Motorola Mobility LLC T56KT1 User Manual

When implementing a single ended speaker design, it is required to place a series 
capacitor and resistor on the speaker output line, as illustrated in 

The capacitor should be of low tolerance with values of C = 10-22 uF.
The resistor value depends on the speaker application:
- For a handset device, the resistor value should be R = 0

Ω

 at the design stage, but 

may be changed to a different value during audio safety testing, in case speaker 
level limitation is required.
- For a headset device, safety regulations require the resistors value to be R > 2R

L

Ω

, 

where R

L

 is the speaker impedance (e.g. 32

Ω

).

For example, when using a 32

Ω

 speaker the series resistance would be R > 64

Ω

.

The mono speaker port can be used for voice calls and DTMF tones. It is located at pin 47 on the 
G30 81 pin LGA interface, named HDST_SPK.

It is designed as a single-ended output with 32

Ω

 impedance, referenced to the G30 analog ground.

 shows the headset speaker circuit and 

 gives the headset speaker 

specifications.

Output 
Voltage

No load
Single ended

2.7

V

PP

Gain

Programmable in 
3 dB steps

-15

+9

dB

AC Output 
Impedance

8

Ω

DC Voltage

VCC/2

V

THD

8 Ω load
300 Hz - 4 kHz

1

%

Isolation

Speech, f> 4 kHz

60

dB