MPC8548E datasheet(62/143 Pages) FREESCALE

62 / 143 page

MPC8548E PowerQUICC III Integrated Processor Hardware Specifications, Rev. 8

Freescale Semiconductor

High-Speed Serial Interfaces (HSSI)

each have a peak-to-peak swing of A – B volts. This is also referred as each signal wire’s

single-ended swing.

•

Differential output voltage, VOD (or differential output swing):

The differential output voltage (or swing) of the transmitter, VOD, is defined as the difference of

the two complimentary output voltages: VSD_TX –VSD_TX. The VOD value can be either positive

or negative.

•

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: VSD_RX –VSD_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

Because 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-to-peak voltage can also be calculated as VTX-DIFFp-p = 2 × |VOD|.

•

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 =

VSD_TX + VSD_TX = (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 is also referred to as the DC

offset.

Figure 38. 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

Differential Swing, VID or VOD = A – B

A Volts

B Volts

SD_TX or

SD_RX

SD_TX or

SD_RX

Differential Peak Voltage, VDIFFp = |A – B|

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

Vcm = (A + B)/2

MPC8548E Datasheet(PDF) 62 Page - Freescale Semiconductor, Inc

MPC8548E Datasheet(HTML) 62 Page - Freescale Semiconductor, Inc

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

Datasheet Download

Link URL