TH7122 Datasheet, PDF (23/44 Pages) Melexis Microelectronic Systems – 27 to 930MHz FSK/FM/ASK Transceiver

TH7122
27 to 930MHz
FSK/FM/ASK Transceiver
5.1.3 B – word
Name
RT
ROMIN
ROMAX
OA2
AFC
Bits
Description
[9:0]
4d .. 1023d
Reference divider ratio in TX operation mode
000
001
010
[12:10] ₀₁₁
100
101
110
111
Set the desired steady state current of the reference oscillator
0 μA
75 μA
150 μA _#default
225 μA
300 μA
375 μA
450 μA
525 μA
The control circuitry regulates the current of the oscillator core
between the values ROMAX and ROMIN. As the regulation input
signal the amplitude on pin RO is used. If the ROMIN value is
sufficient to achieve an amplitude of about 400mV on pin RO the
current of the reference oscillator core will be set to ROMIN.
Otherwise the current will be permanently regulated between
ROMAX and ROMIN. If ROMIN and ROMAX are equal no
regulation of the oscillator current occurs. Please also note the
block description of the reference oscillator in para. 3.1.1
Set the start-up current of the reference oscillator
000
001
010
[15:13] ₀₁₁
100
101
110
111
0 μA
75 μA
150 μA
225 μA
300 μA
375 μA
450 μA
525 μA #default
Set the start-up current of the reference oscillator core. Please
also note the description of the ROMIN register and the block
description of the reference oscillator which can be seen above.
OA2 operation
[16]
0 disabled
1 enabled
#default
OA2 can be enabled in FSK receive mode. OA2 is disabled in ASK mode receive.
[17]
0 disabled
1 enabled
Internal AFC feature
#default
LNAHYST [18] _{0 disabled}
1 enabled
Hysteresis on pin GAIN_LNA
#default
DELPLL
not used
Delayed start of the PLL
0 undelayed start
PLL starts at the reference oscillator start-up
[19]
1 starts after 8 valid RO-cycles
#default
PLL starts after 8 valid RO-cycles before entering an active mode to ensure reliable oscillation
of the reference oscillator.
[20]
set to ‘1’ for correct function
PKDET
RSSI Peak Detector
0 disabled
#default
[21]
The RSSI output signal directly feeds the data slicer setup by means of OA1.
1 enabled
In ASK receive mode the RSSI Peak Detector output is multiplexed to pin INT2/PDO.
39010 07122
Rev. 008
Page 23 of 44
Data Sheet
June/07