Dual-Synchronous Buck Controllers for Point-of-Load, Tracking, and DDR Memory Power Supplies

Active: In Production.

The MAX8537/MAX8539 controllers provide a complete power-management solution for both double-data-rate (DDR) and combiner supplies. The MAX8537 and MAX8539 are configured for out-of-phase and in-phase DDR power-supply operations, respectively, and generate three outputs: the main memory voltage (V_DDQ), the tracking sinking/sourcing termination voltage (V_TT), and the termination reference voltage (V_TTR). The MAX8538 is configured as a dual out-of-phase controller for point-of-load supplies. Each buck controller can source or sink up to 25A of current, while the termination reference can supply up to 15mA output.

The MAX8537/MAX8538/MAX8539 use constant-frequency voltage-mode architecture with operating frequencies of 200kHz to 1.4MHz. An internal high- bandwidth (25MHz) operational amplifier is used as an error amplifier to regulate the output voltage. This allows fast transient response, reducing the number of output capacitors. An all-N-FET design optimizes efficiency and cost. The MAX8537/MAX8538/MAX8539 have a 1% accurate reference. The second synchronous buck controller in the MAX8537/MAX8539 and the V_TTR amplifier generate 1/2 V_DDQ voltage for V_TT and V_TTR, and track the V_DDQ within ±1%.

This family of controllers uses a high-side current-sense architecture for current limiting. ILIM pins allow the setting of an adjustable, lossless current limit for different combinations of load current and R_DSON. Alternately, more accurate overcurrent limit is achieved by using a sense resistor in series with the high-side FET. Overvoltage protection is achieved by latching off the high-side MOSFET and latching on the low-side MOSFET when the output voltage exceeds 17% of its set output. Independent enable, power-good, and soft-start features enhance flexibility.

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