HC705JB2GRSSLASHH datasheet(81/128 Pages) NXP

81 / 128 page

August 28, 1998

GENERAL RELEASE SPECIFICATION

UNIVERSAL SERIAL BUS MODULE

REV 1.1

10-13

10.4.3 Receiver Characteristics

USB data transmission is done with differential signals. A differential input receiver

is used to accept the USB data signal. A differential 1 on the bus is represented by

D+ being at least 200 mV more positive than D- as seen at the receiver, and a

differential 0 is represented by D- being at least 200 mV more positive than D+ as

seen at the receiver. The signal cross over point must be between 1.3V and 2.0V.

The receiver features an input sensitivity of 200 mV when both differential data

inputs are in the range of 0.8 V to 2.5 V with respect to the local ground reference.

This is called the common mode input voltage range. Proper data reception is also

achieved when the differential data lines are outside the common mode range, as

shown in Figure 10-13.

The receiver can tolerate static input voltages between

–0.5V to 3.8 V with respect to its local ground reference without damage. In

addition to the differential receiver, there is a single-ended receiver (schmitt

trigger) for each of the two data lines.

Figure 10-13. Differential Input Sensitivity Over Entire Common Mode Range

10.4.3.1 Receiver Data Jitter

The data receivers for all types of devices must be able to properly decode the

differential data in the presence of jitter. The more of the bit cell that any data edge

can occupy and still be decoded, the more reliable the data transfer will be. Data

receivers are required to decode differential data transitions that occur in a

window plus and minus a nominal quarter bit cell from the nominal (centered) data

edge position.

Jitter will be caused by the delay mismatches and by mismatches in the source

and destination data rates (frequencies). The receive data jitter budget for low

speed is given in the electrical section of the this speciﬁcation. The speciﬁcation

includes the consecutive (next) and paired transition values for each source of

jitter.

COMMON MODE INPUT VOLTAGE (VOLTS)

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

2.2

2.4

2.6

2.8

3.0

3.2

1.0

0.8

0.6

0.4

0.2

Freescale Semiconductor, Inc.

For More Information On This Product,

Go to: www.freescale.com

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