VSC8504-02 datasheet(105/131 Pages) MICROSEMI

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Electrical Specifications

VMDS-10507 VSC8504-02 Datasheet Revision 4.2

5.1.8

Thermal Diode

The VSC8504-02 device includes an on-die diode and internal circuitry for monitoring die temperature

(junction temperature). The operation and accuracy of the diode is not guaranteed and should only be

used as a reference. Care should be taken to find compatible grounded cathode temperature monitoring

device.

A thermal sensor, located on the board or in a stand-alone measurement kit, can monitor and display the

die temperature of the switch for thermal management or instrumentation purposes.

Temperature measurement using a thermal diode is very sensitive to noise.

The following table provides the diode parameter and interface specifications. Note that the ThermDC pin

is connected to VSS internally in the device.

Note: Microsemi does not support or recommend operation of the thermal diode under reverse bias.

The ideality factor, n, represents the deviation from ideal diode behavior as exemplified by the diode

equation:

where, Is = saturation current, q = electronic charge, Vd = voltage across the diode, k = Boltzmann Constant, and T =

absolute temperature (Kelvin).

5.2

AC Characteristics

This section provides the AC specifications for the VSC8504-02 device.

5.2.1

Reference Clock

The following table shows the AC specifications for a 125 MHz differential reference clock source.

Performance is guaranteed for 125 MHz differential clocks only; however, 125 MHz single-ended clocks

are also supported for QSGMII interfaces.

25 MHz clock implementations are available but are limited to SGMII interfaces. For more information,

contact your Microsemi representative.

Table 106 •

Thermal Diode Parameters

Parameter

Symbol

Typical

Maximum

Unit

Forward bias current

IFW

Diode ideality factor

1.008

Table 107 •

Reference Clock AC Characteristics for QSGMII 125 MHz Differential Clock

Parameter

Symbol

Minimum

Typical Maximum

Unit Condition

Reference clock

frequency,

REFCLK_SEL2 = 1

125.00

MHz

±100 ppm

Duty cycle

Rise time and fall time

tr, tf

1.5

20% to 80%

threshold

RefClk input RMS jitter

requirement, bandwidth

between 12 kHz and

500 kHz(1)

To meet jitter

generation of 1G

output data per

IEEE 802.3z

IFW

nkT

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