Z8F0830HH020SG Datasheet, PDF (179/257 Pages) Zilog, Inc. – High-Performance 8-Bit Microcontrollers

Z8 Encore!^® F0830 Series
Product Specification
161
Internal Precision Oscillator
The Internal Precision Oscillator (IPO) is designed for use without external components.
The user can either manually trim the oscillator for a nonstandard frequency or use the
automatic factory-trimmed version to achieve a 5.53 MHz frequency with ± 4% accuracy
and 45%~55% duty cycle over the operating temperature and supply voltage of the device.
The maximum start-up time of the IPO is 25 µs. IPO features include:
• On-chip RC oscillator that does not require external components
• Output frequency of either 5.53MHz or 32.8kHz (contains both a FAST and a SLOW
mode)
• Trimming possible through Flash option bits, with user override
• Elimination of crystals or ceramic resonators in applications where high timing accu-
racy is not required
Operation
The internal oscillator is an RC relaxation oscillator with a minimized sensitivity to power
supply variations. By using ratio-tracking thresholds, the effect of power supply voltage is
cancelled out. The dominant source of oscillator error is the absolute variance of chip-
level fabricated components, such as capacitors. An 8-bit trimming register, incorporated
into the design, compensates for absolute variation of oscillator frequency. Once trimmed,
the oscillator frequency is stable and does not require subsequent calibration. Trimming
was performed during manufacturing and is not necessary for the user to repeat unless a
frequency other than 5.53 MHz (FAST mode) or 32.8 kHz (SLOW mode) is required.
Note: The user can power down the IPO block for minimum system power.
By default, the oscillator is configured through the Flash option bits. However, the user
code can override these trim values, as described in the Trim Bit Address Space section on
page 129.
Select one of two frequencies for the oscillator: 5.53 MHz or 32.8 kHz, using the OSCSEL
bits described in the Oscillator Control chapter on page 151.
PS025113-1212
Internal Precision Oscillator