ML6695 データシートの表示（PDF） - Micro Linear Corporation

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ML6695

100BASE-X Fiber Physical Layer With 5-bit Interface

Micro Linear Corporation 

FUNCTIONAL DESCRIPTION

TRANSMIT SECTION

The ML6695 transmit section accepts parallel NRZ data

nibbles, creates a serial NRZI data stream using the

internal 125MHz clock multiplier, and provides an open-

collector output IOUT to directly drive an LED. IOUT

must be connected to VCC through a 15W resistor. The

internal clock multiplier accepts an external 25MHz

clock input.

The LED driver at IOUT is a current mode switch which

develops the output light by sinking current through the

network LED into IOUT. RTSET'S value determines the

output current:

  RTSET = 1.25V ´ 140W

  IOUT

(1)

where IOUT is the desired output current.

RECEIVE SECTION

The ML6695 receive section includes a fiber optic

quantizer and a 125MHz receive clock recovery circuit.

The quantizer is a wide-bandwidth limiting amplifier with

ML6695

DC offset correction. The quantizer output drives a data

comparator with a controlled slicing threshold. The

comparator provides a large-amplitude receive signal. The

clock recovery circuit extracts 125MHz receive clock

from the large-amplitude signal, and provides the clock

for the parallel data output registers. Received NRZ data

nibbles appear at the RSM outputs synchronously with

RXC falling edges. Received signals exceeding the preset

signal detect amplitude threshold for more than 5µs cause

the SDO output to go high. Received signals that fall

below the preset threshold for more than 5µs cause SDO

to go low.

OTHER MODES

The ML6695 will enter a power down mode when the

PWRDN pin is tied low. In this state the ML6695 powers

down to a low-current (less than 20mA), inoperative state.

Driving it high enables normal operation of the ML6695.

Loopback mode is entered when the LPBK is tied to

ground. In this mode, the data at TSM0-4 are serialized,

then sent to the quantizer, followed by the receive PLL for

clock recovery, and finally to the RSM0-4 outputs. Tying

LPBK to VCC places the ML6695 in its normal mode of

operation.

15Ω

15Ω

38

IOUT

39

IOUT

ML6695

Figure 1. Test Load

7

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