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UC6580 Hardware Reference Design
UC-06-C21 EN R1.0 Attention 5
2.4 TCXO
The CLK_I pin connects an external TCXO of 26 MHz. The power supply of TCXO can be
LDO_X or an external independent LDO power supply.
In order to ensure the chip boots normally, the 26 MHz clock should work stably no later
than 10 ms after the chip is powered.
The basic parameter requirements for TCXO are as follows:

Frequency and temperature: 26 MHz ± 0.5 ppm (-40 ° C to +85 °C);
 Short-term frequency stability: < 5 ppb/s.
Special attentions should be paid to the layout and routing of TCXO in addition to the
general rules:
 It is recommended to maintain copper void for the layer where TCXO is placed and
the adjacent layers, and keep the reference ground complete for other layers, so as
to reduce the impact of heat conduction on the performance of TCXO.
 Place TCXO as close to the chip as possible, with ground shields for the
surrounding
circuits.

Avoid placing any high-power or strong interference devices, signals, traces, etc.
around the TCXO. Keep a distance of more than 3 times the trace width between the
clock signal trace and other traces.