TDA5204E1 Datasheet, PDF (16/40 Pages) Infineon Technologies AG – ASK Single Conversion Receiver 390MHz

TDA 5204 E1
preliminary
Functional Description
3.3 Functional Block Diagram
VCC
IF
Filter
LNO
6
MI MIX IFO
8 9 12
LIM
LIMX
17
18
FFB
OPP
SLP
SLN
22
21
19
20
RF
3 _LNA
RSSI
25 _DATA
SLICER
TAGC 4
VDD 14
DGND 13
2/7
5/10
VCC
AGND
: 1/2
11
FSEL
VCO
Loop
Filter
15
LF
TDA 5204
: 128/64
Φ
DET
16
CSEL
Crystal
OSC
AGC
Reference
U_REF
Bandgap
Reference
1 28
27
PDWN
Crystal
Figure 3-2 Main Block Diagram
26 ^PDO
23 THRES
24 3VOUT
Function_5204.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 2dB, 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-
mined by connecting a capacitor to the TAGC pin (Pin 4) and should be chosen
along with the appropriate threshold voltage according to the intended operat-
Wireless Components
3-8
Specification, December 2000