U4314B TELEFUNKEN Semiconductors Logarithmic AM Demodulator / RSSI Description The U4314B is a monolithic Integrated Circuit in bipolar technology for low current super-heterodyne receivers. It can be used as a logarithmic Received Signal Strength Indicator (RSSI) or as a logarithmic AM demodulator. Its bandwidth is optimized for intermediate frequencies of 9 to 10.7 MHz (see figure 9). Its low current consumption and wide power supply voltage range make this IC predestined to add a temperature compensated field strength indication to new or existing receiver or instrumentation designs, missing such a function. It can also be used as a logarithmic AM demodulator. Its dynamic range in excess of 60 dB (see figure 10) supports a receiver design without the need of an automatic gain control (AGC). The usable data rate is up to several hundred kBauds. Typical applications are keyless entry and alarm systems for cars and buildings. The U4314B supports a superhet receiver design with less than 1 mA total current consumption, which is a peremptory requirement claimed by international car manufacturers. As this IC needs only 3.0 V supply voltage, the front end may be a stacked design in order to reach this extremely low total receiver current consumption. A proposal for a discrete RF front end with a surface acoustic wave (SAW) resonator based local oscillator special low current UHF-transistors like S822T or S852T can be found in the application notes ANT012 and ANT013. Features D Logarithmic RSSI / AM demodulator output D Sensitive IF-amplifier for 10.7 MHz operating frequency D Usable for ASK data systems up to several hundred kBauds D Extreme low current consumption typically 0.8 mA D Wide power supply voltage range 3 to 12 V D Temperature compensated reference voltage of 2.4 V externally available D Only one additional part (capacitor) necessary D ESD hardened Block diagram VS 8 5 IFin 8 IF – amplifier VRef Bandgap VRef internal CRef 4 Log RSSI / AM demodulator log RSSI log AMout 1, 2, 3, 6 95 10215 GND Figure 1. Block diagram Rev. A1: 26.06.1995 1 (7) U4314B TELEFUNKEN Semiconductors Pin Description 1 GND 8 VS GND 2 7 VRef GND 3 6 GND AMout 4 5 IFin Pin 1, 2, 3, 6 4 5 7 8 Symbol GND Function Ground AMout IFin VRef VS RSSI / AM current output IF input Reference voltage Supply voltage 95 10461 Figure 2. Pin description Absolute Maximum Ratings Parameters Supply voltage Power dissipation at Tamb = 85°C Junction temperature Ambient temperature Storage temperature Symbol VS Ptot Tj Tamb Tstg Value 13 220 125 –40 to +85 –55 to +125 Unit V mW °C °C °C Symbol RthJA Value 180 Unit K/W Thermal Resistance Parameters Junction ambient 2 (7) Rev. A1: 26.06.1995 U4314B TELEFUNKEN Semiconductors Electrical Characteristics VS = 5 V, Tamb = 25°C, fin = 10.7 MHz unless otherwise specified. Test circuit see figure 8. IF voltage levels are referred to the input of the matching network and therefore approximately 5.6 dB higher than referred to Pin 5. Parameters Characteristics Supply voltage range Supply current Bandgap Regulated voltage (without external load) Source resistance Output current External capacitor Power supply rejection ratio IF amplifier Input resistance Input capacitance –3 dB limiting point Maximum AM input voltage AMout quiescent current Maximum AMout current Test Conditions / Pins f = 50 Hz Symbol Min. Pin 8 Pin 8 VS IS 3 Pin 7 Vref 2.3 Pin 7 Pin 7 Pin 7 Pin 7 Rref Iref Cref psrr Pin 5 Pin 5 Pin 5 Pin 5 Rin Cin VIFin VIFinmax 200 IAMout 10 75 Rload = 10 kW VIFin = 96 dBmV, Rload = 10 kW Pin 4 IAMoutmax Typ. Max. Unit 0.8 12 1.25 V mA 2.4 2.5 V 2 5 5 4.7 60 26 W mA mF dB 330 5 36 96 650 W 46 pF dBmV dBmV 22 105 38 125 mA mA Pin 4 Circuit Description General functions The integrated circuit U4314B includes the following functions: IF-amplifier, logarithmic RSSI / AM demodulator and voltage-regulator. 1, 2, 3, 6 95 10216 Figure 3. Pin 1, 2, 3, 6 7 GND 95 10219 The 10.7 MHz IF-signal from the front end passes the integrated IF-amplifier which operates to a logarithmic RSSI / AM-demodulator. A logarithmic demodulator was implemented to avoid settling time problems effected by use of an AGC. The temperature compensated reference voltage of 2.4 V is externally available. The value of the external blocking capacitor can be adapted to the maximum expected load current out of the voltage regulator. The total supply current is typically 0.8 mA plus this load current. 4 Figure 4. Pin 4 AMout Rev. A1: 26.06.1995 3 (7) U4314B TELEFUNKEN Semiconductors VS 95 10220 VRef 56 CRef = 4.7 mF 4.7 mF 5 IFin 300 100 nF W W 10 nF 8 6 7 5 Figure 5. Pin 5 IFin 95 10224 U4314B 1 8 2 3 4 Rload = 10 k W RSSI / AMout 7 Figure 8. Test circuit 120 Figure 6. Pin 7 VRef AM Output Current (m A ) 95 10222 90 dBmV 100 80 70 dBmV 60 50 dBmV 40 30 dBmV 20 8 0 5 6 95 10463 95 10223 Figure 7. Pin 8 VS 4 (7) 7 8 9 10 11 12 13 14 15 16 IF–Frequency ( MHz) Figure 9. IF-Frequency response Rev. A1: 26.06.1995 U4314B TELEFUNKEN Semiconductors 70 +85°C 60 100 AM Output Current ( m A ) AM Output Current (m A ) 120 +25°C 80 –40°C 60 40 20 50 40 30 20 10 0 0 10 30 95 10462 50 70 IF–Input Level ( dBmV ) 90 110 0 95 10335 20 40 60 80 100 IF–Input Level ( dBmV ) Figure 10. AM-demodulator characteristic (fin = 10.7 MHz) Figure 11. IAMout of U4314B in the application circuit of figure 12 (fin = 107 MHz) The following circuit is a mere proposal, how to improve sensitivity and extend the dynamic range of U4314B to more than 90 dB. However in most applications the basic dynamic range of more than 60 dB is sufficient. TEMIC TELEFUNKEN microelectronic GmbH makes no representation that the use of this circuit will not refringe on existing or future patents and no responsibility for the use of the information contained herein is assumed. This circuit is neither optimized concerning tolerances of the components nor tested versus temperature. It should work with a single supply voltage of 3 to 12 V. A npn transistor array CA3045 or similar is used. At least four transistors are needed to realize two current mirrors and the fifth acts as a preamplifier. The variable resistor P1 is used to compensate the quiescent current of the logarithmic demodulator output and may be replaced by a fixed resistor (typ. 3.3 kW). The total supply current depends on the IF-input level and varies between 2 and 7 mA. It is mainly determined by the current through the PIN diode. We recommend to use the BA679S PIN diode available from TEMIC TELEFUNKEN microelectronic GmbH. The input impedance of this application circuit is approximately 1.5 kW || 13 pF. Rev. A1: 26.06.1995 5 (7) U4314B VS TELEFUNKEN Semiconductors VRef GND BA679S 4.7 mF 4.7 mF 6.8 k W 10 nF 10 nF 8 7 6 6.8 kW 750 W 270 W 10 nF 10 nF IFin VIFin 10 nF 14 5 13 12 11 10 9 8 5 6 7 50 W 56 k W P1 2 Vg [ CA3045 U4314B 1 Rg = 50W 3 4 10 k W 1 2 3 4 5.1 k W 10 nF 100 nF 100 mA 95 10225 IAMout Figure 12. Application circuit with a dynamic range in excess of 90 dB Ordering Information Extended Type Number U4314B-AFP Package SO8 Remarks Dimensions in mm Package SO8 94 8862 6 (7) Rev. A1: 26.06.1995 TELEFUNKEN Semiconductors U4314B 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 Rev. A1: 26.06.1995 7 (7)