Analog Devices LT7170 Reference Manual
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Analog Devices LT7170 Reference Manual

Analog Devices LT7170 Reference Manual

Pmbus/i2c
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OVERVIEW

This reference manual describes the digital communications capabilities of the LT7170/LT7170-1, including the functionality of each LT7170/
LT7170-1 PMBus command. Refer to these specifications for more information regarding the bus protocol details.
PMBus Specification Revision 1.3.1
►
SMBus Specification Revision 3.1
►
analog.com
PLEASE SEE THE LAST PAGE FOR AN IMPORTANT WARNING AND
LEGAL TERMS AND CONDITIONS.
LT7170/LT7170-1 PMBus/I
Reference Manual
LT7170/LT7170-1
2
C Reference Manual
Rev. A | 1 of 40

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Summary of Contents for Analog Devices LT7170

  • Page 1: Overview

    C Reference Manual OVERVIEW This reference manual describes the digital communications capabilities of the LT7170/LT7170-1, including the functionality of each LT7170/ LT7170-1 PMBus command. Refer to these specifications for more information regarding the bus protocol details. PMBus Specification Revision 1.3.1 ►...

  • Page 2: Table Of Contents

    Reference Manual LT7170/LT7170-1 TABLE OF CONTENTS Overview..............1 General Configuration........12 PMBus/SMBus/I C..........3 PWM Configuration.......... 14 PMBus/SMBus/I C Capabilities......3 Input Voltage and Limits........16 Similarities Between PMBus, SMBus, and Output Voltage and Limits........ 17 C 2-Wire Interface..........3 Output Current Limits........21 Communication Protection.........

  • Page 3: Pmbus/Smbus/I 2 C

    All read operations return a valid PEC if the PMBus controller requests it. If Bit 2 of the MFR_CONFIG_ALL_LT7170 command is set, the PMBus write operations are not acted upon until a valid PEC is received by the LT7170/LT7170-1. If a PEC is included in a command write, that PEC must be valid or a PEC write error occurs, regardless of the value of Bit 2 of the MFR_CONFIG_ALL_LT7170 command.

  • Page 4: Addressing And Communications

    If PMBus commands are received faster than they are being processed, the LT7170/LT7170-1 may become too busy to handle new commands. If a command is written when the LT7170/LT7170-1 are busy processing a command, the devices ignore that command, set Bit 7 of STATUS_BYTE, and pull the ALERT pin low.

  • Page 5: Pmbus Command Summary

    IEEE floating point numbers. All commands from 0xC0 through 0xFF not listed in Table 1 are implicitly reserved by the manufacturer. Users must avoid blind writes within this range of commands to avoid undesired operation of the LT7170/LT7170-1. All commands from 0x00 through 0xBF not listed in Table 1 are implicitly not supported by the manufacturer.
  • Page 6 Reference Manual LT7170/LT7170-1 PMBUS COMMAND SUMMARY Table 1. Supported PMBus and MFR Commands (Continued) Command Data Command Name Code Description Type Format Unit Default Value FREQUENCY_SWITCH 0x33 Switching frequency of the regulator. IEEE 1000.0, 0x63D0 word VIN_ON 0x35 Input voltage at which the unit must start power 1.4, 0x3D9A...
  • Page 7 R block MFR_SERIAL 0x9E Unique part serial number. R block IC_DEVICE_ID 0xAD Identification of the IC in ASCII. R block LT7170 or LT7170-1 IC_DEVICE_REV 0xAE Revision of the IC. R block MFR_NVM_UNLOCK 0xBD Contact factory. Only used for MFR_NVM_DATA bulk programming.
  • Page 8 Do not assume compatibility of commands between different devices based upon command names. Always refer to the data sheet of the manufacturer for each device for a complete definition of the function of the command. Analog Devices strives to keep command functionality compatible between all Analog Devices devices. However, differences can be introduced to address specific product requirements.
  • Page 9 Reference Manual LT7170/LT7170-1 PMBUS COMMAND SUMMARY Table 2. Abbreviations of Supported Data Formats PMBus Specification PMBus Terminology Reference Definition Example Register Per bit meaning defined in each command description. PMBus STATUS_BYTE command N − 15 value = −1 × 2 ×...

  • Page 10: Pmbus Command Details

    0x5B (7-bit address). The LT7170/LT7170-1 have only one channel, and the PAGE command can only be 0x00 or 0xFF. Both values have the same effect. PAGE 0xFF is used to select all channels in multichannel devices. The PAGE command is included only for compatibility with other PMBus devices.
  • Page 11 Active zone WRITE_PROTECT The WRITE_PROTECT command is used to control writing to the LT7170/LT7170-1. When WRITE_PROTECT is set to 0x00, writes to all commands are enabled. The PAGE_PLUS_WRITE command can be used to write any command that is not write protected. The PAGE_PLUS_READ command can be used to read any command.

  • Page 12: General Configuration

    After changing the device address, leave at least 10 µs for the new address to take effect before starting a new PMBus transaction. The LT7170/LT7170-1 always respond to the global addresses, Address 0x5A and Address 0x5B. Writes to Address 0x5A affect all pages, and reads target Page 0, as if PAGE = 0xFF.
  • Page 13 0 = Valid PEC not required. 1 = Valid PEC required. 0 = Disable PMBus clock stretching. If the LT7170/LT7170-1 are too busy to process a command, the devices refuse to acknowledge the command and set Bit 7 in STATUS_BYTE and STATUS_WORD.

  • Page 14: Pwm Configuration

    50 kHz, the nearest multiple is used. Regardless of the value of FREQUENCY_SWITCH, if an external clock is present on the SYNC/PWM_CFG pin, the LT7170/LT7170-1 attempt to synchronize the PWM to the external clock, unless Bit 1 or Bit 0 in the MFR_SYNC_CONFIG_LT7170 command is set. If an external clock is to be used for synchronization, it is recommended to program FREQUENCY_SWITCH to the same frequency as the external clock.
  • Page 15 Reserved. Reserved. The LT7170-1 per-phase current limits are half of the LT7170 current limit settings. For example, for current limit 0, the LT7170-1 positive current limit is 4.5 A per phase, for a total of 9 A. When Bit 6 of the MFR_CONFIG_ALL_LT7170 command is 0, configuration resistors, if populated, override stored NVM values for the MFR_PWM_MODE_LT7170 command at power-up.

  • Page 16: Input Voltage And Limits

    (that is, Bit 6 of the MFR_CONFIG_ALL_LT7170 command is set to its factory default value of 0 in NVM), the LT7170/LT7170-1 configure internal settings as described in the Theory of Operation section of the main data sheet.

  • Page 17: Output Voltage And Limits

    The VIN_UV_WARN_LIMIT command sets the value of the input voltage that causes an input voltage low warning. This alarm is masked until the input exceeds the warning limit at least one time since the LT7170/LT7170-1 have been powered. In response to the VIN_UV_WARN_LIMIT being exceeded, the device also does the following: Sets the NONE_OF_THE_ABOVE bit in the STATUS_BYTE command ►...
  • Page 18 VOUT_MARGIN_HIGH The VOUT_MARGIN_HIGH command loads the LT7170/LT7170-1 with the voltage to which the output is to be regulated when the OPERA- TION command is set to 0xA8 (margin high). When OPERATION is set to 0xA8 and VOUT_MARGIN_HIGH is greater than VOUT_MAX, the output voltage is limited to VOUT_MAX.
  • Page 19 The VOUT_OV_WARN_LIMIT command sets the value of the output voltage measured at the VSENSE pins, which causes and output overvoltage warning. In response to the VOUT_OV_WARN_LIMIT being exceeded, the LT7170/LT7170-1 also do the following: Set the NONE_OF_THE_ABOVE bit in the STATUS_BYTE command.
  • Page 20 Reference Manual LT7170/LT7170-1 PMBUS COMMAND DETAILS Notify the host by asserting the ALERT pin low, unless masked. ► The VOUT_UV_WARN_LIMIT command uses half-precision floating point format. Maximum = 5.5 V ► Minimum = 0.0 V ► The value must be less than VOUT_OV_WARN_LIMIT and VOUT_OV_FAULT_LIMIT, or an invalid data error occurs.

  • Page 21: Output Current Limits

    The IOUT_OC_WARN_LIMIT command sets the value of the output current that causes an output overcurrent warning in amperes. This value is the total current limit, not per phase. In response to the IOUT_OC_WARN_LIMIT being exceeded, the LT7170/LT7170-1 do the following: Set the NONE_OF_THE_ABOVE bit in the STATUS_BYTE command.

  • Page 22: Timing

    When TON_RISE is commanded to change during TON ramp-up, the LT7170/LT7170-1 act on the command as soon as possible. However, the new ramp rate is calculated for a full ramp from 0 V. Because the output is partially ramped and time has already passed, the actual total ramp time differs from the new value for TON_RISE.
  • Page 23 DAC. During V ramp-down, the LT7170/LT7170-1 use continuous conduction mode if either Bit 2 of MFR_PWM_MODE_LT7170 is set to 1, or Bit 0 of MFR_PWM_MODE_LT7170 is set to 0. Otherwise, V decays only due to the external load (and the 200 Ω internal pull-down if Bit 6 of MFR_CHAN_CONFIG_LT7170 is set to 1).

  • Page 24: Fault Response

    Notify the host by asserting the ALERT pin low, unless masked. ► The special data value of 0 ms means that there is no limit and that the LT7170/LT7170-1 can attempt to turn off the output voltage indefinitely. The TOFF_MAX_WARN_LIMIT command uses half-precision floating-point format.
  • Page 25 R/W byte 0x00 detected VOUT_OV_FAULT_RESPONSE The VOUT_OV_FAULT_RESPONSE command sets the action the LT7170/LT7170-1 take in response to an output overvoltage fault. The LT7170/LT7170-1 also do the following: Set the VOUT_OV bit in the STATUS_BYTE. ► Set the VOUT bit in the STATUS_WORD.
  • Page 26 000 is default. X means don't care. VOUT_UV_FAULT_RESPONSE The VOUT_UV_FAULT_RESPONSE command sets the action the LT7170/LT7170-1 take in response to an output undervoltage fault. The LT7170/LT7170-1 also do the following: Set the NONE_OF_THE_ABOVE bit in the STATUS_BYTE command.
  • Page 27 000 is the default. X means don't care. TON_MAX_FAULT_RESPONSE The TON_MAX_FAULT_RESPONSE command sets the action the LT7170/LT7170-1 take in response to a TON MAX fault. The LT7170/LT7170-1 also do the following: Set the NONE_OF_THE_ABOVE bit in the STATUS_BYTE command.
  • Page 28 Action to be taken when an internal overtemperature fault is detected R/W Byte 0xC0 OT_FAULT_RESPONSE The OT_FAULT_RESPONSE command sets the action the LT7170/LT7170-1 take in response to an internal overtemperature fault. The LT7170/LT7170-1 also do the following: Set the MFR bit in the STATUS_WORD command. ►...

  • Page 29: Identification

    Unless masked by SMBALERT_MASK, any asserted bit in a STATUS_x register (including any fault or warning) also pulls the ALERT pin low. With some exceptions, the SMBALERT_MASK command can be used to prevent the LT7170/LT7170-1 from pulling the ALERT pin low for bits in these registers on a bit by bit basis.
  • Page 30 Clear all fault bits Send byte SMBALERT_MASK 0x1B Mask ALERT pin Block R/W STATUS_BYTE 0x78 One-byte summary of the faults and warnings of the LT7170/ R/W byte LT7170-1 STATUS_WORD 0x79 One-word summary of the faults and warnings of the LT7170/ R/W word LT7170-1...
  • Page 31 ALERT pin low. The CLEAR_FAULTS command does not cause the LT7170/LT7170-1 that have latched off for a fault condition to restart. The LT7170/ LT7170-1 devices that have shut down for a fault condition are restarted only when the following situations occur: The output is commanded to turn off and then to turn back on via the RUN pin and/or the OPERATION command.
  • Page 32 An input voltage fault or warning has occurred. MFR_SPECIFIC A fault or warning specific to the LT7170/LT7170-1 has occurred. POWER NOT GOOD This bit is set when the LT7170/LT7170-1 are forcing the PGOOD pin low. [10:8] Unsupported Not supported (device returns 0).
  • Page 33 During initialization, the LT7170/LT7170-1 check for various illegal pin configurations. If a pin configuration fault is detected, the LT7170/ LT7170-1 pull down the PGOOD pin and set Bit 6 of STATUS_MFR_SPECIFIC. The regulator outputs are also locked off until the LT7170/ LT7170-1 are reset.
  • Page 34 A frequency of less than 300 kHz is detected on the SYNC/PWM_CFG pin during initialization. This may occur if a higher frequency clock starts in the middle of the initialization process. If an external clock is to be applied to the SYNC/PWM_CFG pin, it must start before the LT7170/LT7170-1 initialization begins, or after initialization is complete.

  • Page 35: Telemetry

    IOUT_CAL_OFFSET set to zero. Then write IOUT_CAL_OFFSET to the negation of the recorded READ_IOUT value at no load. This value of IOUT_CAL_OFFSET can be systematically stored in NVM for all devices and does not need to be calibrated for every LT7170/LT7170-1 individually.
  • Page 36 Reference Manual LT7170/LT7170-1 PMBUS COMMAND DETAILS READ_TEMPERATURE_1 The READ_TEMPERATURE_1 command returns the internal device temperature. This command uses half-precision floating point format. READ_FREQUENCY The READ_FREQUENCY command returns the top switch switching frequency in kilohertz (kHz). This command uses half-precision floating point format.
  • Page 37 Reference Manual LT7170/LT7170-1 PMBUS COMMAND DETAILS Bit 1 enables lower-frequency telemetry measurements in order to reduce input supply quiescent current. When this bit is set, the telemetry runs with a typical period of 110 ms (compared to a typical period of 5.5 ms when this bit is zero).

  • Page 38: Nvm Commands

    If a nonvolatile memory write fails, Bit 5 is set in STATUS_MFR_SPECIFIC, indicating that a nonvolatile memory fault has occurred. If the LT7170/LT7170-1 are reset or bias power is removed while a nonvolatile memory fault is present, the devices address is set to 0x7C on the next power-up.
  • Page 39 Reference Manual LT7170/LT7170-1 PMBUS COMMAND DETAILS MFR_DISABLE_OUTPUT When written to 0xFF, the MFR_DISABLE_OUTPUT command disables the regulator outputs until reset. The value of MFR_DISABLE_OUT- PUT is not stored in NVM, which allows anything to be programmed into ON_OFF_CONFIG, OPERATION, and so forth, without powering up the output.
  • Page 40 Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other rights of third parties that may result from its use. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices. Trademarks and registered trademarks are the property of their respective owners.

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Lt7170-1

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