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PDF U4254BM-MPG3 Data sheet ( Hoja de datos )
| Número de pieza | U4254BM-MPG3 | |
| Descripción | Low-noise AM/FM Antenna Impedance Matching IC | |
| Fabricantes | ATMEL Corporation | |
| Logotipo |  |
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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
1 page  
AMIN
AMOUT, AMOUT1
U4254BM-M
The AM input has an internal bias voltage. The DC voltage at this pin is VRef1/2. The input
resistance is about 470 kΩ. The input capacitance is less than 10 pF.
Figure 8. Internal Circuit at Pin AMIN
VREF1/2
8
AMIN
470 kΩ
ESD
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's 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 9. Internal Circuit at Pins AMOUT1 and AMOUT
AMOUT1
11
ESD
AMOUT
10
ESD
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 be con-
nected to ground via an external capacitor of about 1 µF.
4772B–AUDR–11/03
5
5 Page 
U4254BM-M
Figure 14. Test Circuit for AM Large Signal Behavior
LPF
fcutoff = 500 kHz
50 Ω
f = 500 kHz
V0
1 nF
50 Ω
AMOUT1 100 nF
DUT
AMIN
AMOUT
100 nF
Analyzer
5 kΩ
Rin = 50 Ω
115 dBµV 75 dBµV
Figure 15. AM Harmonic Distortion
VAMOUT
(dBµV)
115 dBµV
110
90
70
55 dBµV
50 45 dBµV
0.5 1.0 1.5
f (MHz)
4772B–AUDR–11/03
11
11 Page | ||
| Páginas | Total 14 Páginas | |
| PDF Descargar | [ Datasheet U4254BM-MPG3.PDF ] | |
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