ESD > 2000V per MIL-STD-883, Method 3015; > 200V using
machine model (C = 200pF, R = 0)
Hot insertion capability
Very low power dissipation
Available in QSOP, SOIC, SSOP, and TSSOP Packages
DESCRIPTION:
The FST3244 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 FST3244 is an octal TTL-compatible bus switch. The
OE
pins
provide output enable control for all 8 bits. This device is pin-compatible
with and functionally similar to the FCT244T.
FUNCTIONAL BLOCK DIAGRAM
1
OE
1
A
0
1
A
1
1
A
2
1
A
3
1
B
0
1
B
1
1
B
2
1
B
3
PIN CONFIGURATION
1
OE
1
A
0
2
B
3
1
2
3
4
5
6
7
8
9
10
SO20-2
SO20-8
SO20-9
SO20-7
20
19
18
17
16
15
14
13
12
11
Vcc
2
OE
1
B
0
2
A
3
1
B
1
2
A
2
1
B
2
2
A
1
1
A
1
2
B
2
1
A
2
2
B
1
1
A
3
2
B
0
2
OE
2
A
0
2
A
1
2
A
2
2
A
3
2
B
0
2
B
1
1
B
3
2
A
0
GND
2
B
2
2
B
3
QSOP/ SOIC/ SSOP/ TSSOP
TOP VIEW
INDUSTRIAL TEMPERATURE RANGE
1
c
2001
Integrated Device Technology, Inc.
APRIL 2001
DSC-5522/-
IDT74FST3244
OCTAL BUS SWITCH
INDUSTRIAL 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
x
OE
xAx
xBx
Description
Output Enable Inputs (Active LOW)
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
2
OE
(1)
Description
H
L
H
L
H
H
L
L
Disconnect
Connect 1A to 1B
Connect 2A to 2B
Connect 1A to 1B and 2A to 2B
CAPACITANCE
(1)
Symbol
Parameter
C
IN
Control Input Capacitance
C
I/O
Switch Input/Output
Capacitance
Conditions
(2)
Switch Off
Typ.
8
13
Unit
pF
pF
NOTE:
1. H = HIGH
L = LOW
NOTES:
1. Capacitance is characterized 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
V
IK
I
OFF
I
CC
Parameter
Control Input HIGH Voltage
Control Input LOW Voltage
Control Input HIGH Current
Control Input LOW Current
Current during
Bus Switch DISCONNECT
Clamp Diode Voltage
Switch Power Off Leakage
Quiescent Power Supply Current
V
CC
= Min., I
IN
= –18mA
V
CC
= 0V, V
IN
or V
O
≤
5.5V
V
CC
= Max., V
IN
= GND or V
CC
V
CC
= Max., V
O
= 0 to 5V
Test Conditions
Guaranteed Logic HIGH Level
Guaranteed Logic LOW Level
V
CC
= Max.
V
I
= V
CC
V
I
= GND
Min.
2
—
—
—
—
—
—
—
—
Typ.
(1)
—
—
—
—
—
—
–0.7
—
0.1
Max.
—
0.8
±1
±1
±1
±1
–1.2
±1
3
V
µA
µA
µA
Unit
V
V
µA
BUS SWITCH IMPEDANCE OVER OPERATING RANGE
Following Conditions Apply Unless Otherwise Specified:
Operating Conditions: T
A
= -40°C to +85°C, V
CC
= 5.0V ±5%
Symbol
R
ON
Parameter
Switch CONNECT Resistance, A to B
(2)
Test Conditions
Vcc = Min., V
IN
= 0V
I
ON
= 30mA
Vcc = Min., V
IN
= 2.4V
I
ON
= 15mA
A(B) = 0V, B(A) = V
CC
Min.
—
—
100
Typ.
(1)
5
10
—
Max.
7
15
—
mA
Unit
Ω
I
OS
Short Circuit Current, A to B
(3)
NOTES:
1. Typical values are at Vcc = 5.0V, +25°C ambient.
2. The voltage drop between the indicated ports divided by the current through the switch.
3. Not more than one output should be shorted at one time. Duration of the test should not esceed one second.
2
IDT74FST3244
OCTAL BUS SWITCH
INDUSTRIAL 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
1 Enable Pin Toggling
50% Duty Cycle
V
CC
= Max.
Outputs Open
2 Enable Pins Toggling
fi = 10MHz
50% Duty Cycle
Min.
—
—
Typ.
(2)
0.5
120
Max.
1.5
160
Unit
mA
µ A/
MHz/
Enable
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
—
2.9
4.7
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. C
PD
= I
CCD
/V
CC
C
PD
= Power Dissipation Capacitance
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:
Operating Conditions: 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
A to B, B to A
(2)
Switch CONNECT Delay
xOE to A or B
Switch DISCONNECT Delay
xOE to A or B
Charge Injection During Switch DISCONNECT,
xOE to A or B
(3)
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. The bus switch contributes no propagation delay other than the RC delay of the load interacting with the RC of the switch.
3. IQ
CI
I is the charge injection for a single switch DISCONNECT and applies to either single switches or multiplexers.
IQ
DCI
I is the charge injection for a multiplexer as the multiplexed port switches from one path to another. Charge Injection is reduced becasue the injection
from the DISCONNECT of the first path is compensated by the CONNECT of the second path.
3
IDT74FST3244
OCTAL BUS SWITCH
INDUSTRIAL 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
C
L
PROPAGATION DELAY
7.0V
SAME PHASE
INPUT TRANSITION
t
PL H
OUTPUT
t
PL H
t
PH L
t
PH L
3V
1.5V
0V
V
OH
1.5V
V
OL
3V
1.5V
0V
V
O UT
500
Ω
OPPOSITE P HASE
INPUT TRANSITION
SWITCH POSITION
Test
Open Drain
Disable Low
Enable Low
All Other Tests
Open
FCT LINK
SET-UP, HOLD, AND RELEASE TIMES
Switch
Closed
DATA
INPUT
t
SU
TIMING
INPUT
ASYNCHRONOUS
CONTROL
SYNCHRONOUS
CONTROL
t
REM
t
H
3V
1.5V
0V
3V
1.5V
0V
3V
1.5V
0V
3V
1.5V
0V
DEFINITIONS:
C
L
= Load capacitance: includes jig and probe capacitance.
R
T
= Termination resistance: should be equal to Z
OUT
of the Pulse
Generator.
t
SU
t
H
CHARGE INJECTION
V
CC
ENABLE AND DISABLE TIMES
ENABLE
DISABLE
3V
V
O U T(3 )
Switch
O ut
1 M Hz
Signal
G enerator
Enable/Select
Switch In
(1 )
D.U.T.
(2 )
CONTROL
INPUT
t
PZL
OUTPUT
NORMALLY
LOW
SW ITCH
CLOSED
t
PZH
3.5V
1.5V
0.3V
t
PHZ
0.3V
1.5V
0V
t
PLZ
1.5V
0V
3.5V
V
OL
V
OH
Switch In (M UX)
C
L
=
50pF
NOTES:
1. Select is used with multiplexers for measuring IQ
DCI
I during multiplexer
select. During all other tests Enable is used.
2. Used with multiplexers to measure IQ
DCI
I only.
3. Charge Injection =
∆V
OUT
C
L
, with Enable toggling for IQ
CI
I or Select toggling
for IQ
DCI
I.
∆V
OUT
is the change in V
OUT
and is measured with a 10MΩ
probe.
OUTPUT
NORMALLY
HIGH
SW ITCH
OPEN
0V
PULSE WIDTH
LOW -HIGH-LOW
PULSE
t
W
HIGH-LOW -HIGH
PULSE
1.5V
1.5V
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
IDT74FST3244
OCTAL BUS SWITCH
INDUSTRIAL TEMPERATURE RANGE
ORDERING INFORMATION
IDT
XX
Tem p. Range
FST
X
Fam ily
XX
Device Type
X
Package
PY
SO
Q
PG
Shrink Small Outline Package (SO20-7)
Sm all O utline IC (SO20-2)
Quarter-size Sm all O utline Package (SO20-8)
Thin Shrink Small Outline Package (SO20-9)
244
8-Bit Switch
3
Octal Bus Switch
74
−
40
°
C to +85
°
C
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