AD9546SLASHPCBZ datasheet(172/205 Pages) AD

172 / 205 page

AD9546

Data Sheet

Rev. 0 | Page 172 of 205

Figure 117 shows the FPE vs. temperature curve resulting from

these coefficients. The trace is the predicted FPE vs.

temperature curve based on the coefficients, and the solid

points are the temperature vs. FPE data from Table 96.

1400

1300

1200

1100

1000

900

800

700

600

–50 –40 –30 –20 –10

10 20 30 40 50 60 70 80 90 100

TEMPERATURE (°C)

Figure 117. FPE vs. Temperature

Given a set of coefficients like C0 to C5, the user must convert

the numeric values to suitable register contents (see the

Programming the Coefficients (Cx) for Compensation Method 1

section for details).

Programming the Coefficients (Cx) for Compensation

Method 1

Compensation Method 1 makes use of six coefficients, Cx,

where the index, x, ranges from 0 to 5. Coefficient C0 is

represented by a 40-bit (signed) coefficient value (CV) residing

in Register 0x0289 to Register 0x028D.

The relationship between the value of CV and the value of C0 is

CV = C0/2−45

The value of CV has no units and is proportional to the system

clock period.

For example, convert C0 = 1.0046936 × 10−3 to its

corresponding register value (C0_RegVal).

C0_RegVal = C0/2−45

= 1.0046936 × 10−3/2−45

= 35,349,513,305 (nearest integer)

= 0x 08 3AFE C459 (hexadecimal)

Coefficient C1 to Coefficient C5 are represented by employing

two components: a 16-bit (signed) significand and an 8-bit

(signed) exponent. The significand and exponent components

reside in the register map per Table 97.

Table 97. System Clock Compensation Coefficients

Coefficient

Significand

Exponent

0x028E to 0x028F

0x0290

0x0291 to 0x0292

0x0293

0x0294 to 0x0295

0x0296

0x0297 to 0x0298

0x0299

0x029A to 0x029B

0x029C

C1 through C5 apply scale factors to corresponding powers

of T. The C1 through C5 coefficients have the following format:

Cx = Sx × 2Ex

where:

x is the coefficient index.

Sx is the significand component.

Ex is the exponent component.

In practice, Cx is a base 10 number, as are Sx and Ex. However,

the AD9546 requires Sx and Ex to be signed integers. The

following procedure explains how to convert base 10 Cx values

to the necessary signed integers corresponding to the

significand register value (Cx_S) and the exponent register value

(Cx_E).

There are three cases for Cx.

•

The trivial case (Cx = 0)

•

The case where Cx is less than the quantization limit

•

The case where Cx is greater than the quantization limit

For the first two cases (that is, Cx = 0 or Cx is less than the

quantization limit),

Cx_S = 0 (0x0000 hexadecimal)

Cx_E = 0 (0x00 hexadecimal)

To test if Cx is less than the quantization limit, check whether

the following inequality is true:

log |

| 1 127

log2



+ < −





(26)

where:

log(x) is the logarithm of x (for example, ln(x), log2(x), log10(x)).

|x| is the absolute value of x.

⌊x⌋isthenotationforsignifyingthenearestintegertoxinthe

direction of −∞.

If Cx is nonzero and the inequality in Equation 26 is false, then

log |

log 2





Cx_E = E

Cx_S = round(Cx × 215 − E)

AD9546/PCBZ Datasheet(PDF) 172 Page - Analog Devices

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