Si5345-44-42-D-RM
Si5342
Rev. 1.0
215
14.5.7. Page 9 Registers Si5342
The IO_VDD_SEL configuration bit selects the option of operating the serial interface voltage thresholds from the
VDD or the VDDA pin. The serial interface pins are always 3.3 V tolerant even when the device's VDD pin is
supplied from a 1.8 V source. When the I
2
C or SPI host is operating at 3.3 V and the Si5345/44/42 at VDD = 1.8 V,
the host must write the IO_VDD_SEL configuration bit to the VDDA option. This will ensure that both the host and
the serial interface are operating at the optimum voltage thresholds.
When a clock input is disabled, it is powered down.
Input 0 corresponds to IN_SEL 0x0949 [0], IN_PULSED_CMOS_EN 0x0949 [4]
Input 1 corresponds to IN_SEL 0x0949 [1], IN_PULSED_CMOS_EN 0x0949 [5]
Input 2 corresponds to IN_SEL 0x0949 [2], IN_PULSED_CMOS_EN 0x0949 [6]
Input 3 corresponds to IN_SEL 0x0949 [3], IN_PULSED_CMOS_EN 0x0949 [7]
Register 0x090E XAXB Configuration
Reg Address
Bit Field
Type
Name
Description
0x090E
0
R/W
XAXB_EXTCLK_EN
0 to use a crystal at the XAXB pins
1 to use an external clock source at the
XAXB pins
Register 0x0943 Control I/O Voltage Select
Reg Address
Bit Field
Type
Name
Description
0x0943
0
R/W
IO_VDD_SEL
0 for 1.8 V external connections
1 for 3.3 V external connections
Register 0x0949 Clock Input Control and Configuration
Reg Address
Bit Field
Type
Name
Description
0x0949
3:0
R/W
IN_EN
0: Disable and Powerdown Input Buffer.
1: Enable Input Buffer for IN3–IN0.
0x0949
7:4
R/W
IN_PULSED_CMOS_EN
0: Standard Input Format.
1: Pulsed CMOS Input Format for IN3–
IN0. See "5. Clock Inputs" on page 21
for more information.