PLL with
I
2
C Bus for AM/FM Receivers
SDA 4331X
1
1.1
•
•
•
•
•
Overview
Features
155 MHz FM and 40 MHz AM input frequency
30 mVeff AM and 50 mVeff FM sensitivity
Additional open drain ports controlled by
I
2
C Bus
2-pin quartz oscillator
Fast phase detector with short anti-backlash pulses
P-DSO-24-1
and polarity reversal
• Charge pump current programmable in four steps
up to 4.5 mA
• Frequency resolution of 1, 5 and 10 kHz AM and 12.5, 25 and 50 kHz FM
• P-DSO-24 package
Type
SDA 4331X
1.2
Application
Ordering Code
Q67100-H5139
Package
P-DSO-24-1
The SDA 4331X provides separated input and output ports for AM and FM and is well
suited for extremely fast loop settling times in the FM mode.
Semiconductor Group
1
04.96
SDA 4331X
1.4
Pin Definitions and Functions
Input (I)
Output (O)
I
I/O
I
Function
Supply voltage digital (5 V)
Clock
I
2
C Bus
Data
I
2
C Bus
Address selection, sets the LSB of the IC-address
10 V open drain output, controlled via
I
2
C Bus
10 V open drain output, indicating the operation
mode (H = AM)
Input for the FM signal from VCO
Ground analog
I
Input for the AM signal from VCO
Pin No. Symbol
1
2
3
4
5
6…9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
V
DD1
SCL
SDA
A0
N.C.
SA1 … SA4 O
AM/FM
FM
IN
GND
AN
AM
IN
N.C.
N.C.
O
I
I
REF
PD
FM
PD
AM
PD
FMA
PD
AMA
I
O
O
O
O
Reference current, setting the base current level
for the charge pumps
FM charge pump output
AM charge pump output
Source follower output FM
Source follower output AM
Supply voltage digital for charge pump and source
followers (up to 10 V)
V
DD2
OSC
FB
OSC
IN
GND
I/O
I
Oscillator feedback, quartz terminal
Oscillator input, quartz terminal, optionally input
for external reference
Ground digital
Semiconductor Group
3
04.96
SDA 4331X
2
Functional Description
The SDA 4331X is a radio PLL controlled via
I
2
C Bus for frequency synthesis in the AM
and FM range.
3
Circuit Description
The reference frequency for the PLL is derived from the quartz oscillator OSC
1)
. The
R-prescaler can be adapted to quartz frequencies of 4, 8 or 10.25 MHz, respectively,
yielding an internal 50 kHz reference. Programming the R-counter sets the phase
detector reference frequency to 1, 5 or 10 kHz in the AM mode or to 12.5, 25 or 50 kHz
in the FM mode. The VCO frequency is set by programming the A/N-counter which
operates as dual-modulus counter for FM and AM using a divide by 4/5 swallow counter.
The phase detector drives two different charge pumps for AM and FM mode. Additional
source followers are connected to the charge pump. There are four programmable
current levels for each charge pump. The supply voltage for the charge pump and the
source followers is supplied via the
V
DD2
pin and can reach 10 V maximum. AM/FM is an
open drain output as well as the additional outputs SA1 … SA4 which are controlled by
I
2
C Bus.
The
I
2
C Bus interface provides slave receiver functions. There are two addresses
selected by the A0 pin. The
I
2
C-protocol (see
diagram 1)
contains one string for
programming all counters and functions. The transfer may be stopped optionally after
each word if the remaining functions are not to be altered. After power ON all control
signals are undefined, so that the complete write sequence must be executed.
1)
The power dissipation of the quartz is given by:
P
v
= 2
×
R
1
(Π
×
f
Q
×
(
C
O
+
C
L
)
×
V
DD
)
2
R
1
… Series resistance of the quartz
f
Q
… Quartz frequency
C
O
… Parallel capacitance of the quartz
C
L
… Load capacitance, including input capacitance of the IC
Semiconductor Group
5
04.96
Talking
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