User Manual

ZSTAR3 Sensor Board Description
ZSTAR3 Reference Design Manual, Rev. 0.1
Freescale Semiconductor 3-23
Preliminary
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Figure 3-6. ZSTAR3 Antenna Layout
The matching is provided by L1 coil. L2 and L3 coils bias the transmitter output transistors to the CT_Bias
level.
The inductors used in this design are from TDK:
• L1 (3.3nH) MLG1608B3N3DT
• L2, L3 (22nH) MLG1608B22NJT
3.3.7 Clocking Options of MC9S08QG8
Due to the availability of accurate timing provided by the MC13213 internal transceiver, an internal
oscillator (ICG) in the MC13213 microcontroler is used as the main clock source for the microcontroller.
The protocol related timing is derived from RF modem timers, the microcontroller itself is clocked from
an internal oscillator. Microcontroler clock run with 20MHz on bus.
3.3.8 LED Indicator
On the design is used only a one LED, because the ZSTAR3 board is designed to fit a plastic box, that has
only a one position for light indicators. The LED is connected with current limiting serial resistor R1 direct
to PTC5 microcontroler pin.
3.3.9 Power Supply
The Sensor Board is powered by a Lithium coin-sized battery. The primary choice was the popular
CR2032.
A surface mounted SMTU series battery holder from Renata
TM
is placed on the underside of the PCB. The
SMTU series holders provide (by mechanical construction) battery reverse protection, so no additional
circuitry is required.