ARA2000 Datasheet, PDF (13/20 Pages) ANADIGICS, Inc – Address-Programmable Reverse Amplifier with Step Attenuator

APPLICATION INFORMATION
ARA2000
Transmit Enable / Disable
The ARA2000 includes two amplification stages that
each can be shut down through external control pins
Vg1 and Vg2 (pins 6 and 23, respectively.) By
applying a slightly positive bias of typically +1.0 Volts,
the amplifier is enabled. In order to disable the
amplifier, the control pin needs to be pulled to
ground.
Amplifier Bias Current
The ISET pins (7 and 22) set the bias current for the
amplification stages. Grounding these pins results
in the maximum possible current. By placing a
resistor from the pin to ground, the current can be
reduced. The recommended bias conditions use
the configuration shown in the test circuit schematic
in Figure 4.
A practical way to implement the necessary control
is to use bias resistor networks similar to those
shown in the test circuit schematic (Figure 4.) Each
network includes a resistor shunted to ground that
serves as a pull-down to disable the amplifier when
no control voltage is applied. When a positive voltage
is applied, the network acts as a voltage divider that
presents the required +1.0 Volts to enable the
amplifier. By selecting different resistor values for
the voltage divider, the network can accommodate
different control voltage inputs.
The Vg1 and Vg2 pins may be connected together
directly, and controlled through a single resistor
network from a common control voltage.
Thermal Layout Considerations
The device package for the ARA2000 features a heat
slug on the bottom of the package body. Use of the
heat slug is an integral part of the device design.
Soldering this slug to the ground plane of the PC
board will ensure the lowest possible thermal
resistance for the device, and will result in the longest
MTF (mean time to failure.)
A PC board layout that optimizes the benefits of the
heat slug is shown in Figure 18. The via holes located
under the body of the device must be plated through
to a ground plane layer of metal, in order to provide a
sufficient heat sink. The recommended solder mask
outline is shown in Figure 19.
Figure 18: PC Board Layout
Data Sheet - Rev 2.2
13
06/2004