Instruction Manual

AT8901M Hardware Description

Page 3 - 15 AT8901M User Guide

3.7.2 Power Distribution

The 48 Volts are supplied by the backplane via two independent rails, primary (A) and second-

ary (B). The rails are mixed using power Schottky rectifiers. A 7A fuse protects each -48V line

and a 10A fuse protects each RTN line. A hot swap controller enables the 48V power to the

board.

A quarter brick DC/DC converter transforms the 48 Volts to secondary 12 Volts, which are dis-

tributed on the board. The converter allows a maximum of 14A output current.

Two different management voltages (3.3V and 5V) and five payload voltages (3.3V, 2.5V, 1.8V,

1.25V and 1.2V) are generated by point of load converters. These are either switches or linear

regulators.

The management (or suspend) power is present once the board is connected to the backplane.

It supplies the IPMI part which in turn controls the payload power. The various payload voltages

are sequenced. The initial power up sequence is as follows (20ms delay between steps):

1. 3.3V, 1.8V and fabric mezzanine

2. 2.5V, 1.25V and 1.2V

The Power Down Sequence is performed in reversed order with a 1ms delay.

Table 3-14: Power Connector (P10)

Signal Pin Pin Signal

N.C. 1 2 N.C.

N.C. 3 4 N.C.

HA0 5 6 HA1

HA2 7 8 HA3

HA4 9 10 HA4

HA6 11 12 HA5

SCL_A 13 14 SDA_A

SCL_B 15 16 SDA_B

MT1_TIP(N.C.) 17 18 MT2_TIP(N.C.)

RING_A(N.C.) 19 20 RING_B(N.C.)

MT1_RING(N.

C.)

21 22 MT2_RING(N.

C.)

RRTN_A(N.C.) 23 24 RRTN_B(N.C.)

SHELF_GND 25 26 LOGIC_GND

ENABLE_B 27 28 VRTN_A

VRTN_B 29 30 EARLY_A

EARLY_B 31 32 ENABLE_A

-48V_A 33 34 -48V_B