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U4254BM-M
Low-Noise AM/FM Antenna Impedance Matching IC
Description
The U4254BM-M is an integrated low-noise AM/FM antenna impedance matching circuit in BICMOS technology. The device is designed in particular for car application and is suitable for windscreen and roof antennas. Electrostatic sensitive device. Observe precautions for handling.
Features
D High dynamic range for AM and FM D Integrated AGC for FM D High intercept point 3rd order for FM D FM amplifier adjustable to various cable impedance D High intercept point 2nd order for AM D Low noise output voltage D Low power consumption
Block Diagram
FMIN GND1 FMGAIN AGC VS 1 2 3 4 14 5 IAGC
FM
15
FMOUT
AGC
13
AGCADJ
VREF2
VREF
12
VREF1
11 AMIN 8
AMOUT1 AMOUT
AM
7
10
13932
GND2
Figure 1. Block diagram
Rev. A1, 26-Jul-01
1 (12)
U4254BM-M
Ordering and Package Information
Extended Type Number U4254BM-MFP U4254BM-MPG3 Package SO16 SO16 Taping corresponding, ICE-286-3 Remarks
Pin Description
Pin
FMIN 1 GND1 2 FMGAIN 3 AGC VREF2 NC GND2
Symbol FMIN GND1 AGC VREF2 NC GND2 AMIN NC AMOUT VREF1 FM input
Function Ground for FM part AGC output Reference voltage 2 output Not connected Ground for AM part AM input Not connected AM output Reference voltage 1 output
16 NC 15 FMOUT 14 VS 13 AGCADJ 12 VREF1 11 AMOUT1 10 AMOUT 9
NC
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
FMGAIN FM gain adjustment
4 5 6 7
AMOUT1 AM output AGCADJ Adjustment FM wide-band AGC threshold VS FMOUT NC Supply voltage FM output Not connected
AMIN 8
Figure 2. Pinning
2 (12)
Rev. A1, 26-Jul-01
U4254BM-M
Pin Description
FMIN
FMIN is the input of the FM amplifier. It is the base of a bipolar transistor. A resistor or a coil is connected between FMIN and VREF2. If a coil is used, noise performance is excellent.
AGC 4
ESD
VS 1
FMIN
12392
ESD
12390
Figure 5. Figure 3.
AGCADJ
The threshold of the AGC can be adjusted by variing the DC current at pin AGCADJ. If pin AGCADJ is connected directly to GND1, the threshold is set to 96 dBV 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 dBV.
GND1
To avoid crosstalk 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. In order to influence the AC gain of the amplifier, a resistor is connected in series to an capacitor between FMGAIN and GND1. The capacitor has to be a short at frequencies of 100 MHz.
65 kW
ESD 13 AGCADJ
12397
Figure 6.
ESD FMGAIN 3
12391
FMOUT
The FM amplifiers output is an open collector of a bipolar RF-transistor. It should be connected to VS via a coil.
15 FMOUT
Figure 4.
AGC
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 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 therefore the external components can be omitted.
ESD
12398
Figure 7.
Rev. A1, 26-Jul-01
3 (12)
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 kW. The input capacitance is less than 10 pF.
VREF1/2
VREF1
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 is connected to ground via an external capacitor of about 1 mF.
VS 470 kW 8
AMIN 12 ESD
12394
VREF1 ESD GND1
12396
Figure 8.
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' 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 10.
VREF2
For the DC biasing of the FM amplifier a second voltage reference circuit is integrated. Because of temperature independence of the collector current 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.
AMOUT1
5
ESD
11
VREF2
AMOUT
ESD
ESD
10
GND1
12393
Figure 11.
13768
GND2
Figure 9.
GND2 is the ground for the AM amplifier.
4 (12)
Rev. A1, 26-Jul-01
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 windscreen, 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 W). 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 kW, the input capacitance less than 10 pF. The output resistance is 125 W. An excellent dynamic range is achieved due to the complementary CMOS source follower stage.
Absolute Maximum Ratings
Reference point is ground (Pins 2 and 7) Parameters Supply voltage Power dissipation, Ptot at Tamb = 85C Junction temperature Ambient temperature Storage temperature Electrostatic handling (HBM) Symbol VS Ptot Tj Tamb Tstg "VESD Value 8.8 460 150 -40 to +85 -50 to +150 2000 Unit V mW C C C V
Thermal Resistance
Parameters Junction ambient Symbol RthJA Value 140 Unit K/W
Rev. A1, 26-Jul-01
5 (12)
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See test circuit VS = 8 V, Tamb = 25C, unless otherwise specified
Electrical Characteristics
U4254BM-M
6 (12) AGC output current AGC input voltage threshold AGC input voltage threshold AGC 3rd order output intercept Output noise voltage Power gain Output resistance Input resistance Supply current limit FM amplifier 2nd harmonic Output noise voltage (rms value) Voltage gain Output resistance Input capacitance Input resistance Reference voltage 1 output (I12 = 0) Reference voltage 2 output (I5 = 0) Temperature dependence of VREF2 AM amplifier Supply currents Supply voltage Parameters Pin 15 f = 100 MHz, B = 120 kHz f = 100 MHz Pin 15 Pin 10 S2 switched to 1 fAMIN = 500 kHz, Output voltage = 110 dBV Pin 10 S1 switched to 2; B = 6 kHz 150 kHz to 300 kHz 500 kHz to 6.5 kHz AGC active f = 100 MHz Pin 15 S2 switched to 2; AGC threshold DC current is 10 A at Pin 4 f = 100 MHz Pin 15 S2 switched to 1; AGC threshold DC current is 10 A at Pin 4 f = 100 MHz Pin 15/ Pin 1 f = 100 MHz f = 100 MHz IAGC, IAGCADJ = 0 A, Pin 15 Test Conditions / Pins Pin 10 / Pin 8 Pin 15 Pin 1 Pin 10 Pin 8 Pin 8 Pin 5 Pin 5 Pin 12 Pin 14 Pin 14 VRef2/DT RFMOUT Symbol CAMIN RAMIN RFMIN ROUT VRef2 VRef1 IAGC Vth2 Vth1 VN1 VN2 VN I15 Vs G Is a Min. 7.2 Typ. 0.85 106 132 -65 125 470 2.6 5.5 96 50 50 33 -2 -6 -1 0 5 4 8
Rev. A1, 26-Jul-01 Max. 1.2 8.8 35 10 mV/K dBV dBV dBV dBV dBV dBV Unit dBc mA mA mA kW dB pF W W W V V V
U4254BM-M
Test Circuit
VS
FMOUT
2.2 mH 2.2 nF I14
1 S2
2
5 kW AMOUT I13 2.2mF 100 nF + 9 100 nF
I15 2.2 nF 16 150 W
1 I4 FMIN 2.2 nF 22 W 2.2 mH 51 W VS 2.2 nF 1
8
S1 2 15 pF
1 nF 2.2 nF
Figure 12.
AMIN
Rev. A1, 26-Jul-01
7 (12)
U4254BM-M
FM Intermodulation Distortion
dBmV Input 103 dBmV
dBmV
Output 108 dBmV
58 dBmV Gain = 5 dB AGC not active
90
95
100
105
MHz
90
95
100
105
MHz
dBmV
Input 118 dBmV
dBmV Output 100 dBmV
AGC active
50 dBmV
90
95
100
105
MHz
90
95
100
105
MHz
12400
Figure 13.
8 (12)
Rev. A1, 26-Jul-01
U4254BM-M
Test Circuit for AM Large Signal Behavior
Analyzer 100 nF
AMOUT1 LPF AMIN fcutoff = 500 kHz 1 nF AMOUT 50 W DUT
5 kW 100 nF
Rin = 50 W
115 dBmV 75 dBmV 50 W f = 500 kHz V0
13935
Figure 14.
AM Harmonic Distortion
VAMOUT (dBmV) 115 dBmV 110
90
70 55dBmV 50 0.5 1.0 45 dBmV 1.5 f (MHz)
13936
Figure 15.
Rev. A1, 26-Jul-01
9 (12)
ANTENNA V = 8.2 V S
Application Circuit
U4254BM-M
10 (12)
2.2 nF R1 2.2 m H FMIN FMOUT 2.2 nF 22 W FMGAIN R2 AGC AGC I AGC VS 1 kW VREF2 VRef 2.2 nF VREF1 + 1m F AMOUT1 AMIN 1 nF AMGND AM AMOUT 100 nF 100 nF 2.2 m H Vs AGCADJ Output FMGND FM 39 pF R 1 ( W) 150 270 33 51 86 160 390 470 620 22 R 2 ( W)
AM
FM
PIN
BA679
2.2 nF
2.2 nF
510 W
BC558
200 nF
Figure 16.
V
Protection circuit
13937
R 1 and R2 depend on used FM cable impedance
FM cable impedance
50
75
100
125
Rev. A1, 26-Jul-01
150
U4254BM-M
Package Information
Package SO16
Dimensions in mm
94 8875
Rev. A1, 26-Jul-01
11 (12)
U4254BM-M
Ozone Depleting Substances Policy Statement
It is the policy of Atmel Germany 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. Atmel Germany GmbH 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. Atmel Germany GmbH 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 Atmel Wireless & Microcontrollers products for any unintended or unauthorized application, the buyer shall indemnify Atmel Wireless & Microcontrollers 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. Atmel Germany GmbH, P.O.B. 3535, D-74025 Heilbronn, Germany Telephone: 49 (0)7131 67 2594, Fax number: 49 (0)7131 67 2423
12 (12)
Rev. A1, 26-Jul-01

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