U4255BM-MFN Atmel, U4255BM-MFN Datasheet - Page 10

• Manufacturer Part Number: U4255BM-MFN
• Description: IC RCVR AM/FM FRONT-END 44-SSOP
• Manufacturer: Atmel

Specifications of U4255BM-MFN

• Frequency: 70MHz ~ 160MHz
• Modulation Or Protocol: AM, FM
• Applications: AM/FM Radio Receiver
• Current - Receiving: 50mA
• Data Interface: PCB, Surface Mount
• Antenna Connector: PCB, Surface Mount
• Voltage - Supply: 7.5 V ~ 10 V
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 44-SSOP
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Features: -
• Sensitivity: -
• Memory Size: -
• Data Rate - Maximum: -

FM Demodulator
10
U4255BM-M
For weather band reception, the gain of the FM demodulator is increased and can be
adjusted by means of Bit 71, Bit 72 in order to increase the output voltage to compen-
sate the low frequency deviation in weather band.
An integrated demodulator fine adjustment allows automatic fine tuning of the demodu-
lator center frequency to the average frequency of the received signal. This feature is
implemented for use in weather band mode and can be activated by setting Bit 53 to 0.
Figure 5. FM Demodulator Automatic Fine Tuning
The center frequency of the FM demodulator can be adjusted by means of Bit 56 to 59.
At the center frequency, the DC voltage at the MPX output Pin 11 is equal to the MPX
offset voltage that can be measured at Pin 11 while MPX mute is active (Bit 7 = 1). This
adjustment will affect the center frequency of all integrated filters as mentioned before.
Table 15. Demodulator Gain in Weather Band Mode
Table 16. Demodulator Fine Adjustment
Demodulator Gain in Weather Band Mode Relative to FM Mode
Demodulator Fine Adjustment
center freq.
FM Demod
adjustment
Frequency
Automatic
Fine tuning OFF
Fine tuning ON
+
Bit 53
12 dB
15 dB
18 dB
21 dB
AM
AGC
B92
IFAGCH
V3
MPX
(10nF)
Bit 72
Bit 53
0
0
1
1
0
1
4519A–AUDR–03/02
Bit 71
0
1
0
1