Rainbow-electronics MAX3629 Manual do Utilizador descarregar pdf (Página 12)

MAX3629

+3.3V, Low-Jitter, Precision Clock Generator

with Multiple Outputs

Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are

implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.

____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600

Interface Models

Figures 7 and 8 show examples of interface models.

Layout Considerations

The inputs and outputs are the most critical paths for

the MAX3629 and great care should be taken to mini-

mize discontinuities on these transmission lines

between the connector and the IC. Here are some sug-

gestions for maximizing the performance of the

MAX3629:

• An uninterrupted ground plane should be posi-

tioned beneath the clock outputs. The ground

plane under the crystal should be removed to mini-

mize capacitance.

• Ground pin vias should be placed close to the IC

and the input/output interfaces to allow a return

current path to the MAX3629 and the receive

devices.

• Supply decoupling capacitors should be placed

close to the supply pins, preferably on the same

layer as the MAX3629.

• Take care to isolate crystal input traces from the

MAX3629 outputs.

• The crystal, trace, and two external capacitors

should be placed on the board as close as possi-

ble to the X_IN and X_OUT pins to reduce

crosstalk and active signals into the oscillator.

• Maintain 100Ω differential (or 50Ω single-ended)

transmission line impedance into and out of the

part.

• Use good high-frequency layout techniques and

multilayer boards with an uninterrupted ground

plane to minimize EMI and crosstalk.

Refer to the MAX3629 evaluation kit for more information.

Exposed-Pad Package

The exposed pad on the 32-pin TQFN package pro-

vides a very low inductance path for return current trav-

eling to the PCB ground plane. The pad is also

electrical ground on the MAX3629 and must be sol-

dered to the circuit board ground for proper electrical

performance.

180kΩ

1.4V

ESD

STRUCTURES

OSC_IN

Figure 7. Simplified OSC_IN Pin Circuit Schematic

10Ω

ESD

STRUCTURES

Q5 TO Q7

DDO_SE

Figure 8. Simplified LVCMOS Output Circuit Schematic

Chip Information

PROCESS: BiCMOS

Package Information

For the latest package outline information and land patterns, go

to www.maxim-ic.com/packages

PACKAGE TYPE PACKAGE CODE DOCUMENT NO.

32 TQFN-EP T3255+5

21-0140

1 2 ... 7 8 9 10 11 12

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