The RT6551A/B provides a complete power supply for DDR2/DDR3/DDR3L/LPDDR3/DDR4 memory systems. It integrates a synchronous PWM Buck controller with a 1.5A sink/source tracking linear regulator and buffered low noise reference.
The PWM controller provides the low quiescent current, high efficiency, excellent transient response, and high DC output accuracy needed for stepping down high-voltage batteries to generate low-voltage chipset RAM supplies in notebook computers. The constant on-time PWM control scheme handles wide input/output voltage ratios with ease and provides 100ns "instant-on" response to load transients while maintaining a relatively constant switching frequency.
The RT6551A/B achieves high efficiency at a reduced cost by eliminating the current-sense resistor found in traditional current mode PWMs. Efficiency is further enhanced by its ability to drive very large synchronous rectifier MOSFETs. The Buck conversion allows this device to directly step down high-voltage batteries for the highest possible efficiency.
The 1.5A sink/source LDO maintains fast transient response only requiring a 10µF ceramic output capacitor. In addition, the LDO supply input is available externally to significantly reduce the total power losses. The RT6551A/B supports all of the sleep state controls placing VTT at high-Z in S3 and discharging VDDQ, VTT and VTTREF (soft-off) in S4/S5.
The RT6551A/B provides protections including OVP, UVP, and thermal shutdown. The RT6551A/B is available in the WQFN-20L 3x3 package.
Applications
- DDR2/DDR3/DDR3L/LPDDR3/DDR4 Memory Power Supplies
- Notebook computers
- SSTL18, SSTL15 and HSTL bus termination