Table 26-3. Oscillator modes (continued)
Mode Frequency Range
High-frequency mode1, high-gain
f
osc_hi_1
(3 MHz) up to f
osc_hi_1
(8 MHz)
High-frequency mode1, low-power
High-frequency mode2, high-gain
f
osc_hi_2
(8 MHz) up to f
osc_hi_2
(32 MHz)
High-frequency mode2, low-power
NOTE
For information about low power modes of operation used in
this chip and their alignment with some OSC modes, see the
chip's Power Management details.
26.8.2.1 Low-Frequency, High-Gain Mode
In Low-frequency, high-gain mode, the oscillator uses a simple inverter-style amplifier.
The gain is set to achieve rail-to-rail oscillation amplitudes.
The oscillator input buffer in this mode is single-ended. It provides low pass frequency
filtering as well as hysteresis for voltage filtering and converts the output to logic levels.
In this mode, the internal capacitors could be used.
26.8.2.2
Low-Frequency, Low-Power Mode
In low-frequency, low-power mode, the oscillator uses a gain control loop to minimize
power consumption. As the oscillation amplitude increases, the amplifier current is
reduced. This continues until a desired amplitude is achieved at steady-state. This mode
provides low pass frequency filtering as well as hysteresis for voltage filtering and
converts the output to logic levels. In this mode, the internal capacitors could be used, the
internal feedback resistor is connected, and no external resistor should be used.
In this mode, the amplifier inputs, gain-control input, and input buffer input are all
capacitively coupled for leakage tolerance (not sensitive to the DC level of EXTAL).
Also in this mode, all external components except for the resonator itself are integrated,
which includes the load capacitors and feeback resistor that biases EXTAL.
Functional Description
K22F Sub-Family Reference Manual, Rev. 4, 08/2016
586 NXP Semiconductors
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