Skyworks Si5338 - Configuring the Output Drivers; Output Signal Type

Si5338-RM
22 Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
Rev. 1.4 • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice • 2021
9. Configuring the Output Drivers
The output drivers offer several programmable features which are configured or controlled with register access
through the I
2
C serial port. The following sections describe each of these features.
9.1. Output Signal Type
Each of the outputs can be configured as CMOS, SSTL, HSTL, LVDS, LVPECL, HSCL. Registers 36-39 define the
output type as shown in Figure 11.
Figure 11. Setting Output Signal Type
The Si5338 has a CML driver that can be used to replace an LVPECL driver in AC coupled applications and save
~15 mA for each output driver in the process. The output voltage swing of the CML driver is very similar to the
LVPECL driver. When using the CML driver, no external bias resistors to ground or Vtt should be connected. The
CML driver can be used anytime a large swing AC coupled output is needed. The CML driver is individually
available for all 4 differential outputs.
The Si5338 CML output driver can be used as long as the following conditions are met
1. Both pins of the differential output pair are ac coupled to the load
2. The load at the receiver is effectively 100  differential
3. The Si5338 PLL is not bypassed
4. The VDDOx supply voltage is 3.3 V or 2.5 V
The CML driver has the following output swing specifications:
1. Max Vsepp = 1.07 V
2. Min Vsepp = 0.67 V
3. Typ Vsepp = 0.85 V
Figure 11 shows the selection of the CML driver and Figure 13 shows the driver trim settings for the CML driver.
The output common mode voltage of the CML driver is not specified.
37[7:0]
01234567
38[7:0]
01234567
39[7:0]
01234567
36[7:0]
01234567
DRVx_FMT
x=0,1,2,3
001
010
011
100
110
CMOS/SSTL/HSTL. A enabled, B disabled.
Output Signal Type
CMOS/SSTL/HSTL. A disabled, B enabled.
CMOS/SSTL/HSTL. A enabled, B enabled.
LVPECL
LVDS
101
CML
111
HCSL
000
Reserved
DRV0_FMT[2:0]
DRV1_FMT[2:0]
DRV2_FMT[2:0]
DRV3_FMT[2:0]