RFD21733 Datasheet, PDF (27/76 Pages) List of Unclassifed Manufacturers – Compliance Approved 2.4 GHz RF Transceiver Modules with Built-In RFDP8 Application Protocol

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7/10/2011 1:40 AM
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RFD21733 • FCC • IC
RFD21743 • FCC
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RFDP8
RF Module
RFD21733
RFD21735
RFD21737
RFD21738
RFD21739
RFDP8
RFDANT
RFD21742
RFD21743
RFD21772
RFD21773
KEYFOBs
If possible, use a 470 ohm resistor or larger,
to allow for highest logic level on the LEARN
input as possible, due to the resistive divider
that forms when pressing the LEARN button.
Reset Pin
The RESET pin on all part numbers of RF Modules and RFDANT are active low and have an internal 3.3k ohm
pull up resistor. So at 3V you will need to source at least 1mA to be able to pull it low to cause a reset. You can
leave the reset pin open, you do not need to connect it. The only reason you would need to connect the reset pin
is if you needed a way to reset the Module or RFDANT while in your circuit. A common cause to require this is if
you wanted to change modes while powered up and therefore you need to assert a reset to cause the 3 mode
pins to be re-read to change modes. Note keeping reset low all the time will draw about 1mA of current so if you
plan on conserving current, you will want to bring it low only briefly to cause the reset and then let it go high again
using its internal 3.3k ohm pull up.
Layout Trace Routing and VIAs
When doing your layout for the RFD21733 and RFD21735 avoid placing routs under the module if at all possible.
Having traces under the module as long as they are fully covered by soldermask is typically fine, however placing
VIAs under the module is not at all recommended since soldermask covering VIAs are typically not fully plugged
and protected. Therefore, if there is any exposes soldermask under the module near an area were your board
has an exposed via, there is a chance of a short. There is a slim chance of this ever happening, however if
possible, make effort to avoid having VIAs under the Modules.
Dual Placement Layouts for Modules and RFDANTs
When ever possible, it is always recommended when you do your layout for the RFD21733 or RFD21735 to also
place a footprint for one of the 11 pin RFDANT connectors. This gives you the option to do testing by not placing
the RFD21733 or RFD21735 module on some of your PCBs and just placing the RFDANT 11 pin connector and
plugging an RFDANT into your board. If your board does not have room for this, then of course, this is not in any
way required, its just a recommendation to give you as much optional choices as possible. The RFDANT has
about 4x the range of the RFD21733 so if you happen to need the extra range, it would always be available with a
simple connector interface.
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