U4255BM-MFN Atmel, U4255BM-MFN Datasheet - Page 12

• 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: -

MPX Output
Receiving Condition
Analyzer
Field Strength Sensor
Search Stop Detector
12
U4255BM-M
The output of the AM demodulator (AM mode) or the output of the FM demodulator
(FM/WB mode) are available at the MPX output (Pin 11).
The MPX output signal can be muted by setting Bit 7 to 1.
The bandwidth of the lowpass filter at the MPX output can be set by means of Bit 79 to
90 kHz or 180 kHz.
Table 19. MPX Output Mute
Table 20. MPX Output Bandwidth
The U4255BM-M implements several sensors that provide information about the receiv-
ing condition of the selected station.
The field strength sensor provides a DC voltage at Pin 9 which represents the logarith-
mic field strength of the signal in the reception band.
The field strength information can be retrieved either from a level detector at the input of
the 2
width of the field strength detection in the AGC is smaller than by using the level
detector because of additional selectivity between the 2
particularly in AM and WB, but the field strength detection in the AGC is limited to the IF
AGC range. Usually the field strength from the level detector is used in FM mode and
the AGC field strength is used in AM mode.
Table 21. Field Strength Selection
A search stop detector is available in AM and FM/WB mode. A STOP condition is
signaled if the frequency of the ZF signal is within a window around the center frequency
of 450 kHz. The width of this search stop window can be set by Bit 85 to 87 in the range
of 0.5 kHz to 80 kHz. The frequency of the ZF signal is measured by counting the num-
ber of periods of the ZF signal during a measurement time which is determined by Bit 73
to 78. The inverted STOP signal is available at Pin 21 according to Table 24. The fre-
quency of 10.25 MHz at Pin 22 is used as time reference.
nd
mixer (Pin 26) or from the IF-AGC depending on the setting of Bit 80. The band-
MPX out, Pin 11 normal operation
Field Strength Narrow Band / Wide Band
Fieldstrength from IF-AGC (narrow band)
Bandwidth MPX Lowpass Filter
Fieldstrength at Pin 26 (wide band)
MPX Output
Mute ON
180 kHz
90 kHz
nd
mixer and the 2
Bit 7
0
1
4519A–AUDR–03/02
nd
Bit 79
IF amplifier
Bit 80
0
1
0
1