TDA5210 Datasheet, PDF (17/53 Pages) Infineon Technologies AG – ASK/FSK Single Conversion Receiver

3.3 Functional Block Diagram
TDA 5210
Functional Description
VCC
IF
Filter
LNO
6
MI
MIX IFO
8 9 12
LIM
LIMX
17 18
MSEL
15
FFB
OPP
22
21
SLP
SLN
19 20
LNI ₃
RF
LNA
TAGC 4
LIMITER
FSK
PLL Demod
-
+ FSK
- ASK
+
TDA 5210
OTA
-
SLICER
25 DATA
OP
+
PEAK _{26 PDO}
DETECTOR
23 THRES
VCC ₁₄
DGND
13
2,7 5,10
:1/2
11
VCO
: 128 / 64
Loop
Filter
16
Φ
DET
CRYSTAL
OSC
1
28
U_REF
AGC
Reference
Bandgap
Reference
27
24 3VOUT
VCC AGND
FSEL
CSEL
Crystal
Figure 3-2 Main Block Diagram
PDWN
Function_5200.wmf
3.4 Functional Blocks
3.4.1 Low Noise Amplifier (LNA)
The LNA is an on-chip cascode amplifier with a voltage gain of 15 to 20dB. The
gain figure is determined by the external matching networks situated ahead of
LNA and between the LNA output LNO (Pin 6) and the Mixer Inputs MI and MIX
(Pins 8 and 9). The noise figure of the LNA is approximately 3dB, the current
consumption is 500µA. The gain can be reduced by approximately 18dB. The
switching point of this AGC action can be determined externally by applying a
threshold voltage at the THRES pin (Pin 23). This voltage is compared internally
with the received signal (RSSI) level generated by the limiter circuitry. In case
that the RSSI level is higher than the threshold voltage the LNA gain is reduced
and vice versa. The threshold voltage can be generated by attaching a voltage
divider between the 3VOUT pin (Pin 24) which provides a temperature stable
3V output generated from the internal bandgap voltage and the THRES pin as
described in Section 4.1. The time constant of the AGC action can be deter-
Wireless Components
3-9
Specification, May 2001