TDA7210 Infineon Technologies, TDA7210 Datasheet - Page 23

• Manufacturer Part Number: TDA7210
• Description: IC RECEIVER FSK/ASK 28-TSSOP
• Manufacturer: Infineon Technologies
• Type: ASK/FSK Single Conversion Receiverr

Specifications of TDA7210

• Package / Case: 28-TSSOP
• Frequency: 810MHz ~ 870MHz, 400MHz ~ 440MHz
• Sensitivity: -110dBm
• Data Rate - Maximum: 100 kbps
• Modulation Or Protocol: ASK, FSK
• Applications: Remote Control, RKE, Security Systems
• Current - Receiving: 5.9mA
• Data Interface: PCB, Surface Mount
• Antenna Connector: PCB, Surface Mount
• Voltage - Supply: 4.5 V ~ 5.5 V
• Operating Temperature: -40°C ~ 85°C
• Operating Supply Voltage: 5 V
• Maximum Operating Temperature: + 85 C
• Minimum Operating Temperature: - 40 C
• Mounting Style: SMD/SMT
• Supply Current: 7.7 mA
• Supply Voltage (max): 5.5 V
• Supply Voltage (min): 4.5 V
• Operating Supply Voltage (typ): 5V
• Operating Supply Voltage (min): 4.5V
• Operating Supply Voltage (max): 5.5V
• Operating Temp Range: -40C to 85C
• Operating Temperature Classification: Industrial
• Mounting: Surface Mount
• Pin Count: 28
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Features: -
• Memory Size: -
• Lead Free Status / Rohs Status: Compliant
• Other names: SP000524274; TDA7210; TDA7210INTR

Wireless Components
4.1 Choice of LNA Threshold Voltage and Time Constant
In the following figure the internal circuitry of the LNA automatic gain control is
shown.
Figure 4-1
The LNA automatic gain control circuitry consists of an operational transimped-
ance amplifier that is used to compare the received signal strength signal
(RSSI) generated by the Limiter with an externally provided threshold voltage
U
value between approximately 0.8 and 2.8V to provide a switching point within
the receive signal dynamic range.
This voltage U
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. If the RSSI level generated by the
Limiter is higher than U
yields a voltage rise on the TAGC pin (Pin 4). Otherwise, the OTA generates a
negative current. These currents do not have the same values in order to
achieve a fast-attack and slow-release action of the AGC and are used to
charge an external capacitor which finally generates the LNA gain control volt-
age.
thres
. As shown in the following figure the threshold voltage can have any
LNA Automatic Gain Control Circuitry
Pins:
RSSI > U
RSSI < U
thres
is applied to the THRES pin (Pin 23) The threshold voltage
threshold
threshold
24
4 - 2
thres
: I
: I
load
load
20k
Ω
=4.2µA
= -1.5µA
, the OTA generates a positive current I
+3.1 V
C
4
R4
U
I
C
load
U
U
U
U
c
c
cmax
cmin
:< 2.6V : Gain high
:> 2.6V : Gain low
23
= V
= 1.67V
OTA
CC
U
threshold
- 0.7V
Gain control
R5
voltage
VCC
RSSI (0.8 - 2.8V)
Data Sheet, December 2008
LNA
Applications
TDA7210
load
LNA_autom.wmf
. This