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CMOS (Complementary Metal-Oxide Semiconductor)
| Logic Levels: 1: |
90% of Input Voltage |
|
2: |
10% of Input Voltage |
| Duty Cycle: |
Measured at 50% of Input Voltage |
| Typical Fan-out: |
10 Loads (Specified in pF, 50 pF max) |
| Types of CMOS: |
CMOS, HCMOS, and ACMOS |
ECL (Emitter Coupled Logic)
| Logic Levels: 1: |
-0.9 V |
|
2: |
-1.75 V |
| Duty Cycle: |
Measured at 50% Output Swing |
| Typical Fan-out: |
50 Ohms to (supply voltage-2V) |
| Types of ECL: |
10kECL, 100kECL, MECL, Eclips |
Fan-out (Loads) – the number of logic chips the IC can drive.
Drive Capability - Indicating the maximum load the oscillator
can drive specified at pF in CMOS logic and the number of gates in TTL logic.
If this value exceeds the maximum rated load of the oscillator, signal
degradation can occur.
Startup Time - The startup time is specified as the time that
an oscillator take to reach its specified RF output amplitude.
The startup time is determined by the closed loop time constant and the
loading condition of its circuit.
Rise & Fall Time (tr & tf) - The
rise time of an oscillator is defined as the transition time of the output
waveform from low stage (logic “0”) to high stage (logic “1”).
The fall time of an oscillator is defined as the transition time of the
output waveform from high stage (logic “1”) to low stage (logic “0”).
Fast rise & fall time requirements can steer a user to using ECL,
even for frequencies typically satisfied by HCMOS/TTL.
Increasing the load will increase the rise and fall times of the device.
Symmetry or
Duty Cycle - The measure of output waveform uniformity or the shape of
the waveform, which is made up of logic “1” and logic “0” cycle times. It is defined as the ratio of the time periods of the logic 1
level (TH) to the time periods of one complete cycle (T), measured at
1.4 volts for TTL logic and 50% of the peak-to-peak voltage for CMOS and ECL
logic. Sym = TH/T x
100%.
Tri-state Enable – By applying a command input signal to the
oscillators, the output of the clock oscillators is turned off or disabled.
When this feature is activated, the oscillators assume a high impedance
state.
Input Current and Supply Voltage
Input current is the amount of current drain by an oscillator in its
operating condition. Different
logic oscillators require different input current.
Supply voltage is the voltage necessary to operate the oscillator. It is typically 5 V or 3.3 V.
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