DS1077L EconOscillator Architecture and Online Interactive Frequency Calculator
Abstract: Theory of operation and description of the DS1077 dual-output all-silicon EconOscillator. A link to an interactive frequency calculator permits calculation of available frequencies online.
ECONOSCILLATOR ARCHITECTURE QUICK OVERVIEW AND INTERACTIVE
CALCULATOR
The DS1077L is a dual output, 3V EconOscillator™ available in an 8-SO or 8-µSOP package.
EconOscillators are all-silicon squarewave oscillators requiring no external clock reference or timing
components for operation. They provide an alternative to crystal-based oscillators in applications where size
and cost are important but absolute frequency accuracy is not. Important features include the following:
4.8kHz to 66.666MHz frequency range, 1.25% frequency tolerance over temperature and voltage, 5µA
power-down mode, and single or dual synchronous outputs. It may be used as a standalone oscillator or as a
processor-controlled peripheral device. The DS1077L is available in four standard master frequencies with
custom master frequencies available on request. A brief description of the architecture of the device and an
interactive frequency calculator follows:
Block Diagram and Theory of Operation
The DS1077L 3V EconOscillator is comprised of five major blocks (Figure 1): an internal master
squarewave oscillator, dual programmable prescalers, a single divider chain, gated output drivers, and a set
of EEPROM configuration registers that are accessible via a 2-wire bus.
Figure 1. Dual Synchronous Outputs From 4kHz to 66.6MHz.
Internal Master Squarewave Oscillator
The master oscillator used in the DS1077L is a CMOS oscillator with compensation circuitry to eliminate
most frequency variation over voltage and temperature.
Four standard master frequency options are available: 40MHz, 50MHz, 60MHz, and 66.66MHz. These
frequencies are calibrated at the factory and cannot be changed by the end user. In reality, the master
oscillator can be factory calibrated to any frequency between 40MHz and 66.66MHz and special frequencies
are available in volume quantities on request. Frequencies faster than 66.66MHz are in development at the
time of the publication of this document.
Dual Programmable Prescalers
The output of the master oscillator is fed directly to two independent prescalers. These can be programmed
by the user to provide an initial divide-by of the master frequency of 1, 2, 4, or 8. The prescaler settings are
stored in EEPROM memory that is accessible to the end user via a 2-wire interface. These registers can be
preset before installation (for fixed-frequency applications) or can be changed by a microprocessor via the 2-
wire interface during operation.
The output of the first prescaler is fed directly to a gated output buffer. The second prescaler is fed into a
1-to-1025 divider chain.
Divider Chain
The 1-to-1025 divider chain receives the prescaled clock from the second prescaler and divides the clock
signal down further. The division value can be programmed to any value between 1 and 1025. The divider
chain settings are stored in EEPROM memory that is accessible via a 2-wire interface. These can be preset
before installation into the application (for fixed-frequency applications) or can be interfaced to a
microprocessor for dynamic frequency changes. The output of the divider is applied directly to a gated
output buffer.
Gated Output Drivers
Two gated output buffers receive the clock signal from the first prescaler and the divider chain, respectively.
The status of these buffers is determined by the values of EEPROM in the EEPROM block. These gates can
be turned off and on either via the 2-wire interface via the EEPROM registers or the DS1077L can be
configured so that the input status of the two control pins determine the status of the outputs. The control
inputs may also be configured to put the DS1077L into a powerdown mode. Output gate switching and
powerdown are configured to occur only when the clock output is low. This guarantees that only full clock
pulses are generated.
EEPROM Configuration Registers
EEPROM configuration registers store all configuration information. These are accessible via a 2-wire
interface and may be preprogrammed before installation for fixed-frequency applications or may be
controlled by a processor in applications where dynamic frequency changes or configuration changes are
necessary.
For more detailed information on the DS1077L refer to the data sheet:
DS1077L.
Available Output Frequencies
With four options for the master oscillator and dual divider chains, thousands of different combinations of
output frequencies are available. To ease in evaluation of the DS1077L for a possible application, an
interactive frequency calculator (Microsoft Excel format) is available for download.
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