Linx Technologies HUM-xxx-RC - Manual (Page 17)

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Receiver Duty Cycle
The module can be configured to automatically power on and off while
in receive mode. Instead of being powered on all the time looking for
transmissions from an IU, the receiver can wake up, look for data and go
back to sleep for a configurable amount of time. If it wakes up and receives
valid data, then it stays on and goes back to sleep when the data stops.
This significantly reduces the amount of current consumed by the receiver.
It also increases the time from activating the IU to getting a response from
the RU.
The duty cycle is controlled by the Duty Cycle serial command through the
CDI. DCycle sets the number of seconds between receiver turn-on points
as shown in Figure 32.
The module’s average current consumption can be calculated with the
following equation.
T
ON
is fixed at about 0.326 seconds and T
SBY
= DCycle - T
ON
. The receiver
current (I
RX
) and standby current (I
SBY
) vary with supply voltage, but some
typical values are in Figure 34.
DCycle
T
ON KeepOn
Activity
ON
Standby
T
SBY
I
T I T I
DCycle
AVG
ON RX SBY SBY
=
×
( )
+ ×
( )
Figure 32: Receiver Duty Cycle
Figure 33: Receiver Duty Cycle Average Current Consumption Equation
HumRC TM Series Typical Current Consumption
V
CC
(VDC)
2.5 3.3 3.6
HUM-2.4-RC
I
RX
(mA)
21.45 21.82 22.03
I
SBY
(mA)
0.00040 0.00058 0.00063
HUM-900-RC
I
RX
(mA)
22.94 23.73 24.02
I
SBY
(mA)
0.00040 0.00058 0.00063
Figure 34: HumRC TM Series Transceiver Typical Current Consumption
Figure 20 and Figure 21 show graphs of the average current consumption
vs. duty cycle for several supply voltages. They show that the average
current consumption can be significantly reduced with even a small duty
cycle value. This is ideal for battery-powered applications that need
infrequent updates or where response time is not critical.
The KeepOn time is used to keep the receiver on after it has completed
some activity. This activity includes completing a transmission and receiving
a valid packet. After KeepOn seconds have elapsed with no transmit or
valid receive activity, the module resumes duty cycle operation by going
into standby for DCycle seconds.
Please see Reference Guide RG-00104: the HumRC TM Series Command
Data Interface for details on configuring the receiver duty cycle.