1
COMMERCIAL AND INDUSTRIAL TEMPERATURE RANGES
IDT8737-11
LOW SKEW, ÷÷
÷÷
÷1/÷÷
÷÷
÷2 DIFFERENTIAL-TO-3.3V LVPECL
AUGUST 2004
2004 Integrated Device Technology, Inc. DSC 6168/5c
IDT8737-11
COMMERCIAL AND INDUSTRIAL TEMPERATURE RANGES
LOW SKEW, ÷÷
÷÷
÷1/÷÷
÷÷
÷2
DIFFERENTIAL-TO-3.3V
LVPECL FANOUT BUFFER
The IDT logo is a registered trademark of Integrated Device Technology, Inc.
FEATURES:
• Two divide-by-1 and two divide-by-2 differential 3.3V LVPECL
outputs
• Selectable differential CLK, xCLK, or LVPECL clock inputs
• CLK, xCLK pair can accept the following differential input levels:
LVDS, LVPECL, LVHSTL, SSTL, and HCSL
• PCLK, xPCLK supports the following input types: LVPECL, CML,
and SSTL
• Maximum output frequency: 650MHz
• Translates any single-ended input signal (LVCMOS, LVTTL, GTL)
to LVPECL levels with resistor bias on xCLK input
• Output skew: 60ps (max.)
• Part-to-part skew: as low as 200ps
• Bank skew:
- Bank A, as low as 20ps
- Bank B, as low as 35ps
• Propagation delay: 1.7ns (max.)
• 3.3V operating supply
• Available in TSSOP package
DESCRIPTION:
The IDT8737-11 is a low skew, high performance differential-to-3.3V
LVPECL fanout buffer-divider. It has two selectable clock inputs. The CLK/
xCLK pair can accept most standard differential input levels. The PCLK/
xPCLK pair can accept LVPECL, CML, or SSTL input levels. The clock enable
is internally synchronized to eliminate runt pulses on the outputs during
asynchronous assertion/deassertion of the clock enable pin.
Guaranteed output and part-to-part skew characteristics make the IDT8737-
11 ideal for clock distribution applications that demand well-defined perfor-
mance and repeatability.
FUNCTIONAL BLOCK DIAGRAM
CLK_EN
CLK
xCLK
PCLK
xPCLK
CLK_SEL
MR
0
1
D
LE
Q
÷1
÷2
QA0
xQA0
QA1
xQA1
QB0
xQB0
QB1
xQB1
2
COMMERCIAL AND INDUSTRIAL TEMPERATURE RANGES
IDT8737-11
LOW SKEW, ÷÷
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÷2 DIFFERENTIAL-TO-3.3V LVPECL
PIN CONFIGURATION
NOTE:
1. Stresses beyond those listed under ABSOLUTE MAXIMUM RATINGS may cause
permanent damage to the device. These are stress ratings 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-rated conditions for extended periods may affect device reliability.
ABSOLUTE MAXIMUM RATINGS(1)
Symbol Description Max Unit
VDD Power Supply Voltage 4.6 V
VIInput Voltage –0.5 to VDD+0.5 V
VOOutput Voltage –0.5 to VDD+0.5 V
θJA Package Thermal Impedance (0 lfpm) 92.6 °C/W
TSTG Storage Temperature –65 to +150 °C
CAPACITANCE(TA = +25°C, f = 1MHz, VIN = 0V)
Parameter Description Typ. Max. Unit
CIN Input Capacitance — 4 pF
RPULLUP Input Pullup Resistor 51 — KΩ
RPULLDOWN Input Pulldown Resistor 51 — KΩ
TSSOP
TOP VIEW
1
2
3
4
5
6
7
8
9
10
20
19
18
17
16
15
14
13
12
11
VEE
CLK_EN
CLK_SEL
CLK
xCLK
PCLK
xPCLK
NC
MR
VDD
QA0
xQA0
VDD
QA1
xQA1
QB0
xQB0
VDD
QB1
xQB1
PIN DESCRIPTION(1)
Symbol Number Type Description
VEE 1 Power Negative Supply Pin
CLK_EN 2 Input Pullup Synchronizing Clock Enable. When HIGH, clock outputs follow clock input. When
LOW, Q outputs are forced LOW, xQ outputs are forced HIGH. LVTTL / LVCMOS
interface levels.
CLK_SEL 3 Input Pulldown Clock Select Input. When HIGH, selects PCLK / xPCLK inputs. When LOW, selects
CLK / xCLK inputs. LVTTL / LVCMOS interface levels.
CLK 4 Input Pulldown Non-Inverting Differential Clock Input
xCLK 5 Input Pullup Inverting Differential Clock Input
PCLK 6 Input Pulldown Non-Inverting Differential LVPECL Clock Input
xPCLK 7 Input Pullup Inverting Differential LVPECL Clock Input
NC 8 Unused No Connection
MR 9 Input Pulldown Master Reset. Resets the output divider. LVTTL / LVCMOS interface levels.
VDD 10, 13, 18 Power Positive Supply Pins
xQB1, QB1 11, 12 Output Differential Output Pair. LVTTL / LVCMOS interface levels.
xQB0, QB0 14, 15 Output Differential Output Pair. LVTTL / LVCMOS interface levels.
xQA1, QA1 16, 17 Output Differential Output Pair. LVTTL / LVCMOS interface levels.
xQA0, QA0 19, 20 Output Differential Output Pair. LVTTL / LVCMOS interface levels.
NOTE:
1. Pullup and Pulldown refer to internal input resistors. See Capacitance table for typical values.
3
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IDT8737-11
LOW SKEW, ÷÷
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÷2 DIFFERENTIAL-TO-3.3V LVPECL
CONTROL INPUT FUNCTION TABLE(1,2)
Inputs Outputs
MR CLK_EN CLK_SEL Selected Source QA0, QA1 xQA0, xQA1 QB0, QB1 xQB0, xQB1
1 X X X LOW HIGH LOW HIGH
0 0 0 CLK, xCLK Disabled; LOW Disabled; HIGH Disabled; LOW Disabled; HIGH
0 0 1 PCLK, xPCLK Disabled; LOW Disabled; HIGH Disabled; LOW Disabled; HIGH
0 1 0 CLK, xCLK Enabled Enabled Enabled Enabled
0 1 1 PCLK, xPCLK Enabled Enabled Enabled Enabled
NOTES:
1. After CLK_EN switches, the clock outputs are disabled or enabled following a rising and falling input clock edge as shown in the CLK_EN Timing Diagram below.
2. In active mode, the state of the outputs is a function of the CLK / xCLK and PCLK / xPCLK inputs as described in the Clock Input Function table.
CLOCK INPUT FUNCTION TABLE(1)
Inputs Outputs
CLK or PCLK xCLK or xPCLK QAx xQAx QBx xQBx Input to Output Mode Polarity
0 1 L H L H Differential to Differential Non-Inverting
1 0 H L H L Differential to Differential Non-Inverting
0 Biased(2) L H L H Single-Ended to Differential Non-Inverting
1 Biased(2) H L H L Single-Ended to Differential Non-Inverting
Biased(2) 1 L H L H Single-Ended to Differential Inverting
Biased(2) 0 H L H L Single-Ended to Differential Inverting
NOTES:
1. H = HIGH
L = LOW
2. See Single-Ended Signal diagram under Application Information at the end of this datasheet.
CLK_EN
CLK, PCLK
xCLK, xPCLK
QA0, QA1,
QB0, QB1
xQA0, xQA1,
xQB0, xQB1
≈
≈
Disabled Enabled
≈
CLK_EN Timing Diagram
4
COMMERCIAL AND INDUSTRIAL TEMPERATURE RANGES
IDT8737-11
LOW SKEW, ÷÷
÷÷
÷1/÷÷
÷÷
÷2 DIFFERENTIAL-TO-3.3V LVPECL
NOTES:
1. For single-ended applications, the max. input voltage for PCLK / xPCLK is VDD + 0.3V.
2. Common mode voltage is defined as VIH.
3. Outputs terminated with 50Ω to VDD - 0.2V.
DC ELECTRICAL CHARACTERISTICS, LVPECL- COMMERCIAL
Symbol Parameter Test Conditions Min. Typ. Max. Unit
IIH Input Current HIGH PCLK VIN = VDD = 3.465V 5 μA
xPCLK VIN = VDD = 3.465V 150
IIL Input Current LOW PCLK VIN = 0V, VDD = 3.465V -150 μA
xPCLK VIN = 0V, VDD = 3.465V -5
VPP Peak-to-Peak Input Voltage 0.3 1 V
VCMR Common Mode Input Voltage(1,2) VEE + 1.5 VDD V
VOH Output Voltage HIGH(3) VDD - 1.4 VDD - 1 V
VOL Output Voltage LOW(3) VDD - 2 VDD - 1.7 V
VSWING Peak-to-Peak Output Voltage Swing 0.65 0.9 V
POWER SUPPLY CHARACTERISTICS - COMMERCIAL
Symbol Parameter Test Conditions Min. Typ. Max. Unit
VDD Positive Supply Voltage 3.135 3.3 3.465 V
IEE Power Supply Current — — 50 mA
DC ELECTRICAL CHARACTERISTICS, LVCMOS / LVTTL - COMMERCIAL
Symbol Parameter Test Conditions Min. Typ. Max. Unit
VIH CLK_EN, CLK_SEL, MR 2 VDD + 0.3 V
VIL CLK_EN, CLK_SEL, MR -0.3 0.8 V
IIH Input Current HIGH CLK_EN VIN = VDD = 3.465V 5 μA
CLK_SEL, MR VIN = VDD = 3.465V 150
IIL Input Current LOW CLK_EN VIN = 0V, VDD = 3.465V -150 μA
CLK_SEL, MR VIN = 0V, VDD = 3.465V -5
NOTES:
1. For single-ended applications, the max. input voltage for CLK / xCLK is VDD + 0.3V.
2. Common mode voltage is defined as VIH.
DC ELECTRICAL CHARACTERISTICS, DIFFERENTIAL - COMMERCIAL
Symbol Parameter Test Conditions Min. Typ. Max. Unit
VPP Peak-to-Peak Input Voltage 0.15 0.3 V
VCMR Common Mode Input Voltage(1,2) VEE + 0.5 VDD - 0.85 V
IIH Input Current HIGH xCLK VIN = VDD = 3.465V 5 μA
CLK VIN = VDD = 3.465V 150
IIL Input Current LOW xCLK VIN = 0V, VDD = 3.465V -150 μA
CLK VIN = 0V, VDD = 3.465V -5
5
COMMERCIAL AND INDUSTRIAL TEMPERATURE RANGES
IDT8737-11
LOW SKEW, ÷÷
÷÷
÷1/÷÷
÷÷
÷2 DIFFERENTIAL-TO-3.3V LVPECL
NOTES:
1. Measured from the differential input crossingpoint to the differential output crossingpoint.
2. Defined as skew between outputs as the same supply voltage and with equal load conditions. Measured at the output differential crosspoints
3. Defined as skew between outputs on different devices operating at the same supply voltages and with equal load conditions. Using the same type of inputs on each
device, the outputs are measured at the differential crosspoints.
4. This parameter is defined in accordance with JEDEC Standard 65.
AC ELECTRICAL CHARACTERISTICS - COMMERCIAL
All parameters measured at 500MHz unless noted otherwise;
Cycle-to-cycle jitter = jitter on output; the part does not add jitter
Symbol Parameter Test Conditions Min. Typ. Max. Unit
FMAX Output Frequency 650 MHz
tPD Propagation Delay(1) CLK, xCLK f ≤ 650MHz 1 1.7 ns
PCLK, xPCLK 1 1.6
tSK(O) Output Skew(2,4) 60 ps
tSK(B) Bank Skew(4) Bank A 20 ps
Bank B 35
tSK(PP) Part-to-Part Skew(3,4) 200 ps
tROutput Rise Time 20 - 80% @ 50MHz 300 700 ps
tFOutput Fall Time 20 - 80% @ 50MHz 300 700 ps
o d c Output Duty Cycle 48 50 5 2 %
POWER SUPPLY CHARACTERISTICS - INDUSTRIAL
Symbol Parameter Test Conditions Min. Typ. Max. Unit
VDD Positive Supply Voltage 3.135 3.3 3.465 V
IEE Power Supply Current — — 55 mA
DC ELECTRICAL CHARACTERISTICS, LVCMOS / LVTTL - INDUSTRIAL
Symbol Parameter Test Conditions Min. Typ. Max. Unit
VIH CLK_EN, CLK_SEL, MR 2 VDD + 0.3 V
VIL CLK_EN, CLK_SEL, MR -0.3 0.8 V
IIH Input Current HIGH CLK_EN VIN = VDD = 3.465V 5 μA
CLK_SEL, MR VIN = V DD = 3.465V 150
IIL Input Current LOW CLK_EN VIN = 0V, VDD = 3.465V -150 μA
CLK_SEL, MR VIN = 0V, VDD = 3.465V -5
NOTES:
1. For single-ended applications, the max. input voltage for CLK / xCLK is VDD + 0.3V.
2. Common mode voltage is defined as VIH.
DC ELECTRICAL CHARACTERISTICS, DIFFERENTIAL - INDUSTRIAL
Symbol Parameter Test Conditions Min. Typ. Max. Unit
VPP Peak-to-Peak Input Voltage 0.15 1.3 V
VCMR Common Mode Input Voltage(1,2) VEE + 0.5 VDD - 0.85 V
IIH Input Current HIGH xCLK VIN = VDD = 3.465V 5 μA
CLK VIN = VDD = 3.465V 150
IIL Input Current LOW xCLK VIN = 0V, VDD = 3.465V -150 μA
CLK VIN = 0V, VDD = 3.465V -5
6
COMMERCIAL AND INDUSTRIAL TEMPERATURE RANGES
IDT8737-11
LOW SKEW, ÷÷
÷÷
÷1/÷÷
÷÷
÷2 DIFFERENTIAL-TO-3.3V LVPECL
NOTES:
1. For single-ended applications, the max. input voltage for PCLK / xPCLK is VDD + 0.3V.
2. Common mode voltage is defined as VIH.
3. Outputs terminated with 50Ω to VDD - 0.2V.
DC ELECTRICAL CHARACTERISTICS, LVPECL- INDUSTRIAL
Symbol Parameter Test Conditions Min. Typ. Max. Unit
IIH Input Current HIGH PCLK VIN = VDD = 3.465V 5 μA
xPCLK VIN = VDD = 3.465V 150
IIL Input Current LOW PCLK VIN = 0V, VDD = 3.465V -150 μA
xPCLK VIN = 0V, VDD = 3.465V -5
VPP Peak-to-Peak Input Voltage 0.3 1 V
VCMR Common Mode Input Voltage(1,2) VEE + 1.5 VDD V
VOH Output Voltage HIGH(3) VDD - 1.4 VDD - 1 V
VOL Output Voltage LOW(3) VDD - 2 VDD - 1.7 V
VSWING Peak-to-Peak Output Voltage Swing 0.6 0.9 V
NOTES:
1. Measured from the differential input crossingpoint to the differential output crossingpoint.
2. Defined as skew between outputs as the same supply voltage and with equal load conditions. Measured at the output differential crosspoints
3. Defined as skew between outputs on different devices operating at the same supply voltages and with equal load conditions. Using the same type of inputs on each
device, the outputs are measured at the differential crosspoints.
4. This parameter is defined in accordance with JEDEC Standard 65.
AC ELECTRICAL CHARACTERISTICS - INDUSTRIAL
All parameters measured at 500MHz unless noted otherwise;
cycle-to-cycle jitter = jitter on output; the part does not add jitter
Symbol Parameter Test Conditions Min. Typ. Max. Unit
FMAX Output Frequency 650 MHz
tPD Propagation Delay(1) CLK, xCLK f ≤ 650MHz 1 1.8 ns
PCLK, xPCLK 1 1.7
tSK(O) Output Skew(2,4) 75 ps
tSK(B) Bank Skew(4) Bank A 30 ps
Bank B 45
tSK(PP) Part-to-Part Skew(3,4) 300 ps
tROutput Rise Time 20 - 80% @ 50MHz 300 700 ps
tFOutput Fall Time 20 - 80% @ 50MHz 300 700 ps
o d c Output Duty Cycle 47 50 5 3 %
7
COMMERCIAL AND INDUSTRIAL TEMPERATURE RANGES
IDT8737-11
LOW SKEW, ÷÷
÷÷
÷1/÷÷
÷÷
÷2 DIFFERENTIAL-TO-3.3V LVPECL
LVPECL 50Ω
50Ω
Z = 50Ω
VDD
VEE = -1.3V ± 0.135V
VDD = 2V Z = 50Ω
Qx
xQx
Scope
VDD
VEE
xCLK, xPCLK
CLK, PCLK
VPP VCMR
Cross Points
xQx
Qx
xQy
Qy
tSK(0)
P ARAMETER MEASUREMENT INFORMATION
Output Skew
Output Load Test Circuit
Differential Input Level
8
COMMERCIAL AND INDUSTRIAL TEMPERATURE RANGES
IDT8737-11
LOW SKEW, ÷÷
÷÷
÷1/÷÷
÷÷
÷2 DIFFERENTIAL-TO-3.3V LVPECL
VSWING
tRtF
20%
80% 80%
20%
Clock Inputs
and Outputs
xCLK, xPLK
CLK, PCLK
xQA0, xQA1, xQB0, xQB1
QA0, QA1, QB0, QB1
tPD
xQx
Qx
xQy
Qy
tSK(PP)
Part 1
Part 2
xQA0, xQA1, xQB0, xQB1
QA0, QA1, QB0, QB1
odc =
tW
tPERIOD
Pulse Width
tPERIOD
odc and tPERIOD
Propagation Delay
Part-to-Part Skew
Input and Output Rise and Fall Time
P ARAMETER MEASUREMENT INFORMATION - CONTINUED
9
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LOW SKEW, ÷÷
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÷2 DIFFERENTIAL-TO-3.3V LVPECL
APPLICATION INFORMATION
WIRING THE DIFFERENTIAL INPUT TO ACCEPT SINGLE-ENDED LEVELS
The diagram below shows how the differential input can be wired to accept single-ended levels. The reference voltage VREF ∼ VDD/2 is generated by the
bias resistors R1, R2, and C1. This bias circuit should be located as close as possible to the input pin. The ratio of R1 and R2 might need to be adjusted to
position the VREF in the center of the input voltage swing. For example, if the input clock swing is only 2.5V and VDD = 3.3V, VREF should be 1.25V and R2/
R1 = 0.609.
Single-Ended Signal Driving Differential Input
VDD
VREF
+
-
C1
0.1uF
CLK_IN
R1
1K
R2
1K
TERMINATION FOR LVPECL OUTPUTS
The clock layout topology shown below is a typical termination for LVPECL outputs. The two different layouts mentioned are recommended only as guidelines.
FOUT and xFOUT are low impedance follower outputs that generate ECL/LVPECL compatible outputs. Therefore, terminating resistors (DC current path to
ground) or current sources must be used for functionality. These outputs are designed to drive 50Ω transmission lines. Matched impedance techniques should
be used to maximize operating frequency and minimize signal distortion. The diagrams below show two different layouts which are recommended only as
guidelines. Other suitable clock layouts may exist. It is recommended that the board designers simulate to guarantee compatibility across all printed circuit and
clock component process variations.
LVPECL Output Termination, layout A LVPECL Output Termination, layout B
FOUT
50Ω50Ω
Zo = 50Ω
VDD - 2V
Zo = 50Ω
RTT
FIN
RTT =
(VOH + VOL / VDD - 2) - 2
1
Zo
FOUT
Zo = 50Ω
Zo = 50Ω
FIN
Zo
3
2Zo
3
2
Zo
5
2Zo
5
2
3.3V
10
COMMERCIAL AND INDUSTRIAL TEMPERATURE RANGES
IDT8737-11
LOW SKEW, ÷÷
÷÷
÷1/÷÷
÷÷
÷2 DIFFERENTIAL-TO-3.3V LVPECL
POWER CONSIDERATIONS
This section provides information on power dissipation and junction temperature for the IDT8737-11. Equations and example calculations are also provided.
POWER DISSIPATION:
The total power dissipation for the IDT8737-11 is the sum of the core power plus the power dissipated in the load(s). The following is the power dissipation
for the VDD = 3.3V + 5% = 3.465V, which gives worst case results. Please refer to the following section, Calculations and Equations, for details on calculating
power dissipated in the load.
Power (core)MAX = VDD_MAX * ICC_MAX = 3.465 * 55mA = 190.57mW
Power (outputs)MAX = 30.2mW/Loaded Output Pair
If all outputs are loaded, the total power is 4 * 30.2mW = 120.8mW
Total Power_MAX (3.465V, with all outputs switching) = 190.57mW + 120.8mW = 311.37mW
JUNCTION TEMPERATURE:
Junction temperature (tJ) is the temperature at the junction of the bond wire and bond pad. It directly affects the reliability of the device. The maximum
recommended junction temperature for this device is 125°C.
The equation for is as follows: tJ = θJA * Pd_total + TA
tJ = Junction Temperature
θJA = Junction-to-Ambient Thermal Resistance
Pd_total = Total Device Power Dissipation (example calculation is in Power Dissipation, above)
TA = Ambient Temperature
In order to calculate junction temperature, the appropriate junction-to-ambient thermal resistance (θJA) must be used. Assuming a moderate air flow of 200
linear feet per minute and a multi-layer board, the appropriate value is 77.6°C/W per the following Thermal Resistance table. Therefore, tJ for an ambient
temperature of 85°C with all its outputs switching is:
85°C + 0.311W * 77.6°C/W = 109.16°C. This is well below the limit of 125°C.
This calculation is only an example. tJ will obviously vary depending on the number of loaded outputs, supply voltage, air flow, and the type of board (single-
layer or multi-layer).
THERMAL RESISTANCE
θJA for 20-pin TSSOP, forced convection
θθ
θθ
θJA by Velocity (Linear Feet per mInute)
0 200 400 Unit
Multi-Layer PCB, JEDEC Standard Test boards 92.6 77.6 70.9 °C/W
11
COMMERCIAL AND INDUSTRIAL TEMPERATURE RANGES
IDT8737-11
LOW SKEW, ÷÷
÷÷
÷1/÷÷
÷÷
÷2 DIFFERENTIAL-TO-3.3V LVPECL
CALCULATIONS AND EQUATIONS
VDD
Q1
VOUT
RL
50
VDD - 2V
LVPECL Output Driver Circuit and Termination
To calculate worst case power dissipation into the load, use the following equations, which assume a 50Ω load and a termination voltage of VDD – 2V.
For Logic HIGH: VOUT = VOH_MAX = VDD_MAX – 1V.
(VDD_MAX – VOH_MAX) = 1V
For Logic LOW: VOUT = VOL_MAX = VDD_MAX – 1.7V.
(VDD_MAX – VOL_MAX) = 1.7V
Pd_H is power dissipation when the output drives HIGH.
Pd_L is power dissipation when the output drives LOW.
Pd_H = {[ VOH_MAX – (VDD_MAX – 2V)] / RL} * (VDD_MAX – VOH_MAX) = {[ 2V – (VDD_MAX – VOH_MAX)] / RL} * (VDD_MAX – VOH_MAX) = [( 2V – 1V) / 50Ω] *
1V = 20mW.
Pd_L = {[ VOL_MAX – (VDD_MAX – 2V)] / RL} * (VDD_MAX – VOL_MAX) = {[ 2V – (VDD_MAX – VOL_MAX)] / RL} * (VDD_MAX – VOL_MAX) = [( 2V – 1.7V) / 50Ω] *
1.7V = 10.2mW.
Total Power Dissipation per output pair = Pd_H + Pd_L = 30.2mW
12
COMMERCIAL AND INDUSTRIAL TEMPERATURE RANGES
IDT8737-11
LOW SKEW, ÷÷
÷÷
÷1/÷÷
÷÷
÷2 DIFFERENTIAL-TO-3.3V LVPECL
ORDERING INFORMATION
IDT XXXXX XX X
Package Process
Device Type
Blank
I
8737-11 Low Skew, ÷1/ ÷2 Differential-to-3.3V LVPECL
Fanout Buffer
Thin Shrink Small Outline Package
TSSOP - Green
PG
PGG
Commercial (0°C to +70°C)
Industrial (-40°C to +85°C)
CORPORATE HEADQUARTERS for SALES: for Tech Support:
6024 Silver Creek Valley Road 800-345-7015 or 408-284-8200 clockhelp@idt.com
San Jose, CA 95138 fax: 408-284-2775
www.idt.com
