The RT8870A is a dual-output PWM controller for AMD SVI mobile CPU power supply. The RT8870A provides a two-phase PWM controller to power the CPU Core (VDD) and a single-phase PWM controller to power the Northbridge portion of the CPU (VDDNB). This part has three integrated MOSFET drivers and is fully compliant with AMD Voltage Regulator Specification to meet AMD’s mobile CPU power supply requirements. The RT8870A features CCRCOT (Constant Current Ripple Constant On-Time) control with G-NAVPTM (Green-Native AVP), which is a Richtek proprietary topology. The CCRCOT control provides superior output voltage ripple performance over the entire input/output range. G-NAVPTM makes this device an easy setting controller to meet the droop requirement for all AMD mobile CPUs. The droop is easily programmed by setting the DC gain of the error amplifier. With proper compensation, the load transient response can achieve optimized AVP performance. The droop function is selectable for both VDD and VDDNB outputs. The RT8870A uses Serial VID Interface (SVI) for individual controller output voltage and operation mode programming. A built-in high-accuracy DAC converts the serial VID code for output voltage ranging from 0.5V to 1.55V with up to 0.8% system accuracy. This device supports VID on-the-fly and operation mode transition onthe-fly functions that are fully compliant with the AMD specification. Both VDD and VDDNB controllers provide diode emulation mode to improve efficiency at light load condition. The RT8870A supports inductor DCR and sense resistor current sensing. It also provides power good indication and complete fault protection functions, including over voltage, out-of-spec, negative voltage, over current and under voltage lockout thermal shutdown. The RT8870A is available in a WQFN-40L 5x5 small footprint package.
