All-band AM/FM Receiver and Audio Amplifier IC U2510B

Transcription

1 Features Superior Strong Signal Behavior by Using an RF AGC Soft Mute and HCC for Decreasing Interstation Noise in Mode Level Indicator (LED Drive) for and DC Mode Control:, and Tape Wide Supply-voltage Range and Low Quiescent Current High AF Output Power: 1 W Electronic Volume Control Electronic AF Bandwidth Control (Treble and High Cut) Output Stage for Headphone and Speaker Drive Benefits Excellent AFC Performance (Level Controlled, Both Polarities Available) Description The U251B is an integrated bipolar one-chip / radio circuit. It contains an front-end with preamplifier, IF and demodulator, a complete receiver, an AF amplifier and a mode switch for, and tape. This circuit is designed for clock radios and portable radio-cassette recorders. All-band / Receiver and Audio Amplifier IC U251B Rev.

2 Figure 1. Block Diagram antenna RF tank osc. tank IF BPE (Replaceable) RF BPE AGC ant. osc. tank V Ref front end AGC front end Voltage stab. and mode control AFC RF AGC / AFC control IF AGC IF amp. and detect. AGC IF IF amp. Level indic. discr. Power amp. AF preamp. Volume Mute HCC S 2 Tape AFC mode LED Treble Vol 2 U251B

3 U251B Pin Configuration Figure 2. Pinning SDIP28 MUTE 1 28 AF-GND -DISCR 2 27 AFOUT CF 3 26 VS VOL CTRL IN 4 25 RIPPLE IN OSC 5 24 AFIN -AFC 6 23 / DETECT OSC 7 22 VAGC/AFC VREF 8 21 AFC SWITCH TANK 9 2 IF-GND TANK 1 19 LED DRIVE -AGC VTREBLE IN IN IFIN FE-GND IFIN / IFOUT MODE CTRL SWITCH 3

4 Pin Description Pin Symbol Function 1 Mute Mute voltage output. The time constant (C 23 ), mute depth and threshold are adjustable by load resistance (R 3 ) 2 -DISCR discriminator filter connection, ceramic resonator or equivalent LC-circuit 3 CF Audio negative feedback input. The blocking capacitor (C 8 ) determines the audio amplifiers low-end cut-off frequency 4 VOL CTRL IN Input for volume control voltage 5 OSC oscillator tank circuit input. The recommended load impedance is approximately 2.5 kω. 6 -AFC AFC diode connection. The coupling capacitor (C 19 ) determines the AFC characteristic (holding range and slope) 7 OSC oscillator tank circuit input. The recommended load impedance is approximately 3 kω. 8 VREF Regulated voltage output (2.4 V) 9 TANK RF tank circuit connection. The recommended load impedance is approximately 3 kω. 1 TANK RF tank circuit connection. The recommended load impedance is approximately 2 kω. 11 -AGC AGC voltage output, time constant (C 2 ). Loading this pin by a resistor (to GND) will increase the AGC threshold, grounding this pin will switch off the AGC function 12 in RF input (common-base preamplifier transistor). The recommended (RF) source impedance is approximately 1 Ω. 13 FE-GND front-end ground 14 / IFOUT / IF output (collector output of the IF preamplifier) Mode control input: MODE Pin Function 15 CTRL open SWITCH Ground (R 4 = 1 kω) Tape 16 -IFIN IF input, input impedance = 3.1 kω 17 -IFIN IF input, input impedance = 33 Ω 18 VTREBLE IN Treble control voltage input 19 LED DRIVE Level indicator output (open-collector output, LED drive) 2 IF-GND IF ground AFC function control input: Pin Function AFC 21 open AFC off SWITCH Ground f OSC > f in f OSC < f in 22 VAGC/AFC AGC/AFC voltage, time constant adjust (C 1 ). The input impedance is approximately 42 kω 23 / DETECT / detector output. The load capacitor (C 11 ) in conjunction with the detector output resistance (7.5 kω) determines the () de-emphasis as well as the (modulation) frequency response of the detector. Audio amplifier input. The input resistance is approximately 1 kω, the coupling capacitor (C 24 AFIN 9 ) determines the low frequency response 25 RIPPLE IN Ripple filter connection. The load capacitance (C 12 ) determines the frequency response of the supply-voltage ripple rejection 4 U251B

5 U251B Pin Description (Continued) Pin Symbol Function 26 VS Supply voltage input 27 AFOUT Audio amplifier output 28 AF-GND Ground of the audio power stage Terminal Voltages Voltage/V = 3 V = 6 V Pin Function Symbol TAPE TAPE 1 Mute voltage (R 3 = ) V discriminator V Negative feedback V Volume control input (S 4 = A) V oscillator V AFC V oscillator V V Ref V RF tank V input V AGC V input V Front-end ground V / IF output V Mode control switch V IF input V IF input V Treble control input (S 5 = A) V LED V IF ground V 2 21 AFC switch (S 3 = off) V AGC ()/AFC () V Detector output V AF input V Ripple filter V Supply voltage V AF output V AF ground V 28 5

6 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. Parameters Symbol Value Unit Supply voltage 13 V Power dissipation P tot 9 mw Ambient temperature range -2 to +75 C Electrical Characteristics = 6 V,, Test Circuit on page 12, unless otherwise specified Parameters Test Conditions Pin Symbol Min. Typ. Max. Unit Supply voltage range (1) V Oscillator stop voltage 2.2 V Operating temperature range T C Supply quiescent current V i1 = V i2 = V 4 = ; (S 2 = ) (S 2 = ) TAPE (S 2 = Tape) Regulated voltage 8 V Ref 2.4 V Audio Amplifier V i3 (pin 24), test point: V o (pin 27) f = 1 khz AF measuring range: 3 Hz to 2 khz, S 2 = Tape, S 4 = A, S 5 = A Input resistance 24 R j 1 kω GV Closed loop voltage gain af1 = 2 log (V o /V i3 ) V i3 = 1 mv GV af1 4 db Output voltage V i3 = 1 mv, S 4 = B V o.7 3 mv High-end cut-off frequency Supply-voltage rejection ratio f c (-3 db) S 5 = B I S I S I S f c f c 13.8 SVRR = 2 log (V hum /V o ) V hum = 2 mv, f hum = 2 Hz, S 4 = B SVRR 32 db Noise voltage S 4 = B, V i3 = V n 3 1 µv THD = 1%, R L = 8 Ω = 4.5 V = 6. V = 9. V P AF output power o 225 P o 4 42 P o 1 Distortion P o = 5 mw, R L = 8 Ω d.6 % Section, V i2 = 6 dbµv, f i2 = 98 MHz, f m = 1 khz, deviation = ±22.5 khz, f iif = 1.7 MHz, AF measuring range: 3 Hz to 2 khz, S 2 =, S 1 = A, S 6 = B, test point: V D (pin 23) front-end voltage gain GV = 2 log (V iif /V i2 ) S 1 = B, V i2 = 4 dbµv GV 3 db Recovered audio voltage 23 VD af 85 mv Detector output resistance 23 R Do 7.5 kω Note: 1. U251B-M_T: maximum 6 V ma ma ma khz khz mw mw mw 6 U251B

7 U251B Electrical Characteristics (Continued) = 6 V,, Test Circuit on page 12, unless otherwise specified Parameters Test Conditions Pin Symbol Min. Typ. Max. Unit Detector output distortion dev. = ±75 khz V i2 = 6 dbµv V i2 = 15 dbµv rejection ratio m = 3% RR 25 db RF sensitivity (S+N)/N = 26 db (S+N)/N = 46 db THD THD.5.8 V i2 9 V i2 22 Limiting threshold (-3 db) V i2 3 dbµv Mute voltage Mute depth AFC holding range Test point: Mute V i2 = V i2 = 6 dbµv Referred to V at V i2 = S 6 = A S 6 = C f OSC > f in, S 3 = A, S 6 = A V i2 1 dbµv V i2 = 2 dbµv V i2 = 8 dbµv V mute V mute MD MD FHR FHR FHR 26 2 no AFC ±18 ±22 LED current I LED 5.5 ma Oscillator voltage ez load = 2.5 kω 7 V OSC 18 mv Section V i1 = 6 dbµv, f i1 = 1.6 MHz, f m = 1 khz, m = 3%, f iif = 455 khz, AF measuring range: 3 Hz to 2 khz, (S 2 =, S 1 = B, test point: V D ) front-end voltage gain GV = 2 log (V iif /V i1 ) V i1 = 2 dbµv, S 1 = A GV 25 db Recovered audio voltage V D af1 7 mv Detector output resistance 23 R Do 7.5 kω Detector output distortion RF sensitivity AGC figure of merit referred to V Daf V i1 = 6 dbµv V i1 = 15 dbµv (S+N)/N= 1 db (S+N)/N= 26 db (S+N)/N= 46 db V i1 = 15 dbµv, voltage drop (V Daf ) = -1 db THD THD V i1 V i1 V i % % dbµv dbµv V V db db khz khz % % dbµv dbµv dbµv FOM 1 db IF input resistance 16 Z i 3.1 kω LED current I LED 5.5 ma Oscillator voltage 5 V OSC 16 mv Note: 1. U251B-M_T: maximum 6 V 7

8 d (%) V U (db) I S (ma) Figure 3. Quiescent Current Tape (V) 12 Figure 4. AF Section 5 4 without treble control 3 with treble control 2 V i = 5 mv 1 = 6 V R L = 8 Ω f (khz) 1 Figure 5. AF Section: Distortion 1 8 f = 1 khz 6 4 = 3 V = 6 V = 9 V R L = 32 Ω R L = 8 Ω R L = 8 Ω P o (mw) 1 8 U251B

9 V o (dbv) P o (mw) P o (mw) U251B Figure 6. AF Section: Maximum Output Power 1 1 R L = 4 Ω Ω 16 Ω 32 Ω 1 (V) f = 1 khz d = 1% 5 Figure 7. AF Section: Supply-voltage Rejection Ratio 4 32 f = 2 Hz (V) f = 1 Hz V hum = 2 mv = 6 V R L = 8 Ω 12 Figure 8. Section: Mute Voltage R 3 = = 6 V kω kω V i (dbµv)

10 I LED (ma) V o (dbv) V D (dbv) Figure 9. Section: Demodulator Output Level S+N (m = 8%) N S+N (m = 3%) = 6 V f i1 = 1.6 MHz f AF = 1 khz -8 d (m = 8%) V i (dbµv) d (m = 3%) Figure 1. Volume Control Range Characteristics -2 = 6 V V i3 = 1 mv f AF = 1 MHz f AF = 1 khz -4 Treble Voltage V V 4 (V) Treble Voltage = 2.5 Figure 11. / Level Indicator Current 6 5 I LED = 6 V V i (dbµv) U251B

11 V o (dbv) V D (dbv) V AGC (V) U251B Figure 12. Section: AGC Voltage (at Pin 22) = 6 V.4 f i1 = 1.6 MHz V i (dbµv) Figure 13. Section: Demodulator Output Level -2-4 S+N( f = ±75 khz) S+N( f = ±22.5 khz) (m = 3%) = 6 V f i2 = 98 MHz f AF = 1 khz V i (dbµv) N d( f = ±75 khz) d( f = ±22.5 khz) Figure 14. Section: Audio Output Level 68 kω 1 kω R 3 = N S+N = 6 V R L = 8 Ω P o = 5 mw at V i2 = 6 dbµv f i2 = 98 MHz f AF = 1 khz f = ±22.5 khz m = 3% d V i (dbµv)

12 V o (dbv) Figure 15. Section: Audio Output Level S+N d V i (dbµv) N P o = 5 mw at V i1 = 6 dbµv R L = 8 Ω f i1 = 98 MHz f AF = 1 khz m = 8% Figure 16. Test Circuit V i1 (5 Ω) R 6 1 Ω C 24 1 nf R 5 15 Ω L A 15 µh C 2 43 pf C 3 22 pf L 1 L 2 C 4 18 pf R kω T 2 C 5 22 pf A S 4 B A S 5 B V i2 (5 Ω) R 8 5 Ω IFT T 1 R 7 75 Ω 455 khz C 25 1 nf 14 C 2 22 nf 4.7 µf C 7 C 6 22 nf C pf T 4 C 25 1 pf C 8 C µf 18 pf R 3 15 kω C nf C S 6 A B V mute CF 1 U251B B A S 1 B A CF MHz R 1 D 1 C 22 1 nf LED off A C 9 S 3 B 1 nf C 15 V iif Tape 39 Ω R 2 22 µf R 9 3 kω S 2 C 21 1 nf 1 kω C 14 C 1 1 nf 1 µf C 11 1 nf C 12 1 µf C µf R L 8 Ω/ 2 W I LED V D V i3 V o GND 12 U251B

13 U251B Application General Circuit Example The U251B is a bipolar monolithic IC for use in radio sets such as headphone receivers, radio recorders and clock radios. The IC contains all,, AF and switching function blocks necessary to design these kinds of radio receivers using only few components around the IC. In the design, special efforts were made to get good performance for all bands (short and long wave). The implementation of enhanced functions (options) makes it possible to improve the radio's performance and to produce radios with interesting features. In this case few (external) parts have to be changed or added. By using all or some of the options offered by the U251B different types or classes of radios can be designed to the customer's requirements with the same IC. One of the main advantages of the U251B is that all receiver functions (including the options) are integrated and tested on a system level. This allows cost savings due to: 1. Shorter development time 2. Higher reproductivity and low reject level in the set production line Another advantage is the wide operating voltage range, especially the upper limit (13 V). This feature allows the use of a soft power supply for line powered radios which can also reduce the set's total cost. Figure 17 on page 15 shows a circuit diagram for low-end /AF radios using the U251B. Figure 18 on page 16 shows a circuit diagram of an /AF radio for higher class designs using all possible options of the U251B. The layout of the PC board, shown in Figure 19 on page 16, is suitable for both the circuit example shown in Figure 17 on page 15 and the circuit example shown in Figure 18 on page 16. The associated coil, varicon and filter specifications are listed in the table: Coil Data and Components on page 17. The circuit diagram in Figure 18 on page 16, has the following options compared to the circuit diagram in Figure 17 on page 15 (the additional parts, which have to be provided, are listed in parentheses): a) Soft mute and high cut control in mode (1 capacitor) b) Electronic treble control in, and TAPE mode (1 pot.) c) On-chip mode control for TAPE application d) RF AGC in mode (1 capacitor) e) AFC, adjustable to the correct polarity and slope (1 capacitor) f) Tuning indication using a LED as an indicator (1 LED, 1 capacitor) Option a) reduces the interstation noise by the two functions: soft mute and HCC. Both are controlled by the mute voltage (pin 1). The soft mute reduces the loudness only, while the HCC reduces the high-end audio cut-off frequency of the audio preamplifier, when the signal level falls below a given threshold. This signal level threshold as well as the mute depth can be reduced by adding a resistor (R 3 ) or by increasing the frontend gain. Option b) allows the treble control for all operating modes without the need of an additional capacitor. This concept leads to a smooth and correct treble control behavior which is an improvement compared to the controlled RC network normally used. 13

14 Option c) is very useful for applications in radio cassette-recorders, for instance. In TAPE mode, the / receiver blocks are completely switched off and the signal from the tape recorder can be fed to the audio amplifier's input directly. This saves quiescent current and makes the TAPE switching easy. However, to minimize switching noise by the mode switch, the following switch sequence should be chosen:,, TAPE. Option d) improves the strong signal behavior by protecting the mixer against overload. This is provided by the integrated broad-band-width RF AGC. If necessary, the AGC threshold can be decreased by a resistor, loading pin 11 to GND (not shown). Option e) improves the tuning behavior substantially. The special design of the on-chip AFC function means that common disadvantages such as asymmetrical slope, (chip-) temperature effects and unlimited holding range are avoided. As mentioned in the Pin Description on page 4, the AFC slope has to be inverted when the local oscillator (LO) frequency has to be below the receiving frequency. This can be achieved by connecting pin 21 to the potential of pin 8. In addition to the options described above, the following proposals are implemented in the circuit diagram (Figure 18 on page 16), too: An IFT is applied. This improves the channel selectivity and minimizes substantially the spurious responses caused by the ceramic filter (CF2). With the choice of the winding ratio of this IFT, the front-end gain can be matched to other values if necessary. In the RF input section, the low cost antenna filter (L 5, C 15 ) is replaced by a special band-pass filter (PFWE8). Such a BPF protects the front-end against the out-off-band interference signals (TV channels, etc.) which could disturb the reception. Design Hints The value of the power supply blocking capacitor C 13 should not be below 47 µf. In addition, this capacitor should be placed near pin 26. This will help to avoid unacceptable noise generated by noise-radiation from the audio amplifier via the bar-antenna. In designs where the supply voltage goes below 2.5 V, the value of the blocking capacitor (C 7 ) should be chosen as 47 µf or even higher. To achieve a high rejection of short wave reception in medium wave operation, the LO amplitude at pin 5 should not exceed approximately 2 mv. This LO amplitude depends on the LO transformer's Q and its turns ratio. For the LO transformer type described in the Table Coil Data and Components on page 17, a resistor R 4 (2.2 kω for example) in parallel to the secondary side of the LO transformer T 2 is recommended. To minimize feedback effects in the RF/IF part in mode, the capacitor C 6 should be placed as near to pins 8 and 2 as possible. As shown in the application circuit diagrams (Figure 17 on page 15 and Figure 18 on page 16), in mode ceramic filter devices are used for channel selection (CF 2 ) while for, demodulation in LC-discriminator circuit (T 4, C 24, C 25 ) is used instead of a ceramic discriminator device. Such an LC discriminator circuit can be easily matched to the IF selectivity block by its alignment. The zero-crossing of the discriminator can be detected at the demodulator output (pin 23). The zero-crossing voltage is equal to half of the regulated voltage at pin 8. The alignment of the LC-discriminator circuit should be done with little or no effect on the AFC function. This can be realized by: switching pin 21 to an open-circuit connecting pin 1 to a voltage source of 2 V using a low signal level for alignment 14 U251B

15 U251B In principle, ceramic discriminator devices can also be used. In this case, the effect of unavoidable spreads in the frequency characteristics of these case ceramic devices have to be considered. For example, mismatches of the characteristics between selectivity block and discriminator will lead to an increased signal-to-noise ratio at low signal levels as well as to a higher demodulation distortion level or to an asymmetrical AFC. Application Circuits Figure 17. Application Circuit for Low-cost Applications Antenna C pf L 3 C 2 2 pf C 3 22 pf L 1 L 2 C 4 27 pf T 2 C 5 Volume P 1 6 pf 5 kω C 18 C pf 33 pf L 4 C 7 C 6 T 4 C 25 1 pf 4.7 µf 22 nf IFT C µf C pf T khz CF 1 U251B CF 2 C 9 R 1 39 Ω 1.7 MHz 1 nf 1 nf C µf S 1 C 14 Z = 8 Ω S 2 C µf C 11 C 12 C 13 1 nf 4.7 µf 47 µf 15

16 Figure 18. Application Circuit (Upgraded), R 2 Only if > 8 V Antenna L 3 C 2 C 3 C 4 T 2 2 pf 22 pf L 1 L 2 27 pf 6 pf C 5 Volume Treble P 1 P 2 5 kω 5 kω BPF 1 R kω T 4 C 7 C 6 C 25 1 pf C 23 IFT 14 C 2 22 pf 4.7 µf 22 nf C pf C µf C pf (R 3 ) Mute Adj. 68 nf T khz CF 1 U251B IFT T 3 CF 2 C 22 C 9 1 pf 1.7 MHz D 1 1 nf LED 22 nf 1 nf C µf S 1 R 2 C 14 Tape S 2 C 21 1 nf 1 kω C 1 1 µf C 11 C 12 C 13 1 nf 4.7 µf 47 µf IN Tape Figure 19. PC Board 16 U251B

17 U251B Coil Data and Components Part Stage L or C Wire Diameter/mm Terminal Number Number of Turns Type Manufacturer T 1 IFT 18 pf 1 to to to to 6 7 7MC-7789N Toko 21K7-H5 Mitsumi T 2 OSC 27 mh 1 to to to TRS-8441 Toko L 5K7-H5 Mitsumi T 3 IFT (optional) 1 pf 1 to to to to 6 2 7P A119 AC Toko T 4 discriminator 1 pf 1 to to 3 1 7P A119 AC Toko L 1 RF air coil 4 mm diameter L 2 OSC air coil 4 mm diameter L 4 antenna air coil 4 mm diameter Part Stage Type Manufacturer L 3 bar antenna L: 63 µh total turns : 96 tap: 19 BPF1 (optional) PFWE8 (88 to 18 MHz) Soshin Electric Co. CF 1 CF 2 Figure 2. Figure of Wirewound Components SFU-455B BFCFL-455 SFE1.7MA5 CFSK 17M1 Murata Toko Murata Toko CF 3 (optional) CDA1.7MC1 Murata C 1 Variable capacitor HD22124 / Toko 4 mm 3 mm 8 mm mm 1 6 C 1 Pin 1 Pin 8 Coil, bottom view Air coil bar antenna 17

18 Ordering Information Extended Type Number Package Remarks U251B-M SDIP28 Package Information Package SDIP28 Dimensions in mm technical drawings according to DIN specifications 18 U251B

19 Atmel Corporation 2325 Orchard Parkway San Jose, CA 95131, USA Tel: 1(48) Fax: 1(48) Regional Headquarters Europe Atmel Sarl Route des Arsenaux 41 Case Postale 8 CH-175 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(48) Fax: 1(48) Microcontrollers 2325 Orchard Parkway San Jose, CA 95131, USA Tel: 1(48) Fax: 1(48) La Chantrerie BP Nantes Cedex 3, France Tel: (33) Fax: (33) ASIC/ASSP/Smart Cards Zone Industrielle 1316 Rousset Cedex, France Tel: (33) Fax: (33) East Cheyenne Mtn. Blvd. Colorado Springs, CO 896, USA Tel: 1(719) Fax: 1(719) Scottish Enterprise Technology Park Maxwell Building East Kilbride G75 QR, Scotland Tel: (44) Fax: (44) RF/Automotive Theresienstrasse 2 Postfach Heilbronn, Germany Tel: (49) Fax: (49) East Cheyenne Mtn. Blvd. Colorado Springs, CO 896, 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 24. All rights reserved. Atmel and combinations thereof are the registered trademarks of Atmel Corporation or its subsidiaries. Toko is a registered trademark of TOKO KABUSHIKI KAISHA TA Toko, Inc. Mitsumi is a registered trademark of MITSUMI DENKI KABUSHIKI KAISHA CORPORATION JAPAN. Murata is a registered trademark of Murata Manufacturing Co., Ltd. CORPORATION Japan. Other terms and product names may be the trademarks of others. Printed on recycled paper.