TDA7421N Datasheet, PDF (18/38 Pages) STMicroelectronics – AM/FM TUNER FOR CAR RADIO AND HI-FI APPLICATIONS

TDA7421N
3.2.4 INLOCK DETECTOR
The charge pump is switched in low current mode as the truth table and the related figure shows.
CURRHIGH
LOCKENA
LOCK (by inlock detector) Charge PumpCurrent
0
X
X
low current
1
1
1
low current
1
1
0
High current
1
0
1
High current
1
0
0
High current
The charge pump is forced in low current mode when a phase difference of 10-40 usec is reached.
A phase difference larger than the programmed values will switch the charge pump immediately in the high cur-
rent mode.
Few programmable delays are available for inlock detection.
4.0 IF COUNTER SYSTEM FOR AM/FM
The IF counter mode is controlled by IFCM register:
IFCM1
IFCM0
0
0
0
1
1
0
1
1
FUNCTION
NOT USED
FM MODE
AM MODE
NOT USED
A sample timer to generate the gate signal for the main counter is built with a 14 bit programmable counter to
have the possibility to use any frequency. In FM mode a 6.25 KHz, in AM mode a 1KHz signal is generated.
This counter is followed by an asynchronous divider to generate several sampling times.
ADDRESS ORGANIZATION (PLL and IF Counter)
MSB
LSB
FUNCTION
SUBAD BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0
PLL CHARGE PUMP 00H
LPIN1/2 CURRH B1
B0
A3
A2
A1
A0
LL COUNTER
01H
PC7
PC6
PC5
PC4
PC3
PC2
PC1
PC0
PLL COUNTER
02H
PC15 PC14 PC13 PC12 PC11 PC10 PC9
PC8
LL REF COUNTER 03H
RC7
RC6
RC5
RC4
RC3
RC2
RC1
RC0
LL REF COUNTER 04H
RC15 RC14 RC13 RC12 RC11 RC10 RC9 RC8
LL LOCK DETECT 05H
LDENA
-
D3
D2
D1
D0
PM1 PM0
FC REF COUNTER 06H
IRC7 IRC6 IRC5 IRC4 IRC3 IRC2 IRC1 IRC0
FC REF COUNTER 07H
IFCM1 IFCM0 IRC13 IRC12 IRC11 IRC10 IRC9 IRC8
FC CONTROL
08H
IFENA
-
-
-
-
EW2 EW1 EW0
C CONTROL
09H
IFS2 IFS1 IFS0
CF4
CF3
CF2
CF1
CF0
18/38