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TELEFUNKEN Semiconductors
U4314B
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 Wide power supply voltage range 3 to 12 V D Temperature compensated reference voltage of 2.4 V
externally available
D Usable for ASK data systems up to several hundred
kBauds
D Only one additional part (capacitor) necessary D ESD hardened
D Extreme low current consumption typically 0.8 mA
Block diagram
VS 8 5 IFin IF - amplifier VRef internal Log RSSI / AM demodulator 1, 2, 3, 6
95 10215
8 Bandgap
VRef
CRef 4 log RSSI log AMout GND
Figure 1. Block diagram
Rev. A1: 26.06.1995
1 (7)
U4314B
Pin Description
VS VRef GND
TELEFUNKEN Semiconductors
GND
1
8
GND GND AMout
2
7
3
6
Pin 1, 2, 3, 6 4 5 7 8
Symbol GND AMout IFin VRef VS
Function Ground RSSI / AM current output IF input Reference voltage Supply voltage
4
95 10461
5
IFin
Figure 2. Pin description
Absolute Maximum Ratings
Parameters Supply voltage Power dissipation at Tamb = 85C 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
Thermal Resistance
Parameters Junction ambient Symbol RthJA Value 180 Unit K/W
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Rev. A1: 26.06.1995
TELEFUNKEN Semiconductors
U4314B
Electrical Characteristics
VS = 5 V, Tamb = 25C, 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 Pin 8 Pin 8 Pin 7 Pin 7 Pin 7 Pin 7 Pin 7 Symbol VS IS Vref Rref Iref Cref psrr Min. 3 0.8 2.3 2.4 2 4.7 60 Typ. Max. 12 1.25 2.5 5 5 Unit V mA V
W
mA
mF W
f = 50 Hz
dB
Pin 5 Pin 5 Pin 5 Pin 5 Rload = 10 kW VIFin = 96 dBmV, Rload = 10 kW Pin 4 Pin 4
Rin Cin VIFin VIFinmax IAMout IAMoutmax
200 26
330 5 36 96 22 105
650 46
pF dBmV dBmV
10 75
38 125
mA mA
Circuit Description
General functions The integrated circuit U4314B includes the following functions: IF-amplifier, logarithmic RSSI / AM demodulator and voltage-regulator. 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
1, 2, 3, 6
95 10216
Figure 3. Pin 1, 2, 3, 6
7
GND
95 10219
Rev. A1: 26.06.1995
3 (7)
U4314B
95 10220
TELEFUNKEN Semiconductors
VS VRef CRef = 4.7 mF IFin 56
5
4.7 mF
W W
300 100 nF
10 nF 8 Figure 5. Pin 5 IFin 7 6 5
U4314B
95 10224
8
1
2
3
4
10 k W
Rload =
RSSI / AMout
7
Figure 8. Test circuit
95 10222
120 90 dBmV AM Output Current (m A ) 100 80 70 dBmV 60 50 dBmV 40 30 dBmV 20 0 56
95 10463 95 10223
Figure 6. Pin 7 VRef
8
7
8
9 10 11 12 13 14 15 16 IF-Frequency ( MHz)
Figure 7. Pin 8 VS
Figure 9. IF-Frequency response
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Rev. A1: 26.06.1995
TELEFUNKEN Semiconductors
U4314B
+85C AM Output Current ( m A ) 110
95 10335
120 AM Output Current (m A ) 100 +25C 80 60 40 20 0 10
95 10462
70 60 50 40 30 20 10 0
-40C
30
50
70
90
0
20
40
60
80
100
IF-Input Level ( dBmV )
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 4.7 mF 10 nF 10 nF 8 7 6 5 56 kW 10 nF 14 13 12 11 10 VRef BA679S 4.7 mF 270 W 750 W 6.8 kW 6.8 kW 10 nF
TELEFUNKEN Semiconductors
GND
10 nF
IFin VIFin
Rg = 50W
9
8
50 W
Vg
[
U4314B
P1 1 2 3 4 10 kW 1 2 3
CA3045
4
5
6 10 nF
7 5.1 kW
100 nF
95 10225
100 mA 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
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