IDTQS3389Q [IDT]
QUICKSWITCH PRODUCTS LAST VALUE LATCH 20 ACTIVE BUS TERMINATORS; 快速切换产品最后的值LATCH 20有源总线终结器
| 型号： | IDTQS3389Q |
| 厂家： | 
INTEGRATED DEVICE TECHNOLOGY |
| 描述： | QUICKSWITCH PRODUCTS LAST VALUE LATCH 20 ACTIVE BUS TERMINATORS |
| 文件： | 总5页 (文件大小：45K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
QUICKSWITCH® PRODUCTS
IDTQS3389
LAST VALUE LATCH
20 ACTIVE BUS TERMINATORS
(BUS HOLD)
FEATURES:
DESCRIPTION:
• Active termination pulls bus pins to rails
• Holds last value of input signal
• Ideal replacement for resistive termination
• Ultra low 3µA DC quiescent current
• Bus-hold eliminates floating bus lines and reduces static
power consumption
TheQS3389providesasetof20activeterminationcircuitswhichpulldata
bussignalstothevoltagerails.Thisfeaturepreventsbussignalsfromfloating
in the threshold region of standard TTL I/O devices. The QS3389 can
replaceresistorterminationsolutionswhichaddDCpowerdissipationand
increase component count. Input clamp diodes help to reduce reflections
andundershootintransmissionlineenvironments. Importantly, thetermi-
natorcircuitspullsignalstowhicheverlogicstatethesignalpreviouslyheld
(high or low). For this reason, this device is also referred to as a last value
latch.Thisdeviceisappropriatefordatabusapplicationswhereinterfacing
devices have CMOS inputs with low input currents. These terminators
provide sufficient drive to overcome leakage currents and drive corre-
sponding signals away from the TTL threshold region.
• Low power QCMOS technology
• Operates over 2.7V to 5.5V Vcc range
• TTL-compatible input and output levels
• No added noise or ground bounce
• 20 independent terminator circuits
• Available in QSOP package
The QS3389 is characterized for operation at 0°C to +70°C.
APPLICATIONS:
• Bus termination
• Extend data hold time
FUNCTIONALBLOCKDIAGRAM
T0
7KΩ
T19
7KΩ
TheIDTlogoisaregisteredtrademarkofIntegratedDeviceTechnology,Inc.
COMMERCIAL TEMPERATURE RANGE
DECEMBER 1999
1
c
1999 Integrated Device Technology, Inc.
DSC-5733/1
IDTQS3389
COMMERCIALTEMPERATURERANGE
LASTVALUELATCH20ACTIVETERMINATORS(BUSHOLD)
PINCONFIGURATION
ABSOLUTEMAXIMUMRATINGS(1)
Symbol
Description
Supply Voltage to Ground
DC Switch Voltage VS
Max
–0.5 to +7
–0.5 to +7
–3
Unit
V
(2)
VTERM
(3)
VCC
T0
24
23
22
21
20
19
18
17
16
15
14
13
VCC
T10
T11
VTERM
V
1
VAC
AC Input Voltage (pulse width ≤20ns)
DC Output Current
V
2
IOUT
PMAX
TSTG
120
mA
W
T1
3
Maximum Power Dissipation (TA = 85°C)
Storage Temperature
0.5
T12
T13
T14
T15
T16
T17
T18
T19
GND
T2
T3
T4
T5
T6
T7
4
–65 to +150
°C
5
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 terminals.
3. All terminals except VCC .
6
7
8
9
T8
T9
10
11
12
GND
CAPACITANCE (TA = +25°C, f = 1MHz, VIN = 0V, VOUT = 0V)
Pins
Typ.
Max.(1)
Unit
T19 -T0
3
4
pF
QSOP
TOP VIEW
NOTE:
1. This parameter is guaranteed but not production tested.
2
IDTQS3389
COMMERCIALTEMPERATURERANGE
LASTVALUELATCH20ACTIVETERMINATORS(BUSHOLD)
DCELECTRICALCHARACTERISTICSOVEROPERATINGRANGE
FollowingConditionsApplyUnlessOtherwiseSpecified:
Commercial: TA = 0°C to +70°C, VCC = 5V ± 5%
Symbol
Parameter
Input HIGH Voltage
Test Conditions
Min.
Typ.(1) Max.
Unit
VIH
Guaranteed Logic HIGH for Control Pins
2
—
—
V
VIL
VT
IIN
InputLOWVoltage
GuaranteedLogicLOWforControlPins
—
—
—
—
—
—
1.5
—
—
—
0.8
—
V
ThresholdVoltage
V
InputLeakageCurrent (2)
InputCurrent(5)
VIN = Vcc or GND
Vcc = Max., VIN = 0V or Vcc
±5
µA
µA
IBH
±20
±500(4)
(2,3)
Input HIGH or LOW Bus Hold Inputs
Vcc = Max., 0.8V < VIN < 2V
IBHH
IBHL
RT
BusHoldSustainingCurrent(6,7)
Bus Hold Inputs
Vcc = Min., VIN = 2V
Vcc = Min., VIN = 0.8V
–60
+60
—
—
—
7k
—
—
—
µA
µA
Ω
TerminatorResistance
NOTES:
1. Typical values are at VCC = 5.0V, TA = 25°C.
2. Trip current definition (see Functional Block Diagram):
An external driver must source at least ITL to switch the node from LOW to HIGH.
An external driver must sink at least ITH to switch the node from HIGH to LOW.
3. Hold current definition (see Functional Block Diagram):
IHH is the Maximum Curent the QS3389 can sink without raising the node above VIL max.
IHL is the Maximum Curent the QS3389 can source without lowering the node below VIH min.
4. An external driver must provide at least IBH during transition to guarantee that the Bus-Hold input will change states.
5. IBH is the magnitude of the input current specified under two conditions:
a) Input voltage at GND or Vcc. This indicates the input current under steady-state condition.
b) Input voltage between 0.8V and 2V (TTL input threshold range). This indicates the maximum input current during transient condition. The driver connected to the
input must overcome this current requirement in order to switch the logic state of the bus-hold circuit.
6. IBHL is the minimum sustaining “sink” current at the input for VIN = 0.8V. This parameter signifies the latching capability of the bus-hold circuit in logic LOW state.
7. IBHH is the minimum sustaining “source” current at the input for VIN = 2V. This parameter signifies the latching capability of the bus-hold circuit in logic HIGH state.
POWERSUPPLYCHARACTERISTICS
Symbol
Parameter
TestConditions(1)
Max.
Unit
ICCQ
Quiescent Power Supply Current
VCC = Max., VIN = GND or VCC, f = 0
1.5
mA
NOTE:
1. For conditions shown as Min. or Max., use the appropriate values specified under DC Electrical Characteristics.
3
IDTQS3389
COMMERCIALTEMPERATURERANGE
LASTVALUELATCH20ACTIVETERMINATORS(BUSHOLD)
ACTIVE TERMINATOR OR ‘BUS-HOLD’ CIRCUIT
The Active Terminator circuit, also known as the Bus-hold circuit, is configured as a “weak latch” with positive feedback. When connected to a TTL
orCMOSinputport, theBus-holdcircuitholdsthelastlogicstateattheinputwhentheinputis“disconnected”fromthedriver. Whentheoutputofadevice
connectedtosuchaninputattemptsalogicleveltransition, itwillover-drivetheBus-holdcircuit. TheprimarybenefitofthiscircuitisthatitpreventsCMOS
inputsfromfloating, asituationwhichshouldbeavoidedtopreventspuriousswitchingofinputsandunnecessarypowerdissipation. Bus-holdisabetter
solutionthanthetraditionalapproachofusingresistiveterminationtoVCC orGNDtopreventbusfloating, becausetheBus-holdcircuitdoesnotconsume
any static power.
V-I CHARACTERISTICS OF BUS-HOLD CIRCUIT
IBH
+500
Sinking
Current
( + )
Voltage
+20 IBH
IBHL
IBH
+60
+20
+60
IBHL
VT
– 20 IBH
– 20
– 60
Vcc
IBHH
– 60 IBHH
VIL
VIH
Sourcing
Current
( – )
IBH
– 500
0.8V
2V
VT ≡ Threshold Voltage ≈ 1.5V
VIL ≈ .8 VIH ≈ 2V
ThefigureaboveshowstheinputV-IcharacteristicsofaBus-holdimplementation. Theinputcharacteristicsresemblearesistor. Astheinputvoltage
is increased from 0 volts, the ‘sink’ current increases linearly. When the TTL threshold of the circuit is reached (typically 1.5 volts), the latch changes the
logic state due to positive feedback and the direction of current is reversed. As the voltage is further increased towards VCC, the input ‘source’ current
begins to decrease, reaching the lowest level at VIN = VCC.
4
IDTQS3389
COMMERCIALTEMPERATURERANGE
LASTVALUELATCH20ACTIVETERMINATORS(BUSHOLD)
ORDERINGINFORMATION
XX
IDTQS
XXXXX
X
Package
Process
Device Type
Commercial (0°C to +70°C)
Blank
Q
Quarter Size Outline Package
Last Value Latch 20 Active Terminators (Bus Hold)
3389
CORPORATE HEADQUARTERS
2975StenderWay
Santa Clara, CA 95054
for SALES:
800-345-7015 or 408-727-6116
fax: 408-492-8674
for Tech Support:
logichelp@idt.com
(408) 654-6459
www.idt.com
5
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