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Low-noise AM/FM Antenna Impedance Matching IC U4254BM-M

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Features High Dynamic Range for AM and FM Integrated for FM High Intercept Point 3rd-order for FM FM Amplifier Adjustable to Various Cable Impedances High Intercept Point 2nd-order for AM Low-noise Output
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Features High Dynamic Range for AM and FM Integrated for FM High Intercept Point 3rd-order for FM FM Amplifier Adjustable to Various Cable Impedances High Intercept Point 2nd-order for AM Low-noise Output Voltage Low-power Consumption Electrostatic sensitive device. Observe precautions for handling. Low-noise AM/FM Antenna Impedance Matching IC Description The U4254BM-M is an integrated low-noise AM/FM antenna impedance matching circuit in BiCMOS technology. The device is designed specifically for car applications and is suitable for windshield and roof antennas. U4254BM-M Figure 1. Block Diagram FMIN GND1 1 (14) 2 (15) FM 15 (13) FMOUT FMGAIN VS 3 (16) 4 (2) 14 (11) I 13 (10) ADJ VREF2 5 (3) VREF 12 (9) VREF1 AMIN 8 (6) AM 11 (8) 10 (7) AMOUT1 AMOUT 7 (5) GND2 () Pin numbers in brackets = QFN 4 4 package Rev. Pin Configuration Figure 2. Pinning SO16 Figure 3. Pinning QFN FMIN 1 16 NC GND FMOUT FMGAIN 3 14 VS FMGAIN FMGND FMIN FMOUT VREF2 NC GND ADJ VREF1 AMOUT1 AMOUT n.c. VREF2 n.c GND2 AMIN AMOUT AMOUT1 n.c. Vs ADJ VREF1 AMIN 8 9 NC Pin Description Pin SSO16 Pin QFN16 Symbol Function 1 14 FMIN FM input 2 15 GND1 Ground for FM part 3 16 FMGAIN FM gain adjustment 4 2 output 5 3 VREF2 Reference voltage 2 output 6 1 NC Not connected 7 5 GND2 Ground for AM part 8 6 AMIN AM input 9 4 NC Not connected 10 7 AMOUT AM output 11 8 AMOUT1 AM output 12 9 VREF1 Reference voltage 1 output ADJ Adjustment FM wide-band threshold VS Supply voltage FMOUT FM output NC Not connected 2 U4254BM-M U4254BM-M Pin Description FMIN FMIN, a bipolar transitor s base is the input of the FM amplifier. A resistor or a coil is connected between FMIN and VREF2. If a coil is used, the noise performance is excellent. Figure 4. Internal Circuit at Pin FMIN 1 FMIN GND1 FMGAIN To avoid cross-talk between AM and FM signals, the circuit has two separate ground pins. GND1 is the ground for the FM part. The DC current of the FM amplifier transistor is adjusted by an external resistor which is connected between FMGAIN and GND1. To influence the AC gain of the amplifier, a resistor is connected in series to a capacitor between FMGAIN and GND1. The capacitor has to shorten frequencies of 100 MHz. Figure 5. Internal Circuit at pin FMGAIN FMGAIN 3 DC current flows into the pin at high FM antenna input signals. This current has to be amplified via the current gain of an external PNP transistor that feeds a PIN diode. This diode dampens the antenna s input signal and protects the amplifier input against overload. The maximum current which flows in the pin is approximately 1 ma. In low-end applications, the function is not necessary and the external components can therefore be omitted. 3 Figure 6. Internal Circuit at Pin 4 V S ADJ The threshold of the can be adjusted by varying the DC current at pin ADJ. If pin ADJ is connected directly to GND1, the threshold is set to 96 dbµv at the FM amplifier output. If a resistor is connected between ADJ and GND1, the threshold is shifted to higher values with increasing resistances. If ADJ is open, the threshold is set to 106 dbµv. Figure 7. Internal Circuit at Pin ADJ 65 kω 13 ADJ FMOUT The FM amplifier output is an open collector of a bipolar RF transistor. It should be connected to V S via a coil. Figure 8. Internal Circuit at Pin FMOUT 15 FMOUT 4 U4254BM-M U4254BM-M AMIN The AM input has an internal bias voltage. The DC voltage at this pin is V Ref1/2. The input resistance is about 470 kω. The input capacitance is less than 10 pf. Figure 9. Internal Circuit at Pin AMIN VREF1/2 470 kω 8 AMIN AMOUT, AMOUT1 The buffered AM amplifier consists of a complementary pair of CMOS source followers. The transistor gates are connected to AMIN. The pin AMOUT is the NMOS transistor's source, pin AMOUT1 is the PMOS transistor's source. Due to the two different DC levels of these pins, they have to be connected together via an external capacitor of about 100 nf. By means of this technique an excellent dynamic range can be achieved. Figure 10. Internal Circuit at Pins AMOUT1 and AMOUT AMOUT1 11 AMOUT 10 VREF1 VREF1 is the stabilized voltage for the AM amplifier and the block. To achieve excellent noise performance at LW frequencies, it is recommended that this pin be connected to ground via an external capacitor of about 1 µf. 5 Figure 11. Internal Circuit at Pin VREF1 VS 12 VREF1 GND1 VREF2 For the DC biasing of the FM amplifier, a second voltage reference circuit is integrated. Since the collector current is temperature independent, the output voltage has a negative temperature coefficient of about -1 mv/k. To stabilize this voltage, an external capacitor to ground of a few nf is recommended. Figure 12. Internal Circuit at Pin VREF2 5 VREF2 GND1 GND2 GND2 is the ground for the AM amplifier. 6 U4254BM-M U4254BM-M Functional Description The U4254BM-M is an integrated AM/FM antenna impedance matching circuit. It compensates cable losses between the antenna (for example windshield, roof or bumper antennas) and the car radio which is usually placed far away from the antenna. The FM amplifier provides excellent noise performance. External components are used to adjust the gain and the input-output matching impedance. Therefore, it is possible to adjust the amplifier to various cable impedances (usually 50, 75 or 150 Ω). To protect the amplifier against input overload, an Automatic Gain Control () is included on the chip. The observes the AC voltage at the FM amplifier output, rectifies this signal, and delivers DC current to dampen the input antenna signal via an external PIN diode. The threshold for the is adjustable. Simple and temperature-compensated biasing is possible due to the integrated voltage reference V Ref2. The AM part consists of a buffer amplifier. The voltage gain of this stage is approximately one. The input resistance is 470 kω, the input capacitance less than 10 pf. The output resistance is 125 Ω. An excellent dynamic range is achieved due to the complementary CMOS source follower stage. Absolute Maximum Ratings Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. This is a stress rating only and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. Reference point is ground (pins 2 and 7) Parameters Symbol Value Unit Supply voltage V S 8.8 V Power dissipation, P tot at T amb = 85 C P tot 460 mw Junction temperature T j 150 C Ambient temperature T amb -40 to +85 C Storage temperature T stg -50 to +150 C Electrostatic handling (HBM at S.5.1) ±V ±1000 V Thermal Resistance Parameters Symbol Value Unit Junction ambient R thja 140 K/W 7 Electrical Characteristics V S = 8 V, T amb = 25 C, unless otherwise specified (see Figure 13 on page 9). Parameters Test Conditions Pin Symbol Min. Typ. Max. Unit Supply voltage 14 V S V Supply currents 14 I S ma Reference voltage 1 output (I 12 =0) 12 V Ref V Reference voltage 2 output (I 5 =0) 5 V Ref V Temperature dependence of VREF2 5 V Ref2 / T -1 mv/k AM Amplifier Input resistance 8 R AMIN 470 kω Input capacitance 8 C AMIN 10 pf Output resistance 10 R OUT 125 Ω Voltage gain 8, 10 a 0.85 Output noise voltage (rms value) 2nd harmonic FM Amplifier S1 switched to 2 B=6kHz 150 khz to 300 khz 500 khz to 6.5 khz S2 switched to 1 f AMIN =500kHz Output voltage = 110 dbµv 10 V N1-2 V N2-6 dbµv dbµv dbc Supply current limit I, I ADJ =0A 15 I ma Input resistance f = 100 MHz 1 R FMIN 50 Ω Output resistance f = 100 MHz 15 R FMOUT 50 Ω Power gain f = 100 MHz 1, 15 G 5 db Output noise voltage f = 100 MHz B = 120 khz 15 V N 0 dbµv 3rd-order output intercept f = 100 MHz dbµv input voltage threshold input voltage threshold f = 100 MHz S2 switched to 1; threshold DC current is 10 µa at pin 4 f = 100 MHz, S2 switched to 2; threshold DC current is 10 µa at pin V th1 96 dbµv V th2 106 dbµv output current active I 1.2 ma 8 U4254BM-M U4254BM-M Figure 13. Test Circuit V S FMOUT 2.2 µh 1 2 S2 5 kω AMOUT I 15 I 14 I µf nf 100 nf Ω 1 8 I 4 FMIN 22 Ω 2.2 µh 51 Ω 1 S pf V S 1 nf AMIN 9 Figure 14. FM Intermodulation Distortion dbµv dbµv Output Input 108 dbµv 103 dbµv 58 dbµv Gain = 5 db not active MHz MHz dbµv Input 118 dbµv dbµv Output 100 dbµv active 50 dbµv MHz MHz 10 U4254BM-M U4254BM-M Figure 15. Test Circuit for AM Large Signal Behavior Analyzer LPF AMOUT1 100 nf f cutoff = 500 khz 50 Ω f = 500 khz 1 nf 50 Ω DUT AMIN 5 kω R in = 50 Ω AMOUT 100 nf 115 dbµv 75 dbµv V 0 Figure 16. AM Harmonic Distortion V AMOUT (dbµv) 115 dbµv dbµv 45 dbµv f (MHz) 11 ANTENNA AM FM PIN 510 Ω BC558 Protection circuit BA679 V 200 nf 1 nf 1 kω 51 Vs R 1 and R 2 depend on used FM cable impedance FMIN FMGND FMGAIN VS VREF2 AMIN R 2 (Ω) FM ADJ I AM AMGND FMOUT VREF1 AMOUT1 AMOUT + V S = 8.2 V 1 µf 2.2 µh 100 nf 100 nf 39 pf 2.2 µh Output Figure 17. Application Circuit R 1 V Ref R 2 FM cable impedance R 1 (Ω) 12 U4254BM-M U4254BM-M Ordering Information Extended Type Number Package Remarks U4254BM-MFP SO16 U4254BM-MPG3 SO16 Taping corresponding, ICE U4254BM-MPH QFN16 U4254BM-MPG3H QFN16 Taping corresponding, ICE Package Information Package SO16 Dimensions in mm technical drawings according to DIN specifications 14 U4254BM-M Atmel Corporation 2325 Orchard Parkway San Jose, CA 95131, USA Tel: 1(408) Fax: 1(408) Regional Headquarters Europe Atmel Sarl Route des Arsenaux 41 Case Postale 80 CH-1705 Fribourg Switzerland Tel: (41) Fax: (41) Asia Room 1219 Chinachem Golden Plaza 77 Mody Road Tsimshatsui East Kowloon Hong Kong Tel: (852) Fax: (852) Japan 9F, Tonetsu Shinkawa Bldg Shinkawa Chuo-ku, Tokyo Japan Tel: (81) Fax: (81) Atmel Operations Memory 2325 Orchard Parkway San Jose, CA 95131, USA Tel: 1(408) Fax: 1(408) Microcontrollers 2325 Orchard Parkway San Jose, CA 95131, USA Tel: 1(408) Fax: 1(408) La Chantrerie BP Nantes Cedex 3, France Tel: (33) Fax: (33) ASIC/ASSP/Smart Cards Zone Industrielle Rousset Cedex, France Tel: (33) Fax: (33) East Cheyenne Mtn. Blvd. Colorado Springs, CO 80906, USA Tel: 1(719) Fax: 1(719) Scottish Enterprise Technology Park Maxwell Building East Kilbride G75 0QR, Scotland Tel: (44) Fax: (44) RF/Automotive Theresienstrasse 2 Postfach Heilbronn, Germany Tel: (49) Fax: (49) East Cheyenne Mtn. Blvd. Colorado Springs, CO 80906, USA Tel: 1(719) Fax: 1(719) Biometrics/Imaging/Hi-Rel MPU/ High Speed Converters/RF Datacom Avenue de Rochepleine BP Saint-Egreve Cedex, France Tel: (33) Fax: (33) Literature Requests Disclaimer: Atmel Corporation makes no warranty for the use of its products, other than those expressly contained in the Company s standard warranty which is detailed in Atmel s Terms and Conditions located on the Company s web site. The Company assumes no responsibility for any errors which may appear in this document, reserves the right to change devices or specifications detailed herein at any time without notice, and does not make any commitment to update the information contained herein. No licenses to patents or other intellectual property of Atmel are granted by the Company in connection with the sale of Atmel products, expressly or by implication. Atmel s products are not authorized for use as critical components in life support devices or systems. Atmel Corporation All rights reserved. Atmel and combinations thereof are the registered trademarks of Atmel Corporation or its subsidiaries. Other terms and product names may be the trademarks of others. Printed on recycled paper.
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