SH3000 SEMTECH [Semtech Corporation], SH3000 Datasheet - Page 10

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

Real Time Support
specifically designed for various real time support
functions. They are the Real Time Clock and the
Periodic Interrupt / Wakeup Timer. Both of these units
as well as other functions of the SH3000 depend on the
internal 32 kHz clock for accuracy.
system and its accuracy.
support components provides sufficient accuracy.
These units can operate with processor clock accuracy
of ±0.5% and the accuracy of the real time system of
±3%.
component (a 32.768 kHz watch crystal), the SH3000
can provide a processor clock accuracy of ±256ppm
(±0.0256%) and the accuracy of the real time system of
±4ppm (±0.0004%).
Low Frequency (LF) Oscillator System
circuits and to the dedicated output pin, CLK32.
operations when V
available.
Copyright ©2003-2005 Semtech Corporation
SYSTEM MANAGEMENT
Watch Crystal
12.5 pF Load
Capacitance
Reference
1M 1% or
X-
Resistor
External
32768 Hz
variable
The SH3000 has two support modules that are
The SH3000 allows a trade-off between the cost of a
For some devices, a single SH3000 without any
At the other end of the spectrum, with one external
This module provides the 32 kHz clock to all internal
If enabled, the CLK32 output continues normal
TAL
RC
V
REG
CLK
X
X
R
V
V
DD
IN
OUT
REF
SEL
SS
SS
5
6
7
9
8
1
is absent and backup power is
Lock / Unlock
Logic
Figure 5. Simplified LF Oscillator System
4-bit Value
6-bit Value
I
R
NTERNAL
REF
10
O
N
RC oscillator takes over. It supplies the 32 kHz clock for
start-up and initialization. However, if the CLK
set high, then the crystal oscillator is enabled. Once the
crystal has started and stabilized, the internal 32 kHz
clock switches to the very accurate crystal frequency;
see Figure 5.
default calibration values for the RC oscillator are loaded
on power-up from the factory-programmed OTP
nonvolatile memory. They can be re-programmed at any
time or they can be permanently protected from any
changes by setting the Lock flag or an OTP write-protect
flag. Factory calibration brings the frequency of the RC
oscillator within ±3% of the 32768 Hz for the internal
reference resistor, and ±2% for the external
1M 1% resistor, over the entire temperature and supply
voltage range.
modulated by varying the external reference resistor,
which should be located as close as possible to R
pin 9.
4-bit Value
Oscillator
When the power is first applied to the SH3000, the
Just like the V
The frequency of the RC oscillator can be tuned or
X-tal stable?
RC
Internal R
Lock Logic
REF
BO
value for the Reset circuit, the
SH3000 MicroBuddy™
V1.15
CLK32 O
Internal
32 kHz
Clock
From / To
Serial I/O
www.semtech.com
N
SEL
REF
CLK32
13
pin is
,