Cell phone system design with STCD10x0 clock solution

AN2760

10/14

Figure 5.

Connection of the DC-CUT capacitor and bias

2.4

Connecting STCD10x0 outputs to application modules

DC-CUT capacitors are required at each of the outputs in most applications.

2.5

Power-down sequence

If the STCD10x0 shares the same power supply with TCXO (clock source), it is suggested

to power up the TCXO before enabling each of the clock outputs since normally it will take

several milliseconds for the TCXO to stabilize its output.

If the STCD10x0 uses different power supplies with TCXO, it is not recommended to power

(when no clock output is enabled, the STCD10x0 enters standby mode). If shutdown of the

STCD10x0 is preferred, the following power-down steps must be followed:

1.

Shut down clock source TCXO output

2.

Disable EN pins, pull low

3.

If the power-down sequence is not strictly followed as above, the user may find the clock

shutdown, and EN pins active. This possibility is illustrated in Figure 6.

ai13957

STCD1020

STCD1030

STCD1040

VCTCXO

MCLK

OUT

VCC

R1

R2

DC-CUT

0.1

μF