ARA2000_11 Datasheet, PDF (14/21 Pages) ANADIGICS, Inc – Address-Programmable Reverse Amplifier with Step Attenuator

ARA2000
application information
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
14
Data Sheet - Rev 2.3
043/2011