LMK01000ISQX/NOPB National Semiconductor, LMK01000ISQX/NOPB Datasheet - Page 17

• Manufacturer Part Number: LMK01000ISQX/NOPB
• Description: IC CLK BUFFER/DVDR/DISTR 48-LLP
• Manufacturer: National Semiconductor
• Type: Fanout Buffer (Distribution), Dividerr

Specifications of LMK01000ISQX/NOPB

• Number Of Circuits: 1
• Ratio - Input:output: 2:8
• Differential - Input:output: Yes/Yes
• Input: Clock
• Output: LVDS, LVPECL
• Frequency - Max: 1.6GHz
• Voltage - Supply: 3.15 V ~ 3.45 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 48-LLP
• Frequency-max: 1.6GHz
• For Use With: LMK01000EVAL - BOARD EVALUATION FOR LMK01000
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: LMK01000ISQX

LVPECL drivers require a DC path to ground. When AC cou-
pling an LVPECL signal use 120 Ω emitter resistors close to
the LVPECL driver to provide a DC path to ground as shown
in
be biased to the DC bias level (common mode voltage) spec-
ified by the receiver. The typical DC bias voltage (common
mode voltage) for LVPECL receivers is 2 V. A Thevenin
3.4.3 Termination for Single-Ended Operation
A balun can be used with either LVDS or LVPECL drivers to
convert the balanced, differential signal into an unbalanced,
single-ended signal.
FIGURE 5. Differential LVPECL Operation, DC Coupling,
Figure
10. For proper receiver operation, the signal should
Thevenin Equivalent
FIGURE 7. Differential LVPECL Operation, AC Coupling, Thevenin Equivalent
FIGURE 6. Differential LVDS Operation, AC Coupling
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3.4.2 Termination for AC Coupled Differential Operation
AC coupling allows for shifting the DC bias level (common
mode voltage) when driving different receiver standards.
Since AC coupling prevents the driver from providing a DC
bias voltage at the receiver it is important to ensure the re-
ceiver is biased to its ideal DC level.
When driving LVDS receivers with an LVDS driver, the signal
may be AC coupled by adding DC blocking capacitors, how-
ever the proper DC bias point needs to be established at the
receiver. One way to do this is with the termination circuitry in
Figure
equivalent circuit (82 Ω resistor connected to Vcc and a 120
Ω resistor connected to ground with the driver connected to
the junction of the 82 Ω and 120 Ω resistors) is a valid termi-
nation as shown in
Thevenin circuit is different from the DC coupled example in
Figure
It is possible to use an LVPECL driver as one or two separate
800 mV p-p signals. When DC coupling one of the LMK01000
family LVPECL drivers, the termination should still be 50 Ω to
Vcc - 2 V as shown in
circuit (120 Ω resistor connected to Vcc and an 82 Ω resistor
connected to ground with the driver connected to the junction
6.
5.
Figure
Figure 7
8. Again the Thevenin equivalent
for Vcc = 3.3 V. Note: this
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