MP2884A datasheet(16/107 Pages) MPS

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MP2884A – DIGITAL PWM CONTROLLER WITH PMBUS AND PWM-VID

MP2884A Rev. 1.01

www.MonolithicPower.com

12/25/2018

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

Dynamic Voltage Identification (DVID)

The MP2884A supports dynamical output

voltage transition by changing VID via the

PMBus commands or the duty of the PWM-VID

signal.

The DVID process is active after VOUT is settled

and can be either upward or downward.

In PMBus-VID control mode, the DVID linear

slew rate is set with register MFR_DVID_SR

(BAh) and ranges from 0.12 - 125mV/µs, as

shown in Equation (8):





6.25m V

Sle w Ra te

M F R _ D V ID _ S R

0 .0 5 s

(8)

There are two slew rate modes in PWM-VID

control mode: R-C filter mode and linear mode.

The DVID R-C filter slew rate is set with register

MFR_PARM_RC_CONST (B5h) and ranges

from 10.40 - 655.36µs, as shown in Equation

(9):









 11

0.32 s

DV ID _ R C

(9)

Where DVID_RC is the value in register

MFR_PARM_RC_CONST (B5h).

The DVID linear slew rate is set with register

MFR_DVID_SR (BAh) and ranges from 0.12 -

125mV/µs (see Equation (8)).

VID Offset

The MP2884A supports two types of VID offset.

The first type is VID step offset, which ranges

from -0.69375V to 0.7V with 6.25mV of

resolution. When the PMBus writes a new offset

to register VOUT_OFFSET (23h), the VR

ramps with the slew rate shown in Equation (8).

The second type is fine-tune offset for the VID

set point, which ranges from -31.5mV to

31.5mV with 0.5mV of resolution at a unity gain

of the differential voltage sense amplifier and

ranges from -50.4mV to 50.4mV with 0.8mV of

resolution at a half-gain of differential voltage

sense amplifier. Refer to the register map

MFR_RSAMP_OFFSET (2Dh) section on page

44 for details.

Inductor Current Sensing

The MP2884A works with the Intelli-Phase for

inductor current sensing (see Figure 4). The

voltage on CSs is sampled, calculated, and

stored in the registers. The results are used for

multi-phase current balancing and thermal

balancing and can be monitored via the PMBus.

The MP2884A provides cycle-by-cycle per-

phase current limitation.

The resistor (RCS) is connected from CSx to

CSSUM. CSSUM is a 1.23V constant voltage

and can sink or source current to provide

voltage shifts that meet the operating voltage

range of CSs.

Short any unused CSx pin to AGND or CSSUM.

Figure 4: Phase Current Sense

Different types of Intelli-Phase products have

different operating voltage ranges for CS

(VCS_MIN and VCS_MAX). Refer to each Intelli-

Phase’s datasheet to determine the minimum

and

maximum

operating

voltage

ranges.

Calculate a proper RCS value with Equation (10):

C S

M I N

L O A D

C S

M A X

1 . 2 3 V









(10)

By working with the Intelli-Phase, the MP2884A

does not need temperature compensation and

impendence matching compared with traditional

DCR sensing to achieve an accurate current

sense.

Total Current Sensing

The total current is summed from CSSUM, and

a 1/16 proportional current emerges to IMON.

Connect a resistor from IMON to AGND to

generate a voltage proportional to the output

current. The IMON voltage

is sampled,

calculated, and stored in the registers. This

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