FN6667 datasheet(20/34 Pages) RENESAS

20 / 34 page

ISL12020M

FN6667 Rev 6.00

Page 20 of 34

January 9, 2015

ALPHA Register (ALPHA)

The ALPHA variable is 8 bits and is defined as the temperature

coefficient of crystal from -40°C to T0, or the ALPHA Cold (there

is an Alpha Hot register that must be programmed as well). It is

normally given in units of ppm/°C2, with a typical value of

-0.034. The ISL12020M device uses a scaled version of the

absolute value of this coefficient in order to get an integer value.

Therefore, ALPHA<7:0> is defined as the (|Actual ALPHA Value| x

2048) and converted to binary. For example, a crystal with Alpha

of -0.034ppm/°C2 is first scaled (|2048*(-0.034)| = 70d) and

then converted to a binary number of 01000110b.

The practical range of Actual ALPHA values is from -0.020 to

-0.060.

The ISL12020M has a preset ALPHA value corresponding to the

crystal in the module. This value is recalled on initial power-up

and should remain unchanged for best compensation

performance, although the user can override this preset value if

so desired.

The ALPHA register should only be changed while the TSE (Temp

Sense Enable) bit is “0”. Note that both the ALPHA and the

ALPHA Hot registers need to be programmed with values for full

range temperature compensation.

BETA Register (BETA)

TEMPERATURE SENSOR ENABLED BIT (TSE)

This bit enables the Temperature Sensing operation, including the

temperature sensor, A/D converter and FATR/FDTR register

adjustment. The default mode after power-up is disabled (TSE = 0).

To enable the operation, TSE should be set to 1 (TSE = 1). When

temp sense is disabled, the initial values for IATR and IDTR registers

are used for frequency control.

All changes to the IDTR, IATR, ALPHA and BETA registers must be

made with TSE = 0. After loading the new values, TSE can be

enabled and the new values are used. When TSE is set to 1, the

temperature conversion cycle begins and will end when two

temperature conversions are completed. The average of the two

conversions is in the TEMP registers.

TEMP SENSOR CONVERSION IN BATTERY MODE BIT

(BTSE)

This bit enables the Temperature Sensing and Correction in battery

mode. BTSE = 0 (default) no conversion, Temp Sensing or

Compensation in battery mode. BTSE = 1 indicates Temp Sensing

and Compensation enabled in battery mode. The BTSE is disabled

when the battery voltage is lower than 2.7V. No temperature

compensation will take place with VBAT<2.7V.

-8

-9

-10

-11

-12

-13

-14

-15

-16

-17

-18

-19

-20

-21

-22

-23

-24

-25

-26

-27

-28

-29

-30

-31

TABLE 13. IATRO TRIMMING RANGE (Continued)

IATR05

IATR04

IATR03

IATR02

IATR01

IATR00

TRIMMING RANGE

TABLE 14. ALPHA REGISTER

ADDR

210

0Ch

ALPHA

TABLE 15.

ADDR

0Dh

TSE BTSE BTSR BETA4 BETA3 BETA2 BETA1 BETA0

FN6667 Datasheet(PDF) 20 Page - Renesas Technology Corp

FN6667 Datasheet(HTML) 20 Page - Renesas Technology Corp

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34

Datasheet Download

Link URL