ESD > 2000V per MIL-STD-883, Method 3015; > 200V using
machine model (C = 200pF, R = 0)
Available in PDIP, SOIC, QSOP, and TSSOP Packages
Pin-compatible with FCT245
DESCRIPTION:
The FST3245 belongs to IDT's family of Bus switches. Bus switch
devices perform the function of connecting or isolating two ports without
providing any inherent current sink or source capability. Thus they
generate little or no noise of their own while providing a low resistance path
for an external driver. These devices connect input and output ports through
an n-channel FET. When the gate-to-source junction of this FET is
adequately forward-biased the device conducts or the resistance between
input and output ports is small. Without adequate bias on the gate-to-source
junction of the FET, the FET is turned off, therefore with no V
CC
applied, the
device has hot insertion capability.
The low on-resistance and simplicity of the connection between input
and output ports reduces the delay in this path to close to zero.
The FST3245 is an octal TTL-compatible bus switch. The
OE
pin
provides output enable control for all 8 bits. The direction control pin (DIR)
of the FCT245 is replaced with a "No connect" (NC) in the FST3245. Bus
switch devices provide an inherently bidirectional connection between
ports, thus eliminating the purpose of the direction control pin.
FUNCTIONAL BLOCK DIAGRAM
A
0
A
1
A
2
A
3
A
4
A
5
A
6
A
7
B
0
PIN CONFIGURATION
NC
1
2
3
4
5
6
7
8
9
10
P20-1
SO20-2
SO20-8
SO20-9
20
19
18
17
16
15
14
13
12
11
Vcc
OE
B
0
B
1
B
2
B
3
B
4
B
5
B
6
B
7
B
1
B
2
B
3
B
4
B
5
B
6
B
7
A
0
A
1
A
2
A
3
A
4
A
5
A
6
A
7
GND
OE
PDIP/ SOIC/ QSOP/ TSSOP
TOP VIEW
COMMERCIAL TEMPERATURE RANGE
1
c
1999 Integrated Device Technology, Inc.
OCTOBER 1999
DSC-5529/-
IDT74FST3245
OCTAL BUS SWITCH
COMMERCIAL TEMPERATURE RANGE
ABSOLUTE MAXIMUM RATINGS
(1)
Symbol
V
TERM(2)
T
STG
I
OUT
Rating
Terminal Voltage with Respect to GND
Storage Temperature
Maximum Continuous Channel Current
Max.
–0.5 to +7
–65 to +150
128
Unit
V
°C
mA
FST LINK
PIN DESCRIPTION
Pin Names
OE
NC
A
0-
A
7
B
0-
B
7
Description
Output Enable Input (Active LOW)
No connect
A Port Bits
B Port Bits
NOTES:
1. Stresses greater than those listed under ABSOLUTE MAXIMUM
RATINGS may cause permanent damage to the device. This is a
stress rating only and functional operation of the device at these or
any other conditions above those indicated in the operational sections
of this specification is not implied. Exposure to absolute maximum
rating conditions for extended periods may affect reliability.
2. Vcc, Control, and Switch terminals.
FUNCTION TABLE
(1)
OE
H
L
B
0-7
X
A
0-7
Disconnect
Connect
Description
CAPACITANCE
(1)
Symbol
Parameter
C
IN
Control Input Capacitance
C
I/O
Switch Input/Output
Capacitance
Conditions
(2)
Switch Off
Typ.
4
Unit
pF
pF
NOTE:
1. H = HIGH
L = LOW
X = Don’t Care
NOTES:
1. Capacitance is characteriszed but not tested.
2. T
A
= 25°C, f = 1MHz, V
IN
= 0V, V
OUT
= 0V
DC ELECTRICAL CHARACTERISTICS OVER OPERATING RANGE
Following Conditions Apply Unless Otherwise Specified:
Operating Conditions: T
A
= -40°C to +85°C, V
CC
= 5.0V ±5%
Symbol
V
IH
V
IL
I
IH
I
IL
I
OZH
I
OZL
I
OS
V
IK
R
ON
I
OFF
I
CC
Parameter
Input HIGH Voltage
Input LOW Voltage
Input HIGH Current
Input LOW Voltage
High Impedance Output Current
(3-State Output Pins)
Short Circuit Current
Clamp Diode Voltage
Switch On Resistance
(4)
Input/Output Power Off Leakage
Quiescent Power Supply Current
V
CC
= Max., V
O
= GND
(3)
V
CC
= Min., I
IN
= –18mA
V
CC
= Max., V
O
= 0V, I
ON
= 30mA
V
CC
= Max., V
O
= 2.4V, I
ON
= 15mA
V
CC
= 0V, V
IN
or V
O
≤
4.5V
V
CC
= Max., V
I
= GND or V
CC
V
CC
= Max.
Test Conditions
(1)
Guaranteed Logic HIGH for Control Inputs
Guaranteed Logic LOW for Control Inputs
V
CC
= Max.
V
I
= V
CC
V
I
= GND
V
O
= V
CC
V
O
= GND
Min.
2
—
—
—
—
—
—
—
—
—
—
—
Typ.
(2)
—
—
—
—
—
—
300
–0.7
5
10
—
0.1
Max.
—
0.8
±1
±1
±1
±1
—
–1.2
7
15
±1
3
µA
µA
mA
V
Ω
µA
Unit
V
V
µA
NOTES:
1. For conditions shown as Max. or Min., use appropriate value specified under Electrical Characteristics for the applicable device type.
2. Typical values are at V
CC
= 5.0V, +25°C ambient.
3. Not more than one output should be tested at one time. Duration of the test should not exceed one second.
4. Measured by voltage drop between ports at indicated current through the switch.
2
IDT74FST3245
OCTAL BUS SWITCH
COMMERCIAL TEMPERATURE RANGE
POWER SUPPLY CHARACTERISTICS
Symbol
∆I
CC
I
CCD
Parameter
Quiescent Power Supply Current
TTL Inputs HIGH
Dynamic Power Supply Current
(4)
Test Conditions
(1)
V
CC
= Max.
V
IN
= 3.4V
(3)
V
CC
= Max.
Outputs Open
Enable Pin Toggling
50% Duty Cycle
V
CC
= Max.
Outputs Open
Enable Pin Toggling
(8 Switches Toggling)
fi = 10MHz
50% Duty Cycle
Min.
—
—
Typ.
(2)
0.5
30
Max.
1.5
40
Unit
mA
µ A/
MHz/
Switch
mA
V
IN
= V
CC
V
IN
= GND
I
C
Total Power Supply Current
(6)
V
IN
= V
CC
V
IN
= GND
V
IN
= 3.4
V
IN
= GND
—
2.4
3.2
—
2.7
4
NOTES:
1. For conditions shown as Max. or Min., use appropriate value specified under Electrical Characteristics for the applicable device type.
2. Typical values are at V
CC
= 5.0V, +25°C ambient.
3. Per TTL driven input (V
IN
= 3.4V). All other inputs at V
CC
or GND.
4. This parameter is not directly testable, but is derived for use in Total Power Supply Calculations.
5. Values for these conditions are examples of the I
CC
formula. These limits are guaranteed but not tested.
6. I
C
= I
QUIESCENT
+ I
INPUTS
+ I
DYNAMIC
I
C
= I
CC
+
∆I
CC
D
H
N
T
+ I
CCD
(f
i
N)
I
CC
= Quiescent Current
∆I
CC
= Power Supply Current for a TTL High Input (V
IN
= 3.4V)
D
H
= Duty Cycle for TTL Inputs High
N
T
= Number of TTL Inputs at D
H
I
CCD
= Dynamic Current Caused by an Input Transition Pair (HLH or LHL)
f
i
= Input Frequency
N = Number of Switches Toggling at f
i
All currents are in milliamps and all frequencies are in megahertz.
SWITCHING CHARACTERISTICS OVER OPERATING RANGE
Following Conditions Apply Unless Otherwise Specified:
Commercial: T
A
= -40°C to +85°C, V
CC
= 5.0V ± 5%
Symbol
t
PLH
t
PHL
t
PZH
t
PZL
t
PHZ
t
PLZ
|Q
CI
|
Description
Data Propagation Delay
Ai to Bi, Bi to Ai
(3,4)
Switch Turn on Delay
OE
to Ai, Bi
Switch Turn off Delay
OE
to Ai, Bi
(3)
Charge Injection
(5,6)
Condition
(1)
C
L
= 50pF
R
L
= 500Ω
Min.
(2)
—
1.5
1.5
—
Typ.
—
—
—
1.5
Max.
0.25
6.5
5.5
—
Unit
ns
ns
ns
pC
NOTES:
1. See test circuit and waveforms.
2. Minimum limits guaranteed but not tested.
3. This parameter is guaranteed by design but not tested.
4. 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 0.25 ns for 50 pF load. Since this time is constant and 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.
5. Measured at switch turn off, load = 50 pF in parallel with 10 MΩ scope probe, V
IN
= 0 volts.
6. Characterized parameter. Not 100% tested.
3
IDT74FST3245
OCTAL BUS SWITCH
COMMERCIAL TEMPERATURE RANGE
TEST CIRCUITS AND WAVEFORMS
TEST CIRCUITS FOR ALL OUTPUTS
V
CC
500
Ω
V
IN
Pulse
Generator
D.U.T.
50pF
R
T
SWITCH POSITION
Test
Open Drain
Disable Low
Enable Low
All Other Tests
Open
FCT LINK
7.0V
Switch
Closed
V
OUT
500
Ω
C
L
DEFINITIONS:
C
L
= Load capacitance: includes jig and probe capacitance.
R
T
= Termination resistance: should be equal to Z
OUT
of the Pulse
Generator.
O ctal lin k
SET-UP, HOLD, AND RELEASE TIMES
DATA
INPUT
t
SU
TIM ING
INPUT
ASYNCHRONOUS C ONTROL
PRES ET
CLEAR
ETC.
SYNCHRO NOUS CONTRO L
PRES ET
CLEAR
CLOCK ENABLE
ETC.
t
REM
t
H
3V
1.5V
0V
3V
1.5V
0V
3V
1.5V
0V
3V
1.5V
0V
O ctal lin k
PULSE WIDTH
LO W -HIGH-LOW
PULSE
t
W
HIGH-LOW -HIGH
PULSE
O ctal lin k
1.5V
1.5V
t
SU
t
H
PROPAGATION DELAY
SAM E PHASE
INPUT TRANSITION
t
PLH
OUTPUT
t
PLH
OPPOSITE P HASE
INPUT TRANSITION
t
PH L
t
PH L
3V
1.5V
0V
V
OH
1.5V
V
OL
3V
1.5V
0V
O ctal lin k
ENABLE AND DISABLE TIMES
ENAB LE
DISA BLE
3V
CO NTROL
INPUT
t
PZL
OUTPUT
NO RM A LLY
LO W
SW ITCH
CLOSE D
t
PZH
OUTPUT
NO RM A LLY
HIGH
SW ITCH
OPEN
3.5V
1.5V
0.3V
t
PHZ
0.3V
1.5V
0V
0V
O ctal lin k
1.5V
t
PLZ
0V
3.5V
V
OL
V
OH
NOTES:
1. Diagram shown for input Control Enable-LOW and input Control Disable-
HIGH
2. Pulse Generator for All Pulses: Rate
≤
1.0MHz; t
F
≤
2.5ns; t
R
≤
2.5ns
4
IDT74FST3245
OCTAL BUS SWITCH
COMMERCIAL TEMPERATURE RANGE
ORDERING INFORMATION
IDT
XX
Temp. Range
FST
XX
Device Type
X
Package
P
SO
Q
PG
3245
Plastic DIP (P20-1)
Small Outline IC (SO20-2)
Quarter-size Small Outline Package(SO20-8)
Thin Shrink Sm all Outline Package (SO20-9)
Octal Bus Switch
74
−
40
°
C to +85
°
C
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