ATR4258 Datasheet, PDF (30/38 Pages) ATMEL Corporation – AM/FM RECEIVER IC

Local Oscillator and AM
Prescaler Settings
Table 38 gives an example for the VCO prescaler divider and AM prescaler divider set-
tings and the reception frequencies.
e.g.,
f_VCO = 195.9 MHz ... 237.9 MHz
f_IF = +10.7 MHz or -10.7 MHz
f_VCO = (f_rec + f_IF) × VCO Prescaler × AM Prescaler
Table 38. VCO and AM Prescaler (Divider) Settings and Reception Frequencies
Band
FM
WB
JPN
LW/MW
16m
120m
Prescaler
Minimum Reception Maximum Reception
VCO IF [MHz] Frequency [MHz] Frequency [MHz]
2
+10.7
87.5
108
1.5
-10.7
162.4
162.55
3
-10.7
76
90
2
+10.7
0.15
1.605
1
+10.7
17.5
17.9
2
+10.7
2.3
2.5
Minimum VCO
Frequency
196.4
227.55
195.9
195.3
225.6
208
Maximum VCO
Frequency
237.4
227.775
237.9
221.49
228.8
211.2
AM
Prescaler
-
-
-
9
8
8
U4256 N- and R-divider
Calculation
AM Mode
N = ------------------------------------------^f-^V----^C---^O-------------------------------------------
VCO-divider × AM Prescaler × f_step
f_rec
=
⎛
⎝
-_V---_C-----_O-----_---_d---_i-_v---_i--_d---_e---_r--^f-^V-_×--^C----_A^O----_M------_P----_r--_e---_s---_c----_a---_l-_e----_{r⎠⎞}
– f_IF
FM/WB Mode
N = --------------------^f--^V---^C---^O----------------------
VCO-divider × f_step
f_rec
=
⎛
⎝
V^----C^-----O^--f--V--^--d^C---i^O-v^---i^-d^----e^---r^{-⎠⎞}
– f_IF
All Modes
R = --^f--^r--^e--^f--
f_step
f_ref = reference oscillator frequency (e.g. 10.25 MHz)
f_VCO = VCO frequency
f_rec = reception frequency
f_step = step frequency (of the PLL)
30 ATR4258
4838A–AUDR–10/04