RFD21733 Datasheet, PDF (28/76 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
Using CR2032 Batteries
The CR2032 battery is very commonly used for power. The peak current draw for the Modules and RFDANTs
are at about 17mA, and the background current is 2uA depending on the mode setting of course. Quite often
capacitors are used in parallel with the CR2032 to help limit the amount of peak current the CR2032 is exposed
to, so as to help it have a longer run time, since the CR2032 does not handle peak current very well over long
durations of time. We recommend if you choose to place bypass capacitors tied to the CR2032 for this purpose,
then do testing to compare if they really provide you a benefit or not. Quite often the leakage current of the
capacitors are so high that they will have negative impact on the battery runtime rather then provide an
advantage. At least if you have the room, place the pads, but before you place the caps for production, do testing
to make sure they are really helping and not reducing your runtime.
Mode Pins
The mode pins are read just once, right after the Module or RFDANT comes out of reset or upon power up. If you
change them and want them to be read again, then do a reset or power down and up again.
Mode Select 0, Mode Select 1 and Modes Select 2, are three binary inputs which are to be terminated either high
or low, they must not be left open at any time. Mode Select 2 and 1 are open and high Z inputs, so you can use a
47k resistor to pull them up or down, or you can connect directly to +V or GND.
The Mode Select 0 has an internal 13k internal switched pull down. At power up or when the module comes out
of reset, it will internally apply a 13k pull down on this pin just for an instant to check if it is high or not. After the
mode selection test, which is done just once at start up lasts just microseconds. It is done like this to allow you to
have an optional external switch to select between mode 0 and mode 1 without drawing extra current through an
external pull down resistor which would statically be there all the time.
If you will be directly connecting Mode Select 0 directly to +V or to GND that is fine. However if you will be adding
a pull up, note you will be working against a 10k to 16k internal pull down at the time the pin is read, so take that
into account since it will form a voltage divider and maybe not provide the expected level and cause the module to
go into the wrong mode. So for Mode Select 0, we recommend using a 1k or smaller resistor for a pull up to
make sure you get 90% +V for a logic high, we often use 220 ohms or just tie it directly to +V. If you will add a
pull down, note that it will be in parallel with the internal 13k typical pull down for microseconds duration, after
reset or power up.
The Mode Select 0 can be left open, if you leave it open it will register as a LOW. However if you will know what
mode you want in advance and will not be switching it, then we always recommend direct tie to +V or GND.
Wake Up Time
The Modules and RFDANTs wake up very fast. After a reset or after power on, 3mS later they are ready to
transmit or receive.
Output Drive Current - source and sink.
The Module and RFDANT output pins and IO pins when in an output mode should not be expected to drive higher
then 0.5mA each. This is done by design to keep as much high current sources from flowing through the Module
or RFDANT. The amount of source and sink current available at the pins are actually quite a bit more, therefore
they are seen in applications were they can directly drive LEDs with a series resistor of about 220 ohm and the
LED still comes on at a couple milliamps, but we don’t recommend that for production. For prototyping that is
fine, since its quick and simple to hookup, but for production, we prefer to use a driver like a transistor or FET to
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