CMT2157A
Rev 0.8 | Page 25/31
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CMT2157A
XTAL
Crystal Model
Rm
Cm
C
L
C0
Lm
CMT2157A
XTAL
C
L
RCLK
26 MHz
Cc
0. 3
–
0. 7 Vpp
If a 26 MHz RCLK (reference clock) is available in the system, the user can directly use it to drive the CMT2157A by feeding
the clock into the chip via the XTAL pin. This further saves the system cost due to the removal of the crystal. A coupling
capacitor is required if the RCLK is used. The recommended amplitude of the RCLK is 0.3 to 0.7 Vpp on the XTAL pin. Also,
the user should set the internal load capacitor C
L
to its minimum value. See Figure 28 for the RCLK circuitry.
Figure 28. RCLK Circuitry
Figure 27. XTAL Circuitry and Crystal Model
