MPC8610EC datasheet(55/96 Pages) FREESCALE

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Electrical Characteristics

MPC8610 Integrated Host Processor Hardware Specifications, Rev. 0

Freescale Semiconductor

Differential input voltage, VID (or differential input swing):

The differential input voltage (or swing) of the receiver, VID, is defined as the difference of the two complimentary

input voltages: VSDn_RX –VSDn_RX. The VID value can be either positive or negative.

Differential peak voltage, VDIFFp

The peak value of the differential transmitter output signal or the differential receiver input signal is defined as

differential peak voltage, VDIFFp = |A – B| volts.

Differential peak-to-peak, VDIFFp-p

Since the differential output signal of the transmitter and the differential input signal of the receiver each range from

A – B to -(A – B) volts, the peak-to-peak value of the differential transmitter output signal or the differential receiver

input signal is defined as differential peak-to-peak voltage, VDIFFp-p = 2 * VDIFFp = 2 * |(A – B)| volts, which is twice

of differential swing in amplitude, or twice of the differential peak. For example, the output differential peak-peak

voltage can also be calculated as VTX-DIFFp-p = 2 * |VOD|.

Differential waveform

The differential waveform is constructed by subtracting the inverting signal (SDn_TX, for example) from the

noninverting signal (SDn_TX, for example) within a differential pair. There is only one signal trace curve in a

differential waveform. The voltage represented in the differential waveform is not referenced to ground. Refer to

Figure 38 as an example for differential waveform.

Common mode voltage, Vcm

The common mode voltage is equal to one half of the sum of the voltages between each conductor of a balanced

interchange circuit and ground. In this example, for SerDes output, Vcm_out = (VSDn_TX + VSDn_TX)/2 = (A + B)/2,

which is the arithmetic mean of the two complimentary output voltages within a differential pair. In a system, the

common mode voltage may often differ from one component’s output to the other’s input. Sometimes, it may be even

different between the receiver input and driver output circuits within the same component. It’s also referred as the DC

offset in some occasion.

Figure 29. Differential Voltage Definitions for Transmitter or Receiver

To illustrate these definitions using real values, consider the case of a CML (current mode logic) transmitter that has a common

mode voltage of 2.25 V and each of its outputs, TD and TD, has a swing that goes between 2.5 and 2.0 V. Using these values,

the peak-to-peak voltage swing of each signal (TD or TD) is 500 mV p-p, which is referred as the single-ended swing for each

signal. In this example, since the differential signaling environment is fully symmetrical, the transmitter output’s differential

swing (VOD) has the same amplitude as each signal’s single-ended swing. The differential output signal ranges between 500 mV

and –500 mV, in other words, VOD is 500 mV in one phase and –500 mV in the other phase. The peak differential voltage

(VDIFFp) is 500 mV. The peak-to-peak differential voltage (VDIFFp-p) is 1000 mV p-p.

Differential Swing, VID or VOD = A – B

A Volts

B Volts

n_TX or

n_RX

n_TX or

n_RX

Differential Peak Voltage, VDIFFp = |A – B|

Differential Peak-Peak Voltage, VDIFFpp = 2*VDIFFp (not shown)

Vcm = (A + B) / 2

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