U4255BM-MFN Atmel, U4255BM-MFN Datasheet - Page 5

• 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: -

AM RF-AGC
FM 1
AM 1
4519A–AUDR–03/02
st
st
Mixer
Mixer
Table 3. FM-AGC Threshold
Figure 3. FM RF-AGC Bit 92
The AM RF-AGC controls the current into the AM pin diodes (Pin 7) and the source
drain voltage of the MOSFET in the AM preamplifier stage (Pin 6) to limit the level at the
AM mixer input (Pin 3, Pin 41). This threshold level can be set by Bit 62 and Bit 63. If the
level at the AM mixer input exceeds the selected threshold, the current into the AM pin
diodes is increased. If this step is not sufficient, the source drain voltage of the MOSFET
is decreased. The time constant of the AGC control loop can be adjusted by changing
the value of the capacitor at Pin 8.
Table 4. AM-AGC Threshold
In the 1
frequency. The VCO frequency is used as LO frequency for the mixer.
The AM 1
frequency. Therefore, an AM prescaler is implemented to generate the necessary LO
frequency from the VCO frequency. The divide factor of the AM prescaler can be
selected according to Table 5.
st
FM mixer stage, the FM reception frequency is down converted to the 1
st
mixer is used for up-conversion of the AM reception frequency to the 1
FM-AGC Threshold
AM-AGC Threshold
AGC
102 dB V
102 dB V
104 dB V
105 dB V
99 dB V
97 dB V
92 dB V
99 dB V
B92
VS
Pin 5
Pin 42
C111
Bit 65
Bit 63
R115
0
1
0
1
0
0
1
1
PIN Diode
U4255BM-M
Bit 64
Bit 62
0
0
1
1
0
1
0
1
st
st
IF
IF
5