LM4985 Evaluation Board
User’s Guide
Quick Start Guide
Connect the I
2
C signal generation and interface board to a
computer’s parallel port.
Install LM4985 control software: “LM4985_Software_ver1-
52.”
Amplifier output mode:
For OCL (Output CapacitorLess) mode, place a jumper
across the pins of JP10 and JP11 and across pins 1 and 2 on
JP8.
For C-CUPL (Capacitor Coupled) mode, place a jumper
across pins 2 and 3 on JP8. Leave JP10 and JP11 open.
Apply a 2.3V to 5.0V power supply’s positive voltage output
to the “+” pin on jumpers JP1 and JP2. Apply the power
supply’s ground return to the “-“ on JP1 and JP2.
Connect the supplied 5-wire cable between the I
2
C signal
generation and interface board and the 5-pin connector (JP7
and JP9) on the LM4985 demonstration board.
Apply a stereo audio signal to jumpers JP3 and JP5. Apply
the source’s signal and ground to the “+” pin and the “-“ pin,
respectively.
Connect a load (
≥
16
Ω
) to JP4 and another load to JP6.
JP4’s “+” pin and JP6’s “+” pin carries the output signals from
the two amplifiers found on pins OUT1 and OUT2, respec-
tively.
Apply power. Make measurements. Plug in a pair of head-
phones. Enjoy.
Introduction
To help the user investigate and evaluate the LM4985’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 (2.3V to 5V), a signal source and an I
2
C controller (or
signal source), the LM4985 demonstration board easily dem-
onstrate the amplifier’s features.
20184902
FIGURE 1. The LM4985 Demonstration Board
National Semiconductor
Application Note 1452
Kevin Hoskins
May 2006
LM4985
Evaluation
Board
User
’s
Guide
AN-1452
© 2006 National Semiconductor Corporation
AN201849
www.national.com
