MSM7584C 데이터 시트보기 (PDF) - Oki Electric Industry

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MSM7584C

π/4 Shift QPSK MODEM/ADPCM CODEC

Oki Electric Industry 

¡ Semiconductor

MSM7584C

(RSSI-ADC)

RSSI, RSGAIN

RSSI input and level adjustment.

RSSI is connected to the inverting input pin of the internal amplifier. RSGAIN is connected to

the output pin of the amplifier.

Adjust the gain and DC so that the signal amplitude is between 0.7 V and 2.1 V on the RSGAIN

pin. See Fig. 7 for connection.

Gain: A = R2/R1 = 1.4/ (Vmax - Vmin)

if R1 + R2 ≥ 20 kW

DC adjustment value : Vadj = A/(1+A) ¥ ((Vmax + Vmin) /2– 1.4)

Set the register CR20 to the DC adjustment value nearest to Vadj.

See the control register map (CR20) for setup values.

SGRS

Internal reference voltage output for the RSSI - ADC.

The output voltage is 2.0 V. Insert an approx. 0.1 mF bypass capacitor between this pin and the

AGM pin.

RSSI signal

R2

R1

Gain = R2/R1

RSGAIN

RSSI

–

+

Control

ADC

register

CR19:B7 to B0

DC

ADJUST

CR20:B7 to B3

Reference

voltage

generator

Figure 7 RSSI-ADC Interface

19/57

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