The LTM8031 is a low noise DC/DC step-down μModule regulator that operates from input voltages from 3.6V to 36V and is independently certified to be compliant with the stringent requirements of EN55022 class B. Its output can be programmed to provide voltages from 0.8V to 10V at up to 1A. A nearly complete converter solution is contained in the 15mm × 9mm × 2.82mm package. As seen in Figure 1, the LTM8031 just requires one resistor to set the output voltage, another resistor to set the operating frequency, and some input and output capacitance.
The LTM8031 comes with many of the features often required in modern power supplies. It can be sequenced via its RUN/SS pin, which also serves to allow the user to control the output behavior at turn on. A PGOOD pin indicates when the output is within 10% of the target regulation voltage. The SYNC pin is used to synchronize the LTM8031 to a desired system frequency.
Through the incorporation of a high Q pi filter and electromagnetic interference reduction design techniques, the LTM8031 is purpose built with low radiated emissions in mind. It has been independently verified to be compliant with EN55022:2006 (Information Technology Equipment – Radio Disturbance Characteristics – Limits and Methods of Measurement). EN55022 has two classes, A and B. The LTM8031 is certified compliant with class B, the more stringent of the two. More than that, the LTM8031 beats the EN55022B limits by a wide margin, better than 20dB in some bands. This is shown in Figures 2, 3 and 4, where the LTM8031 is operated from 36VIN to produce 10VOUT, 5VOUT and 2.5VOUT at 1A, respectively. The 36VIN, 10VOUT at 1A configuration is a worst case radiated emissions scenario, because the LTM8031 is operating with both maximum rated switching voltage and output power.
The LTM8031 is rated to provide 1A, but what about other load currents? Linear Technology offers three other EN55022 class B compliant μModule DC/DC converters, as well: the LTM8020 for 200mA loads, the LTM8021 for 500mA, and the LTM8032 for 2A loads. These are summarized in Table 1, and the worst case emissions for each are given in Figures 5, 6, and 7, respectively.
|Product||VIN Range||VOUT Range||ILOAD(MAX)|
|LTM8020||4V to 36V||1.25V to 5V||200mA|
|LTM8021||3.6V to 36V||0.8V to 5V||500mA|
|LTM8031||3.6V to 36V||0.8V to 10V||1A|
|LTM8032||3.6V to 36V||0.8V to 10V||2A|
It is not uncommon to have to design a power system that requires numerous power rails at different load currents, low radiated emissions, and small size. For ease of design, take a look at the LTM8031 and its family of low noise μModule DC/DC step-down converters.