T49C101ACF8-07 查看數據表（PDF） - Exar Corporation

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T49C101ACF8-07

High Frequency Clock Multiplier

Exar Corporation 

ST49C101A-XX

MULTIPLICATION FACTOR AND OUTPUT FRE-

QUENCY SELECTION

The ST49C101A-XX contains an analog phase locked

loop (PLL) circuit with digital closed loop dividers and

a final output divider to achieve the desired dividing

ratios for the clock output. The preprogrammed multi-

plication factor and output frequency are shown on

Table 1. The accuracy of the output frequency pro-

duced by the ST49C101A-XX depends on its input

frequency and multiplication factor.

APPLICATIONS

Two application examples are shown in Figure 2 and 3.

Figure 2 shows a lower cost high frequency crystal

oscillator circuit using the ST49C101-xx to increase

the fundamental crystal frequency. The crystal Y1 is

connected to XTAL1 and XTAL2 pins to use the

internal oscillator circuit. The oscillator provides the

reference clock to the PLL circuit for clock rate multi-

plication. Figure 3 shows a similar circuit using

external clock input on XTAL1 pin instead.

If a sinewave is used for external clock, it may be

necessary to AC couple the signal with a 0.047uF

capacitor to XTAL1 pin so that the internal circuitry

can establish the proper bias. Also, keep the peak-to-

peak signal, at XTAL pin, above ground level (AGND)

and below AVCC.

As a general board layout rule, it is recommended to

use two 0.01µF bypass capacitors on DVCC and

AVCC power supply pins, and put them as closely as

possible to the chip.

Table 1. Preprogrammed Options

ST49C101A-XX

Factor

Max. Output

Frequency1

VCC1

ST49C101A-01

12

ST49C101A-03

8

ST49C101A-05

6

ST49C101A-06

4

ST49C101A-07

3

ST49C101A-08

2

ST49C101A-09

5

200 MHz

140 MHz

200 MHz

140 MHz

200 MHz

140 MHz

120 MHz

80 MHz

70 MHz

80 MHz

70 MHz

200 MHz

140 MHz

5.0 V

3.3 V

5.0 V

3.3 V

5.0 V

3.3 V

5.0 or

3.3 V

5.0 V

3.3 V

5.0 V

3.3 V

5.0 V

3.3 V

ST49C101A-10

10

180 MHz 3.3 V

ST49C101A-13

8

180 MHz 3.3 V

ST49C101A-15

6

180 MHz 3.3 V

Notes

1See AC electrical characteristics for maximum operating

frequency.

Rev. 2.20

4

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