November 2006
rev 0.2
Spread spectrum selection
P2041A
Table 1 illustrates the possible spread spectrum options. The optimal setting should minimize system EMI to the fullest
without affecting system performance. The spreading is described as a percentage deviation of the center frequency
( Note: the center frequency is the frequency of the external reference input on XIN/CLK, Pin 1).
Example of a typical printer or scanner application that operates on a clock frequency of 40MHz:
A spreading selection of SR1=1 and SR0=1 provides a percentage deviation of +/-1.00%* (see Table 1) of Center
Frequency. This results in the frequency on ModOUT being swept from 40.40MHz to 39.60MHz at a modulation rate of
(40/40)*34.72 = 34.72KHz (see Table 1). This particular example (see Figure below) given here is a common EMI reduction
method for scanners and has already been implemented by most of the leading manufacturers.
NOTE:
Spreading range selection varies from different system manufacturers and their designs. The spreading range of P2041A can be set to +/-2.5% when
working with certain scanner model.
P2041A Application Schematic for Flat-Bed Scanner
VDD
40MHz
1 XIN/CLK
2 XOUT
3 SR1
4 VSS
VDD 8
SR0 7
ModOUT 6
SSON 5
P2041A
0.1µF
Modulated 40MHz signal with ± 1.00%
Deviation and modulation rate of
34.72KHz. This signal is connected back
to the clock crystal Input pin of the
system ASIC.
NOTE: The above schematic indicates
The exact setting of this example:
Default setting (no connection on pin 3,
7 and 5)
Absolute Maximum Ratings
Symbol
VDD, V
IN
T
STG
T
A
T
s
T
J
T
DV
Storage temperature
Operating temperature
Max. Soldering Temperature (10 sec)
Junction Temperature
Static Discharge Voltage
(As per JEDEC STD22- A114-B)
Parameter
Voltage on any pin with respect to Ground
Rating
-0.5 to +7.0
-65 to +125
-40 to +85
260
150
2
Unit
V
°C
°C
°C
°C
KV
Note: These are stress ratings only and are not implied for functional use. Exposure to absolute maximum ratings for prolonged periods of time may affect
device reliability.
Versatile EMI Reduction IC
Notice: The information in this document is subject to change without notice.
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PULSECORE [ PulseCore Semiconductor ]
