8A step-down regulator comes in surface-mount module
The LTM4608 is part of the µModule family that Linear characterizes as having low input voltage and medium power.
By Graham Prophet, Editor, EDN Europe -- EDN, January 17, 2008
Linear Technology has released the latest in its series of dc/dc converters. The company’s µModules are complete, packaged power-conversion devices, including inductors, capacitors, and compensation, in a low-profile, molded package with land-grid-array-style contact pads for direct soldering to a PCB (printed-circuit board).
The LTM4608 is part of the µModule family that Linear characterizes as having low input voltage and medium power, according to Afshin Odabaee, product-marketing engineer. With an 8A, 10A-peak current rating, it accepts an input of 2.375 to 5.5V and a maximum of 6V and delivers an output voltage of 0.8 to 5V. The package measures 9×15×2.8 mm; output regulation is ±1%. You can connect multiple modules to supply higher currents. Current sharing is beneficial when you use a simple parallel connection, and all of the chips in such a connection will always start, Odabaee says. You can also chain-clock connections between parallel-connected modules for polyphase operation. The LTM4608 has tracking for controlled ramp-up, ramp-down, and sequencing of the output voltage, as well as output-voltage margining for system-level testing: A power-good output signal tracks the margining to indicate when the output is within limits. You can synchronize the switching to an external clock.
The µModules suit use as providers of core voltage to large FPGAs; the devices also have noise performance that is within the range of the on-chip SERDES (serializer/deserializer) functions that the FPGAs require. “Linear is the only supplier that has demonstrated that it can produce such modules with very high reliability,” says Odabaee, claiming essentially zero failures for the series. The modules target designers who lack the expertise to build compact regulator functions themselves.
Linear fabricates its own power MOSFETs for the µModules but says it has no intention of making these MOSFETs available separately: “The economics [of supplying] the MOSFET market are different from those of the specialist-linear-IC market,” Odabaee says. Linear builds the FETs for low on-resistance and low gate charge and with a voltage rating tailored for each µModule. The LTM4608 operates at –40 to +85°C and costs $11.30 (1000). It brings the number of µModules to eight, and Linear plans to extend the series in four categories: high input voltage and high power, low input voltage and low power, very-high voltage and low to medium power, and buck-boost devices that transparently switch from step-down to step-up as the input voltage falls through the level of the regulated output.
