AN568| Application Note
Maxim > App Notes > OSCILLATORS/DELAY LINES/TIMERS/COUNTERS Keywords: EconOscillator, DS1075, online calculator, interactive calculator, econ oscillator
Apr 06, 2001
APPLICATION NOTE 568
Tech Brief 15: DS1075 EconOscillator: Power Dissipation Models
Abstract: The data sheet specification for DS1075 supply current is a worst-case parameter representing the highest current configuration under worst-case operating conditions. However, in the majority of applications the DS1075 will consume less than this value. This application brief describes some models which can be used to predict the supply current of the DS1075 for any given operating configuration. Different factors such as master oscillator frequency, divider setting, output configuration (dual or single) or output loading can drastically effect current consumption in the device. This application note is intended as a tool to help the design engineer predict accurately the current consumption of the DS1075 in a specific configuration/application. An Online calculator is available to make these calculations. The data sheet specification for DS1075 supply current is a worst-case parameter representing the highest current configuration under worst-case operating conditions. However, in the majority of
applications the DS1075 will consume less than this value. This application brief describes some models which can be used to predict the supply current of the DS1075 for any given operating configuration.
Power Dissipation Capacitance
This power dissipation parameter is often used with CMOS circuits to provide an indication of operating current. Simple CMOS circuits have a linear relationship between current drawn and operating frequency. Hence at any given frequency the current can be shown in this form: ICC = Cpd VCC f + k Where ICC Cpd VCC f k = = = = = Supply current Power dissipation capacitance Supply voltage Operating frequency A constant equal to the current drawn in the quiescent (dc) state
If the device is driving a load that must also be comprehended, the expression now becomes: ICC = Cpd VCC f + k+ CL VO2 f / VCC Where CL VO = = Load capacitance Output voltage swing
Except at high frequencies or with highly capacitive loads this can be simplified to: ICC = (Cpd + CL ) VCC f + k
Applying this model to the DS1075
A similar model can be applied to the DS1075, but since the DS1075 is a complex device several additional items must be considered:
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