LM4681 Demonstration
Board User’s Guide
Quick Start Guide
Connect the I
2
C signal generation and interface board to a
computer’s parallel port.
Install LM4681 control software: “LM4681_Software_ver1-
1.”
Apply a 3.0V to 5.0V power supply’s positive voltage output
to the “I2CVDD” pin on jumper JP6. Apply the power supply’s
ground return to the “GND“ pin on JP6.
Apply a 9.0V to 15.5V power supply’s positive voltage output
to the “VDD” pin on JP1. Apply the power supply’s ground
return to the “GND” pin on JP1.
Connect the supplied 5-wire cable between the I
2
C signal
generation and interface board and the 5-pin connector
(JP7) on the LM4681 demonstration board.
Apply a stereo audio signal to jumpers JP4 and JP2. Apply
the source’s signal and ground to the “IN1” pin and the
“GND“ pin, respectively.
Connect a load (
≥
8
Ω
) between the pins on JP5 and another
load between the pins on JP3.
Apply power. Make measurements. Plug in a pair of head-
phones. Enjoy.
Introduction
To help the user investigate and evaluate the LM4681’s
performance and capabilities, a fully populated demonstra-
tion board is available from the Audio Products Group. This
board is shown in Figure 1. Connected to an external power
supply, a signal source and an I
2
C or SPI controller (or signal
source), the LM4681 demonstration board easily demon-
strates the amplifier’s features.
20195901
FIGURE 1. The LM4681 Demonstration Board
National Semiconductor
Application Note 1488
Kevin Hoskins
May 2006
LM4681
Demonstration
Board
User
’s
Guide
AN-1488
© 2006 National Semiconductor Corporation
AN201959
www.national.com
