General Description

The RT8845B is a 4/3/2/1 phase synchronous Buck PWM

controller which is optimized for high performance graphic

microprocessor and computer applications. The RT8845B

adopts G-NAVPTM (Green Native AVP) which is Richtek's

proprietary topology derived from finite DC gain of EA

amplifier with current mode control. By utilizing the GNAVPTM

topology, the operating frequency of the RT8845B

varies with VID, load and input voltage to further enhance

the efficiency even in CCM. Moreover, the G-NAVPTM with

CCRCOT (Constant Current Ripple COT) technology

provides superior output voltage ripple over the entire input/

output range. The RT8845B provides complete fault

protection functions including Over-Voltage (OV), Negative

Voltage (NV), Over-Current (OC) and Under-Voltage

Lockout (UVLO). The RT8845B is available in the WQFN-

32L 4x4 package.

The RT8845B features external reference input and PWMVID

dynamic output voltage control, in which the feedback

voltage is regulated and tracks external input reference

voltage. Other features include adjustable switching

frequency, dynamic phase number control, internal/external

soft- start, power good indicator, and enable functions.

特性 Features

? Multi-Phase PWM Controller

? Power State Indicator

? 1P-CCM/4P-CCM/1P-DEM

? Support 1.8V PWM-VID Interface

? External Reference Input Control

? PWM-VID Dynamic Voltage Control

? Dynamic Phase Number Control

? Internal/External Soft-Start

? Adjustable Current Limit Threshold

? Adjustable Switching Frequency

? UVP/OVP Protection

? Support an Ultra-Low Output Voltage as Standby

Voltage

? Thermal Shutdown

? Power Good Indicator

Applications

? GPU Core Supply for nVidia OVR4 + Spec.