Power Subsystem
Intel® Server System R2000LH2/T2 Product Family TPS
Revision 1.0
30
3.7
Cold Redundancy Support
The power supplies that support cold redundancy can be enabled to go into a low-power state
(that is, cold redundant state) in order to provide increased power usage efficiency when system
loads are such that both power supplies are not needed. When the power subsystem is in Cold
Redundant mode, only the needed power supply to support the best power delivery efficiency is
ON. Any additional power supply, including the redundant power supply, is in Cold Standby
state.
Each power supply has an additional signal that is dedicated to supporting Cold Redundancy,
CR_BUS. This signal is a common bus between all power supplies in the system. CR_BUS is
asserted when there is a fault in any power supply or the power supplies output voltage falls
below the Vfault threshold. Asserting the CR_BUS signal causes all power supplies in Cold
Standby state to power ON.
Enabling power supplies to maintain best efficiency is achieved by looking at the Load Share
bus voltage and comparing it to a programmed voltage level via a PMBus command. Whenever
there is no active power supply on the Cold Redundancy bus driving a HIGH level on the bus,
all power supplies are ON no matter their defined Cold Redundant roll (active or Cold Standby).
This guarantees that incorrect programming of the Cold Redundancy states of the power supply
will never cause the power subsystem to shut down or become over loaded. The default state of
the power subsystem is all power supplies ON. There needs to be at least one power supply in
Cold Redundant Active state or Standard Redundant state to allow the Cold Standby state
power supplies to go into Cold Standby state.
3.7.1
Powering on Cold Standby Supplies to Maintain Best Efficiency
The power supplies in Cold Standby state monitor the shared voltage level of the load share
signal to sense when it needs to power on. Depending upon which position (1, 2, or 3) the
system defines that power supply to be in the cold standby configuration, will slightly change the
load share threshold that the power supply shall power on at.
Table 22. Example Load Share Threshold for Activating Supplies
Enable Threshold for
V
CR_ON_EN
Disable Threshold for
V
CR_ON_DIS
CR_BUS
De-asserted/Asserted
States
Standard Redundancy
NA; Ignore dc/dc_ active# signal; power supply is
always ON
OK = High
Fault = Low
Cold Redundant Active
NA; Ignore dc/dc_ active# signal; power supply is
always ON
OK = High
Fault = Low
Cold Standby 1 (02h)
3.2V (40% of max)
3.2V x 0.5 x 0.9 = 1.44V
OK = Open
Fault = Low
Cold Standby 2 (03h)
5.0V (62% of max)
5.0V x 0.67 x 0.9 = 3.01V
OK = Open
Fault = Low
Cold Standby 3 (04h)
6.7V (84% of max)
6.7V x 0.75 x 0.9 = 4.52V
OK = Open
Fault = Low
Notes:
Maximum load share voltage = 8.0V at 100% of rated output power
These are example load share bus thresholds; for a given power supply, these shall be customized to maintain the
best efficiency curve for that specific model.
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