VPC3232D datasheet(60/78 Pages) MICRONAS

60 / 78 page

VPC 323xD, VPC 324xD

ADVANCE INFORMATION

Micronas

4.6.3. Recommended Crystal Characteristics

Symbol

Parameter

Min.

Typ.

Max.

Unit

Operating Ambient Temperature

–65

°C

Parallel Resonance Frequency

with Load Capacitance CL = 13 pF

–

20.250000

–

MHz

∆f

P/fP

Accuracy of Adjustment

–

±20

ppm

∆f

P/fP

Frequency Temperature Drift

–

±30

ppm

Series Resistance

–

Ω

Shunt Capacitance

–

Motional Capacitance

–

Load Capacitance Recommendation

CLext

External Load Capacitance 1) from

pins to Ground

(pin names: Xtal1 Xtal2)

–3.3

–pF

DCO Characteristics 2,3)

CICLoadmin

Effective Load Capacitance @ min.

DCO–Position, Code 0,

package: 68PLCC

34.3

5.5

CICLoadrng

Effective Load Capacitance Range,

DCO Codes from 0..255

12.7

1) Remarks on defining the External Load Capacitance:

External capacitors at each crystal pin to ground are required. They are necessary to tune the effective load capacitance of the

PCBs to the required load capacitance CL of the crystal. The higher the capacitors, the lower the clock frequency results. The

nominal free running frequency should match fp MHz. Due to different layouts of customer PCBs the matching capacitor size

should be determined in the application. The suggested value is a figure based on experience with various PCB layouts.

Tuning condition: Code DVCO Register=–720

2) Remarks on Pulling Range of DCO:

The pulling range of the DCO is a function of the used crystal and effective load capacitance of the IC (CICLoad +CLoadBoard).

The resulting frequency fL with an effective load capacitance of CLeff = CICLoad + CLoadBoard is:

1 + 0.5 * [ C1 / (C0 + CL) ]

fL = fP * _______________________

1 + 0.5 * [ C1 / (C0 + CLeff) ]

3) Remarks on DCO codes

The DCO hardware register has 8 bits, the fp control register uses a range of –2048...2047

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