Maxim-integrated MAX15301 PMBus Command Set Manuel d'utilisateur télécharger pdf (Page 13)

MAX15301 PMBus Command Set User’s Guide

Rev 1 Page 13 of 53

VOUT_TRANSITION_RATE

Reference:

Standard Command

Lockable:

Yes

Command Code:

0x27

Format:

Linear

Data Bytes:

Units:

mV/μs (or V/ms, kV/s)

Transfer:

Read/Write Word

Factory Value:

0x9B33 (0.1V/ms, see Description)

Description/Notes:

See Section 13.8 of the PMBus Specification Part II.

To achieve output voltage slew-rate control, the MAX15301 has an 8-bit timer with approximately

243ns resolution. When the timer expires, the 12-bit voltage setpoint is incremented or decremented

until the setpoint reaches its final value. This limits the minimum and maximum possible slew-rates

for each feedback divider range as follows:

Feedback

VOUT_TRANSITION_RATE, kV/s

Divider

Min

Max

≈ 0.005

≈ 1.171

≈ 0.005

≈ 1.323

≈ 0.006

≈ 1.519

≈ 0.007

≈ 1.782

≈ 0.008

≈ 2.16

≈ 0.011

≈ 2.736

≈ 0.015

≈ 3.725

≈ 0.023

≈ 5.862

For each divider range, the minimum transition rate is also the resolution (minimum step size).

The desired value of VOUT_TRANSITION_RATE is retained in memory, regardless of hardware

limitations imposed by the feedback divider range, but the read-back value is

based on actual

hardware register settings.

If a commanded value of VOUT_TRANSITION_RATE exceeds the maximum possible slew-rate for the

feedback divider range, the MAX15301 sets the slew-rate control timer to zero, and the output

voltage setpoint is updated to the new setpoint value immediately and without delay. In this case,

VOUT_TRANSITION_RATE will read back as 0mV/μs to avoid a divide-by-zero operation.

VOUT_DROOP

Reference:

Standard Command

Lockable:

Yes

Command Code:

0x28

Format:

Linear

Data Bytes:

Units:

mΩ (or mV/A)

Transfer:

Read/Write Word

Factory Value:

0x0000 (0mΩ)

Description/Notes:

See Section 13.9 of the PMBus Specification Part II.

The MAX15301 uses low-pass filtered inductor DCR current-sense information (i.e. the READ_IOUT

signal) to establish the load-line characteristic according to the VOUT_DROOP value. Because of this

low-pass filtering of the load current information, there will be some settling time in the output

voltage positioning when VOUT_DROOP is non-zero.

It is also important to calibrate READ_IOUT using IOUT_CAL_GAIN and IOUT_CAL_OFFSET to achieve

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Maxim-integrated MAX15301 PMBus Command Set Manuel d'utilisateur Page 13

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