SH3002 Datasheet, PDF (9/22 Pages) Semtech Corporation – Reset Management and Clock Management Support IC for Microcontrollers

SYSTEM MANAGEMENT
Low Frequency (LF) Oscillator System
This module provides the 32 kHz clock to all internal
circuits and to the dedicated output pin, CLK32.
If enabled, the CLK32 output continues normal
operations when VDD is absent and backup power is
available.
Just like the VBO value for the Reset circuit, the
default calibration values for the RC oscillator are loaded
on power-up from the factory-programmed 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 a 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 1 MΩ 1% resistor,
over the entire temperature and supply voltage range.
The frequency of the RC oscillator can be tuned or
modulated by varying the external reference resistor,
which should be located as close as possible to RREF,
pin 9.
SH3002 MicroBuddy™
External
Reference
Resistor
1 MΩ 1% or
variable
RREF
9
VSS
Lock / Unlock
8
Logic
4-bit Value
VSS
1
INTERNAL
RREF ON
RC
Oscillator
Internal RREF
6-bit Value 4-bit Value Lock Logic
Figure 5. Simplified LF Oscillator System
CLK32 ON
Internal
32.768 kHz
Clock
From / To
Serial I/O
CLK32
13
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9
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