Linear’s New µModule®
Tiny 1.5W Isolated Low Noise DC/DC µModule Converters Include Transformer
I had the pleasure to talk with Afshin Odabaee, Product Marketing Manager, DC/DC µModule Products at Linear Technology Corporation. Afshin explained that current loops in different parts of a system may result in voltage spikes on the supply rail and ground plane, often referred to as noise. High current devices such as motors, pumps and microprocessors with dynamic power demands are primary sources of noise on the supply rail and ground plane. This noise alters signals that are transmitted and received between sensors, data converters and control circuits such as in industrial and commercial control systems, for example. In some instances, the noise corrupts signals to a level that they become undecipherable. The transformer has always been the weakest link and Linear has integrated this into these new converters with an extremely high reliability process.
To improve signal integrity, a power plane needs to be clean starting with the switching regulator circuit. This ideal regulator solution must not only be capable of minimizing the influence of ground loops on its regulated output voltage but also reduce the noise that itself generates: mainly reduce the amplitude of the output ripple on the supply rail produced by the switching operation of the regulator.
The first challenge is addressed by galvanically isolating the input supply (primary side) from the regulated output (secondary side) using a transformer. The transformer blocks DC ground loop current flow from the input supply side to the output side where it shares a common ground plane with a transducer. This method of stopping the flow of ground loop current is popularly referred to as “breaking the ground loop”.
The second challenge of the DC/DC regulator’s self-generated noise on the output voltage, is alleviated by placing a low noise linear regulator after the isolated output thus reducing the switchmode regulator’s output ripple on the secondary side. This is referred to as post regulation.
Linear Technology’s New Solution
The LTM8048 1.5W DC/DC µModule regulator is the first device in the new family of µModule power products with 725VDC galvanic isolation and includes a low noise post regulator in a small 9mm x 11.25mm x 4.92mm BGA (ball grid array) package. The transformer, regulator IC, power switches, compensation circuitry and low noise post regulator are all housed in this small package.
Linear’s LTM8047 and LTM8048 are 1.5W output DC/DC µModule® converters with 725VDC galvanic isolation in a 9mm x 11.25mm x 4.92mm BGA (ball grid array) package. All components, including the transformer, control circuitry and power switches are housed in a small enclosed BGA package for superior interconnect reliability in high vibration applications. These compact and reliable products break ground loops in applications such as industrial, avionics and instrumentation equipment. Both devices operate from an input voltage of 3.1V to 32V, delivering a regulated output voltage on the secondary side, adjustable from 2.5V to 12V (LTM8047) and 1.2V to 12V (LTM8048). The LTM8048 includes a low noise linear post regulator that reduces the output ripple noise to 20µVrms at 300mA.
The LTM8048’s isolated post regulator delivers an output voltage accuracy of 2.5%. The low noise performance of the LDO delivers a clean supply rail, improving the performance of high accuracy mixed signal converters. Additional features available on both products include overcurrent protection and adjustable soft start.
Summary of Features: LTM8047/LTM8048
- 725VDC Isolation Tested
- 1.5W Output Power
- Wide 3.1V to 32V Input Voltage Range
- Adjustable Output Voltage 2.5V to 12V
- 80% / 75% Efficiency (24VIN to 5VOUT) for LTM8047 & LTM8048, Respectively
- Low Noise LDO Output with 20µVrms Ripple at 300mA (LTM8048 only)
- Up to +125°C Operating Junction Temperature
- Compact, Thermally Enhanced 9mm × 11.25mm × 4.92mm BGA Package
The LTM8047 and LTM8048 are available for immediate delivery from stock in three temperature grades, E and I from -40°C to +125°C and MP for the -55°C to +125°C operating junction temperature range. Pricing starts at $8.25 and $8.75 each for 1,000-piece quantities for the LTM8047 and LTM8048, respectively.