LM48555 Evaluation Board
National Semiconductor
Application Note 1611
Nisha Patel
April 2007
Quick Start Guide
1)
Apply power supply voltage to positive terminal of JU4, and
source ground to the negative terminal.
2)
Short the terminals of JU1 to release the device from shut-
down mode.
3)
Connect a ceramic speaker, and series resistance load
across the output terminals of JU3.
4)
Apply a differential audio signal to the positive and negative
terminals of JU2.
Introduction
The LM48555 is an audio power amplifier designed to drive
ceramic speakers in portable applications. The LM48555
outputs15.5V
P-P
with less than 1% THD+N while operating
from a 3.2V power supply. The LM48555 features differential
inputs for improved noise rejection and a low power shutdown
mode.
The LM48555 includes advanced click and pop suppression
that eliminates audible turn-on and turn-off transients. Addi-
tionally, the integrated boost regulator features a soft start
function that minimizes transient current during power-up.
The LM48555 is unity-gain stable and uses external gain-set-
ting resistors.
The LM48555 Evaluation board (shown in Figure 1) allows
the user to easily evaluate the performance and characteris-
tics of the LM48555 device. It provides connectors for audio
inputs, audio outputs, power supply, and shutdown control.
The ceramic speaker load is not included on the demo board,
an external ceramic speaker plus series resistor is needed for
evaluation.
Operating Conditions
• Temperature Range
-40°C
≤
T
A
≤
+85°C
• Supply Voltage
2.7V < V
DD
< 6.5V
LM48555 Evaluation Board
30014812
FIGURE 1. LM48555 Evaluation Board
© 2007 National Semiconductor Corporation
300148
www.national.com
LM48555 Evaluation Board
AN-1611
