CC400 Chipcon, CC400 Datasheet - Page 18

• Manufacturer Part Number: CC400
• Description: Single Chip High Performance RF Reansceiver
• Manufacturer: Chipcon

Demodulator Precharging For Reduced Turn-on Time
The demodulator data slicer has an
internal AC coupling giving a time constant
of approximately 30 periods of the bit rate
period. This means that before proper
demodulation can take place, a minimum
of 30 start-bits has to be received.
In critical applications where the start-up
time should be decreased in order to
In the example shown in figure 10, data is
transmitted
transmitter (all 1’s). At t=t
turned on, and then the precharging is
Chipcon AS
Data
transmitted
Data received
without
precharging
PRECHARGE
Data received with
precharging
t1
Data not valid
5 bit periods
continuously
5 bit periodes
t2
SmartRF
Figure 10: Demodulation using precharging.
1
the receiver is
TM
CC400
from
Data not valid
Data valid
the
Datasheet (rev. 3.1) 2003-11-12
SmartRF
reduce the power consumption, this time
constant can be reduced to 5 periods
using the optional precharging possibility.
The precharging is done during data
reception by setting the precharging bit in
the configuration register active with
duration
kept on for about 5 bit periods. At t=t
received data is valid and precharging is
turned off. When not using precharging,
data is not valid until 30 bit periods, at t=t
30 bit periodes
of
t3
Data valid
at
least
®
5
CC400
bit
Page 18 of 27
periods.
2
Time
the
3
.