MAX7313 Input/Output Expander

and SMBus Interface

The MAX5946L EV kit features a MAX7313 I/O

expander (U2) and PC board pads for connecting to an

SMBus system (SDA and SCL signals). The I/O

expander interfaces with the PRES-DET, FAULT, ON,

and OUT signals of the MAX5946L for each channel.

Header J3 (16 pins) is provided to enable easy access

to each channel’s signals through a ribbon cable or

scope probe. Green and yellow LEDs (D3–D6) are also

provided for user applications such as status indica-

tion. Jumpers JU3 (MRLA) and JU4 (MRLB) are provid-

ed to mimic a PCI Express mechanical retention

locking (MRL) signal. Surface-mount resistors R19–R24

configure the MAX7313 SMBus serial address. The

MAX7313 default SMBus address is 0x40.

If the MAX7313 I/O expander is used to control the ON

signals and read back other MAX5946L signals of each

channel, jumpers JU5–JU8 must be reconfigured or

U2 will be destroyed when switching logic states.

Pads are provided on the EV kit’s PC board to interface

signals.

If a user’s SMBus system is not available, a Windows-

based computer can be interfaced with the EV kit by

connecting the CMODUSB SMBus interface board to

connector J4. The CMODUSB SMBus interface board

enables the computer to interface with the EV kit’s

SMBus signals. The SMBus interface board and soft-

ware provide the user with the capability of “bit bang-

ing” signals to and from the MAX7313 I/O expander’s

various registers.

Software Startup

A mouse or the tab key is used to navigate the Main

Window items. Upon starting the program, the General-

Purpose Two-Wire Interface Utility is launched by

selecting the Interface button. Hexadecimal or binary

data can be entered into the Hexadecimal or Binary

Data combo boxes and then the alternate combo box

will display the corresponding number in the respective

number base. This is used as an easy means of con-

verting between hexadecimal and binary data.

MAX5946L Evaluation Kit/Evaluation System

6

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Table 4. MAX5946L Channel A and B On Signals Configuration

JUMPER

SHUNT LOCATION

MAX5946L PIN CONNECTION

EV KIT OPERATION

JU5

1 and 2

AUXONA controlled by SW6

Local switch control

JU6

1 and 2

ONA controlled by SW5

Local switch control

JU7

1 and 2

ONB controlled by SW3

Local switch control

JU8

1 and 2

AUXONB controlled by SW4

Local switch control

JU5

2 and 3

AUXONA controlled by U2, MAX7313

through SMBus

SMBus or computer control

JU6

2 and 3

ONA controlled by U2, MAX7313 through

SMBus

SMBus or computer control

JU7

2 and 3

ONB controlled by U2, MAX7313 through

SMBus

SMBus or computer control

JU8

2 and 3

AUXONB controlled by U2, MAX7313

through SMBus

SMBus or computer control

Figure 1. MAX5946L Evaluation Software’s Main Window for

Accessing the General-Purpose Two-Wire Interface Utility