New switching regulator for DDR termination complies with DDR/DDR2/DDR3 standards

New switching regulator for DDR termination complies with DDR/DDR2/DDR3 standards

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By eeNews Europe

An internal resistor divider sets the V TT DDR termination supply and VTTR reference voltages equal to half the voltage applied to the input, with output current capability of ±6 A (sinking/sourcing) at V TT and ±10 mA at VTTR. The outputs are capable of operation down to 0.5 V.

The LTC3617 operates from an input voltage range of 2.25 V to 5.5 V and allows switching frequencies as high as 4 MHz, allowing for very small externals. This creates a small, compact solution footprint that is preferred for laptop computers and graphics card applications, which need ±6 A or less for DDR termination. The internal synchronous top and bottom power switches have an R DS(ON) of only 35 mOhm and 25 mOhm respectively, enabling the LTC3617 to attain efficiencies as high as 93%, eliminating the need for an external catch diode while minimizing external component count and board space.

The LTC3617 utilizes a constant frequency, current-mode architecture. The switching frequency can be set between 300 kHz and 4 MHz by a single external resistor. This high frequency capability enables use of smaller capacitor values, while maintaining low output voltage ripple. For noise-sensitive switching applications, the LTC3617 can be synchronized to an external clock up to 4 MHz. Forced continuous mode operation helps reduce noise and RF interference. Optional external compensation allows optimization of transient response over a wide range of loads and output capacitors. The device uses an input overvoltage lockout circuit to protect the input supply from back-boosting.

For optimal thermal performance, the LTC3617 is offered in a thermally enhanced 24-pin 3 mm x 5 mm QFN package. The device is guaranteed for operation from -40 to 125°C. 1,000-piece pricing starts at $3.80 for the E grade and $4.20 for the I grade.

More information about the LTC3617 monolithic synchronous step-down switching regulator at

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