Host

(e.g. FPGA)

LMH0303

#1

GPO

SCL

SDA

RSTI

RSTO

LMH0303

#2

RSTI

RSTO

LMH0303

#N

RSTI

RSTO

3.3V

LMH0303

www.ti.com

SNLS285G – APRIL 2008 – REVISED APRIL 2013

Figure 4. SMBus Configuration for Multiple LMH0303 Cable Drivers

The RSTI pin of the first device is controlled by the system with a GPO pin from the host. The first LMH0303

RSTO pin is then daisy chained to the next device's RSTI pin. That device’s RSTO pin is connected to the next

device and so on.

The procedure at initialization is to:

1. Hold the host GPO pin Low in RESET, to the first device. RSTO output default is also Low which holds the

next device in RESET in the chain.

2. Raise the host GPO signal to LMH0303 #1 RSTI input pin.

3. Write to Address 8’h2E (7’h17) Register 0 with the new address value (e.g. 8’h2C (7’h16).

4. Upon writing Register 0 in LMH0303 #1, its RSTO signal will switch High. Its new address is 8’h2C (7’h16),

and the next LMH0303 in the chain will now respond to the default address of 8’h2E (7’h17).

5. The process is repeated until all LMH0303 devices have a unique address loaded.

6. Direct SMBus writes and reads may now take place between the host and any addressed device.

The 7-bit address field allows for 128 unique addresses. The above procedure allows for the reprogramming of

the LMH0303 devices such that multiple devices may share the two-wire SMBus. Make sure all devices on the

bus have unique device IDs.

If power is toggled to the system, the SMBus address routine needs to be repeated.

Copyright © 2008–2013, Texas Instruments Incorporated

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