¡ Semiconductor

MSM7717-01/02/03

4/19

PIN AND FUNCTIONAL DESCRIPTIONS

AIN+, AIN–, GSX

Transmit analog input and transmit level adjustment.

AIN+ is a non-inverting input to the op-amp; AIN– is an inverting input to the op-amp; GSX is

connected to the output of the op-amp.

The level adjustment should be performed in any method shown below. When not using AIN–

and AIN+, connect AIN– to GSX and AIN+ to SG. During power-saving and power-down

modes, the GSX output is at AG voltage.

AG

Analog signal ground.

VFRO

Receive filter output.

when the digital signal of +3 dBm0 is input to PCMIN and can drive a load of 20 kW or more.

For driving a load of less than 20 kW, connect a resistor of 20 kW or more between the pins VFRO

and PWI.

During power-saving mode this output is in a high impedance state, and during power-down

mode, the VFRO output is at an SG level.

When adjusting the receive signal on the basis of frequency characteristics, refer to the Frequency

Characteristics Adjustment Circuit.

–

+

AIN–

AIN+

C1

Analog input

1) Inverting input type

R1 : variable

R2 > 20 kW

C1 > 1/(2 ¥ 3.14 ¥ 30 ¥ R1) (F)

Gain = R2/R1 < 10

R2

GSX

SG

+

–

AIN+

AIN–

2) Noninverting input type

R3 > 20 kW

R4 > 20 kW

R5 > 50 kW

C2 > 1/ (2 ¥ 3.14 ¥ 30 ¥ R5) (F)

Gain = 1 + R4 / R3 £ 10

R4

GSX

SG

C2

Analog input

R3

R5

R1