Digital Voice Systems AMBE-3000 Specifikace stáhnout pdf (Strana 29)

AMBE-3000F™ Vocoder Chip Users Manual

Version 3.4, April, 2014

ardware Information

2.7 Crystal / Oscillator Usage

The AMBE-3000F™ Vocoder Chip has an on-chip, PLL-based clock module and requires an input clock frequency of 29.4912

MHz. The PLL-based clock module provides all the necessary clocking signals for the device, as well as control for low-

power mode entry. The AMBE-3000F™ Vocoder Chip two modes of operation:

External clock source operation (See Figure 7 X1/XCLKIN and X2 with TTL/CMOS Clock Source)

 Th

is mode allows the internal oscillator to be bypassed. The device clocks are generated from an external clock

source input on the X1/XCLKIN pin.

Crystal-operation (See Figure 8 X1/XCLKIN and X2 with Crystal Oscillator)

 Th

is mode allows the use of an external crystal/resonator to provide the time base to the device.

The following points should be noted when designing any printed circuit board layout:

 Keep X1/XCLKIN and X2 away from high frequency digital traces to avoid coupling.

 Keep the crystal and external capacitors as close to the X1/XCLKIN and X2 pins as possible to minimize board stray

capacitance.

2.7.1 External Clock Source

When an external source is used as the clock input. Connect X1/XCLKIN and X2 as follows:

Figure 7 X1/XCLKIN and X2 with TTL/CMOS Clock Source

2.7.2 Crystal Oscillator

To use a crystal oscillator with the AMBE-3000F™ Vocoder Chip, connect the crystal across X1/XCLKIN and X2 along with

one external capacitor from each of these pins to ground.

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Digital Voice Systems AMBE-3000 Specifikace Strana 29