TH71111
868/915MHz
FSK/FM/ASK Receiver
1.3
Block Diagram
IN_MIX1
OUT_MIX2
FBC1
IF1N
VCC_MIX
VEE_LNAC
GAIN_LNA
OUT_LNA
VEE_MIX
OUT_IFA
IN_DEM
IF1P
VEE_IF
IN_IFA
2
3
4
5
6
7
8
9
RSSI
1
10
11
12
13
21
14
15
16
IN_LNA
31
MIX1
LNA
LO
IF
MIX2
IF
MIX3
OUTP
OUTN
23
24
IFA
OAP
OA
20
OAN
19
DIV_32
PFD
RO
OUT_OA
BIAS
VCC_BIAS
VEE_BIAS
VCC_PLL
VEE_RO
18
VCO1
VCC_LNA
VEE_LNA
CP
ENRX
32
30
29
LF
26
RO
25
27
28
22
17
Fig. 1: TH71111 block diagram
1.4
Mode Configurations
ENRX
0
1
Mode
RX standby
RX active
Description
RX disabled
RX enable
Note:
ENRX are pulled down internally
1.5
LNA GAIN Control
V
GAIN_LNA
< 0.8 V
> 1.4 V
Mode
HIGH GAIN
LOW GAIN
Description
LNA set to high gain
LNA set to low gain
Note:
hysteresis between gain modes to ensure stability
1.6
Frequency Planning
Frequency planning is straightforward for single-conversion applications because there is only one IF that
can be chosen, and then the only possible choice is low-side or high-side injection of the LO signal (which is
now the one and only LO signal in the receiver).
The receiver’s single-conversion architecture requires careful frequency planning. Besides the desired RF
input signal, there are a number of spurious signals that may cause an undesired response at the output.
Among them is the image of the RF signal that must be suppressed by the RF front-end filter.
39010 71111
Rev. 013
Page 4 of 22
Data Sheet
June/07
MELEXIS [ Melexis Microelectronic Systems ]
