ML6510CQ-80 Ver la hoja de datos (PDF) - Micro Linear Corporation

Número de pieza

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Fabricante

ML6510CQ-80

Series Programmable Adaptive Clock Manager (PACMan™)

Micro Linear Corporation 

ML6510

ADAPTIVE DESKEW BUFFERS

Each copy of the clock is driven by an adaptive deskew

buffer. The deskew buffer compensates for skew time

automatically in accordance to the flight time delay it

senses from the reflection on the transmission line.

Figure 4 shows the simplified functional block diagram of

the deskew circuit. The phase of the sense signal and the

driver signal is presented to a three-input phase

comparator and compared with the reference signal. The

phase comparator then controls the voltage controlled

delay in the output drive line to match the delay of the

fixed reference delay line. Therefore, the sum of the delay

of the driver circuit, PCB trace delay, rise time delay at the

load and the adjustable delay will always equal the fixed

maximum delay.

The sense circuit has an internal level detect such that any

skew caused by loading is also accounted for. Since the

delay of the circuit is matched for the entire loop, the

phase of all the drivers are in close alignment at the inputs

of the load.

CLOCK IN

FIXED

MAX

DELAY

PHASE

DETECTOR

SENSE

LOAD CONDITIONS

The ML6510 has been designed to drive the wide range of

load conditions that are encountered in a high frequency

system. The eight output clock loads can each vary within a

range of trace length and lumped capacitive load, and the

ML6510 will maintain the low skew characteristics specified

in Electrical Characteristics. The clock skew can be further

minimized by providing some first-order matching

between any two loads that require particularly well-

matched clocks.

The ML6510-80 produces a 5V swing at the load and

requires a single external termination resistor for each

output. The ML6510-130 produces a 3V swing at the load

and requires two external termination resistors for each

output. The FB input pin is connected to the other side of

the termination resistor R1 or R2, with a short connection.

Termination resistor valves should be chosen as follows:

R1= Z0 R2 = 1.5 × Z0 R3 = 3 × Z0

TRACE

IMPEDANCE

Z0

40Ω

50Ω

63Ω

RESISTOR

VALUES

R1

R2

R3

40

60

120

50

75

150

63

95

189

VOLTAGE

CONTROLLED

DELAY

DRIVE

LOAD

Figure 4. Deskew Circuit Block Diagram.

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