Preliminary Information
RF Power Amplifier (PA) Bias Controller
FEATURES
• Programmable Bias Controller IC for Class A and
AB LDMOS Power Amplifiers
• Adaptive System on Chip Solution
• Bias Current Calibration to better than ±4%
using Reference Trim DCP
• Automatic Bias Point Tracking and Calibration
— I
DQ
Sensing and Tracking
—Programmable Instrumentation Amplifier to
Scale Wide Range of I
DQ
—Programmable Gate Bias Driver
—All Programmable settings are Nonvolatile
—All Settings Recalled at Power Up.
• 28V Maximum V
DD
• 2 Wire Interface for Programming Bias Setting
and Optimizing I
DQ
Set Point
• Bias Level Comparator
• Shutdown Control pin for PA Signal
• Slave address to allow for multiple devices
• 24-pin TSSOP Package
• Applications: Cellular Base Stations (GSM,
UMTS, CDMA, EDGE), TDD applications, Point-
to-multipoint, and other RF power transmission
systems
DESCRIPTION
X9470
TYPICAL APPLICATION
INC/DEC
A2
A1
A0
in
ar
y
In
fo
V
OUT
The Xicor X9470 RF PA Bias Controller contains all of
the necessary analog components to sense the PA
drain current through an external sense resistor and
automatically control the gate bias voltage of an
LDMOS PA. The external sense resistor voltage is
amplified by an instrumentation amplifier and the out-
put of the amplifier along with an external reference
voltage is fed to the inputs of a comparator. The com-
parator output indicates which direction the LDMOS
gate bias voltage will move in the next calibration
cycle. System calibration is accomplished by enabling
the X9470 and providing a clock to the SCL pin. The
LDMOS drain current can be maintained constant over
temperature and aging changes by periodic calibra-
tion. The VOUT pin can be used to monitor the aver-
age power by tracking the drain current. Up to eight
X9470 or additional Xicor Digital Potentiometers can
be controlled via a two-wire serial bus.
rm
V+
V
BIAS
at
i
∆V
RW
REF
RH
REF
RL
REF
R
REF
AGND
on
V
DD
V
SENSE+
V
SENSE–
choke
el
im
C
BULK
R
SENSE
V
REF
Instrumentation
Amplifier
VREF
control
R
BIAS
Comparator
VP
SDA
SCL
Pr
I2C
interface
Vbias
control
+
–
V
BIAS (Unbuffered)
FILTER
Control &
Status Registers
RF
out
RF PA in
Matching
RF Impedance
EEPROM
VCC
VSS
CS
RH
BIAS
RW
BIAS
RL
BIAS
SHDN
Class A Example
REV 11.16 3/20/03
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XICOR [ XICOR INC. ]
