MP2935 datasheet(13/42 Pages) MPS

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MP2935 — 4-PHASE PWM CONTROLLER FOR VR12.5 APPLICATIONS

MP2935 Rev. 1.02

www.MonolithicPower.com

8/25/2015

MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.

PWM Operation and Power States

The user can select the total number of operating

phases for MP2935, as described in “Switching

Frequency and the Number of Operating

Phases.” Based on the power states, the actual

operating phase dynamically switches between

full phases or single phase to optimize the power

conversion efficiency at heavy and light CPU

loads.

In PS0, MP2935 runs in full-phase PWM mode.

While in light-load mode, PS1 to PS3, only Phase

1 is in operation to maximize power conversion

efficiency. During the dynamic VID transition

issued by SVID commands of either SetVID_Fast

or SetVID_Slow, the power state changes to PS0

by default and runs in full-phase PWM mode.

In addition to changing the number of phases,

the operation mode can change dynamically. In

PS0 mode, MP2935 runs in multiphase PWM

mode with switching frequency controlled by the

master clock. In other power states, MP2935

switches to AAM mode where the switching

frequency is no longer controlled by the master

clock, but by the ripple voltage on the COMP pin.

Thus, the switch frequency varies with the load

current, resulting in maximum power conversion

efficiency in low power states.

In PS2 and PS3, diode emulation mode is

enabled to maximize the efficiency at light load

condition.

The VR will switch back to AAM mode if the over

current alarm is clear before latch-off.

Table 1 summarizes the dynamically changes to

phase number and operation modes based on

the power state register set through SVID

commands.

The power states are listed in order of power

savings:

•

PS0 represents full power or Active mode

•

PS1 is used in Active Mode or Idle Mode and

represents a low current state, similar to PSI#

definition in VR11.1 or IMVP6.5; it typically

has a load < 20A. MP2935 runs in single

phase (PWM1 only) AAM/continuous current

modulation (CCM) mode.

•

PS2 is used in Sleep Mode and it represents

a lower current state than PS1; it typically has

a load < 5A. MP2935 runs in single phase

(PWM1 only) AAM with diode emulation

enabled.

•

PS3 (Mode[1,0]= “11”) is ultra-low current

mode, lower than PS2; it typically has a load

< 1A. MP2935 runs in single phase (PWM1

only) AAM with diode emulation enabled.

Table 1: Phase Number and Operation Modes

Power

State

Operating

Phases

CCM PWM/AAM

Full phases

PWM

AAM

AAM Control Operation and Diode Emulation

With the exception of PS0, all other power states

enable AAM mode and run in single phase

operation. Figure 2 shows typical AAM mode

operation where switching frequency is no longer

controlled by the master clock, but by the ripple

voltage on the COMP pin.

PWM1 is set high when VCOMP reaches the AAM

threshold voltage which is set by two resistors,

from AAM pin to GND and from AAMB pin to

GND.

OUT

MON

AAMB

COMMON

AAM

AAM Threshold Voltage

15400 V









AAMB

16 R





OUT

AAM

AAM _ Fraction

15400 V





AAM_Fraction

OUT

L _ PK PK

0.5 I

10 10

F3.424 10











VCOMMON is about 1V. VAAM_Fraction is part of the

AAM threshold voltage.

N is the number of

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