參數(shù)資料
型號: T4258NFNG3
廠商: ATMEL CORP
元件分類: 接收器
英文描述: AM/FM, AUDIO SINGLE CHIP RECEIVER, PDSO44
封裝: SSOP-44
文件頁數(shù): 35/38頁
文件大?。?/td> 443K
代理商: T4258NFNG3
6
T4258N
4566B–AUDR–02/04
Test Mode
A special test mode is implemented for final production test only. This mode is activated
by setting bit 9 = 1. This mode is not intended to be used in customer applications.
For normal operation, bit 9 has to be set to 0. Bit 22 to bit 30 are deactivated in normal
operation mode.
VCO/Local Oscillator
Prescaler
An oscillator circuit is implemented to build a VCO as proposed in the application sche-
matic. The VCO frequency is used to generate the LO frequency of the 1
st mixer stages.
The control voltage of the VCO is usually generated by the PLL circuit U4256BM. The
VCO frequency has a range of 70 to 250 MHz to allow the reception of all analog world
bands.
A main element of the implemented oscillator circuit is a bipolar NPN transistor. The
internally biased base is connected to pin 13 and the emitter to pin 14. An AGC circuit
(bit 30) can be activated to increase the emitter current until the appropriate oscillation
level is reached. The fundamental emitter current can be changed by bit 52.
In addition (to the AM prescaler) a special VCO prescaler is implemented for all modes
(AM, WB and FM). The divider factor of the prescaler buffer provides the signal of the
buffered output (at pin 16) and the prescaler VCO provides the signal of the 1
st FM mixer
stage and AM prescaler. Examples of VCO prescaler settings are described in section
The divider factor of the VCO and buffer prescaler can be selected according Table 5 on
Table 1. Operating Mode
AM/FM/Weather Channel
Bit 93
Bit 92
Bit 63
Bit 62
Standby
0
X
FM
010
0
AM
101
1
Weather band
1
0
Table 2. Test Mode
Mode
Bit 9
Normal operation
0
Test mode
1
Table 3. Local Oscillator AGC
Local Oscillator (VCO)
Bit 30
AGC off (default)
0
AGC on
1
Table 4. Local Oscillator Gain
Local Oscillator (VCO)
Bit 52
Low Gain
0
High Gain
1
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