tda7421n STMicroelectronics, tda7421n Datasheet - Page 18

• Manufacturer Part Number: tda7421n
• Description: Am/fm Tuner For Car Radio And Hi-fi Applications
• Manufacturer: STMicroelectronics

TDA7421N
3.2.4 INLOCK DETECTOR
The charge pump is switched in low current mode as the truth table and the related figure shows.
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:
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)
18/38
PLL CHARGE PUMP
FC REF COUNTER
FC REF COUNTER
LL REF COUNTER
LL REF COUNTER
LL LOCK DETECT
PLL COUNTER
FC CONTROL
LL COUNTER
C CONTROL
FUNCTION
CURRHIGH
0
1
1
1
1
IFCM1
0
0
1
1
00H
01H
02H
03H
04H
05H
06H
07H
08H
09H
SUBAD
LPIN1/2 CURRH
LDENA
LOCKENA
IFCM1
IFENA
RC15
BIT 7
PC15
IRC7
MSB
IFS2
PC7
RC7
X
1
1
0
0
IFCM0
PC14
RC14
BIT 6
IRC6
RC6
IFS1
PC6
-
-
IFCM0
0
1
0
1
IRC13
PC13
RC13
BIT 5
LOCK (by inlock detector)
IRC5
IFS0
PC5
RC5
B1
D3
-
IRC12
BIT 4
PC12
RC12
IRC4
PC4
RC4
CF4
D2
B0
-
X
1
0
1
0
IRC11
RC11
PC11
BIT 3
IRC3
RC3
PC3
CF3
D1
A3
-
IRC10
PC10
RC10
BIT 2
IRC2
EW2
RC2
PC2
CF2
D0
A2
Charge PumpCurrent
FUNCTION
NOT USED
NOT USED
FM MODE
AM MODE
High current
High current
High current
low current
low current
BIT 1
IRC1
IRC9
EW1
PC1
RC1
RC9
PM1
PC9
CF1
A1
BIT 0
IRC0
IRC8
EW0
PM0
LSB
PC0
PC8
RC0
RC8
CF0
A0