LTC2977 8-Channel PMBus Power System Manager Featuring Accurate Output Voltage Measurement Description Features n n n n n n n n n n n n n n n n Sequence, Trim, Margin and Supervise Eight Power Supplies Manage Faults, Monitor Telemetry and Create Fault Logs PMBus Compliant Command Set Supported by LTpowerPlay™ GUI Margin or Trim Supplies to 0.
LTC2977 Table of Contents Features...................................................... 1 Applications................................................. 1 Typical Application......................................... 1 Description.................................................. 1 Absolute Maximum Ratings............................... 4 Order Information........................................... 4 Pin Configuration........................................... 4 Electrical Characteristics....................
LTC2977 Table of Contents MFR_FAULTB00_RESPONSE, MFR_FAULTB01_ RESPONSE, MFR_FAULTB10_RESPONSE and MFR_FAULTB11_RESPONSE............................... 52 MFR_VINEN_OV_FAULT_RESPONSE..................53 MFR_VINEN_UV_FAULT_RESPONSE..................54 MFR_RETRY_COUNT..........................................55 MFR_RETRY_DELAY...........................................55 MFR_RESTART_DELAY.......................................55 MFR_VOUT_PEAK...............................................56 MFR_VIN_PEAK......
LTC2977 Supply Voltages: VPWR to GND.......................................... –0.3V to 15V VDD33 to GND........................................ –0.3V to 3.6V VDD25 to GND...................................... –0.3V to 2.75V Digital Input/Output Voltages: ALERTB, SDA, SCL, CONTROL0, CONTROL1............................................. –0.3V to 5.5V PWRGD, SHARE_CLK, WDI/RESETB, WP.....................–0.3V to VDD33 + 0.3V FAULTB00, FAULTB01, FAULTB10, FAULTB11.................................–0.
LTC2977 Electrical Characteristics The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TJ = 25°C. VPWR = VIN_SNS = 12V, VDD33, VDD25, REFP and REFM pins floating, unless otherwise indicated. CVDD33 = 100nF, CVDD25 = 100nF and CREF = 100nF. SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS 15 V 10 13 mA 10 13 mA 2.55 2.8 V Power Supply Characteristics VPWR VPWR Supply Input Operating Range IPWR VPWR Supply Current 4.
LTC2977 Electrical Characteristics The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TJ = 25°C. VPWR = VIN_SNS = 12V; VDD33, VDD25, REFP and REFM pins floating, unless otherwise indicated. CVDD33 = 100nF, CVDD25 = 100nF and CREF = 100nF.
LTC2977 Electrical Characteristics The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TJ = 25°C. VPWR = VIN_SNS = 12V; VDD33, VDD25, REFP and REFM pins floating, unless otherwise indicated. CVDD33 = 100nF, CVDD25 = 100nF and CREF = 100nF. SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS DAC Soft-Connect Comparator Characteristics VOS_CMP Offset Voltage VDACPn = 0.2V l ±1 ±18 mV VDACPn = 1.3V l ±2 ±26 mV VDACPn = 2.
LTC2977 Electrical Characteristics The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TJ = 25°C. VPWR = VIN_SNS = 12V; VDD33, VDD25, REFP and REFM pins floating, unless otherwise indicated. CVDD33 = 100nF, CVDD25 = 100nF and CREF = 100nF.
LTC2977 Electrical Characteristics Note 1: Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. Exposure to any Absolute Maximum Rating for extended periods may affect device reliability and lifetime. Note 2: All currents into device pins are positive. All currents out of device pins are negative. All voltages are referenced to ground unless otherwise specified. If power is supplied to the chip via the VDD33 pin only, connect VPWR and VDD33 pins together.
LTC2977 Typical Performance Characteristics Temperature Sensor Error vs Temperature Reference Voltage vs Temperature 1.2325 ADC Total Unadjusted Error vs Temperature 1.6 0.25 1.2320 1.4 0.20 1.2315 1.2 1.2310 1.0 1.2305 1.2300 0.6 0.4 1.2290 0.2 1.2285 0 –50 –30 –10 10 30 50 70 TEMPERATURE (°C) 90 0.15 0.8 1.2295 110 –0.20 –50 –30 –10 10 30 50 70 TEMPERATURE (°C) 110 90 –0.25 –50 –30 –10 10 30 50 70 TEMPERATURE (°C) 2.5 ERROR (LSBs) 100 50 0 –50 –100 ADC-DNL 0.8 122µV/LSB 2.
LTC2977 Typical Performance Characteristics DAC Full-Scale Output Voltage vs Temperature 2.68 80 2.67 70 60 50 40 30 20 10 GAIN SETTING = 1 THREE TYPICAL PARTS 8 2.66 2.65 2.64 2.63 2.62 2.61 10 0 0 2.
LTC2977 Typical Performance Characteristics VDD33 Regulator Output Voltage vs Temperature VDD33 Regulator Load Regulation THREE TYPICAL PARTS 3.26 3.28 3.24 3.27 OUTPUT VOLTAGE (V) OUTPUT VOLTAGE (V) Supply Current vs Supply Voltage 3.28 3.26 3.25 3.24 –40°C 3.22 3.20 25°C SUPPLY CURRENT (mA) 3.29 105°C 3.18 3.16 3.14 3.23 3.12 3.22 –50 –30 –10 10 30 50 70 TEMPERATURE (°C) 90 110 3.10 0 20 40 60 80 100 CURRENT SOURCING (mA) 2977 G18 4 6 8 12 10 SUPPLY VOLTAGE (V) 13.
LTC2977 Pin Functions PIN NAME VSENSEM6 VSENSEP7 VSENSEM7 VOUT_EN0 VOUT_EN1 VOUT_EN2 VOUT_EN3 VOUT_EN4 VOUT_EN5 VOUT_EN6 VOUT_EN7 VIN_EN DNC VIN_SNS PIN NUMBER PIN TYPE 1* In 2* In 3* In 4 Out 5 Out 6 Out 7 Out 8 Out 9 Out 10 Out 11 Out 12 0ut 13 Do Not Connect 14 In VPWR 15 In VDD33 16 In/Out VDD33 VDD25 WP PWRGD 17 18 19 20 In In/Out In Out SHARE_CLK WDI/RESETB 21 22 In/Out In FAULTB00 23 In/Out FAULTB01 24 In/Out FAULTB10 25 In/Out FAULTB11 26 In/Out SDA SCL ALERTB CONTROL0 CONT
LTC2977 Pin Functions PIN NAME PIN NUMBER PIN TYPE DESCRIPTION 41 Out DAC1 Return. Connect to Channel 1 DC/DC Converter’s GND Sense or Return to GND. VDACM1 42* In DC/DC Converter Differential (+) Output Voltage or Current-1 Sensing Pins VSENSEP1 43* In DC/DC Converter Differential (–) Output Voltage or Current-1 Sensing Pins VSENSEM1 44 Out DAC2 Output VDACP2 45 Out DAC2 Return. Connect to Channel 2 DC/DC Converter’s GND Sense or Return to GND.
LTC2977 Block Diagram 3.3V REGULATOR VOUT VIN VPWR 15 VDD VDD33 16 2.
LTC2977 Operation Operation Overview n The LTC2977 is a PMBus programmable power system controller, monitor, sequencer and voltage supervisor that can perform the following operations: n Accept PMBus compatible programming commands. n n n n n n n n n n n Provide DC/DC converter input voltage and output voltage/current readback through the PMBus interface.
LTC2977 Operation EEPROM Equivalent operating time at 105°C = 86.5 hours. The LTC2977 contains internal EEPROM (nonvolatile memory) to store configuration settings and fault log information. EEPROM endurance, retention, and mass write operation time are specified over the operating junction temperature range. See Electrical Characteristics and Absolute Maximum Ratings sections. So the overall retention of the EEPROM was degraded by 86.
LTC2977 Operation SHARE_CLK input/outputs to a pull-up resistor as a wired OR. In this case the fastest clock will take over and synchronize all LTC2977s. SHARE_CLK can optionally be used to synchronize ON/ OFF dependency on VIN across multiple chips by setting the Mfr_config_all_vin_share_enable bit of the MFR_ CONFIG_ALL_LTC2977 register.
LTC2977 Operation 1 7 S 1 1 SLAVE ADDRESS Wr A COMMAND CODE A x x 1 1 8 P S Sr Rd Wr x START CONDITION REPEATED START CONDITION READ (BIT VALUE OF 1) WRITE (BIT VALUE OF 0) SHOWN UNDER A FIELD INDICATES THAT THE FIELD IS REQUIRED TO HAVE THE VALUE OF x A ACKNOWLEDGE (THIS BIT POSITION MAY BE 0 FOR AN ACK OR 1 FOR A NACK) P STOP CONDITION PEC PACKET ERROR CODE MASTER TO SLAVE SLAVE TO MASTER ... CONTINUATION OF PROTOCOL 2977 F01a Figure 1a.
LTC2977 Operation 1 S 7 1 1 8 1 1 SLAVE ADDRESS Wr A COMMAND CODE A 7 1 1 Sr SLAVE ADDRESS Rd A 8 1 DATA BYTE LOW A 1 1 DATA BYTE HIGH A 8 P 1 2977 F07 Figure 7. Read Word Protocol 1 S 7 1 1 8 1 1 7 1 1 SLAVE ADDRESS Wr A COMMAND CODE A Sr SLAVE ADDRESS Rd A 8 1 DATA BYTE LOW A 8 1 DATA BYTE HIGH A 8 1 1 PEC A P 1 2977 F08 Figure 8.
LTC2977 Operation Device Address The I2C/SMBus address of the LTC2977 equals the base address + N where N is a number from 0 to 8. N can be configured by setting the ASEL0 and ASEL1 pins to VDD33, GND or FLOAT. See Table 1. Using one base address and the nine values of N, nine LTC2977s can be connected together to control 72 outputs. The base address is stored in the MFR_I2C_BASE_ADDRESS register.
LTC2977 Operation Processing Commands The LTC2977 uses a dedicated processing block to ensure quick response to all of its commands. There are a few exceptions where the part will NACK a subsequent command because it is still processing the previous command. These are summarized in the following tables. MFR_COMMON is a special command that may always be read even when the part is busy. This provides an alternate method for a host to determine if the LTC2977 is busy.
LTC2977 PMBus Command Summary Summary Table COMMAND NAME CMD CODE DESCRIPTION TYPE DATA PAGED FORMAT UNITS EEPROM DEFAULT VALUE REF PAGE 0x00 28 PAGE 0x00 Channel or page currently selected for any R/W Byte command that supports paging. N Reg OPERATION 0x01 Operating mode control. On/Off, Margin High and Margin Low. R/W Byte Y Reg Y 0x00 33 ON_OFF_CONFIG 0x02 CONTROL pin & PMBus bus on/off command setting.
LTC2977 PMBus Command summary Summary Table COMMAND NAME CMD CODE DESCRIPTION DEFAULT VALUE REF PAGE OT_WARN_LIMIT 0x51 Overtemperature warning limit. R/W Word N L11 °C Y 70.0 0xEA30 37 UT_WARN_LIMIT 0x52 Undertemperature warning limit. R/W Word N L11 °C Y 0 0x8000 37 UT_FAULT_LIMIT 0x53 Undertemperature fault limit. R/W Word N L11 °C Y –40.0 0xE580 37 UT_FAULT_RESPONSE 0x54 Action to be taken by the device when an undertemperature fault is detected.
LTC2977 PMBus Command summary Summary Table COMMAND NAME CMD CODE DESCRIPTION TYPE DATA PAGED FORMAT UNITS EEPROM DEFAULT VALUE REF PAGE STATUS_CML 0x7E Communication and memory fault and warning status. R Byte N Reg NA 43 STATUS_MFR_SPECIFIC 0x80 Manufacturer specific fault and state information. R Byte Y Reg NA 43 READ_VIN 0x88 Input voltage measured at VIN_SNS pin. R Word N L11 V NA 44 READ_VOUT 0x8B DC/DC converter output voltage.
LTC2977 PMBus Command summary Summary Table COMMAND NAME CMD CODE DESCRIPTION DEFAULT VALUE REF PAGE MFR_FAULTB00_ RESPONSE 0xD5 Action to be taken by the device when the FAULTB00 pin is asserted low. R/W Byte N Reg Y 0x00 52 MFR_FAULTB01_ RESPONSE 0xD6 Action to be taken by the device when the FAULTB01 pin is asserted low. R/W Byte N Reg Y 0x00 52 MFR_FAULTB10_ RESPONSE 0xD7 Action to be taken by the device when the FAULTB10 pin is asserted low.
LTC2977 PMBus Command summary Summary Table CMD CODE DESCRIPTION COMMAND NAME TYPE DATA PAGED FORMAT UNITS EEPROM DEFAULT VALUE REF PAGE MFR_FAULT_LOG_ RESTORE 0xEB Command a transfer of the fault log previously stored in EEPROM back to RAM. Send Byte N NA 67 MFR_FAULT_LOG_CLEAR 0xEC Initialize the EEPROM block reserved for fault logging and clear any previous fault logging locks. Send Byte N NA 68 MFR_FAULT_LOG_STATUS 0xED Fault logging status.
LTC2977 PMBus Command Description Addressing and Write Protect PAGE The LTC2977 has eight pages that correspond to the eight DC/DC converter channels that can be managed. Each DC/DC converter channel can be uniquely programmed by first setting the appropriate page. Setting PAGE = 0xFF allows a simultaneous write to all pages for PMBus commands that support global page programming. The only commands that support PAGE = 0xFF are CLEAR_FAULTS, OPERATION and ON_OFF_CONFIG.
LTC2977 PMBus Command Description MFR_PAGE_FF_MASK The MFR_PAGE_FF_MASK command is used to select which channels respond when the global page command (PAGE=0xFF) is in use.
LTC2977 PMBus Command Description MFR_COMMAND_PLUS, MFR_DATA_PLUS0, MFR_DATA_PLUS1, MFR_STATUS_PLUS0, and MFR_STATUS_PLUS1 Command Plus operations use a sequence of word commands to support the following: • An alternate method for reading block data using sequential standard word reads. • A peek operation that allows up to two additional hosts to read an internal register using PMBus word protocol where each host has a unique page.
LTC2977 PMBus Command Description MFR_STATUS_PLUS0 and MFR_STATUS_PLUS1 Data Contents BIT(S) SYMBOL b[7:2] Reserved b[1] b[0] OPERATION Mfr_status_plus_block_ peek_failed0 Status of most recent block peek for matching host. Mfr_status_plus_block_ peek_failed1 1: Last block peek was aborted due to an intervening fault log EEPROM write, MFR_FAULT_LOG_STORE command, or standard PMBus block read of MFR_FAULT_LOG. The intervening operation is always completed cleanly.
LTC2977 PMBus Command Description Peek Operation using Mfr_data_plus0 Internal words and bytes may be read using Command Plus: Write Mfr_command_plus_pointer=CMD_CODE with Mfr_command_plus_page=page and Mfr_command_plus_id=0. The CMD_CODE’s are listed in the PMBus COMMAND SUMMARY table. Read data from Mfr_data_plus0. Data is always read using a word read. Byte data is returned with the upper byte set to 0.
LTC2977 PMBus Command Description Operation, Mode and EEPROM Commands OPERATION The OPERATION command is used to turn the unit on and off in conjunction with the CONTROLn pin and ON_OFF_ CONFIG. This command register responds to the global page command (PAGE=0xFF). The contents and functions of the data byte are shown in the following tables. A minimum tOFF_MIN wait time must be observed between OPERATION commands used to turn the unit off and then back on.
LTC2977 PMBus Command Description ON_OFF_CONFIG The ON_OFF_CONFIG command configures the combination of CONTROLn pin input and PMBus bus commands needed to turn the LTC2977 on/off, including the power-on behavior, as shown in the following table. This command register responds to the global page command (PAGE=0xFF). After the part has initialized, an additional comparator monitors VIN_SNS. The VIN_ON threshold must be exceeded before the output power sequencing can begin.
LTC2977 PMBus Command Description STORE_USER_ALL and RESTORE_USER_ALL STORE_USER_ALL, RESTORE_USER_ALL commands provide access to User EEPROM space. Once a command is stored in User EEPROM, it will be restored with an explicit restore command or when the part emerges from power-on reset after power is applied. While either of these commands is being processed, the device will indicate it is busy, see Response When Part Is Busy on page 67. STORE_USER_ALL.
LTC2977 PMBus Command Description Output Voltage Related Commands VOUT_COMMAND, VOUT_MAX, VOUT_MARGIN_HIGH, VOUT_MARGIN_LOW, VOUT_OV_FAULT_LIMIT, VOUT_ OV_WARN_LIMIT, VOUT_UV_WARN_LIMIT, VOUT_UV_FAULT_LIMIT, POWER_GOOD_ON and POWER_GOOD_OFF These commands use the same format and provide various servo, margining, and supervising limits for a channel’s output voltage.
LTC2977 PMBus Command Description Temperature Related Commands OT_FAULT_LIMIT, OT_WARN_LIMIT, UT_WARN_LIMIT and UT_FAULT_LIMIT These commands provide supervising limits for temperature. Data Contents BIT(S) SYMBOL OPERATION b[15:0] Ot_fault_limit[15:0], The data uses the L11 format. Ot_warn_limit[15:0], Units: °C.
LTC2977 PMBus Command Description Fault Response for Voltages Measured by the High Speed Supervisor VOUT_OV_FAULT_RESPONSE and VOUT_UV_FAULT_RESPONSE The fault response documented here is for voltages that are measured by the high speed supervisor. These voltages are measured over a short period of time and may require a deglitch period.
LTC2977 PMBus Command Description Fault Response for Values Measured by the ADC OT_FAULT_RESPONSE, UT_FAULT_RESPONSE, VIN_OV_FAULT_RESPONSE and VIN_UV_FAULT_RESPONSE The fault response documented here is for values that are measured by the ADC. These values are measured over a longer period of time and are not deglitched.
LTC2977 PMBus Command Description Timed Fault Response TON_MAX_FAULT_RESPONSE This command defines the LTC2977 response to a TON_MAX_FAULT. It may be used to protect against a short-circuited output at start-up. After start-up use VOUT_UV_FAULT_RESPONSE to protect against a short-circuited output. The device also: • Sets the HIGH_BYTE bit in the STATUS_BYTE, • Sets the VOUT bit in the STATUS_WORD, • Sets the TON_MAX_FAULT bit in the STATUS_VOUT register, and • Notifies the host by asserting ALERTB.
LTC2977 PMBus Command Description Status Commands STATUS_BYTE The STATUS_BYTE command returns the summary of the most critical faults or warnings which have occurred, as shown in the following table. STATUS_BYTE is a subset of STATUS_WORD and duplicates the same information.
LTC2977 PMBus Command Description STATUS_VOUT The STATUS_VOUT command returns the summary of the output voltage faults or warnings which have occurred, as shown in the following table: STATUS_VOUT Data Contents BIT(S) SYMBOL OPERATION b[7] Status_vout_ov_fault Overvoltage fault. b[6] Status_vout_ov_warn Overvoltage warning. b[5] Status_vout_uv_warn Undervoltage warning b[4] Status_vout_uv_fault Undervoltage fault. b[3] Status_vout_max_fault VOUT_MAX fault.
LTC2977 PMBus Command Description STATUS_CML The STATUS_CML command returns the summary of the communication, memory and logic faults or warnings which have occurred, as shown in the following table: STATUS_CML Data Contents BIT(S) SYMBOL OPERATION b[7] Status_cml_cmd_fault Illegal or unsupported command fault has occurred. b[6] Status_cml_data_fault Illegal or unsupported data received. b[5] Status_cml_pec_fault A PEC fault has occurred. Note: PEC checking is always active in the LTC2977.
LTC2977 PMBus Command Description ADC Monitoring Commands READ_VIN This command returns the most recent ADC measured value of the voltage measured at the VIN_SNS pin. READ_VIN Data Contents BIT(S) SYMBOL OPERATION b[15:0] Read_vin[15:0] The data uses the L11 format. Units: V READ_VOUT This command returns the most recent ADC measured value of the channel’s output voltage. When odd channels are configured to measure current, the data contents use the L11 format with units in mV.
LTC2977 PMBus Command Description Manufacturer Specific Commands MFR_CONFIG_LTC2977 This command is used to configure various manufacturer specific operating parameters for each channel. MFR_CONFIG_LTC2977 Data Contents BIT(S) SYMBOL b[15:14] Mfr_config_chan_mode OPERATION Select channel specific sequencing mode. 00 = Channel uses PMBus delay sequencing with immediate off upon fault. 01 = Channel uses PMBus delay sequencing with sequence off upon fault.
LTC2977 PMBus Command Description MFR_CONFIG_LTC2977 Data Contents BIT(S) b[1] SYMBOL Mfr_config_dac_gain b[0] Mfr_config_dac_pol OPERATION DAC buffer gain. 0: Select DAC buffer gain dac_gain_0 (1.38V full-scale) 1: Select DAC buffer gain dac_gain_1 (2.65V full-scale) DAC output polarity. 0: Encodes negative (inverting) DC/DC converter trim input. 1: Encodes positive (noninverting) DC/DC converter trim input.
LTC2977 PMBus Command Description An important feature of the LTC2977 is the ability to control, monitor, and supervise DC/DC converters that are configured to track a master supply on and off. The LTC2977 supports the following tracking features: • Track channels on and off without issuing false UV events when the slave channels are tracking up or down. • Track all channels down in response to a fault from a slave or master.
LTC2977 PMBus Command Description TON_RISE EXPIRES FOR ALL CHANNELS. UV DETECT ENABLED ON ALL CHANNELS TOFF_DELAY ENTERED FOR ALL CHANNELS. UV DETECT DISABLED ON ALL CHANNELS VOUT0 VOUT1 VOUT2 UV FAULT ON CHANNEL 1 BRINGS DOWN MASTER VIA FAULTB0.
LTC2977 PMBus Command Description TOFF_DELAY = Toff_delay_master + Toff_delay_slave Mfr_config_chan_mode = 10b Where: Ton_delay_master – Ton_delay_slave > RUN to TRACK setup time Toff_delay_slave > time for master supply to fall. The system response to a control pin toggle is illustrated in Figure 13b. The system response to a UV fault on a slave channel is illustrated in Figure 13c. MFR_CONFIG_ALL_LTC2977 This command is used to configure parameters that are common to all channels on the IC.
LTC2977 PMBus Command Description MFR_CONFIG_ALL_LTC2977 Data Contents BIT(S) SYMBOL b[2] Mfr_config_all_pec_en b[1] Mfr_config_all_longer_pmbus_ timeout b[0] Mfr_config_all_vinen_wpu_dis OPERATION PMBus packet error checking enable. 0: PEC is accepted but not required 1: PEC is required Increase PMBus timeout internal by a factor of 8. Recommended for fault logging.
LTC2977 PMBus Command Description MFR_PWRGD_EN This command register controls the mapping of the watchdog and channel power good status to the PWRGD pin. Note that odd numbered channels whose ADC is in high res mode do not contribute to power good. MFR_PWRGD_EN Data Contents BIT(S) SYMBOL OPERATION b[15:9] Reserved Read only, always returns 0s.
LTC2977 PMBus Command Description MFR_FAULTB00_RESPONSE, MFR_FAULTB01_RESPONSE, MFR_FAULTB10_RESPONSE and MFR_ FAULTB11_RESPONSE These manufacturer specific commands share the same format and specify the response to assertions of the FAULTB pins. For fault zone 0, MFR_FAULTB00_RESPONSE determines whether channels 0 to 3 shut off when the FAULTB00 pin is asserted, and MFR_FAULTB01_RESPONSE determines whether channels 0 to 3 shut off when the FAULTB01 pin is asserted.
LTC2977 PMBus Command Description MFR_VINEN_OV_FAULT_RESPONSE This command register determines whether VOUT overvoltage faults from a given channel cause the VIN_EN pin to be pulled low. MFR_VINEN_OV_FAULT_RESPONSE Data Contents BIT(S) SYMBOL b[7] Mfr_vinen_ov_fault_response_chan7 OPERATION Response to channel 7 VOUT_OV_FAULT. 1 = Disable (pull low) VIN_EN via fast pull-down. 0 = Do not disable VIN_EN. b[6] Mfr_vinen_ov_fault_response_chan6 Response to channel 6 VOUT_OV_FAULT.
LTC2977 PMBus Command Description MFR_VINEN_UV_FAULT_RESPONSE This command register determines whether VOUT undervoltage faults from a given channel cause the VIN_EN pin to be pulled low. MFR_VINEN_UV_FAULT_RESPONSE Data Contents BIT(S) SYMBOL b[7] Mfr_vinen_uv_fault_response_chan7 OPERATION Response to channel 7 VOUT_UV_FAULT. 1 = Disable (pull low) VIN_EN via fast pull-down. 0 = Do not disable VIN_EN. b[6] Mfr_vinen_uv_fault_response_chan6 Response to channel 6 VOUT_UV_FAULT.
LTC2977 PMBus Command Description MFR_RETRY_COUNT The MFR_RETRY_COUNT is a global command that sets the number of retries attempted when any channel faults off with its fault response retry field set to a non zero value. In the event of multiple or recurring retry faults on the same channel the total number of retries equals MFR_RETRY_ COUNT. If a channel has not been faulted off for 6 seconds, its retry counter is cleared.
LTC2977 PMBus Command Description MFR_VOUT_PEAK This command returns the maximum ADC measured value of the channel’s output voltage. This command is not supported for odd channels that are configured to measure current. This register is reset to 0xF800 (0.0) when the LTC2977 emerges from power-on reset or when a CLEAR_FAULTS command is executed. MFR_VOUT_PEAK Data Contents BIT(S) SYMBOL OPERATION b[15:0] Mfr_vout_peak[15:0] The data uses the L16 format. Units: V.
LTC2977 PMBus Command Description MFR_DAC This command register allows the user to directly program the 10-bit DAC. Manual DAC writes require the channel to be in the ON state,TON_RISE to have expired and MFR_CONFIG_LTC2977 b[5:4] = 10b or 11b. Writing MFR_ CONFIG_LTC2977 b[5:4] = 10b commands the DAC to hard-connect with the value in Mfr_dac_direct_val. Writing b[5:4] = 11b commands the DAC to soft-connect.
LTC2977 PMBus Command Description MFR_PADS The MFR_PADS command provides read only access to slow frequency digital pads (pins). The input values presented in bits[9:0] are before any deglitching logic.
LTC2977 PMBus Command Description MFR_SPECIAL_ID This register contains the manufacturer ID for the LTC2977. MFR_SPECIAL_ID Data Contents BIT(S) SYMBOL OPERATION b[15:0] Mfr_special_id Read only, always returns 0x0130 MFR_SPECIAL_LOT These paged registers contain information that identifies the user configuration that was programmed at the factory. Contact the factory to request a custom factory programmed user configuration and special lot number.
LTC2977 PMBus Command Description MFR_COMMON This command returns status information for the alert pin (ALERTB), share-clock pin (SHARE_CLK), write-protect pin (WP), and device busy state. This is the only command that may still be read when the device is busy processing an EEPROM or other command. It may be polled by the host to determine when the device is available to process a PMBus command.
LTC2977 PMBus Command Description MFR_VOUT_MIN This command returns the minimum ADC measured value of the channel’s output voltage. This register is reset to 0xFFFF (7.999) when the LTC2977 emerges from power-on reset or when a CLEAR_FAULTS command is executed. When odd channels are configured to measure current, this command is not supported. Updates are disabled when undervoltage detection is disabled, such as when Margin Low (Ignore Faults and Warnings) is enabled.
LTC2977 PMBus Command Description MFR_STATUS_2 This command returns additional manufacturer specific fault and state information. Bits marked Sticky = Yes are set by the appropriate event and not cleared until the user issues a CLEAR_FAULTS command or turns the channel back on. Bits marked ALERT = Yes assert ALERTB low when they are set. Bits marked Channel = All are not paged. MFR_STATUS_2 Data Contents BIT(S) SYMBOL b[15:3] Reserved b[2] OPERATION STICKY ALERT CHANNEL Read only, always returns 0s.
LTC2977 PMBus Command Description MFR_TELEMETRY This read-only command enables efficient polling of telemetry data for all output channels via a single 49 byte block read.
LTC2977 PMBus Command Description Watchdog Operation A non zero write to the MFR_WATCHDOG_T register will reset the watchdog timer. Low-to-high transitions on the WDI/RESETB pin also reset the watchdog timer. If the timer expires, ALERTB is asserted and the PWRGD output is optionally deasserted and then reasserted after MFR_PWRGD_ASSERTION_DELAY ms. Writing 0 to either the MFR_WATCH_DOG_T or MFR_WATCHDOG_T_FIRST registers will disable the timer.
LTC2977 PMBus Command Description Bulk Programming the User EEPROM Space The MFR_EE_UNLOCK, MFR_EE_ERASE and MFR_EE_DATA commands provide a method for 3rd party EEPROM programming houses and end users to easily program the LTC2977 independent of any order dependencies or delays between PMBus commands. All data transfers are directly to and from the EEPROM and do not affect the volatile RAM space currently configuring the device.
LTC2977 PMBus Command Description MFR_EE_ERASE The MFR_EE_ERASE command is used to erase the entire contents of the user EEPROM space and configures this space to accept new program data. Writing values other than 0x2B will lock the part. Reads return the last value written.
LTC2977 PMBus Command Description Response When Part Is Busy The part will indicate it is busy accessing the EEPROM by the following mechanism: 1) Clearing Mfr_common_busyb of the MFR_COMMON register. This byte can always be read and will never NACK a byte read request even if the part is busy. 2) NACKing commands other than MFR_COMMON. MFR_EE Erase and Write Programming Time The program time per word is typically 0.17ms and will require spacing the I2C/SMBus writes at greater than 0.
LTC2977 PMBus Command Description MFR_FAULT_LOG_CLEAR This command initializes the EEPROM block reserved for fault logging. Any previous fault log stored in EEPROM will be erased by this operation and logging of the fault log RAM to EEPROM will be enabled. MFR_FAULT_LOG_STATUS Read only. This register is used to manage fault log events. Mfr_fault_log_status_eeprom is set after a MFR_FAULT_LOG_STORE command or a faulted-off event triggers a transfer of the fault log from RAM to EEPROM.
LTC2977 PMBus Command Description MFR_FAULT_LOG Read only. This 2040-bit (255 byte) data block contains a copy of the RAM buffer fault log. The RAM buffer is continuously updated after each ADC conversion as long as Mfr_fault_log_status_ram is clear. With Mfr_config_all_fault_log_enable = 1 and Mfr_fault_log_status_eeprom = 0, the RAM buffer is transferred to EEPROM whenever an LTC2977 fault causes a channel to latch off or a MFR_FAULT_LOG_STORE command is received.
LTC2977 PMBus Command Description Table 2.
LTC2977 PMBus Command Description The data returned between bytes 72 and 237 of the previous table is interpreted using Position_last and the following table. The key to identifying byte 72 is to locate the DATA corresponding to POSITION = Position_last in the next table. Subsequent bytes are identified by decrementing the value of POSITION.
LTC2977 PMBus Command Description BYTE BYTE NUMBER NUMBER DECIMAL HEX DATA DESCRIPTION BYTE BYTE NUMBER NUMBER DECIMAL HEX DATA 16 10 Mfr_vin_peak[7:0] 52 34 Status_mfr1 17 11 Mfr_vin_peak[15:8] 53 35 Mfr_status_2_1[7:0] 18 12 Mfr_vin_min[7:0] 54 36 Status_vout2 19 13 Mfr_vin_min[15:8] 55 37 Status_mfr2 20 14 Mfr_vout_peak2[7:0] 56 38 Mfr_status_2_2[7:0] 21 15 Mfr_vout_peak2[15:8] 57 39 Status_vout3 22 16 Mfr_vout_min2[7:0] 58 3A Status_mfr3 23 17 Mfr_vout_mi
LTC2977 PMBus Command Description LOOP BYTE BYTE BYTE NUMBER NUMBER NUMBER DECIMAL HEX DECIMAL DATA LOOP 1 46 BYTES PER LOOP LOOP BYTE BYTE BYTE NUMBER NUMBER NUMBER DECIMAL HEX DECIMAL DATA LOOP 1 84 54 45 Mfr_status_2_7[7:0] 119 77 10 Read_vin[7:0] 85 55 44 Status_mfr7 120 78 9 Mfr_status_2_1[7:0] 86 56 43 Status_vout7 121 79 8 Status_mfr1 87 57 42 Read_vout7[15:8] 122 7A 7 Status_vout1 88 58 41 Read_vout7[7:0] 123 7B 6 Read_vout1[15:8] 89 59 40 Mfr_status_2
LTC2977 PMBus Command Description LOOP BYTE BYTE BYTE NUMBER NUMBER NUMBER DECIMAL HEX DECIMAL 151 152 97 98 24 23 DATA LOOP 2 46 BYTES PER LOOP LOOP BYTE BYTE BYTE NUMBER NUMBER NUMBER DECIMAL HEX DECIMAL DATA LOOP 3 Read_ temperature_1[15:8] 182 B6 39 Status_mfr6 Read_ temperature_1[7:0] 183 B7 38 Status_vout6 184 B8 37 Read_vout6[15:8] 185 B9 36 Read_vout6[7:0] 186 BA 35 Mfr_status_2_5[7:0] 187 BB 34 Status_mfr5 188 BC 33 Status_vout5 189 BD 32 Read_vout5[15:8] 19
LTC2977 PMBus Command Description LOOP BYTE BYTE BYTE NUMBER NUMBER NUMBER DECIMAL HEX DECIMAL RESERVED BYTES DATA LOOP 3 217 D9 4 Mfr_status_2_0[7:0] 218 DA 3 Status_mfr0 219 DB 2 Status_vout0 220 DC 1 Read_vout0[15:8] 221 DD 0 Read_vout0[7:0] LOOP BYTE BYTE BYTE NUMBER NUMBER NUMBER DECIMAL HEX DECIMAL DATA LOOP 4 46 BYTES PER LOOP 46 BYTES PER LOOP 238 EE 0x00 239 EF 0x00 240 F0 0x00 241 F1 0x00 242 F2 0x00 243 F3 0x00 244 F4 0x00 245 F5 0x00 246 F6 0x0
LTC2977 Applications Information Overview The LTC2977 is a power management IC that is capable of sequencing, margining, trimming, supervising output voltage for OV/UV conditions, providing fault management, and voltage readback for eight DC/DC converters. Input voltage and LTC2977 junction temperature readback are also available. Odd numbered channels can be configured to read back sense resistor voltages to provide current measurements for those channels.
LTC2977 APPLICATIONS INFORMATION On Sequencing Servo Modes The TON_DELAY command sets the amount of time that a channel will wait following the start of an ON sequence before its VOUT_EN pin will enable a DC/DC converter. Once the DC/DC converter has been enabled, the TON_RISE value determines the time at which the device soft-connects the DAC and servos the DC/DC converter output to the VOUT_COMMAND value.
LTC2977 APPLICATIONS INFORMATION • DAC manual with soft-connect. Non servo mode. The DAC soft-connects to the feedback node. Soft-connect drives the DAC code to match the voltage at the feedback node. After connection, the DAC is moved by writing DAC codes to the MFR_DAC register. • DAC manual with hard-connect. Non servo mode. The DAC hard-connects to the feedback node using the current value in MFR_DAC. After connection, the DAC is moved by writing DAC codes to the MFR_DAC register.
LTC2977 APPLICATIONS INFORMATION the ALERTB pin being asserted low and the corresponding bits being set in the status registers. The CLEAR_FAULTS command resets the contents of the status registers and deasserts the ALERTB output. Output Overvoltage and Undervoltage Warnings OV and UV warning threshold voltages are processed by the LTC2977’s ADC. These thresholds are set by the VOUT_OV_ WARN_LIMIT and VOUT_UV_WARN_LIMIT commands respectively.
LTC2977 APPLICATIONS INFORMATION Mfr_faultb00_response, page = 0 Mfr_faultb01_response, page = 0 CHANNEL 0 EVENT PROCESSOR PAGE = 0 Mfr_faultb00_response, page = 1 Mfr_faultb01_response, page = 1 CHANNEL 1 EVENT PROCESSOR PAGE = 1 Mfr_faultb00_response, page = 2 Mfr_faultb01_response, page = 2 CHANNEL 2 EVENT PROCESSOR PAGE = 2 Mfr_faultb00_response, page = 3 Mfr_faultb01_response, page = 3 CHANNEL 3 EVENT PROCESSOR PAGE = 3 Mfr_faultbz0_propagate_ch0 FAULTED_OFF Mfr_faultbz1_propagate_ch0 FAULTB00
LTC2977 APPLICATIONS INFORMATION Multichannel Fault Management Multichannel fault management is handled using the bidirectional FAULTBzn pins. The “z” designates the fault zone which is either 0 or 1. There are two fault zones in the LTC2977. Each zone contains 4-channels. Figure 20 illustrates the connections between channels and the FAULTBzn pins. • A FAULTBzn pin can also be asserted low by an external driver in order to initiate an off-sequence after a 10µs deglitch delay.
LTC2977 APPLICATIONS INFORMATION Application Circuits • WDI/RESETB can be used to put the LTC2977 in the power-on reset state. Pull WDI/RESETB low for at least tRESETB to enter this state. Trimming and Margining DC/DC Converters with External Feedback Resistors • The FAULTBzn lines can be connected together to create fault dependencies. Figure 21 shows a configuration where a fault on any FAULTBzn will pull all others low.
LTC2977 APPLICATIONS INFORMATION Four-Step Resistor Selection Procedure for DC/DC Converters with External Feedback Resistors The following four-step procedure should be used to calculate the resistor values required for the application circuit shown in Figure 23. 1. Assume values for feedback resistor R20 and the nominal DC/DC converter output voltage VDC(NOM), and solve for R10. VDC(NOM) is the output voltage of the DC/DC converter when the LTC2977’s VDACP0 pin is in a high impedance state.
LTC2977 APPLICATIONS INFORMATION Trimming and Margining DC/DC Converters with a TRIM Pin Figure 24 illustrates a typical application circuit for trimming/margining the output voltage of a DC/DC converter with a TRIM Pin. The LTC2977’s VDACP0 pin connects to the TRIM pin through resistor R30, and the VDACM0 pin is connected to the converter’s point-of-load ground. For this configuration, set the DAC polarity bit Mfr_config_ dac_pol in MFR_CONFIG_LTC2977 to 1.
LTC2977 APPLICATIONS INFORMATION LTC2977 bit b[9] = 1 in order to enable high res mode. The VOUT_EN pin will assert low in this mode and cannot be used to control a DC/DC converter. The VDACP output pin is also unavailable. Measuring Current with a Sense Resistor A circuit for measuring current with a sense resistor is shown in Figure 25. The balanced filter rejects both common mode and differential mode noise from the output of the DC/DC converter.
LTC2977 APPLICATIONS INFORMATION SWX1 RCM1 RCM1 RCM1 L RCM2 CCM1 CCM2 VSENSEP1 LTC2977 DCR VSENSEM1 RCM1/3 DCR DCR L 2977 F27 RCM2 CCM1 CCM2 L TO LOAD SWX2 SWX3 Figure 27. Multiphase DCR Current Sensing Circuits DCR divided by the number of phases. Care should to be taken in the layout of the multiphase inductors to keep the PCB trace resistance from the DC side of each inductor to the summing node balanced in order to provide the most accurate results.
LTC2977 APPLICATIONS INFORMATION Sensing Negative Voltages ming, telemetry and system debug. The controller, when used in conjunction with LTpowerPlay software, provides a powerful way to debug an entire power system. Failures are quickly diagnosed using telemetry, fault status registers and the fault log. The final configuration can be quickly developed and stored to the LTC2977’s EEPROM. Figure 29 shows the LTC2977 sensing a negative power supply (VEE).
LTC2977 APPLICATIONS INFORMATION REPEAT OUTLINED CIRCUIT FOR EVERY LTC2977 150k 4.5V TO 15V 49.9k VPWR 0.1µF ISOLATED 3.3V VDD33 Si1303 SCL LTC2977* VDD33 GND 0.1µF SDA VDD25 0.1µF TO DC1613 I2C/SMBUS/PMBUS CONTROLLER 10k 10k 5.49k SCL SDA SHARE_CLK WP TO/FROM OTHER LTC2977s GND 2977 F30 *PIN CONNECTIONS OMITTED FOR CLARITY Figure 30. DC1613 Controller Connections When VPWR Is Used TP0101K-SSOT23 SYSTEM 3.3V LTC4412 VIN IDEAL DIODE 0R’d 3.3V 10k 10k LTC2977_3.3V 5.49k VDD33 0.
LTC2977 APPLICATIONS INFORMATION have body diodes between the SDA/SCL pins and its VDD node because this will interfere with bus communication in the absence of system power. The DC1613 controller’s I2C/SMBus connections are opto-isolated from the PC’s USB port. The 3.3V supply from the controller and the LTC2977’s VDD33 pin can be paralleled because the LTC LDOs that generate these voltages can be backdriven and draw <10μA. The controller’s 3.3V current limit is 100mA.
LTC2977 APPLICATIONS INFORMATION PCB Assembly and Layout Suggestions Exposed Pad Stencil Design Bypass Capacitor Placement The LTC2977’s package is thermally and electrically efficient. This is enabled by the exposed die attach pad on the under side of the package which must be soldered down to the PCB or mother board substrate. It is a good practice to minimize the presence of voids within the exposed pad inter-connection.
LTC2977 APPLICATIONS INFORMATION PC Board Layout QFN PACKAGE APERATURE DESIGN 50% TO 80% REDUCTION Mechanical stress on a PC board and soldering-induced stress can cause the LTC2977’s reference voltage and voltage drift to shift. A simple way to reduce these stressrelated shifts is to mount the IC near the short edge of the PC board, or in a corner. The board edge acts as a stress boundary, or a region where the flexure of the board is minimal. GROUND PLANE Unused ADC Sense Inputs 2977 F32 Figure 32.
LTC2977 Package Description Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings. UP Package 64-Lead Plastic QFN (9mm × 9mm) (Reference LTC DWG # 05-08-1705 Rev C) 0.70 ±0.05 7.15 ±0.05 7.50 REF 8.10 ±0.05 9.50 ±0.05 (4 SIDES) 7.15 ±0.05 PACKAGE OUTLINE 0.25 ±0.05 0.50 BSC RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS APPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED 9 .00 ±0.10 (4 SIDES) 0.75 ±0.05 R = 0.10 TYP R = 0.115 TYP 63 64 0.40 ±0.
LTC2977 Revision History REV DATE DESCRIPTION PAGE NUMBER A 09/13 Improved the voltage range for ADC Total Unadjusted Error (TUE) specification, Voltage Sense Mode, from >1.8V to >1V 5 Added ADC TUE specification for Current Sense Mode 5 Consolidated previous ADC specifications – INL, DNL, Voltage Sense Offset Error, Gain Error – into TUE 5 Updated VOS_CMP Offset Voltage specification 7 VVOUT_ENn Output High Voltage specification: Changed minimum from 11.
LTC2977 Typical Application 0.
