Advantech SOM-ETX Design Guide
5.14.2 Speaker
BUZZER
33
C142
0.01u
0.1u
1N4148
1
2
MMBT3904
2
3
1
VCC
10K
Carryboard
SPKER
SM-ETX
Figure 5-42 Speaker Connections
The SPKR output from the SOM-ETX module is a CMOS level signal. It can control
an external FET or logic gate that drives an external PC speaker. The SOM-ETX
modules SPKR output should not be directly connected to either a pull-up or a pull-
down resistor. The SPKR signal is often used as a configuration strap for the core
chipset in SOM-ETX modules. A pull-up or pull-down on this signal can override the
internal setting in the module and result in malfunction of the module.
Chapter 5 Carrier Board Design Guidelines
109
