1 Mux/Demux With
50Ω Damping Resistor
Q
Q
UALITY
S
EMICONDUCTOR,
I
NC.
Q
2QUALITY SEMICONDUCTOR, INC. MDSL-00044-02
JULY 31, 1997
QS35257 ADVANCE INFORMATION
Now an Company
Table 3. Absolute Maximum Ratings
Supply Voltage to Ground ...........................................–0.5V to +7.0V
DC Switch Voltage VS..................................................–0.5V to +7.0V
DC Input Voltage VIN ...................................................–0.5V to +7.0V
AC Input Voltage (for a pulse width ≤ 20ns) .............................. –3.0V
DC Output Current Max. Sink Current/Pin............................... 120mA
Maximum Power Dissipation ................................................ 0.5 watts
TSTG Storage Temperature ......................................... –65° to +150°C
Name I/O Description
Ixx I Data Inputs
S I Select Input
EI Enable Input
YA-YDO Data Outputs
Figure 2. Pin Configuration
(All Pins Top View)
SOIC (S1), QSOP
Table 2. Function Table
Inputs Outputs
ESY
AYBYCYDFunction
H X Hi-Z Hi-Z Hi-Z Hi-Z Disable
LLI0
AI0BI0CI0DSelect 0
LHI1
AI1BI1CI1DSelect 1
Note: ABSOLUTE MAXIMUM
CONTINUOUS RATINGS are those
values beyond which damage to
the device may occur. Exposure to
these conditions or conditions
beyond those indicated may
adversely affect device reliability.
Functional operation under
absolute-maximum conditions is not
implied.
Note: Capacitance is guaran-
teed, but not production tested
and are typical values. For total
capacitance while the switch is
ON, please see Section 1 under
“Input and Switch Capacitance.”
Table 1. Pin Description
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
S
I0
A
I1
A
Y
A
I0
B
I1
B
Y
B
GND
V
CC
E
I0
D
I1
D
Y
D
I0
C
I1
C
Y
C
Table 4. Capacitance
TA = 25°C, f = 1MHz, VIN = 0V, VOUT = 0V
SOIC, QSOP
Pins Typ Max Unit
Control Inputs 4 5 pF
QuickSwitch Channels Demux 5 7 pF
(Switch OFF) Mux 9 10 pF
MDSL-00044-02 QUALITY SEMICONDUCTOR, INC. 3
JULY 31, 1997
QS35257 ADVANCE INFORMATION
Now an Company
Symbol Parameter Test Conditions Min Typ(1) Max Unit
VIH Input HIGH Voltage Guaranteed Logic HIGH 2.0 — — V
for Control Pins
VIL Input LOW Voltage Guaranteed Logic LOW — — 0.8 V
for Control Pins
| IIN | Input Leakage Current 0V ≤ VIN ≤ VCC —— 1µA
(Control Inputs)
| IOZ | Off-State Current (Hi-Z) 0V ≤ VOUT ≤ VCC — 0.001 1 µA
RON Switch On Resistance(2) VCC = Min., VIN = 0.0V 35 50 70 Ω
ION = 15mA
RON Switch On Resistance(2) VCC = Min., VIN = 2.4V 35 55 75 Ω
ION = 6mA
VPPass Voltage(3) VIN = VCC = 5V, IOUT = –5µA 3.7 4 4.2 V
Table 5. DC Electrical Characteristics Over Operating Range
Commercial TA = –40°C to +85°C, VCC = 5.0V ± 10%
Figure 3. Typical ON Resistance vs. VIN at VCC = 5.0V
Notes:
1. Typical values indicate VCC = 5.0V and TA = 25°C.
2. For a diagram explaining the procedure for RON measurement, please see Section 1 under, “DC Electrical
Characteristics.” RON guaranteed, but not production tested.
3. Pass voltage is guaranteed, but not production tested.
50
75
25
0
100
125
150
175
200
R
ON
(ohms)
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5
V
IN
(Volts)
4QUALITY SEMICONDUCTOR, INC. MDSL-00044-02
JULY 31, 1997
QS35257 ADVANCE INFORMATION
Now an Company
Table 6. Power Supply Characteristics Over Operating Range
TA = –40°C to +85°C, VCC = 5.0V ± 10%
Symbol Parameter Test Conditions(1) Max Unit
ICCQ Quiescent Power VCC = Max., VIN = GND or VCC, f = 0 3.0 µA
Supply Current
∆ICC Power Supply Current(2) VCC = Max, VIN = 3.4V, f = 0 1.5 mA
per Input HIGH per control input
QCCD Dynamic Power Supply VCC = Max, I and Y Pins Open, 0.25 mA/
Current per MHz(3) Control Inputs Toggling @ 50% Duty Cycle MHz
Notes:
1. For conditions shown as Min. or Max., use the appropriate values specified under DC specifications.
2. Per TTL driven-input (VIN = 3.4V, control inputs only). I and Y pins do not contribute to ∆ICC.
3. This parameter applies to the control inputs only and represents the current required to switch internal capacitance
at the specified frequency. The I and Y inputs generate no significant AC or DC currents as they transition. This
parameter is guaranteed, but not production tested.
QS35257
Symbol Description(1) Min Typ Max Unit
tPLH Data Propagation Delays(2,3) — — 2.5(3) ns
tPHL In to Y
tPZH Switch Turn-on Delay 0.5 — 5.2 ns
tPZL Sn to Y
tPHZ Switch Turn-on Delay 0.5 — 5.0 ns
tPLZ En to Y
tPHZ Switch Turn-off Delay(2) 0.5 — 4.8 ns
tPLZ En to Y, Sn to Y
Table 7. Switching Characteristics Over Operating Range
TA = –40°C to +85°C, VCC = 5.0V ± 10%
CLOAD = 50pF, RLOAD = 500Ω unless otherwise noted.
Notes:
1. See Test Circuit and Waveforms. Minimums guaranteed, but not production tested.
2. This parameter is guaranteed, but not production tested.
3. The bus switch contributes no propagation delay other than the RC delay of the ON
resistance of the switch and the load capacitance. The time constant for the switch
alone is of the order of 2.5ns for QS35257 for CL = 50pF. Since this time constant is
much smaller than the rise/fall times of typical driving signals, it adds very little
propagation delay to the system. Propagation delay of the bus switch when used in a
system is determined by the driving circuit on the driving side of the switch and its
interaction with the load on the driven side.
