MICRF112 datasheet(12/20 Pages) MICREL

12 / 20 page

Micrel, Inc.

MICRF112

March 2007

M9999-030107

(408) 944-0800

Functional Diagram

Figure 3. Functional Block Diagram MICRF112 10 Pin ASK / FSK Version

Functional Description

Figure 3 shows a functional block diagram of the

MICRF112 transmitter. The MICRF112 can be best

described as a phase locked transmitter. The system

can be partitioned into six functional blocks; crystal

oscillator, PLL×32, power ampliﬁer, enable control,

under voltage detect and open drain switch for FSK

operation.

Crystal Oscillator

The

reference

oscillator

crystal-based

Pierce

conﬁguration. It is designed to accept crystals with

frequency from 9.375MHz to 14.0625MHz.

Crystal Oscillator Parameters for ASK Operation

Figure

shows

reference

oscillator

circuit

conﬁguration for ASK operation. The reference oscillator

is capable of driving crystals with ESR range from 20

Ω

to 300

Ω.

When the ESR of crystal is at 20

Ω, the crystal parameter

limits are:

ESR 20

Ω

CPAR 2 to 10pF

CMO 10 to 40fF

Figure 4. Reference Oscillator ASK Operation

When the ESR of crystal is at 300

Ω, the crystal

parameter limits are:

ESR

300

Ω

CPAR

2 to 5pF

CMO

10 to 40fF

CLOAD

10 to 30pF

MICRF112 Datasheet(PDF) 12 Page - Micrel Semiconductor

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