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U4254BM-M PDF 데이터시트 : 부품 기능 및 핀배열

부품번호 U4254BM-M
기능 Low-noise AM/FM Antenna Impedance Matching IC
제조업체 ATMEL Corporation
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U4254BM-M 데이터시트, 핀배열, 회로
Features
High Dynamic Range for AM and FM
Integrated AGC for FM
High Intercept Point 3rd-order for FM
FM Amplifier Adjustable to Various Cable Impedances
High Intercept Point 2nd-order for AM
Low-noise Output Voltage
Low-power Consumption
Electrostatic sensitive device.
Observe precautions for handling.
Low-noise
AM/FM Antenna
Impedance
Matching IC
Description
The U4254BM-M is an integrated low-noise AM/FM antenna impedance matching cir-
cuit in BiCMOS technology. The device is designed specifically for car applications
and is suitable for windshield and roof antennas.
Figure 1. Block Diagram
U4254BM-M
FMIN
GND1
FMGAIN
AGC
VS
1
2
3
4
14
5
VREF2
FM
IAGC
VREF
AGC
15
FMOUT
13
AGCADJ
12
VREF1
8
AMIN
AM
7
GND2
11
AMOUT1
10
AMOUT
Rev. 4772B–AUDR–11/03




U4254BM-M pdf, 반도체, 판매, 대치품
AGCADJ
FMOUT
Figure 5. Internal Circuit at Pin AGC
AGC
4
ESD
VS
The threshold of the AGC can be adjusted by varying the DC current at pin AGCADJ. If
pin AGCADJ is connected directly to GND1, the threshold is set to 96 dBµV 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 dBµV.
Figure 6. Internal Circuit at Pin AGCADJ
65 k
ESD
13 AGCADJ
The FM amplifier output is an open collector of a bipolar RF transistor. It should be con-
nected to VS via a coil.
Figure 7. Internal Circuit at Pin FMOUT
15 FMOUT
ESD
4 U4254BM-M
4772B–AUDR–11/03

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U4254BM-M 전자부품, 판매, 대치품
U4254BM-M
Functional Description
The U4254BM-M is an integrated AM/FM antenna impedance matching circuit. It com-
pensates cable losses between the antenna (for example windshield, 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 ). 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 approxi-
mately one. The input resistance is 470 k, the input capacitance less than 10 pF. The
output resistance is 125 . An excellent dynamic range is achieved due to the comple-
mentary CMOS source follower stage.
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.
Reference point is ground (pins 2 and 7)
Parameters
Symbol
Value
Unit
Supply voltage
Power dissipation, Ptot at Tamb = 85° C
Junction temperature
Ambient temperature
Storage temperature
Electrostatic handling (HBM at ESD S.5.1)
VS
Ptot
Tj
Tamb
Tstg
±VESD
8.8
460
150
-40 to +85
-50 to +150
±1000
V
mW
°C
°C
°C
V
Thermal Resistance
Parameters
Junction ambient
Symbol
RthJA
Value
140
Unit
K/W
4772B–AUDR–11/03
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U4254BM-M

Low-noise AM/FM Antenna Impedance Matching IC

ATMEL Corporation
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Low-noise AM/FM Antenna Impedance Matching IC

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