Features • • • • • • • High Dynamic Range for AM and FM Integrated AGC 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 Low-noise AM/FM Antenna Impedance Matching IC Electrostatic sensitive device. Observe precautions for handling. U4254BM-M 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. Figure 1. Block Diagram FMIN GND1 FMGAIN AGC VS VREF2 1 2 15 FM 3 4 14 5 AGC 13 AGCADJ IAGC 12 VREF VREF1 11 AMIN FMOUT 8 AM 10 AMOUT1 AMOUT 7 GND2 Rev. 4772B–AUDR–11/03 Pin Configuration Figure 2. Pinning SO16 FMIN 1 16 NC GND1 2 15 FMOUT FMGAIN 3 14 VS AGC 4 13 AGCADJ VREF2 5 12 VREF1 NC 6 11 AMOUT1 GND2 7 10 AMOUT AMIN 8 9 NC Pin Description Pin 2 Symbol Function 1 FMIN FM input 2 GND1 Ground for FM part 3 FMGAIN FM gain adjustment 4 AGC 5 VREF2 6 NC 7 GND2 Ground for AM part 8 AMIN AM input AGC output Reference voltage 2 output Not connected 9 NC 10 AMOUT Not connected AM output 11 AMOUT1 AM output 12 VREF1 13 AGCADJ 14 VS 15 FMOUT 16 NC Reference voltage 1 output Adjustment FM wide-band AGC threshold Supply voltage FM output Not connected U4254BM-M 4772B–AUDR–11/03 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 3. Internal Circuit at Pin FMIN 1 FMIN ESD GND1 To avoid cross-talk between AM and FM signals, the circuit has two separate ground pins. GND1 is the ground for the FM part. FMGAIN 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 4. Internal Circuit at pin FMGAIN ESD FMGAIN AGC 3 DC current flows into the AGC 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 AGC pin is approximately 1 mA. In low-end applications, the AGC function is not necessary and the external components can therefore be omitted. 3 4772B–AUDR–11/03 Figure 5. Internal Circuit at Pin AGC AGC 4 ESD VS AGCADJ The threshold of the AGC can be adjusted by varying the DC current at pin AGCADJ. If pin AGCADJ is connected directly to GND1, the threshold is set to 96 dBµV at the FM amplifier output. If a resistor is connected between AGCADJ and GND1, the threshold is shifted to higher values with increasing resistances. If AGCADJ is open, the threshold is set to 106 dBµV. Figure 6. Internal Circuit at Pin AGCADJ 65 kΩ ESD 13 FMOUT AGCADJ The FM amplifier output is an open collector of a bipolar RF transistor. It should be connected to VS via a coil. Figure 7. Internal Circuit at Pin FMOUT 15 FMOUT ESD 4 U4254BM-M 4772B–AUDR–11/03 U4254BM-M AMIN The AM input has an internal bias voltage. The DC voltage at this pin is VRef1/2. The input resistance is about 470 kΩ. The input capacitance is less than 10 pF. Figure 8. Internal Circuit at Pin AMIN VREF1/2 470 kΩ 8 AMIN ESD 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 9. Internal Circuit at Pins AMOUT1 and AMOUT AMOUT1 ESD 11 AMOUT ESD VREF1 10 VREF1 is the stabilized voltage for the AM amplifier and the AGC 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 4772B–AUDR–11/03 Figure 10. Internal Circuit at Pin VREF1 VS 12 VREF1 ESD 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 11. Internal Circuit at Pin VREF2 5 VREF2 ESD GND1 GND2 6 GND2 is the ground for the AM amplifier. U4254BM-M 4772B–AUDR–11/03 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 (AGC) is included on the chip. The AGC 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 AGC is adjustable. Simple and temperature-compensated biasing is possible due to the integrated voltage reference VRef2. 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 VS 8.8 V Power dissipation, Ptot at Tamb = 85° C Ptot 460 mW Junction temperature Tj 150 °C Ambient temperature Tamb -40 to +85 °C Storage temperature Electrostatic handling (HBM at ESD S.5.1) Tstg -50 to +150 °C ±VESD ±1000 V Symbol Value Unit RthJA 140 K/W Thermal Resistance Parameters Junction ambient 7 4772B–AUDR–11/03 Electrical Characteristics VS = 8 V, Tamb = 25° C, unless otherwise specified (see Figure 12 on page 9). Parameters Test Conditions Pin Symbol Min. Typ. Max. Supply voltage 14 VS Supply currents 14 IS Reference voltage 1 output (I12 = 0) 12 Reference voltage 2 output (I5 = 0) Temperature dependence of VREF2 Unit 7.2 8 8.8 V 3.5 4.8 5.6 mA VRef1 5.1 5.4 5.7 V 5 VRef2 2.3 2.6 2.8 V 5 VRef2/∆T -1 mV/K Input resistance 8 RAMIN 470 kΩ Input capacitance 8 CAMIN 10 ROUT 125 8, 10 a 0.85 VN1 VN2 -2 -6 dBµV dBµV -65 dBc AM Amplifier Output resistance Voltage gain 10 Output noise voltage (rms value) S1 switched to 2 B = 6 kHz 150 kHz to 300 kHz 500 kHz to 6.5 kHz 10 2nd harmonic S2 switched to 1 fAMIN = 500 kHz Output voltage = 110 dBµV 10 Supply current limit IAGC, IAGCADJ = 0 A 15 I15 33 Input resistance f = 100 MHz 1 RFMIN 50 pF Ω FM Amplifier 35 mA Ω Output resistance f = 100 MHz 15 RFMOUT 50 Ω Power gain f = 100 MHz 1, 15 G 5 dB Output noise voltage f = 100 MHz B = 120 kHz 15 VN 0 dBµV 3rd-order output intercept f = 100 MHz 15 132 dBµV 15 AGC input voltage threshold f = 100 MHz S2 switched to 1; AGC threshold DC current is 10 µA at pin 4 Vth1 96 dBµV 15 AGC input voltage threshold f = 100 MHz, S2 switched to 2; AGC threshold DC current is 10 µA at pin 4 Vth2 106 dBµV AGC output current AGC active AGC 8 IAGC 1.2 mA U4254BM-M 4772B–AUDR–11/03 U4254BM-M Figure 12. Test Circuit VS 1 FMOUT 2 2.2 µH S2 5 kΩ 2.2 nF AMOUT I14 I15 I3 2.2 µF 2.2 nF 100 nF 100 nF + 16 9 1 8 150 Ω I4 FMIN 2.2 µH 2.2 nF S1 2.2 nF 51 Ω 2 1 22 Ω 15 pF VS 1 nF 2.2 nF AMIN 9 4772B–AUDR–11/03 Figure 13. FM Intermodulation Distortion dBµV dBµV Output 108 dBµV Input 103 dBµV 58 dBµV Gain = 5 dB AGC not active 90 95 100 105 Input dBµV 90 MHz 95 100 105 MHz dBµV 118 dBµV Output 100 dBµV 50 dBµV AGC active 90 10 95 100 105 MHz 90 95 100 105 MHz U4254BM-M 4772B–AUDR–11/03 U4254BM-M Figure 14. Test Circuit for AM Large Signal Behavior Analyzer AMOUT1 100 nF LPF AMIN DUT AMOUT fcutoff = 500 kHz Rin = 50 Ω 5 kΩ 1 nF 100 nF 50 Ω 115 dBµV 75 dBµV 50 Ω f = 500 kHz V0 Figure 15. AM Harmonic Distortion VAMOUT (dBµV) 115 dBµV 110 90 70 55 dBµV 45 dBµV 50 0.5 1.0 1.5 f (MHz) 11 4772B–AUDR–11/03 12 PIN V 200 nF BA679 1 nF 2.2 nF 2.2 nF 1 kΩ 2.2 nF 51 R2 Vs 33 51 86 160 150 270 390 470 620 100 125 150 22 R2 (Ω) 75 R1 (Ω) AMIN VREF2 VS AGC FMGAIN FMGND FMIN 50 FM cable impedance R1 and R2 depend on used FM cable impedance Protection circuit BC558 510 Ω 2.2 nF FM ANTENNA AM VRef FM IAGC 2.2 nF AM AMGND AGC R1 AMOUT AMOUT1 VREF1 AGCADJ FMOUT + 1 µF 100 nF 100 nF 2.2 µH VS = 8.2 V 2.2 µH 39 pF Output Figure 16. Application Circuit U4254BM-M 4772B–AUDR–11/03 U4254BM-M Ordering Information Extended Type Number Package Remarks U4254BM-MFP SO16 – U4254BM-MPG3 SO16 Taping corresponding, ICE-286-3 Package Information Package SO16 Dimensions in mm 5.2 4.8 10.0 9.85 3.7 1.4 0.25 0.10 0.4 1.27 6.15 5.85 8.89 16 0.2 3.8 9 technical drawings according to DIN specifications 1 8 13 4772B–AUDR–11/03 Atmel Corporation 2325 Orchard Parkway San Jose, CA 95131, USA Tel: 1(408) 441-0311 Fax: 1(408) 487-2600 Regional Headquarters Europe Atmel Sarl Route des Arsenaux 41 Case Postale 80 CH-1705 Fribourg Switzerland Tel: (41) 26-426-5555 Fax: (41) 26-426-5500 Asia Room 1219 Chinachem Golden Plaza 77 Mody Road Tsimshatsui East Kowloon Hong Kong Tel: (852) 2721-9778 Fax: (852) 2722-1369 Japan 9F, Tonetsu Shinkawa Bldg. 1-24-8 Shinkawa Chuo-ku, Tokyo 104-0033 Japan Tel: (81) 3-3523-3551 Fax: (81) 3-3523-7581 Atmel Operations Memory 2325 Orchard Parkway San Jose, CA 95131, USA Tel: 1(408) 441-0311 Fax: 1(408) 436-4314 RF/Automotive Theresienstrasse 2 Postfach 3535 74025 Heilbronn, Germany Tel: (49) 71-31-67-0 Fax: (49) 71-31-67-2340 Microcontrollers 2325 Orchard Parkway San Jose, CA 95131, USA Tel: 1(408) 441-0311 Fax: 1(408) 436-4314 La Chantrerie BP 70602 44306 Nantes Cedex 3, France Tel: (33) 2-40-18-18-18 Fax: (33) 2-40-18-19-60 ASIC/ASSP/Smart Cards 1150 East Cheyenne Mtn. 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