AN2048 Datasheet, PDF (1/13 Pages) STMicroelectronics – STMicroelectronics has been strongly

AN2048
Application note
PD54008L-E: 8 W - 7 V LDMOS in PowerFLAT packages
for wireless meter reading applications
Introduction
STMicroelectronics has been strongly involved in finding new package solutions for power
integrated circuits to obtain a surface mount device (SMD). The PowerFLAT™ package
introduced in this application note shows the new concept of chip-size packaging
representing a fundamental step to reduce the costs of assembly and to shrink power
amplifier modules. This package helps maximize board space with improved electrical and
thermal performances over traditional packages with leads. This leadless package is an
MLP (micro leadframe package) where the electrical connections are made through landing
pads on the bottom surface of the component. These landing pads are soldered directly to
the pc board.
Figure 1. MLP cross section
Figure 2. Intermodulation distortion versus
peak effective output power
The standard MLP has an exposed die attach pad which enhances the thermal and
electrical characteristics enabling high-power and high-frequency applications. For small
and medium-power applications, such as wireless PMR (private mobile radio) LDMOS
(Laterally Diffused MOS) transistors in PowerFLAT packages offer certain advantages
compared to equivalent bipolar transistors, for example, better intermodulation (IMD3).
Under certain conditions, an LDMOS transistor exhibits better intermodulation distortion
than a bipolar junction transistor. Figure 2 shows intermodulation distortion versus peak
effective output power for equivalently rated bipolar and LDMOS transistors. As we can see,
below 30 W, the LDMOS device has lower intermodulation distortion than the bipolar
transistor.
● Good gain linearity
● Smooth saturation
● Simpler bias circuit
● Thermal stability. The drain current has a positive temperature coefficient, therefore the
MOS transistor is not susceptible to thermal runaway.
● Better ruggedness
February 2008
Rev 2
1/13
www.st.com