Si5345-44-42-D-RM
Si5345
Rev. 1.0
125
14.3.7. Page 9 Registers Si5345
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.
Register 0x094A Input Clock Enable to DSPLL
Reg Address Bit Field Type
Setting Name
Description
0x094A
3:0
R/W
INX_TO_PFD_EN
Value calculated in CBPro