acpm-7813 Avago Technologies, acpm-7813 Datasheet - Page 13

• Manufacturer Part Number: acpm-7813
• Description: Cdma/amps Power Amplifier Module
• Manufacturer: Avago Technologies

3. Dynamic Bias Control Alternate Implementation
Phone designers can use TX_ADC_ADJ pin of the
baseband IC to get dynamic bias control with Vcntl
pin of PA. TX_ADC_ADJ is a PDM output pin produced
by the TX AGC subsystem and used to control the
gain of the Tx signal prior to the PA. The variable
output levels from two inverting operational amplifiers,
generated and compared by TX_ADC_ADJ, provide
dynamic control voltages for the Vcntl of 1.0V ~ 2.7V
with a 0.1V step.
Av = -(V1/Vin) = -R3/R2,
V1 = -(R3/R2)Vin,
Vo = -(R5/R4)V1= [(R5*R3)/(R4*R2)]*Vin
The using of combination of two pins, PDM1 and
TX_ADC_ADJ, is another method of realizing a dynamic
bias control scheme. The two OP Amps control the
Vcntl voltage levels with compared and integrated
circuits.
To Duplexer
13
To Duplexer
Vdd1
Vdd1
Vcntl
Vcntl
Vdd2
Vdd2
PA
PA
Vbias
Vbias
Switch Circuit
Switch Circuit
Battery
Battery
Enable
Enable
R5
+
_
_
TxIC
TxIC
R4
V1
Vcontrol
Vcontrol
R3
_
+
+
_
R2 Vin
C1
R1
PA_ON
PA_ON
TX_ADC_ADJ
PDM1
TX_ADC_ADJ
Baseband IC
Baseband IC