4
www.fairchildsemi.com
RMPA0965 Rev. F
RMPA0965 Cellular CDMA, CDMA2000-1X and WCDMA PowerEdge™ Power Amplifier Module
Efficiency Improvement Applications
In addition to high-power/low-power bias modes, the efficiency of the PA module can be significantly increased at backed-off RF
power levels by dynamically varying the supply voltage (Vcc) applied to the amplifier. Since mobile handsets and power amplifiers fre-
quently operate at 10-20 dB back-off, or more, from maximum rated linear power, battery life is highly dependent on the DC power
consumed at antenna power levels in the range of 0 to +16dBm. The reduced demand on transmitted RF power allows the PA supply
voltage to be reduced for improved efficiency, while still meeting linearity requirements for CDMA modulation with excellent margin.
High-efficiency DC-DC converters are now available to implement switched-voltage operation.
With the PA module in low-power mode (Vmode = +2.0V) at+16dBm output power and supply voltages reduced from 3.4V nominal
down to 1.2V, power-added efficiency is more than doubled from 9.5 percent to nearly 25 percent (Vcc = 1.2V) while maintaining a
typical ACPR1 of –52dBc and ACPR2 of less than –61dBc. Operation at even lower levels of Vcc supply voltage are possible with a
further restriction on the maximum RF output power.
Recommended Operating Conditions
DC Turn-On Sequence
1) Vcc1 = Vcc2 = 3.4V (typical)
2) Vref = 2.85V (typical)
3) High-Power: Vmode = 0V (Pout > 16 dBm)
Low-Power: Vmode = 2V (Pout < 16 dBm)
Symbol Parameter Min Typ Max Units
fOperating Frequency 824 849 MHz
Vcc1, Vcc2 Supply Voltage 3.0 3.4 4.2 V
Vref Reference Voltage
(Operating)
(Shutdown)
2.7
0
2.85 3.1
0.5
V
V
Vmode Bias Control Voltage
(Low-Power)
(High-Power)
1.8
0
2.0 3.0
0.5
V
V
Pout Linear Output Power
(High-Power)
(Low-Power)
+28
+16
dBm
dBm
Tc Case Operating Temperature -30 +85 °C
