Maxim Integrated MAX15303 User Manual

MAX15303 PMBus Command Set

User’s Guide

Rev 0; 1/14

Maxim Integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim Integrated product. No circuit patent licenses are implied. Maxim Integrated reserves the right to change the circuitry and specifications without notice at any time.

Maxim Integrated 160 Rio Robles, San Jose, CA 95134 USA 1-408-601-1000

MAX15303 PMBus Command Set User’s Guide

Reference:

<”Standard” or “Maxim Specific”>

Lockable:

Command Code:

Format:

Data Bytes:

Units:

Transfer:

Factory Value:

Description/Notes:

<Command definition if Maxim-specific, or notes on command functionality where it differs from the

Introduction

Maxim Integrated InTune™ digital power products utilize the PMBus™ command standard for configuration, control, and telemetry.

This document lists and describes the PMBus commands implemented in the MAX15303 digital DC-DC converter. Standard commands from the PMBus specification are not described in detail unless there are deviations from the PMBus specification functionality. Maxim manufacturer-specific commands are fully described in this document.

References for this document are found on the PMBus and SMBus organization websites.

http://pmbus.org/specs.html http://smbus.org/specs/

The commands in this document are presented in the following format:

<COMMAND_NAME>

PMBus specification.>

Table of Contents

Introduction ................................................................................................................................................................................. 2

On, Off, and Margin Testing-Related Commands ........................................................................................................................ 6

OPERATION .............................................................................................................................................................................. 6

ON_OFF_CONFIG ..................................................................................................................................................................... 6

VIN_ON .................................................................................................................................................................................... 7

VIN_OFF ................................................................................................................................................................................... 7

Output Voltage-Related Commands ............................................................................................................................................ 9

VOUT_MODE ........................................................................................................................................................................... 9

VOUT_COMMAND ................................................................................................................................................................... 9

VOUT_TRIM ............................................................................................................................................................................. 9

VOUT_CAL_OFFSET ................................................................................................................................................................ 10

VOUT_MAX ............................................................................................................................................................................ 10

VOUT_MARGIN_HIGH ........................................................................................................................................................... 11

VOUT_MARGIN_LOW ............................................................................................................................................................ 11

VOUT_TRANSITION_RATE ...................................................................................................................................................... 12

Page 2 of 52

MAX15303 PMBus Command Set User’s Guide

VOUT_DROOP ........................................................................................................................................................................ 12

Switching Frequency and PWM Commands .............................................................................................................................. 14

FREQUENCY_SWITCH ............................................................................................................................................................. 14

INTERLEAVE ........................................................................................................................................................................... 14

Output Voltage Sequencing Commands .................................................................................................................................... 16

POWER_GOOD_ON ............................................................................................................................................................... 16

POWER_GOOD_OFF .............................................................................................................................................................. 16

TON_DELAY ............................................................................................................................................................................ 17

TON_RISE ............................................................................................................................................................................... 17

TOFF_DELAY ........................................................................................................................................................................... 17

TOFF_FALL ............................................................................................................................................................................. 18

Fault-Related Commands .......................................................................................................................................................... 19

CLEAR_FAULTS ....................................................................................................................................................................... 19

VOUT_OV_FAULT_LIMIT ........................................................................................................................................................ 19

VOUT_OV_FAULT_RESPONSE ................................................................................................................................................ 19

VOUT_UV_FAULT_LIMIT ........................................................................................................................................................ 20

VOUT_UV_FAULT_RESPONSE ................................................................................................................................................ 20

IOUT_OC_FAULT_LIMIT ......................................................................................................................................................... 21

IOUT_OC_FAULT_RESPONSE ................................................................................................................................................. 21

OT_FAULT_LIMIT ................................................................................................................................................................... 22

OT_FAULT_RESPONSE ........................................................................................................................................................... 23

OT_WARN_LIMIT ................................................................................................................................................................... 23

VIN_OV_FAULT_LIMIT ........................................................................................................................................................... 24

VIN_OV_FAULT_RESPONSE ................................................................................................................................................... 24

VIN_UV_FAULT_LIMIT ........................................................................................................................................................... 25

VIN_UV_FAULT_RESPONSE ................................................................................................................................................... 25

Unit Status Commands .............................................................................................................................................................. 27

STATUS_BYTE ......................................................................................................................................................................... 27

STATUS_WORD ...................................................................................................................................................................... 27

STATUS_VOUT ....................................................................................................................................................................... 27

STATUS_IOUT ......................................................................................................................................................................... 27

STATUS_INPUT ....................................................................................................................................................................... 28

STATUS_TEMPERATURE......................................................................................................................................................... 28

STATUS_CML .......................................................................................................................................................................... 28

Page 3 of 52

MAX15303 PMBus Command Set User’s Guide

Telemetry Commands ................................................................................................................................................................ 29

READ_VIN .............................................................................................................................................................................. 29

READ_VOUT ........................................................................................................................................................................... 29

READ_IOUT ............................................................................................................................................................................ 29

READ_TEMPERATURE_1 ........................................................................................................................................................ 30

READ_TEMPERATURE_2 ........................................................................................................................................................ 30

READ_DUTY_CYCLE ................................................................................................................................................................ 30

READ_FREQUENCY ................................................................................................................................................................. 30

PMB_VALUES ......................................................................................................................................................................... 31

Calibration Commands .............................................................................................................................................................. 33

IOUT_CAL_GAIN ..................................................................................................................................................................... 33

IOUT_CAL_OFFSET ................................................................................................................................................................. 33

EXT_TEMP_CAL ...................................................................................................................................................................... 33

Device Identification Commands ............................................................................................................................................... 35

CAPABILITY ............................................................................................................................................................................. 35

PMBUS_REVISION .................................................................................................................................................................. 35

MFR_ID .................................................................................................................................................................................. 35

MFR_MODEL .......................................................................................................................................................................... 36

MFR_REVISION ...................................................................................................................................................................... 36

MFR_LOCATION ..................................................................................................................................................................... 36

MFR_DATE ............................................................................................................................................................................. 36

MFR_SERIAL ........................................................................................................................................................................... 37

IC_DEVICE_ID ......................................................................................................................................................................... 37

IC_DEVICE_REV ...................................................................................................................................................................... 37

Security Commands ................................................................................................................................................................... 38

WRITE_PROTECT .................................................................................................................................................................... 38

MANUF_CONF ....................................................................................................................................................................... 38

MANUF_LOCK ........................................................................................................................................................................ 39

MANUF_PASSWD ................................................................................................................................................................... 39

USER_CONF ............................................................................................................................................................................ 39

USER_LOCK ............................................................................................................................................................................ 40

USER_PASSWD ....................................................................................................................................................................... 40

SECURITY_LEVEL .................................................................................................................................................................... 41

Memory and Storage Commands .............................................................................................................................................. 42

Page 4 of 52

MAX15303 PMBus Command Set User’s Guide

STORE_DEFAULT_ALL ............................................................................................................................................................ 42

RESTORE_DEFAULT_ALL ........................................................................................................................................................ 43

STORE_USER_ALL ................................................................................................................................................................... 43

RESTORE_USER_ALL .............................................................................................................................................................. 44

RESTORE_MAXIM_ALL ........................................................................................................................................................... 45

STRAP_DISABLE ...................................................................................................................................................................... 45

Control Loop Commands ........................................................................................................................................................... 47

ADAPTIVE_MODE ................................................................................................................................................................... 47

FEEDBACK_EFFORT ................................................................................................................................................................ 48

LOOP_CONFIG ........................................................................................................................................................................ 48

COMP_MODEL ....................................................................................................................................................................... 49

DEADTIME_GCTRL ................................................................................................................................................................. 49

ZETA_P ................................................................................................................................................................................... 50

Trademarks ................................................................................................................................................................................ 51

Revision History ......................................................................................................................................................................... 52

Page 5 of 52

Reference:

Standard Command

Lockable:

Yes

Command Code:

0x01

Format:

Bit field

Data Bytes:

Units:

N/A

Transfer:

Read/Write Byte

Factory Value:

0x40 (see Description table)

Description/Notes:

See Section 12.1 of the PMBus Specification Part II.

On, Off, and Margin Testing-Related Commands

OPERATION

If the values of VOUT_OV_FAULT_LIMIT or VOUT_UV_FAULT_LIMIT are set between the values of

VOUT_MARGIN_HIGH and VOUT_MARGIN_LOW, it is possible that a fault will be detected when

exiting the “Margin High/Low (Ignore Fault)” command states. This occurs when fault detection is reenabled before the output has had time to return to the be avoided in most cases by increasing the value of VOUT_TRANSITION_RATE, thereby decreasing the amount of time required for the output to return to normal VOUT_COMMAND setpoint.

The value of the OPERATION command is maintained in volatile memory, and cannot be stored in the Default Store or User Store nonvolatile memory. This prevents inadvertent preservation of a margin-high or margin-low state. If it is desired to keep the output always enabled or always disabled upon power-up, this can be achieved by storing the appropriate value of the ON_OFF_CONFIG command.

MAX15303 PMBus Command Set User’s Guide

VOUT_COMMAND value. This condition can

Useful values for the OPERATION command: 0x00 Immediate-off, no sequencing: both DH and DL outputs low 0x40 Soft-off, with sequencing (factory setting) 0x80 Output enabled, if allowed by ON_OFF_CONFIG setting (note: same as 0x81-0x8F) 0x94 Margin low, ignore faults (note: same as 0x95-0x97) 0x98 Margin low, act on faults (note: same as 0x99-0x9B) 0xA4 Margin high, ignore faults (note: same as 0xA5-0xA7) 0xA8 Margin high, act on faults (note: same as 0xA9-0xAB)

Invalid values for the OPERATION command:

0x90-0x93 0x9C-0x9F 0xA0-0xA3 0xAC-0xFF

These invalid data bytes will trigger an “Invalid Or Unsupported Data” response per section 10.9.3 of the PMBus specification.

After writing the OPERATION command to enable the output, the PMBus master must either wait for a time equal to (TON_DELAY + TON_RISE + 50ms), or wait for PG to assert, before sending additional PMBus commands.

ON_OFF_CONFIG

An “immediate-off,” “hard-stop,” or “three-state” shutdown means the MAX15303 will stop switching and keep both DH

and DL outputs low, allowing the output voltage to decay naturally according to load and output capacitance.

In this application note (and other InTune documents) a “soft-off,” “soft-stop,” or “ramp-down” shutdown means the MAX15303 actively controls the output voltage along a linear ramp to zero Volts, per the TOFF_DELAY and TOFF_FALL values.

(note: same as 0x41-0x7F)

(note: same as 0x01-0x3F)

Page 6 of 52

Reference:

Standard Command

Lockable:

Yes

Command Code:

0x02

Format:

Bit field

Data Bytes:

Units:

N/A

Transfer:

Read/Write Byte

Factory Value:

0x16 (see Description table)

Description/Notes:

See Section 12.2 of the PMBus Specification Part II.

After writing the ON_OFF_CONFIG command to enable the output, the PMBus master must either

VIN_ON

Reference:

Standard Command

Lockable:

Yes

Command Code:

0x35

Format:

Linear

Data Bytes:

Units:

Transfer:

Read/Write Word

Factory Value:

0xCB00 (6.0V)

Description/Notes:

See Section 14.5 of the PMBus Specification Part II.

Reference:

Standard Command

Lockable:

Yes

Command Code:

0x36

Format:

Linear

Data Bytes:

Units:

Transfer:

Read/Write Word

Factory Value:

0xCAC0 (5.5V)

ON_OFF_CONFIG

MAX15303 PMBus Command Set User’s Guide

Useful Values for the ON_OFF_CONFIG command: 0x00 Output always enabled (note: same as 0x01-0x0F) 0x10 Output always disabled (note: same as 0x11-0x13) 0x14 Ignore bit 7 of OPERATION 0x15 Ignore bit 7 of OPERATION, require EN low to run, immediate-off on loss of EN 0x16 Ignore bit 7 of OPERATION, require EN high to run, soft-off on loss of EN (factory setting) 0x17 Ignore bit 7 of OPERATION, require EN high to run, immediate-off on loss of EN 0x18 Require bit 7 of OPERATION to run, ignore EN (note: same as 0x19-0x1B) 0x1C Require bit 7 of OPERATION and EN low to run, soft-off on loss of EN 0x1D Require bit 7 of OPERATION and EN low to run, immediate-off on loss of EN 0x1E Require bit 7 of OPERATION and EN high to run, soft-off on loss of EN 0x1F Require bit 7 of OPERATION and EN high to run, immediate-off on loss of EN

, require EN low to run, soft-off on loss of EN

In general, odd values of ON_OFF_CONFIG that require a valid EN signal will have an immediate-off shutdown when EN is not valid. Even values that require EN will have a soft-off shutdown when EN is not valid.

wait for a time equal to (TON_DELAY + TON_RISE + 50ms), or wait for PG to assert, before sending additional PMBus commands.

The MAX15303 hardware has 8-bit resolution for the minimum input voltage required for regulation, to a maximum value of ≈14.75V.

The desired value of VIN_ON is retained in memory, regardless limitations imposed by the 8-bit fault limit resolution, but the read-back value is based on actual hardware register settings.

VIN_OFF

Page 7 of 52

Description/Notes:

See Section 14.6 of the PMBus Specification Part II.

VIN_OFF

The MAX15303 hardware has 8-bit resolution for the minimum input voltage required for regulation, to a maximum value of ≈14.75V.

The desired value of VIN_OFF is retained in memory, regardless limitations imposed by the 8-bit fault limit resolution, but the read-back value is based on actual hardware register settings.

MAX15303 PMBus Command Set User’s Guide

Page 8 of 52

Reference:

Standard Command

Lockable:

Command Code:

0x20

Format:

Mixed: bit-field and two’s complement

Data Bytes:

Units:

N/A

Transfer:

Read Byte

Factory Value:

0x14 (Linear Mode, exponent -12)

Description/Notes:

See Section 8.2 of the PMBus Specification Part II.

supports Linear Mode values for output voltage related commands. The

Reference:

Standard Command

Lockable:

Yes

Command Code:

0x21

Format:

Unsigned integer mantissa

Data Bytes:

Units:

Transfer:

Read/Write Word

Factory Value:

0x1334 (1.200V)

Description/Notes:

See Section 8.2 of the PMBus Specification Part II.

must be divided by 4096 to

Reference:

Standard Command

Lockable:

Yes

Command Code:

0x22

Format:

Linear

Data Bytes:

Units:

Transfer:

Read/Write Word

Factory Value:

0x0000 (0V)

Description/Notes:

See Section 13.3 of the PMBus Specification Part II.

Output Voltage-Related Commands

VOUT_MODE

The MAX15303 only VOUT_MODE command is read-only and the value cannot be changed.

The 5-bit exponent for output voltage data is -12, or two’s-complement 10100. This means that voltage command data sent to and from the MAX15303 using either the 2-byte unsigned integer mantissa or Direct mantissa formats must be divided by 4096 to determine the actual voltage value.

VOUT_COMMAND

MAX15303 PMBus Command Set User’s Guide

VOUT_COMMAND mantissa data sent to and from the MAX15303 determine the actual voltage value, according to the fixed value of VOUT_MODE.

The factory value of 0x1334 (1.200V) will be overridden during initialization by the hardware (pinstrap) value determined by the resistance to ground detected at the SET pin, unless a specific value has been written to the User Store. The value of the SET pin resistance is measured only once during initialization (power-up).

In the MAX15303, there are seven possible output voltage ranges based on seven corresponding internal feedback divider taps. The value of VOUT_COMMAND is retained and read back from volatile memory, regardless of limitations imposed by the feedback divider range.

New values of VOUT_COMMAND can be written at any time, but large changes (specifically, those that require a different feedback divider selection; see Table 7 of the MAX15303 IC data sheet) will require the output to be disabled for the feedback divider to change.

VOUT_TRIM

In the MAX15303, the value of VOUT_TRIM is summed with the value of VOUT_COMMAND and

Page 9 of 52

VOUT_CAL_OFFSET, and the result is sent to the control loop as the output voltage setpoint.

ce requirements of a specific load device, while retaining use of a “nominal” voltage

Reference:

Standard Command

Lockable:

Yes

Command Code:

0x23

Format:

Linear

Data Bytes:

Units:

Transfer:

Read/Write Word

Factory Value:

0x0000 (0V)

Description/Notes:

See Section 13.4 of the PMBus Specification Part II.

Note that in the MAX15303, VOUT_CAL_OFFSET is sent as a PMBus Linear value, rather than as a

to match an external reference

Reference:

Standard Command

Lockable:

Yes

Command Code:

0x24

Format:

Unsigned integer mantissa

Data Bytes:

Units:

Transfer:

Read/Write Word

Factory Value:

0x5001 (5.000V)

Description/Notes:

See Section 13.5 of the PMBus Specification Part II.

ing initialization to

VOUT_TRIM

Note that in the MAX15303, VOUT_TRIM is sent as a PMBus Linear value, rather than as a two’s complement binary integer mantissa as specified in the PMBus standard, to avoid introducing another numeric format.

The value of VOUT_TRIM is not subtracted from READ_VOUT, so non-zero VOUT_TRIM values will result in a difference between VOUT_COMMAND and READ_VOUT.

This command is intended to allow an end user of a PMBus device to tailor a specific supply to the performan setpoint for all similar load devices.

VOUT_CAL_OFFSET

MAX15303 PMBus Command Set User’s Guide

In the MAX15303, the value of VOUT_CAL_OFFSET is summed with the value of VOUT_COMMAND and VOUT_TRIM, and the result is sent to the control loop as the output voltage setpoint.

two’s complement binary integer mantissa as specified in the PMBus standard, to avoid introducing another numeric format.

The value of VOUT_CAL_OFFSET is subtracted from READ_VOUT, so VOUT_CAL_OFFSET values never result in a difference between VOUT_COMMAND and READ_VOUT.

This command is intended to allow a PMBus device manufacturer or an end user to calibrate the output voltage of a module (or other power-supply assembly) instrument during their final-test process.

VOUT_MAX

VOUT_MAX mantissa data sent to and from the MAX15303 must be divided by 4096 to determine the actual voltage value, according to the fixed value of VOUT_MODE

The factory value of 0x5001 (5.000V) will be overridden dur

VOUT_COMMAND x 1.15, unless a specific value has been written to the User Store.

Page 10 of 52

Reference:

Standard Command

Lockable:

Yes

Command Code:

0x25

Format:

Unsigned integer mantissa

Data Bytes:

Units:

Transfer:

Read/Write Word

Factory Value:

0x14CD (1.300V)

Description/Notes:

See Section 13.6 of the PMBus Specification Part II.

high operation, the output will fall at a rate

Reference:

Standard Command

Lockable:

Yes

Command Code:

0x26

Format:

Unsigned integer mantissa

Data Bytes:

Units:

Transfer:

Read/Write Word

Factory Value:

0x1001 (1.000V)

Description/Notes:

See Section 13.7 of the PMBus Specification Part II.

of 0x1001 (1.000V) will be overridden during initialization to

VOUT_MARGIN_HIGH

VOUT_MARGIN_HIGH mantissa data sent to and from the MAX15303 must be divided by 4096 to determine the actual voltage value, according to the fixed value of VOUT_MODE

The factory value of 0x14CD (1.300V) will be overridden during initialization to

VOUT_COMMAND

In the MAX15303, there are seven possible output voltage ranges based on seven corresponding internal feedback divider taps. The desired value of VOUT_MARGIN_HIGH is retained and read back from Operating Memory, regardless of hardware limitations imposed by the feedback divider range.

If the MAX15303 is set for margin-high operation prior to the output being enabled, the output will rise directly to VOUT_MARGIN_HIGH at the rate determined by VOUT_COMMAND/TON_RISE Likewise, if the output is disabled from margindetermined by -VOUT_COMMAND/TOFF_FALL.

MAX15303 PMBus Command Set User’s Guide

x 1.05, unless a specific value has been written to the User Store.

VOUT_MARGIN_LOW

VOUT_MARGIN_LOW mantissa data sent to and from the MAX15303 must be divided by 4096 to determine the actual voltage value, according to the fixed value of VOUT_MODE

The factory value

VOUT_COMMAND x 0.95, unless a specific value has been written to the User Store.

In the MAX15303, there are seven possible output voltage ranges based on seven corresponding internal feedback divider taps. The desired value of VOUT_MARGIN_LOW is retained and read back from Operating Memory, regardless of hardware limitations imposed by the feedback divider range.

If the MAX15303 is set for margin-low operation prior to the output being enabled, the output will rise directly to VOUT_MARGIN_LOW at the rate determined by VOUT_COMMAND/TON_RISE Likewise, if the output is disabled from margin-low operation, the output will fall at a rate determined by -VOUT_COMMAND/

TOFF_FALL.

Page 11 of 52

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.

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

based on actual

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.

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

VOUT_TRANSITION_RATE

To achieve output voltage slew-rate control, the MAX15303 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:

MAX15303 PMBus Command Set User’s Guide

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 hardware register settings.

If a commanded value of VOUT_TRANSITION_RATE exceeds the maximum possible slew-rate for the feedback divider range, the MAX15303 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

The MAX15303 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.

Page 12 of 52

accurate adaptive voltage positioning results with the VOUT_DROOP command.

t VOUT_DROOP can accept negative resistance values, allowing a user to compensation for

VOUT_DROOP

Note tha resistive losses between the output voltage remote sense point and the load, if desired. (Setting VOUT_DROOP to a negative value will case output voltage to rise with increasing load.)

Wait at least 500μs for execution after sending the VOUT_DROOP command before sending

additional PMBus commands.

MAX15303 PMBus Command Set User’s Guide

Page 13 of 52

Reference:

Standard Command

Lockable:

Yes

Command Code:

0x33

Format:

Linear

Data Bytes:

Units:

kHz

Transfer:

Read/Write Word

Factory Value:

0x0258 (600kHz)

Description/Notes:

See Section 14.4 of the PMBus Specification Part II.

If the external clock is present at the time of output enable, the operating memory value of

applied after enabling the output, the PWM will synchronize to the external clock, but

Reference:

Standard Command

Lockable:

Yes

Command Code:

0x37

Format:

4 x 4-bit unsigned integer “nibbles”

Data Bytes:

Units:

N/A

Transfer:

Read/Write Word

Factory Value:

0x0000 (see Description)

Description/Notes:

See Section 14.7 of the PMBus Specification Part II.

Switching Frequency and PWM Commands

FREQUENCY_SWITCH

The factory value of 0x0258 (600kHz) will be overridden during initialization by the hardware (pinstrap) value determined by the resistance to ground detected at the SYNC pin, unless a specific value has been written to the User Store. The value of the SYNC pin resistance is measured only once during initialization (power-up).

The MAX15303 can also synchronize to an external clock at the SYNC input. If the external clock is present at or before power-up, the SYNC resistance reading will fail and FREQUENCY_SWITCH will be set to 300kHz.

The MAX15303 has two different PWM “speed modes” to support FREQUENCY_SWITCH values at or below 475kHz, and above 475kHz. It is important to ensure that FREQUENCY_SWITCH is set, either by PMBus command or by successful resistor pin-strap, to a value that is within ±10% of the expected external clock frequency.

MAX15303 PMBus Command Set User’s Guide

FREQUENCY_SWITCH will be updated to reflect the external clock frequency. If the external clock is

FREQUENCY_SWITCH will not be updated.

If the external clock crosses the 475kHz boundary while regulating, unexpected results or output voltage transients may result.

The actual switching frequency can be obtained using the READ_FREQUENCY command.

Wait at least 10ms for execution after sending the FREQUENCY_SWITCH command before sending additional PMBus commands.

INTERLEAVE

The INTERLEAVE command determines the phase delay of the MAX15303, measured from the rising edge of an external clock applied at SYNC to the center of the PWM positive pulse.

The factory value of 0x0000 (zero degrees phase shift) will be overridden during initialization by the hardware (pin-strap) value determined by the resistances to ground detected at the ADDR0 and

Because the MAX15303 has dual-edge modulation, the rising and falling edges of the PWM waveform both “move” relative to the center of the high-side switch on-time.

Page 14 of 52

ADDR1 pins, unless a new value of INTERLEAVE has been written to the User Store. The value of the

), the INTERLEAVE command will show unexpected

AVE command

ibbles of the high byte of INTERLEAVE can be used

INTERLEAVE

MAX15303 PMBus Command Set User’s Guide

ADDR0 and ADDR1 pin resistance is measured only once during initialization (power-up).

Because the MAX15303 uses one of two different PWM “speed modes” depending on the switching frequency selected (see FREQUENCY_SWITCH results if switching frequency crosses the 475kHz speed-mode boundary after initialization.

The MAX15303 includes enhancements beyond the PMBus specification INTERLE functionality:

• Setting the “Number In Group” to zero will be interpreted by the MAX15303 as 16 possible

phases. This allows phase-spreading in 22.5º increments.

• The low nibble of the high byte of INTERLEAVE contains the “Group ID Number” per the

PMBus specification, but this is a value that has no function and no dependent parameters in either the MAX15303 device or in the PMBus specification. As a result, it is not necessary to set a “Group ID Number.” Both n separately or together as “scratchpad” data, if desired.

Page 15 of 52

Reference:

Standard Command

Lockable:

Yes

Command Code:

0x5E

Format:

Unsigned integer mantissa

Data Bytes:

Units:

Transfer:

Read/Write Word

Factory Value:

0x1135 (1.080V)

Description/Notes:

See Section 15.32.1 of the PMBus Specification Part II.

The factory value of 0x1135 (1.080V) will be overridden during initialization to

POWER_GOOD_OFF

Reference:

Standard Command

Lockable:

Yes

Command Code:

0x5F

Format:

Unsigned integer mantissa

Data Bytes:

Units:

Transfer:

Read/Write Word

Factory Value:

0x0F99 (0.980V)

Description/Notes:

See Section 15.32.2 of the PMBus Specification Part II.

The factory value of 0x0F99 (0.980V) will be overridden during initialization to

Output Voltage Sequencing Commands

POWER_GOOD_ON

POWER_GOOD_ON mantissa data sent to and from the MAX15303 must be divided by 4096 to determine the actual voltage value, according to the fixed value of VOUT_MODE

In the MAX15303, there are seven possible output voltage ranges based on seven corresponding internal feedback divider taps. The MAX15303 hardware has 8-bit resolution for the power-good threshold within each of these seven ranges.

The desired value of POWER_GOOD_ON is retained in memory, regardless of limitations imposed by the feedback divider range and the 8-bit fault limit resolution, but the read-back value is based on actual hardware register settings.

MAX15303 PMBus Command Set User’s Guide

VOUT_COMMAND x 0.95, unless a specific value has been written to the User Store.

POWER_GOOD_OFF mantissa data sent to and from the MAX15303 must be divided by 4096 to determine the actual voltage value, according to the fixed value of VOUT_MODE

The desired value of POWER_GOOD_OFF is retained in memory, regardless of limitations imposed by the feedback divider range and the 8-bit fault limit resolution, but the read-back value is based on actual hardware register settings.

VOUT_COMMAND x 0.93, unless a specific value has been written to the User Store.

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Maxim Integrated MAX15303 User Manual

Specifications and Main Features

Frequently Asked Questions

User Manual

Introduction

On, Off, and Margin Testing-Related Commands

OPERATION

VIN_ON

ON_OFF_CONFIG

VIN_OFF

Output Voltage-Related Commands

VOUT_MODE

VOUT_COMMAND

VOUT_TRIM

VOUT_CAL_OFFSET

VOUT_MAX

VOUT_MARGIN_HIGH

VOUT_MARGIN_LOW

VOUT_TRANSITION_RATE

VOUT_DROOP

Switching Frequency and PWM Commands

FREQUENCY_SWITCH

INTERLEAVE

POWER_GOOD_OFF

Output Voltage Sequencing Commands

POWER_GOOD_ON