4/25

¡ Semiconductor

MSM7575

PIN AND FUNCTIONAL DESCRIPTIONS

AIN1+, AIN1–, AIN2, GSX1, GSX2

Transmit analog input and the output for transmit gain adjustment. The pin AIN1– (AIN2)

connects to the inverting input of the internal transmit amplifier, and the pin AIN1+ connects to

the non-inverting input of the internal transmit amplifier. The pin GSX1 (GSX2) connects to

output of the internal transmit amplifier. Gain adjustment should be referred to Fig. 1.

VFRO, AOUT+, AOUT–, PWI, SAO, RINGC

Used for the receive analog output and the output for receive gain adjustment. VFRO is an

output of the receive filter. AOUT+ and AOUT– are differential analog signal outputs which can

directly drive Z

1.

The ORed signal with the control register data CR4-B5 and the external pin RINGC determines

the output pins (AOUT+ and AOUT- /SAO+ and SAO-) for the speech signal and an acoustic

component of the sounder tone, DTMF tone, R tone, F tone, various kinds of tones at either the

VFRO pin or the SAO pin.

Figure 1 Analog Input/Output Interface

= (R2/R1)

¥ (R4/R3)

AIN1–

GSX1

R2

C1

to ENCODER

R1

from

DECODER

Differential

Analog

Output

= 2

¥ (R6/R5)

+ 350

W

AIN2

GSX2

R4

C2

R3

AOUT–

PWI

R6

VFRO

R5

AOUT+

AIN1+

–1

–

+

–

+

–

+

C1

R1

R2

SG

+

–

10

mF

0.1

mF

Differential

Analog Input

Vi

Sounder Output

Signal

SAO

+1

SELECT

RINGC

TOUT1

TOUT2

TOUT3

–

+

from MCU INT.

from MCU INT.