Chapter 3 – Electrical Characteristics
Multi-Tech Systems, Inc. MMCModem GPRS Developer’s Guide (S000445D)
24
Speaker Outputs for SPK1
Speaker outputs SPK1 are push-pull amplifiers and can be loaded down to 50 Ohms and up
to 1nF. These outputs are differential and the output power can be adjusted by step of 2dB.
The output can be directly connected to a speaker. When using a single-ended connection,
be sure to have a very good ground plane, a very good filtering as well as a shielding in order
to avoid any disturbance on the audio path.
SPK1P
+
C1
Differential Connection
SPK1P
SPK1N
Single-Ended Connection
Speaker Output Drawing for SPK1
C1 = from 100nF to 47µF as per the speaker characteristics.
Using a single-ended connection also includes losing half of the output power compared to a
differential connection.
Speaker Output Pin Description for SPK1
Signal
Pin #
I/O
I/O Type*
Description
SPK1P
12
O
Analog
Speaker 1 positive output
SPK1N 14
O Analog Speaker 1 negative output
* See “Operating Conditions” in section on the 50-pin Connector Description.
