Rainbow Electronics MAX2203 - Manual (Page 6)

MAX2203
Applications Information
The MAX2203 uses external termination when using
directional couplers. Figure 1 shows the system level
connection of dual-band power detection. The output of
the detector is typically connected to an ADC in
cdma2000 or WCDMA power-control topology.
Enable Logic Level
The MAX2203 features an enable input (ENA) that
allows the device to be put into shutdown. For normal
operation, drive ENA high. For device shutdown, drive
ENA low. The ENA pin is DC biased through a resistor.
The value of the resistor is recommended to be greater
than 1k
Ω to avoid loading the RF input signal. There is
an internal resistor to GND of approximately 50k
Ω. If
the control source high voltage is greater than 2.8V,
calculate and use a resistor value that ensures the ENA
pin only sees a maximum of 2.7V, which is within speci-
fication. In this manner, the MAX2203 can be driven
from a control device with a logic-high greater than
2.8V.
Layout
The MAX2203 is not particularly sensitive to the layout
since it only needs 3dBm for maximum output voltage.
However, there are two areas that need attention: the
GND pins and the supply bypassing. Connect the GND
pins to the PCB ground with a ground via as close as
possible, and bypass V
CC to ground with a capacitor
as close as possible to the part.
Chip Information
PROCESS: BiCMOS
RMS Power Detector
6 _______________________________________________________________________________________
PA 1
PA 2
COUPLER 1
COUPLER 2
10 Ω
10 Ω
50 Ω
50 Ω
ENABLE
RMS
DETECT
BUFFER
BIAS
DETECTOR
OUTPUT
MAX2203
Figure 1. System Level Connection