MICRF219AAYQS TR Micrel Inc, MICRF219AAYQS TR Datasheet - Page 18

• Manufacturer Part Number: MICRF219AAYQS TR
• Description: IC RECEIVER QWIKRADIO 16QSOP
• Manufacturer: Micrel Inc
• Series: -r

Specifications of MICRF219AAYQS TR

• Frequency: 300MHz ~ 450MHz
• Sensitivity: -112.5dBm
• Data Rate - Maximum: -
• Modulation Or Protocol: ASK, OOK
• Applications: General Purpose
• Current - Receiving: 4.3mA
• Data Interface: PCB, Surface Mount
• Memory Size: -
• Antenna Connector: PCB, Surface Mount
• Features: RSSI Equipped
• Voltage - Supply: 3 V ~ 3.6 V
• Operating Temperature: -40°C ~ 105°C
• Package / Case: 16-SSOP (0.154", 3.90mm Width)
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant
• Other names: 576-3892-2; MICRF219AAYQSTR

Micrel, Inc.
MICRF219A
Crystal Selection
The crystal resonator provides a reference clock for all
the device internal circuits. Crystal tolerance needs to
be chosen such that the down-converted signal is
always inside the IF bandwidth of MICRF219A. From
this consideration, the tolerance should be ±50ppm on
both the transmitter and the MICRF219A side. The ESR
should be less than 300Ω, and the temperature range of
the crystal should match the range required by the
application. With the Abracon crystal listed in the Bill of
Materials, a typical MICRF219A crystal oscillator still
starts up at 105ºC with additional 400Ω series
resistance.
The oscillator of the MICRF219A is a Pierce-type
oscillator. Good care must be taken when laying out the
printed circuit board. Avoid long traces and place the
ground plane on the top layer close to the REFOSC pins
RO1 and RO2. When care is not taken in the layout, and
the crystals used are not verified, the oscillator may not
start or takes longer to start. Time-to-good-data will be
longer as well.
PCB Considerations and Layout
The MICRF219A evaluation board is a good starting
point for prototyping of most applications. The Gerber
files are downloadable from the Micrel website and
contain the remaining layers needed to fabricate this
board. When copying or making one’s own boards,
make the traces as short as possible. Long traces alter
the matching network and the values suggested are no
longer valid. Suggested matching values may vary due
to PCB variations. A PCB trace 100 mils (2.5mm) long
has about 1.1nH inductance. Optimization should always
be done with range tests. Make sure the individual
ground connection has a dedicated via rather then
sharing a few of ground points by a single via. Sharing
ground via will increase the ground path inductance.
Ground plane should be solid and with no sudden
interruptions. Avoid using ground plane on top layer next
to the matching elements. It normally adds additional
stray capacitance which changes the matching. Do not
use Phenolic materials as they are conductive above
200MHz. Typically, FR4 or better materials are
recommended. The RF path should be as straight as
possible to avoid loops and unnecessary turns.
Separate ground and V
lines from other digital or
DD
switching power circuits (such microcontroller…etc).
Known sources of noise should be laid out as far as
possible from the RF circuits. Avoid unnecessary wide
traces which would add more distribution capacitance
(between top trace to bottom GND plane) and alter the
RF parameters.
July 2011
18
M9999-071811-A
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