MC68HC908RF2 Datasheet, PDF (223/254 Pages) Motorola, Inc – HCMOS Microcontroller Unit

PLL Tuned UHF Transmitter Module
Transmitter Functional Description
16.3 Transmitter Functional Description
The transmitter is a phase-locked loop (PLL) tuned low-power UHF
transmitter. The different modes of operation are controlled by the
microcontroller through several digital input pins. The power supply
voltage ranges from 1.9 V to 3.7 V allowing operation with a single
lithium cell.
16.4 Phase-Lock Loop (PLL) and Local Oscillator
The VCO is a completely integrated relaxation oscillator. The phase
frequency detector (PFD) and the loop filter are fully integrated.The
exact output frequency is equal to:
f_RFOUT = f_XTAL x PLL divider ratio
The frequency band of operation is selected through the BAND pin.
Table Table 16-1 provides details for each frequency band selection.
Table 16-1. Frequency Band Selection
and Associated Divider Ratios
BAND Input
Level
High
Low
Frequency
Band (MHz)
315
434
868
PLL Divider
Ratio
32
64
Crystal Oscillator
Frequency (MHz)
9.84
13.56
An out-of-lock function is performed by monitoring the internal PFD
output voltage. When it exceeds its limits, the RF output stage is
disabled.
MC68HC908RF2 — Rev. 1
MOTOROLA
PLL Tuned UHF Transmitter Module
Advance Information
223