max2247ebct Maxim Integrated Products, Inc., max2247ebct Datasheet - Page 7

• Manufacturer Part Number: max2247ebct
• Description: Max2247 2.4ghz Sige Linear Power Amplifier
• Manufacturer: Maxim Integrated Products, Inc.

The MAX2247 linear power amplifier (PA) offers a wide
variety of features incorporated into a tiny UCSP pack-
age. The device includes internal bias circuitry, an inte-
grated power detector with buffered output, low-power
shutdown mode, and internal input matching. The
MAX2247 output power can be optimized for +15dBm to
+24dBm by adjusting the output, first-stage, and second-
stage matching network (see the Typical Operating
Circuit) while exceeding 802.11b ACPR requirements. In
addition, external bias control allows dynamic throttle-
back of the supply current to increase efficiency.
The MAX2247’s performance can be optimized for lower
output power levels. Go to the Maxim website,
www.maxim-ic.com, for MAX2247 application notes cov-
ering performance at +21dBm, +18dbm, and +15dBm.
To improve efficiency at lower output levels, a bias pin
is offered to allow dynamic current control. An external
current DAC or resistor network can be used to throttle-
back current at lower output powers while still maintain-
ing ACPR requirements. By including an internal volt-
age regulator along with the bias circuitry, no external
bias voltage is necessary. The internal voltage regula-
tor maintains stable performance of the bias circuitry
over temperature and supply variations.
Figure 1. Internal Bias Circuitry
_______________________________________________________________________________________
REFERENCE
INTERNAL
VOLTAGE
Detailed Description
MAX2247
2.4GHz SiGe Linear Power Amplifier
INPUT
RF
Bias Circuitry
1.2V
BIAS CURRENT
1ST-STAGE
AMPLIFIER
BIAS
1.2V
The overall current of the MAX2247 is set by the current
sourced through the bias pin. The overall current is 540
times the bias current. An internal bandgap reference pro-
vides +1.2V to each bias stage (see Figure 1). An external
resistor to ground can be placed at the bias pin to set the
bias current (refer to the MAX2247 evaluation kit).
An external current DAC can be connected directly to the
bias pin to adjust the bias current of the MAX2247. Figure
2 shows the MAX2247 connected to the MAX2820 zero-IF
transceiver, which includes a 4-bit DAC.
The MAX2247 features a low-power shutdown mode to
further reduce current consumption. The MAX2247
responds to logic-level signals at the SHDN pin. A
logic-level high enables all circuitry, while a logic-level
low places the device in low-power shutdown mode
and reduces supply current to 0.5µA (typ). Power-ramp
turn-on and turn-off times are guaranteed to be less
than 1.5µs.
This device includes a power detector that samples the
peak voltage of the output and generates a voltage
proportional to the output power. The detector is fully
temperature compensated and allows the user to set
the detector bandwidth with an external capacitor.
BIAS CURRENT
CONNECTED TO EXTERNAL RESISTOR/DAC FOR SETTING THE BIAS CURRENT
2ND-STAGE
AMPLIFIER
1.2V
BIAS CURRENT
3RD-STAGE
AMPLIFIER
RF_OUT
Shutdown Mode
Power Detector
RF
OUTPUT
7