Cooling for Space Applications
Traditionally, solid metallic conductors (heat
sinks) and heat pipes have been used to
cool electronic components. Other
conventional alternatives include
forced-air heat sinks and liquid cool-
ing systems. In many of these conven-
tional systems, electronic devices are
mounted on copper-alloy substrates
using soft or hard die attachments. How-
ever, these conventional systems have disadvan-
tages that limit their applicability and reliability.
NASA Glenn Research Center and Thermacore Inc. have developed a solution to these limitations with their innovative Therma-Base. Therma-Base is a heat pump design that offers several advantages in addition to its basic
passive heat transfer capability: simple and reliable operation; highly effective
thermal conductivity; no moving parts; and quiet, vibration-free operation. The
device improves thermal performance by up to 15 times compared to a solid cop-per-based heat spreader. Its two-phase cooling approach provides reliable thermal
conductivity. A unique planar structure makes it thin, lightweight and compact,
making it ideal for cooling proton exchange membrane (PEM) fuel cells.
◗ NASA Glenn Research Center, www.nasa.gov
Designers of low-power products are
challenged with squeezing more performance from their new designs while
using less energy than the preceding
The tool of choice for many product
designers is an oscilloscope, but for
low-power applications this instrument
isn’t ideal. Equipped with the traditional
clamp-on magnetic field sensing cur-
rent probe, oscilloscopes lack the sensitivity to measure low-level sleep current and
the dynamic range to measure peak current in the presence of sleep current.
The recent introduction of Agilent Technologies’ N2820A Series High-Sensitivity, High Dynamic Range Oscilloscope Current Probe changes this
dynamic. Though labeled as a current probe, the N2820A is actually a highly sensitive oscilloscope voltage probe. By measuring voltages as small as 5 µV, across a current sense resistor, the probe can determine the current flowing through the resistor.
By connecting N2820A’s two probe outputs to two channels of the oscilloscope, the
user can observe both small current and large peak current simultaneously.
◗ Agilent Technologies, www.agilent.com
Faster Semiconductor Inspections
Thermal resistance or junction temperature is a key parameter
for most semiconductor devices, and significantly
affects device efficiency and reliability. Measurement of
thermal resistance is accomplished in two major steps.
The first is the temperature sensitive parameter (TSP)
measurement, which displays the correlation between
device voltage and temperature. The second is to
measure voltage difference after temperature rise. The
process is complex, costly and time consuming.
To help aid in these limitations, Industrial
Technology Research Institute developed the ICTA
In-Line Compact Thermal Analyzer. ICTA technology is a shipping inspection technique used for
LED manufacture. While existing thermal-resistance
analyzers are based on steady-state methods to determine TSP, ICTA is a high-speed TSP measurement using dynamic synchronization technology to analyze
thermoelectric signals simultaneously during the thermal-transient process. The
procedure can be completed in 20 sec, improving the total efficiency of thermal
structure analysis by more than a factor of four.
◗ Industrial Technology Research Institute, www.itri.org.tw/eng/
An Industry First
Texas Instruments’ LDC1000 is the industry’s first inductance-to-digital converter
(LDC). The LDC1000 design team
combined unique circuit and architecture
topologies to create the product. Optimized by
mixing current- and voltage-mode signaling to maximize the
performance of the circuit, the LDC provides both high bandwidth and low power.
The key innovation of the LDC1000 was to combine high-performance eddy
current losses and system inductance measurement capabilities in a small integrated circuit at low power using a patent-pending approach. The device includes
a unique common-mode regulation loop to regulate the common-mode signal
across the tank. As a result, the LDC1000 doesn’t need to incorporate complex
common-mode filtering, which would consume significant power.
In order to combine the benefit of modern high-density CMOS technology with inductive sensing, the LDC team also implemented special tricks to
overcome the limited impedance and signal swing of CMOS. Thanks to these
advancements, the LDC1000 provides 16-bit eddy current losses and 24-bit
inductance values, enabling sub-micrometer resolution in precision position
sensing applications while consuming less than 8. 5 m W of power during standard operation and less than 1.25 m W in standby mode.
◗ Texas Instruments, www.ti.com
Texas Instruments’ bq25570 is a highly integrated
energy-harvesting nanopower management solution
that meets the needs of ultra-low power applications.
Energy harvester design is tricky; it’s important that
power management electronics consume the lowest
amount of power to maximize efficiency. Until now, all
energy-harvesting and power-management integrated
circuits (IC) either offered a reduced feature set (to
minimize power consumption) or offered additional
features by sacrificing the power consumption. The
bq25570 is the first device of its kind to implement a
highly efficient boost charger with a nano-powered
buck converter to efficiently acquire and manage the
microwatts to milliwatts of power generated from a
variety of DC sources like photovoltaic (solar) or ther-
mal electric generators.
Targeted toward systems such as wireless sensor networks (WSN), the bq25570 features a small footprint
and is designed with a DC/DC boost converter/charger
requiring only microwatts of power to begin operating.
The boost charger can start with an input voltage as low
as 330 mV, and once started, continues to harvest energy
down to an input voltage of 100 mV. The bq25570 also
implements a programmable maximum power point
tracking sampling network to optimize the transfer of
power into the device and provides an externally programmable regulated supply via the buck converter. The
regulated output is optimized to provide high efficiency
across low output currents to high currents.
◗ Texas Instruments, www.ti.com