DS4000 データシートの表示（PDF） - Dallas Semiconductor -> Maxim Integrated

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DS4000

Digitally Controlled TCXO

Dallas Semiconductor -> Maxim Integrated 

DS4000 Digitally Controlled TCXO

DIGITAL TUNING THE BASE CRYSTAL FREQUENCY

When using the 2-wire interface for tuning the base frequency, the frequency tuning register is used. The frequency

tuning register contains two’s complement data. The data is used to add or subtract an offset from the crystal

loading register. When the tuning register is programmed with a value, the next temperature-update cycle sums the

programmed value with the factory-compensated value. This allows the user/system to digitally control the base

frequency by a microcontroller using the 2-wire protocol.

FREQUENCY TUNING REGISTER (66h)

Bit

7

6

5

4

3

2

1

0

Name

SIGN

FO6

FO5

FO4

FO3

FO2

FO1

FO0

Default

0

0

0

0

0

0

0

0

FOS[6:0], Frequency Offset: These bits are used to tune the base crystal frequency. Each bit represents

approximately 0.08ppm and, therefore, for a value of 07FH, pushes or pulls the base frequency by approximately

10.16ppm.

SIGN, Sign Bit: This bit is used to determine whether to add or subtract the frequency offset from the crystal

loading.

Table 1. Frequency Tuning Relationship

CALCULATED

FREQUENCY OFFSET

(ppm)

-10.16

-8.00

-5.28

-1.84

-0.08

0.0

+0.08

+1.84

+5.28

+8.00

+10.16

DIGITAL DATA

(Binary)

0111 1111

0110 0100

0100 0010

0001 0111

0000 0001

0000 0000

1111 1111

1110 1000

1011 0011

1001 1100

1000 0000

DIGITAL DATA

(hex)

7Fh

64h

42h

17h

01h

00h

FFh

E8h

B3h

9Ch

80h

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