Shelf Manager ACB-VI
Power Supply
13
R1.2, March 2018
8 Power Supply
Figure 11: Power Supply Block Diagram
8.0.1 DC-DC Converter
The DC-DC converter on the ACB-VI provides the power for all on-board devices and all off-
board I²C devices inside the Shelf.
The 3.6 V local power is routed through two current limiting circuits to create two redundant
voltages,
I2C_PWR_A
and
I2C_PWR_B
.
I2C_PWR_A and I2C_PWR_B are routed to the backplane connector and used to power I²C-
devices on FRUs like the Fan Tray, PEM or SAP. If one of these voltages is short circuited in a
chassis FRU or on the backplane, the short circuit current is limited to 700 - 900 mA so that
the Shelf Manager and the FRUs are still fully operational.
Backplane Connector
5 V for ShMM-700R
I2C_PWR_A
I2C_PWR_B
FAN_24V
Linear-
regulator
20V_MONITOR
-48V_B_FUSED_MON
-48V_A_FUSED_MON
-48V_A_MONIT
OR
-48V_B_MONIT
OR
PCA9555
ADT7490
0x2D
ADT7490
0x2E
CAP
RTC
ADT7490
0x2C
3.6 V/5 V
DC/DC
3.6 V
0x25
3.6 V/3.3 V
DC/DC