U4276B FM Multipath Noise Cancellation Description The U4276B is a bipolar integrated multipath noise cancellation circuit. It is designed for high performance car radio applications. Features D Mute function controllable by microcomputer D Preparation of the fieldstrength signal D Multipath noise cancellation D Suitable for analogue as well as digital processing D Only a few external components necessary Block Diagram BFSOUT VS 6 7 3 2 Buffer FSIN 1 AVFS Multipath detection 4 Bandgap Multipath noise cancellation GND 5 MPXOUT MPXIN 8 95 10619 MUTE Pin Description Pin 1 2 3 4 5 6 7 8 Symbol AVFS FSIN GND MPXIN MPXOUT VS BFSOUT MUTE Function Average of fieldstrength signal Fieldstrength input Ground Multiplex input signal Multiplex output signal Supply voltage Buffered fieldstrength output External mute input TELEFUNKEN Semiconductors Rev. A1, 05-Sep-96 8 MUTE AVFS 1 FSIN 2 7 BFSOUT GND 3 6 VS MPXIN 4 5 MPXOUT 95 10632 1 (8) Preliminary Information U4276B FSIN / BFSOUT MPXIN / MPXOUT VS 40 mA VS 50 kW MPXIN BFSOUT 50 kW FSIN 94 8647 94 8649 All information about reception conditions is derived from the fieldstrength signal. The fieldstrength signal at FSIN is initially buffered so as not to impair the characteristics of the IF IC and is available at BFSOUT. VS VS 60 kW MPXOUT AVFS 40 mA 60 kW 200 mA 94 8650 AVFS 94 8648 The fieldstrength signal at buffer output BFSOUT is averaged over time and applied to input AVFS via an RC low-pass filter with a large time constant. The MPX signal is fed directly from the FM demodulator to input MPXIN and is available amplified by a factor of 1.5 at MPXOUT. The MPX signal is blanked out in the event of multipath interference or when MUTE is activated externally in the circuit part MNC (Multipath Noise Canceller). In all other cases, the MPX signal passes through the IC unchanged. MUTE MUTE 94 8651 The function unit MNC can be controlled externally via this pin. Blanking occurs when the voltage at the MUTE pin falls below 1 V. 2 (8) Preliminary Information TELEFUNKEN Semiconductors Rev. A1, 05-Sep-96 U4276B 1. A linear characteristic, i.e. the output voltage must be proportional to the logarithm of the IF voltage in the range of RF levels encountered in practice. Deviations from linearity lead to a different evaluation of interference signals of the same intensity of the signal levels are different. Functional Description Interference with FM reception can be triggered by various causes, such as multipath reception, adjacent and insufficient field strength. At the same time, multipath reception is responsible for the most frequently occurring types of interference. 2. The “signal level” output has to react to extremely fast dips in the field strength. Total field strength failures lasting 500 ns and occuring a voltage dip to approx. 0 V at the field strength output. Acoustically relevant multipath interference, since it requires a short reaction time, is suppressed directly by the circuit via a Multipath Noise Cancellation (MNC) function. Restrictions The U4276B can be used both in conventional receivers and in receivers with digital signal processing. The field strength voltage becomes increasingly noisy in the range of low RF levels (< 30 dBmV). The noise prevents reliable detection of interference. Therefore, only the average field strength value can be evaluated over a relatively large time constant in this range. The following demands are placed on the field strength output of the IF amplifier: AFleft MPX in MPX out FM – tuner U4276B Digital or analogue signal processing AFright Fieldstrength signal Mute System controller 95 10633 Figure 1. Block diagram Multipath Noise Cancellation (MNC) Extremely strong multipath interference remains audible in spite of the monoblend function. The remaining interference is reduced still further by the MNC circuit if the output MPXOUT is muted for a few microseconds while the interference is still occuring (figure 2). In order to eliminate the possibility of malfunctions, activation of the MNC depends on the following condition: TELEFUNKEN Semiconductors Rev. A1, 05-Sep-96 – The average field strength must exceed a certain value so that the noise in the field strength signal does not cause the MNC to respond at low RF voltages The MNC function can also be activated externally via the MUTE pin (low active). The circuit can therefore also be used as a fast high performance mute stage. 3 (8) Preliminary Information U4276B 94 8663 Figure 2. In order to achieve best performance, the MNC-circuit has to be adapted well to the fieldstrength output of the IF-IC. This can be done by adjustment of the DC-level at Pin Mute (R2/R3, see figure 4) in the range of V/2 The principle behaviour is shown in figure 3. " 1 V. 95 10694 Field strength V Mute V Mute + V2 S t V2 S V Mute u V2 S 1.17 V MNC activation level (AVFS) RF level (dBmV) 30 Figure 3. 4 (8) Preliminary Information TELEFUNKEN Semiconductors Rev. A1, 05-Sep-96 U4276B 95 10695 VS R2 Mute R3 Figure 4. Absolute Maximum Ratings Reference point Pin 1b, unless otherwise specified Parameters Supply voltage Pin 6 Supply current Pin 6 Ambient temperature range Storage temperature range Junction temperature Electrostatic handling (MIL standard 883 C) Symbol VS IS Tamb Tstg Tj VESD Value 10 t.b.d. – 30 to + 85 –55 to +150 125 2000 Unit V mA °C °C °C V Symbol RthJA Maximum t.b.d. Unit K/W " Thermal Resistance Parameters Junction ambient Electrical Characteristics Tamb = 25_C, VS = 8.5 V, unless otherwise specified Parameters Supply voltage Supply current Fieldstrength Input voltage Output voltage Test conditions / Pins Pin 6 Pin 6 Rload Cload Bandwidth Input voltage TELEFUNKEN Semiconductors Rev. A1, 05-Sep-96 Symbol VS IS Min. 8 2 Pin 2 Pin 7 Vi Vout 0 50 Pin 7 Pin 1 BW V 100 0 Typ. 8.5 3 Max. 10 5 Unit V mA 5.0 5000 V mV 5 KHz V 5 (8) Preliminary Information U4276B Parameters Test conditions / Pins Multipath Noise Cancellation MPX input voltage Pin 4 MPX output voltage RL = 10 kW Pin 5 THD RL = 10 kW Pin 5 VMPXIN = 350 mV Bandwidth RL = 10 kW Pin 5 Mute-depth RL = 10 kW Pin 5 Gain RL = 10 kW Pin 5 Mute Input voltage Pin 8 low high Symbol Min. Typ. Max. Unit 0.06 350 525 0.2 VRMS VRMS % VMPXIN VMPXOUT 300 75 kHz dB dB 82 3.5 G VMUTE 0 3 1 VS V Application Circuit VS R1 4.7 mF 100 C3 BFSOUT FSIN 3 2 Buffer R4 C2 1 4 GND Multipath detection Multipath noise cancellation 5 MPXOUT MPXIN 8 95 10620 100 nF Bandgap 56 k 47 k AVFS 680 nF R2 6 7 C1 MUTE R3 mC 56 k 6 (8) Preliminary Information TELEFUNKEN Semiconductors Rev. A1, 05-Sep-96 U4276B Ordering Information Extended type number U4276B-AFP U4276B-AFPG3 Package SO8 plastic SO8 plastic Remarks Taping according to IEC-286-3 Dimensions in mm 94 8862 TELEFUNKEN Semiconductors Rev. A1, 05-Sep-96 7 (8) Preliminary Information U4276B Ozone Depleting Substances Policy Statement It is the policy of TEMIC TELEFUNKEN microelectronic GmbH to 1. Meet all present and future national and international statutory requirements. 2. Regularly and continuously improve the performance of our products, processes, distribution and operating systems with respect to their impact on the health and safety of our employees and the public, as well as their impact on the environment. It is particular concern to control or eliminate releases of those substances into the atmosphere which are known as ozone depleting substances ( ODSs). The Montreal Protocol ( 1987) and its London Amendments ( 1990) intend to severely restrict the use of ODSs and forbid their use within the next ten years. Various national and international initiatives are pressing for an earlier ban on these substances. TEMIC TELEFUNKEN microelectronic GmbH semiconductor division has been able to use its policy of continuous improvements to eliminate the use of ODSs listed in the following documents. 1. Annex A, B and list of transitional substances of the Montreal Protocol and the London Amendments respectively 2 . Class I and II ozone depleting substances in the Clean Air Act Amendments of 1990 by the Environmental Protection Agency ( EPA) in the USA 3. Council Decision 88/540/EEC and 91/690/EEC Annex A, B and C ( transitional substances ) respectively. TEMIC can certify that our semiconductors are not manufactured with ozone depleting substances and do not contain such substances. We reserve the right to make changes to improve technical design and may do so without further notice. Parameters can vary in different applications. All operating parameters must be validated for each customer application by the customer. Should the buyer use TEMIC products for any unintended or unauthorized application, the buyer shall indemnify TEMIC against all claims, costs, damages, and expenses, arising out of, directly or indirectly, any claim of personal damage, injury or death associated with such unintended or unauthorized use. TEMIC TELEFUNKEN microelectronic GmbH, P.O.B. 3535, D-74025 Heilbronn, Germany Telephone: 49 ( 0 ) 7131 67 2831, Fax number: 49 ( 0 ) 7131 67 2423 8 (8) Preliminary Information TELEFUNKEN Semiconductors Rev. A1, 05-Sep-96