SH3100 Datasheet, PDF (75/80 Pages) Semtech Corporation – Supervisory IC with I2C Interface and PWM

POWER MANAGEMENT
Functional Descriptions (continued)
Spectrum Spreading
One other function of the HFDCO is that it has the ability
to implement frequency spreading of the HF clock in order
to reduce EMI radiation. This is achieved by modulating
the LSB bank of the HFDCO using a pseudo random coun-
ter clocked at 32.768kHz. Spread spectrum is enabled by
setting the SSEnable bit and choosing a modulation am-
plitude of 16kHz, 32kHz , 64kHz, or 128kHz depending
on the setting of the 2-bit SS Config register.
Parameter
Min
Minimum programmable frequency
5
Maximum programmable frequency
33.5
Frequency resolution
1.5
Free-running accuracy over 0°C to +70°C -0.5
Free-running accuracy over -40°C to +85°C -1
Free-running accuracy over VDD
-0.1
Short term frequency stability (jitter)
Startup time from standby
Settling time to 0.1% after HFDCO code
Clock duty cycle
40
Spread spectrum modulation (min. code)
± 12
Spread spectrum modulation (max. code) ± 96
Typ
2
0.1
50
± 16
± 128
Max
8
45
2.5
+0.5
+1
+0.1
0.2
2
10
60
± 20
± 160
SH3100
Units
MHz
MHz
kHz
%
%
%
%
μs
μs
%
kHz
kHz
© 2006 Semtech Corp.
75
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