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POWER MANAGEMENT

15

SH3003

POWER MANAGEMENT

Programmable Spectrum Spreading (continued)

Setting

Spreading

Bandwidth kHz

Peak EMI Reduction

(guaranteed db)

Peak EMI Reduction

(measured db)

En

CFG1 CFG0

0x

x

Off

0

0

10

0

32

-3

-3

10

1

64

-6

-7

1

1

0

128

-9

-10

1

1

1

256

-12

-15

Table 2 - EMI reduction with Spectrum Spreading

Spectrum Spreading is created by varying the frequency of the HF oscillator with a pseudo-random sequence (with

a zero-average DC component). The Maximum-Length Sequence (MLS) 8-bit random number generator, clocked by

32.768kHz, is used. Only four, five, six, or seven bits of the generated 8-bit random number are used, according to the

configuration setting.

Maximum fluctuations of the frequency depend on the selected frequency range and the position within the range.

Selecting the HF oscillator frequency to be near the high end of the range limits the peak variations to 0.1%, ±0.2%,

±0.4%, or ±0.8% (corresponding to the configuration setting).