MC33493 Motorola, MC33493 Datasheet - Page 3

• Manufacturer Part Number: MC33493
• Description: PLL tuned UHF Transmitter for Data Transfer Applications
• Manufacturer: Motorola

An out-of-lock function is performed by monitoring the PFD output voltage. When it exceeds defined limits, the
RF output stage is disabled.
RF OUTPUT STAGE
The output stage is a single ended square wave switched current source. Harmonics are present in the output
current drive. Their radiated absolute level depends on the antenna characteristics and output power. Typical
application demonstrates compliance to ETSI standard.
A resistor R
and current consumption.
The output voltage is internally clamped to V
MODULATION
A low logic level has to be applied on pin MODE to select the On Off Keying (OOK) modulation. This modulation
is performed by switching on/off the RF output stage. The logic level applied on pin DATA controls the output
stage state:
If a high logic level is applied on pin MODE, then Frequency Shift Keying (FSK) modulation is selected. This
modulation is achieved by crystal pulling. An internal switch connected to CFSK pin enables to switch the
external crystal load capacitors. Figure 2 shows the possible configurations: serial and parallel.
The logic level applied on pin DATA controls the state of this internal switch:
DATA input is internally re-synchronized by the crystal reference signal. The corresponding jitter on the data duty
cycle cannot exceed ±1 reference period (±75ns for a 13.56MHz crystal).
This crystal pulling solution implies that the RF output frequency deviation equals the crystal frequency deviation
multiplied by the PLL Divider Ratio (see table 1).
DATA=0
DATA=1
DATA=0
DATA=1
MOTOROLA
ext
connected to the REXT pin controls the output power allowing a trade-off between radiated power
→
→
→
→
BAND Input
output stage off,
output stage on.
switch off,
switch on.
Level
High
Low
Table 1: Band selection and associated divider ratios
Freescale Semiconductor, Inc.
For More Information On This Product,
Band (MHz)
Frequency
315
434
868
cc
Go to: www.freescale.com
±2V
MC33493 Technical Data
be
(typ. V
PLL Divider
Ratio
cc
32
64
±1.5V @ T
A
=25°C).
Crystal Oscillator
Frequency (MHz)
13.56
9.84
RF OUTPUT STAGE
3