SH3000 SEMTECH [Semtech Corporation], SH3000 Datasheet - Page 9

• Manufacturer Part Number: SH3000
• Description: Low-Power Programmable Multifunction Support IC for Microcontrollers
• Manufacturer: SEMTECH [Semtech Corporation]

Table 3. EMI reduction with Spectrum Spreading
Programmable Spectrum Spreading
regulatory tests in order to determine the degree of their
Electromagnetic Interference (EMI) affecting other
electronic devices. In some cases compliance with the
EMI standards is costly and complicated.
EMI. It can be a part of the initial design strategy, or it
can be applied in the prototype stage to fix problems
identified during compliance testing. This feature of the
SH3000 may greatly reduce the requirements for
radiofrequency shielding, and permits the use of simple
plastic casings in place of expensive RFI-coated or
metal casings.
Spreading in order to reduce the RF emissions from the
processor’s clock. There are five (5) possible settings;
please see Table 3 for operating and performance
figures in the 8-16 MHz range.
En
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 kHz, is used. Only 4, 5, 6, or 7
bits of the generated 8-bit random number are used,
according to the configuration setting.
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).
Copyright ©2003-2005 Semtech Corporation
SYSTEM MANAGEMENT
0
1
1
1
1
Most commercial electronic systems must pass
The SH3000 offers a technique for reducing the
The SH3000 employs Programmable Spectrum
Spectrum Spreading is created by varying the
Maximum fluctuations of the frequency depend on
CFG1
Setting
X
0
0
1
1
CFG0
X
0
1
0
1
Bandwidth
Spreading
128
256
kHz
Off
32
64
(guaranteed)
Reduction
Peak EMI
-12
db
-3
-6
-9
0
Reduction
Peak EMI
(measured)
-10
-15
db
-3
-7
0
9
Special Operating Modes
connections to the In and Out terminals of the host’s
oscillator. For example, a bank of SH3000 chips can
generate several different frequencies for simultaneous
use in the system, all controlled by a single micro (and
possibly sharing one 32.768 kHz crystal by chaining the
CLK32 pin to X
the CLK
output on the CLK
operating mode is automatically recognized by the
SH3000.
command at all. Still, with the help of the SH3000 this
controller can do a “simulated” STOP by issuing an
instruction to the SH3000 to stop the clock. This
command is accepted only if the Periodic Interrupt /
Wakeup Timer has started (otherwise, once the system
is put to sleep, it would never wake up again). This
mode of operations is only possible if the host processor
is capable of correct operations with clock frequency
down to zero, and keeps all of the internal RAM alive
while the clock is stopped.
The SH3000 can operate stand-alone, without
Likewise, a microcontroller may not have a STOP
IN
pin should be connected to V
IN
pin on the next device). In this case
OUT
pin is continuous; the correct
SH3000 MicroBuddy™
V1.15
www.semtech.com
SS
. The clock