Figure 5.
SMBus Block Diagram
1.25
DDR3 VREF Control Circuit
The ISL90728 chip for Channel B responds to SMBus address 0x7C. the ISL90727 chip
for Channel A responds to SMBus address 0x5C. These digital potentiometer chips
both reside in the DIMM_VREF_SMB segment of the CRB SMBus.
The CRB schematics show the digital potentiometers connected in parallel with 12.1
KΩ / 12.1 KΩ 1% resistor voltage dividers. This must be considered if calculating the
resulting VREF voltage for particular settings of the potentiometer.
Crystal Forest—Introduction
Intel
®
Xeon
®
Processor E3-1125C with Intel
®
Communications Chipset 8910 Development Kit
User Guide
October 2012
20
Order No.: 328009-001US