Tcxo - Nokia 7088 Troubleshooting Manual

7088 (Flower)
Base band Description and Troubleshooting
Figure 4: TCXO & SLEEP_XTAL Block Diagram

TCXO

The MSM device integrates a phase-locked loop from the TCXO clock input.
The PM optimizes TCXO operation that enables and disables appropriate circuits in
the proper sequence. The controller is enabled by the TCXO_EN signal from the
MSM.
When the selected transition occurs at TCXO_EN, the controller quickly enables the
TCXO regulator and the input buffer, and begins counting SLEEP_CLK pulses.
Within the initial power on period, the TCXO will be stabilized to its own calibrated
frequency. This initial period, in units of 32.768 kHz clock pulses, is programmed into
a timer within the controller. When the timer expires, the output buffer is enabled. It
synchronizes with the TCXO input such that the TCXO_OUT (MSM_TCXO in
schematic) signal is glitch free, only valid TCXO pulses are output.
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