TDA7200 - Infineon

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TDA7200 Applications 3.8 ASK Mode In case the receiver is operated in ASK mode the datapath frequency charactersitic is dominated by the data filter alone, thus it is lowpass shaped. The cutoff frequency is determined by the external capacitors C 12 and C 14 and the internal 100k resistors as described in Section 3.2 0dB -3dB -40dB/dec f3dB f Figure 11 Frequency characteristic in case of ASK mode 3.9 Principle of the Precharge Circuit In case the data slicer threshold shall be generated with an external RC network as described in Section 3.5 it is necessary to use large values for the capacitor C attached to the SLN pin (pin 20) in order to achieve long time constants. This results also from the fact that the choice of the value for R1 connected between the SLP and SLN pins (pins 19 and 20) is limited by the 330kΩ resistor appearing in parallel to R1 as can be seen in Figure 9. Apart from this a resistor value of 100kΩ leads to a voltage offset of 1mV at the comparator input. The resulting startup time constant τ 1 can be calculated with: τ ( R 1|| 330k Ω) × 13 1 = C In case R1 is chosen to be 100kΩ and C13 is chosen as 47nF this leads to τ ( 100kΩ || 330kΩ) × 47nF = 77kΩ× 47nF 3. 6ms 1 = = When the device is turned on this time constant dominates the time necessary for the device to be able to demodulate data properly. In the powerdown mode the capacitor is only discharged by leakage currents. Data Sheet 28 V 1.0, 2007-05-02
TDA7200 Applications In order to reduce the turn-on time in the presence of large values of C a precharge circuit was included in the TDA7200 as shown in the following figure. C18 R4+R5=600k R4 R5 U threshold C13 R1 24 23 Uc>Us Uc
Page 1 and 2: Data Sheet, V 1.0, May 2007 TDA7200
Page 3 and 4: Data Sheet, V 1.0, May 2007 TDA7200
Page 5 and 6: TDA7200 Table of Contents Page 1 Pr
Page 7 and 8: TDA7200 Functional Description 2 Fu
Page 9 and 10: TDA7200 Pin No. Functional Descript
Page 15 and 16: TDA7200 Functional Description 2.3
Page 17 and 18: TDA7200 2.4.6 FSK Demodulator Funct
Page 19 and 20: TDA7200 Applications 3 Applications
Page 21 and 22: TDA7200 Applications 3.2 Data Filte
Page 23 and 24: TDA7200 Applications injection of t
Page 25 and 26: TDA7200 Applications C Pins: 26 25
Page 27: TDA7200 Applications asymmetrical o
Page 31 and 32: TDA7200 Applications Uc Us Figure 1
Page 33 and 34: TDA7200 Reference Table 7 Operating
Page 35 and 36: TDA7200 Reference # Parameter Symbo
Page 43 and 44: TDA7200 Reference 4.3 Test Board La
Page 45 and 46: TDA7200 Reference Ref. Value Specif
Page 47 and 48: TDA7200 List of Tables Page Table 1
Page 49: www.infineon.com Published by Infin

TDA7200 - Infineon

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