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LTC3882-1

42

Rev A

For more information 

www.analog.com

APPLICATIONS INFORMATION

Efficiency Considerations

Normally, one of the primary goals of any LTC3882-1 ap-

plication will be to obtain the highest practical conversion 

efficiency. The efficiency of a switching regulator is equal 

to the output power divided by the input power. It is often 

useful to analyze individual losses to determine what is 

limiting the efficiency and to ascertain which change would 

produce the most improvement. Balancing or limiting these 

individual losses plays a dominant role in the component 

selection process outlined over the next few sections.
Percent efficiency can be expressed as:
  %Efficiency = 100% – (L1 + L2 + L3 + …)
where L1, L2, et al, are the individual losses as a percent-

age of input power: 100 • P

L

n

/P

IN

.

Although all dissipative elements in the system produce 

losses, four main sources usually account for most of 

the losses in LTC3882-1 applications: IC supply current, 

I

2

R losses, topside power MOSFET transition losses and 

total gate drive current.
1. The LTC3882-1 IC supply current is a DC value given 

in the Electrical Characteristics table. The absolute loss 

created by the IC itself is approximately this current 

times the V

CC

 supply voltage. IC supply current typically 

results in a small loss (<0.1%).

2. I

2

R losses occur mainly in the DC resistances of the 

MOSFET, inductor, PCB routing, and input and output 

capacitor ESR. Since each MOSFET is only on for part 

of the cycle, its on-resistance is effectively multiplied by 

the percentage of the cycle it is on. Therefore the bot-

tom MOSFET should have a much lower on-resistance 

R

DS(ON)

 than the top MOSFET in high step-down ratio 

applications. It is crucial that careful attention is paid 

to the layout of the power path on the PCB to minimize 

its resistance. In a 2-phase 1.2V system, 1mΩ of PCB 

resistance at the output costs 5% in efficiency with the 

output running at 60A.

3.  Transition losses apply only to the topside MOSFET and 

become significant when operating at high input voltages 

(typically above 12V). This loss can be minimized by 

choosing a driver with very low drive resistance and a 

MOSFET with low gate charge Q

G

, gate resistance R

G

 

and Miller capacitance C

MILLER

. Absolute transition loss 

can be estimated by:

  P

TRANS

 = (1.7) • V

IN

2

 • I

OUT

 • C

MILLER

 • f

PWM

4.  Gate drive current is equal to the sum of the top and bot-

tom MOSFET gate charges multiplied by the frequency of 

operation. These charges are based on the gate voltage 

applied by the FET driver and can be determined from 

manufacturer curves like the one shown in Figure 21

.

 

Many driver ICs employ asymmetrical gate voltages for 

top and bottom FETs.

Other sources of loss include body or Schottky diode 

conduction during the driver dependent non-overlap time 

and inductor core losses. These latter categories generally 

account for less than 2% total additional loss.

PWM Frequency and Inductor Selection

The selection of the PWM switching frequency is a trade-off 

between efficiency, transient response and component size. 

High frequency operation reduces the size of the inductor 

and output capacitor as well as increasing the maximum 

practical control loop bandwidth. However, efficiency is 

generally lower due to increased transition and switch-

ing losses. The inductor value is related to the switching 

frequency f

PWM

 and step-down ratio. It should be selected 

to meet choke ripple current requirements. The inductor 

value can be calculated using the following equation:

 

 

L

=

V

OUT

f

PWM

Δ

I

L


⎝⎜


⎠⎟

• 1–

V

OUT

V

IN


⎝⎜


⎠⎟

Allowing a larger value of choke ripple current (∆I

L

) leads 

to smaller L, but results in greater core loss and higher 

output voltage ripple for a given output capacitance and/

or ESR. A reasonable starting point for setting the ripple 

current is 30% of the maximum output current.
The inductor saturation current rating needs to be higher 

than the peak inductor current during transient conditions. 

If I

OUT

 is the maximum rated load current, then the maxi-

mum transient current I

MAX

 would normally be chosen to 

be some factor greater than I

OUT

 (e.g., 1.6 • I

OUT

).

Summary of Contents for Analog Devices LTC3882-1

Page 1: ...art Stop Sequencing Margining AVP and UV OV OC Limits n 3V VINSNS 38V 0 5V VOUT 5 25V n 0 5 Output Voltage Error n Programmable PWM Frequency or External Clock Synchronization from 250kHz to 1 25MHz n...

Page 2: ...I O 28 Fault Logging 28 Factory Default Operation 31 Serial Interface 32 Serial Bus Addressing 32 Serial Bus Timeout 36 Serial Communication Errors 36 PMBus Command Summary 37 PMBus Commands 37 Data...

Page 3: ...VOUT 87 STATUS_IOUT 87 STATUS_INPUT 88 STATUS_TEMPERATURE 88 STATUS_CML 88 STATUS_MFR_SPECIFIC 89 MFR_PADS_LTC3882 1 89 MFR_COMMON 90 MFR_INFO 90 CLEAR_FAULTS 90 Telemetry 91 READ_VIN 91 MFR_VIN_PEAK...

Page 4: ...8 7 6 5 4 3 2 COMP0 TSNS0 TSNS1 VINSNS IAVG_GND PGOOD0 PWM0 SYNC SCL SDA IAVG1 FB1 COMP1 PGOOD1 PWM1 VCC VDD33 SHARE_CLK VDD25 PHAS_CFG FB0 I AVG0 I SENSE0 I SENSE0 V SENSE0 V SENSE0 V SENSE1 V SENSE...

Page 5: ...ange 1 Set Point Resolution 0 6V VOUT 2 5V 0 6V VOUT 2 5V l 0 5 2 65 0 2 0 6875 0 5 V mV IVSENSE VSENSE Input Current VSENSE 5 5V VSENSE 0V 235 335 A A VLINEREG VCC Line Regulation No Output Servo 4 5...

Page 6: ...PWM Duty Cycle 12 5 2 2 NVOUT VOUT Readback Resolution 244 V VOUT_TUE VOUT Total Unadjusted Readback Error 0 6V VOUT 5 5V Constant Load l 0 5 0 2 0 5 NISENSE IOUT Readback Resolution LSB Step Size at...

Page 7: ...D0 PGOOD1 VDD33 0V FAULT0 FAULT1 SYNC SHARE_CLK 3 6V 0V RUN0 RUN1 5 5V 0V SCL SDA ALERT 5 5V l 1 5 5 1 5 5 A A A tRO PWMn Output Rise Time CLOAD 30pF 10 to 90 5 ns tFO PWMn Output Fall Time CLOAD 30pF...

Page 8: ...ranteed by design characterization and correlation with statistical process controls Minimum retention applies only for devices cycled less than the minimum endurance specification EEPROM read command...

Page 9: ...0 38821 G06 CH1 ISENSE OFFSET TO IDEAL V 400 400 300 200 100 300 200 100 0 9595 UNITS FROM 3 LOTS TA 40 C TJ 22 C CHO MASTER NUMBER OF ICs 3500 2500 1500 500 3000 2000 1000 0 38821 G07 CH1 ISENSE OFFS...

Page 10: ...mV DIV IOUT1 10A DIV 100 s DIV 38821 G15 25 LOAD STEP VOUT 50mV DIV IO 10A DIV 200 s DIV 38821 G16 VOUT 10mV DIV VIN 2V DIV 7V 1 8V 200 s DIV 38821 G17 100 s DIV VOUT 10mV DIV IOUT 10A DIV 38821 G13 V...

Page 11: ...0 40 20 0 PWM FREQUENCY kHz 500 2 500 1 499 9 499 7 500 0 499 8 499 6 499 5 38821 G23 TEMPERATURE C 40 60 80 120 100 20 40 20 0 FREQUENCY_SWITCH 500kHz RUN 2V DIV VOUT 1V DIV 5ms DIV TOFF_DELAY 10ms T...

Page 12: ...1 2 3 5 OUTPUT CURRENT A 0 MEASUREMENT ERROR mA 0 2 4 20 38821 G26 2 4 8 5 10 15 6 8 6 Temperature ADC TUE SHARE_CLK Frequency vs Temperature IC Operating Current vs Temperature ACTUAL TEMPERATURE C...

Page 13: ...al clock can be applied to this pin to synchronize the internal PWM chan nels If the LTC3882 1 is configured as a clock master this pin will also pull to ground at the selected PWM switching frequency...

Page 14: ...nse Inputs These pins must still be properly connected on slave channels for accurate output current telemetry VSENSE0 VSENSE1 Pin36 Pin33 PositiveOutputVoltage Sense Inputs These pins must still be p...

Page 15: ...URE PWM1 VINSNS BIAS AND HOUSEKEEPING 3 3V REGULATOR 2 5V REGULATOR MCU AND CUSTOM LOGIC TSNS1 VSENSE1 ISENSE1 IAVG1 TSNS0 PWM0 VSENSE0 ISENSE0 VINSNS VDD33 VCC PLL SYNC R_CONFIG SHARE_CLK PMBus RAM R...

Page 16: ...s a PMBus compliant digital interface for monitoring and control of important power system parameters The chip operates from an IC power supplybetween3Vand13 2Vandisintendedforconversion from VIN betw...

Page 17: ...ing edge modulation architecture doesnothaveaminimumon timerequirement Minimum duty cycle will be determined by performance limits of the external power stage The IC is also capable of active voltage...

Page 18: ...OOP COMPENSATION NETWORK 2R RS VIN VOC0 CS L1 COUT VOUT MODE 36 IOUT_OC_FAULT_LIMIT VREV EA VC CA S GATE DRIVER PWM LOGIC OSCILLATOR RAMP CLOCK Q 0V R S MASTER ENABLE SLAVE ENABLE 39 SLAVE DETECT FEED...

Page 19: ...ut 20 of its regulated value At that point the internal microcontroller begins initialization A PMBus RESTORE_USER_ALL or MFR_RESET command forces this same initialization The LTC3882 1 features an in...

Page 20: ...on and off ramping control using a shared time reference SHARE_ CLK Powerrailonandoffrelationshipssimilartothoseof conventionalanalogtrackingfunctionscanbeachievedby usingprogrammeddelaysandTON_RISEan...

Page 21: ...rnal bottom MOSFET synchronous rectifier when the induc tor current reaches approximately 0A preventing it from going substantially negative The external gate driver or power block must have short del...

Page 22: ...gether and a small capacitor 50pF to 200pF between IAVG and IAVG_GND stores a voltage corresponding to the average master phase output current The difference in this aver age and the instantaneous pha...

Page 23: ...ng an on chip diode with a VBE measurement and calculation Resistor Configuration Pins Sixinputpinscanbeusedtoconfigurekeyoperatingparam eters with selected 1 resistors arranged between VDD25 and GND...

Page 24: ...Information section for equations to predict retention degradation due to elevated operating temperatures See the Applications Information section or contact the factoryfordetailsonefficientin system...

Page 25: ...IOUT Faults The LTC3882 1 measures average IOUT from the voltage acrosstheISENSEpins takingintoaccountthesenseresistor or DCR value and its associated temperature coefficient BothareprovidedbyPMBusco...

Page 26: ...pecified by the MFR_RETRY_DELAY command This avoids damage to external regulator components caused by repetitive rapid power cycling No retry is attempted for a latch off fault response In the latch o...

Page 27: ...3 2 1 0 PAGED STATUS_IOUT 7 6 5 4 3 2 1 0 PAGED MASKABLE DESCRIPTION General Fault or Warning Event General Non Maskable Event Dynamic Status Derived from Other Bits Yes No No No GENERATES ALERT Yes Y...

Page 28: ...LEAR_FAULTS RESTORE_USER_ALL or MFR_RE SET Command Is Issued The Related Status Bit Is Written to a One The Faulted Channel Is Properly Commanded Off and Back On IC Supply Power Is Cycled For autonomo...

Page 29: ...since last power on or CLEAR_PEAKS command 7 0 14 MFR_IOUT_PEAK PAGE 0 15 8 L11 15 Peak READ_IOUT on Channel 0 since last power on or CLEAR_PEAKS command 7 0 16 MFR_IOUT_PEAK PAGE 1 15 8 L11 17 Peak R...

Page 30: ...x16 Under temperature 0x17 VIN_OV 0x1A Internal temperature 0xFF MFR_FAULT_LOG_STORE Table 4 Fault Log Event Record DATA BITS FORMAT RECORD BYTE INDEX READ_VOUT PAGE 0 15 8 L16 0 7 0 1 READ_VOUT PAGE...

Page 31: ...g Limit 6 3 V Input Voltage ON Threshold 6 5 V Input Voltage OV Fault Limit 15 5 V Input Voltage OV Fault Response Latch off Soft Start Time 8 with no delay ms Maximum Start Up Time TMAX 10 ms TMAX Fa...

Page 32: ...3882 1 to a PMBus system This specification can be found at http www pmbus org specs html TheLTC3882 1usesthefollowingstandardserialinterface protocolsdefinedintheSMBusandPMBusspecifications Quick Com...

Page 33: ...sses is also strongly discouraged Device addressing is the most common means used by a busmastertocommunicatewithanLTC3882 1 Thevalue of the device address is set by the combination of ASEL pin progra...

Page 34: ...TA BYTE LOW 8 DATA BYTE HIGH PEC 8 8 1 1 1 1 1 1 1 1 Sr 1 A 1 Rd A SLAVE ADDRESS COMMAND CODE DATA BYTE LOW Wr A A A P 38821 F09 S 7 8 8 1 DATA BYTE HIGH 8 1 1 1 1 1 1 A SLAVE ADDRESS COMMAND CODE SLA...

Page 35: ...AVE ADDRESS COMMAND CODE SLAVE ADDRESS Wr A A Sr S 7 8 7 1 1 BYTE COUNT N 8 1 1 1 1 1 1 A Rd A A DATA BYTE 1 8 DATA BYTE 2 8 1 1 A A P NA 38821 F16 DATA BYTE N PEC 8 8 1 1 1 SLAVE ADDRESS COMMAND CODE...

Page 36: ...s will the timeout period be less than the tTIMEOUT specification 25ms minimum The LTC3882 1 supports the full PMBus frequency range of 10kHz to 400kHz Serial Communication Errors The LTC3882 1 suppor...

Page 37: ...e are implicitly not supported by the LTC3882 1 All commands from 0xD0 through 0xFF not listed in this table are implicitly reservedbythemanufacturer TheLTC3882 1mayexecute additional commands not lis...

Page 38: ...Y Reg l see CMD details 98 VOUT_MODE 0x20 Voltage related format Linear and exponent R Byte Y Reg 0x14 2 12 79 VOUT_COMMAND 0x21 Nominal VOUT value R W Word Y L16 V l 1 0V 0x1000 79 VOUT_MAX 0x24 Max...

Page 39: ...overvoltage fault limit R W Word N L11 V l 15 5V 0xD3E0 78 VIN_OV_FAULT_RESPONSE 0x56 VIN overvoltage fault response R W Byte Y Reg l 0x80 94 VIN_UV_WARN_LIMIT 0x58 VIN undervoltage warning limit R W...

Page 40: ...l number R String N ASC LTC3882 1 103 MFR_SERIAL 0x9E Device serial number R Block N ASC 103 LTC3882 1 Custom Commands MFR_VOUT_MAX 0xA5 Maximum value of any VOUT related command R Word Y L16 V 5 6V 0...

Page 41: ...xE7 Manufacturer code representing the LTC3882 1 R Word N Reg 0x424X 103 MFR_FAULT_LOG_STORE 0xEA Force transfer of fault log from operating memory to EEPROM Send Byte N 103 MFR_FAULT_LOG_CLEAR 0xEC C...

Page 42: ...0A 3 Transition losses apply only to the topside MOSFET and becomesignificantwhenoperatingathighinputvoltages typically above 12V This loss can be minimized by choosing a driver with very low drive re...

Page 43: ...io and the FET circuit position main or synchronous switch A much smaller and lower input capacitance MOSFET should be used for the top MOSFET in applications that have an output voltage that is less...

Page 44: ...tcouldexceedthemaximum voltage rating of the MOSFET If this ringing cannot be avoided and exceeds the maximum rating of the device choose a higher voltage rated MOSFET MOSFET Driver Selection Gate dri...

Page 45: ...rated electrolyticcapacitorscanbeusedasinputcapacitors but each has drawbacks Ceramics have high voltage coeffi cients of capacitance and may have audible piezoelectric effects tantalumsneedtobesurge...

Page 46: ...rom which the PWM controller derives the required output duty cycle To speedupovershootrecoverytime themaximumpotential at the COMP pin is internally clamped Unlike many regulators that use a transcon...

Page 47: ...he circuitbranches RSENSE willbereplacedwithadeadshort ifDCRsensingisused Formaximumefficiency theswitch Theexternalinductor outputcapacitorcombinationmakes a more significant contribution to loop beh...

Page 48: ...ch they are routed Avoid high frequency switching signals and ideally shield with ground planes Locate any filter component on these traces next to the LTC3882 1 and not at the Kelvin sense location H...

Page 49: ...oefficient of the inductor s DCR is typically high like copper Again consultthemanufacturer sdatasheet TheLTC3882 1can adjust for this non ideality if the correct MFR_IOUT_CAL_ GAIN_TC value is progra...

Page 50: ...information about parasitic inductance In the absence of data measure the voltage drop directly across the sense resistor to extract the magnitude of the ESL step and the following equation to determ...

Page 51: ...of the fall time If TOFF_FALL is shorter than the time required to discharge the load capacitance the output will not reach 0V In this case the power stage will still be commanded off at the end of TO...

Page 52: ...LTC digital power products two signals should be shared between all controlling ICs SHARE_CLK and RUN CONTROL pin on LTC297x products This facilitates synchronized rail sequencing on or off based on...

Page 53: ...not toggle repeatedly at lower values of TON_RISE FALLduetonoiseonVOUT Ifunwantedtransi tions still occur on PGOOD due to noise or longer rise fall settings place a capacitor to ground on the PGOOD p...

Page 54: ...1 will adjust the regulated output voltage based on its related ADC voltage reading Every 90ms the digital servo loop will step the LSB of the DAC nominally 1 375mV or 0 6875mV depending on the voltag...

Page 55: ...operat ing at a known output current of at least 20 of full load READ_IOUT The necessary correction which will typi cally be less than several percent of the no load output voltage is calculated as VO...

Page 56: ...with a value between 100pF and 200pF should be placed between IAVG and IAVG_GND This capacitance can be distributed across LTC3882 1 devices pins for improved noise immunity All IAVG_GND pins for a Po...

Page 57: ...MP0 COMP1 VSENSE0 VSENSE1 VSENSE0 VSENSE1 GND IAVG_GND SHARE_CLK LTC3882 1 0 120 IAVG0 IAVG1 SYSTEM ON OFF BOTH ICs SAME DEFAULT FREQUENCY SWITCH 3 PHASE SENSE 1 PHASE SENSE VINSNS FB0 FB1 RUN0 RUN1 F...

Page 58: ...VINSNS FB0 FB1 RUN0 RUN1 FAULT0 FAULT1 SYNC COMP0 COMP1 VSENSE0 VSENSE1 VSENSE0 GND IAVG_GND LTC3882 1 45 225 IAVG0 IAVG1 SYSTEM ON OFF VINSNS FB0 FB1 RUN0 RUN1 FAULT0 FAULT1 SYNC COMP0 COMP1 VSENSE0...

Page 59: ...t handling across phases Because the LTC3882 1 current sharing loop operates by matching sensed voltage it is important that well matched sense elements be used in the system Current matching paramete...

Page 60: ...906 has a recommended value inthiscommandofapproximatelyMFR_TEMP_1_GAIN 0 991 based on the ideality factor of 1 01 Simply invert the ideality factor to calculate the MFR_TEMP_1_GAIN Different manufact...

Page 61: ...09 500 24 9 7 32 450 24 9 5 76 400 24 9 4 32 350 30 1 3 57 300 30 1 1 96 250 Open 0 External SYNC Only Note that if SYNC pins are shared between LTC3882 1s only one SYNC output should be enabled All...

Page 62: ...re shorted If the internal 3 3V LDO is used it can supply a peak current of 85mA including internal consumption and the VDD33 regulatoroutputmustbebypassedtoGNDwithalowESR X5R or X7R ceramic capacitor...

Page 63: ...617 10 5 1 398 1 403 1 66 indicating the effect is the same as operating the device at 125 C for 10 1 66 16 6 hours resulting in a retention derating of 6 6 hours Configuring Open Drain Pins The LTC38...

Page 64: ...fetching converting to internal format and executing commands so marked for processing Some computationally intensive commands e g timing parameters temperatures voltages and currents have internal p...

Page 65: ...tten It is a good practice to always check for a partial fault log at power up if fault logging is enabled bit 7 of MFR_CONFIG_ALL_LTC3882 1 LTpowerPlay An Interactive Digital Power GUI LTpowerPlay is...

Page 66: ...ate remote diagnostics control and reprogramming of the LTC3882 1 while the host system is fully operational permitting very flexible in system debugging Ifthesystemsupplyisrestoredwhilepowerisstillap...

Page 67: ...Bus PMBus CONTROLLER SCL GND LTC3882 1 VCC VDD33 SDA SCL GND LTC3882 1 10k TP0101K VDD25 IN GND 400mV REFERENCE LT6703 2 OUT 10k 102k 10k 10k 2N2002 Figure 48 DC1613 Connections VDD33 Supply GND ENBA...

Page 68: ...st the designed converter ripple current Four 470 F 9m POSCAPs and two 100 F ceramic capacitors are chosen for the output to maintain supply regulation during severe transient conditions and to minimi...

Page 69: ...TE is used to send a non paged command the Page Number byte is ignored This command uses Write Block protocol An example of the PAGE_PLUS_WRITE command with PEC sending a com mand that has two data by...

Page 70: ...SLAVE ADDRESS PAGE_PLUS COMMAND CODE BLOCK COUNT 2 W A A S 7 8 8 1 PAGE NUMBER 8 1 1 1 1 1 A A COMMAND CODE 8 1 A SLAVE ADDRESS BLOCK COUNT 2 LOWER DATA BYTE R A A Sr 7 8 8 1 UPPER DATA BYTE 8 1 1 1...

Page 71: ...the PMBus device address for this unit right justified Setting this command to a value of 0x80 disables device level addressing The GLOBAL device addresses 0x5A and 0x5B cannot be disabled The LTC388...

Page 72: ...MD CODE DESCRIPTION TYPE PAGED DATA FORMAT UNITS NVM DEFAULT VALUE ON_OFF_CONFIG 0x02 RUN pin and PMBus on off command configuration R W Byte Y Reg l 0x1E OPERATION 0x01 On off and margin control R W...

Page 73: ...d Margin operations that ignore faults are not supported by the LTC3882 1 Supported Values VALUE MEANING 0xA8 Margin high 0x98 Margin low 0x80 On VOUT back to nominal even if bit 3 of ON_OFF_CONFIG is...

Page 74: ...PLL Unlocked status may be reported after changing the value of this command until the new frequency is established Supported Frequencies VALUE PWM FREQUENCY TYPICAL 0x0A71 1 25MHz 0x03E8 1MHz 0x0384...

Page 75: ...a and assert a BUSY fault Supported Values BIT MEANING 7 Reserved must write as 0 6 Reserved must write as 0 5 Reserved 4 SHARE_CLK configuration 0 SHARE_CLK continuously enabled once VINSNS VIN_ON af...

Page 76: ...ycle control 0 No special control Device attempts to follow on off commands exactly as issued 1 Output is immediately disabled if commanded back on while waiting for TOFF_DELAY or TOFF_FALL to expire...

Page 77: ...tage measured by the ADC as T G 1 35 VTSNSn O 4 3e 3 25 For both equations G MFR_TEMP_1_GAIN 2 14 and O MFR_TEMP_1_OFFSET Supported Values BIT MEANING 7 Output voltage range select 0 Maximum VOUT 5 25...

Page 78: ...g is disabled until the input exceeds the input startup threshold value set by the VIN_ON command and the unit has been enabled If the VIN_UV_WARN_LIMIT is then exceeded the device Sets the INPUT Bit...

Page 79: ...UT_UV_FAULT_LIMIT 0x44 VOUT undervoltage fault limit R W Word Y L16 V l 0 9V 0x0E66 Related commands OPERATION STATUS_WORD STATUS_VOUT SMBALERT_MASK READ_VOUT MFR_VOUT_PEAK READ_POUT VOUT_OV_FAULT_ RE...

Page 80: ...IMIT value as full scale current for AVP If MFR_VOUT_AVP is non zero VOUT_COMMAND sets the maximum no load output voltage and servo mode for that channel is automatically disabled Setting MFR_VOUT_AVP...

Page 81: ...The VOUT_UV_WARN_LIMIT command sets the value in volts of the output voltage measured by the ADC at the VSENSE pins that causes an output undervoltage warning If the VOUT_UV_WARN_LIMIT is exceeded th...

Page 82: ...data bytes in Linear_5s_11s format IOUT_OC_WARN_LIMIT TheIOUT_OC_WARN_LIMITcommandsetsthevalueoftheoutputcurrentmeasuredbytheADC inamperes thatcauses anoutputovercurrentwarning Toprovidemeaningfulresp...

Page 83: ...tside of this range Values of TON_RISE less than 0 25ms or resulting slopes greater than 4V ms will result in an output step to the commanded voltage limited only by PWM analog loop response This comm...

Page 84: ...LL The TOFF_FALL command sets the time in milliseconds from the end of TOFF_DELAY until the output voltage is com manded fully to zero The part attempts to linearly reduce the commanded output voltage...

Page 85: ...N_LIMIT The OT_WARN_LIMIT command sets the value of sensed external temperature in degrees Celsius which causes an overtemperature warning If the OT_WARN_LIMIT is exceeded the device Sets the TEMPERAT...

Page 86: ...y may be cleared by writing a 1 to their bit position in the STATUS_BYTE in lieu of a CLEAR_FAULTS command This command has one data byte STATUS REPORTING COMMAND NAME CMD CODE DESCRIPTION TYPE PAGED...

Page 87: ...S_VOUT command returns one byte of VOUT status information STATUS_VOUT Message Contents BIT MEANING 7 VOUT overvoltage fault 6 VOUT overvoltage warning 5 VOUT undervoltage warning 4 VOUT undervoltage...

Page 88: ...t supported LTC3882 1 returns 0 4 External undertemperature fault 3 0 Not supported LTC3882 1 returns 0 ALERT can be asserted if any supported bits are set Any supported bit may be cleared by writing...

Page 89: ...in lieu of a CLEAR_FAULTS command This command has one data byte MFR_PADS_LTC3882 1 The MFR_PADS_LTC3882 1 command provides status of the LTC3882 1 digital I O and control pins in addition to general...

Page 90: ...he EEPROM user space 1 No corrections have been made in the EEPROM user space 4 0 Reserved EEPROM ECC status is updated after each RESTORE_USER_ALL or RESET command a power on reset or an EEPROM bulk...

Page 91: ...last MFR_CLEAR_PEAKS R Word N L11 C READ_DUTY_CYCLE 0x94 Measured commanded PWM duty cycle R Word Y L11 READ_FREQUENCY 0x95 Measured PWM input clock frequency R Word Y L11 kHz MFR_CLEAR_PEAKS 0xE3 Cl...

Page 92: ...reports the output power in watts The value is calculated from the product of the most recent correlated output voltage and current readings This read only command has two data bytes in Linear_5s_11s...

Page 93: ...and current consumption of the LTC3882 1 itself This read only command has two data bytes in Linear_5s_11s format READ_FREQUENCY The READ_FREQUENCY command returns the switching frequency supplied to...

Page 94: ...ils MFR_FAULT_PROPAGATE_ LTC3882 1 0xD2 Configure status propagation via FAULTn pins R W Word Y Reg l 0x6993 MFR_FAULT_RESPONSE 0xD5 PWM response when FAULTn pin is low R W Byte Y Reg l 0xC0 MFR_FAULT...

Page 95: ...e The output is commanded off then on by the RUN pin or OPERATION command The device receives a RESTORE_USER_ALL command The device receives an MFR_RESET command IC supply power is cycled 00 The LTC38...

Page 96: ...o operate indefinitely with the normal hardware response described in the Operation section 10 The LTC3882 1 continues operating with the normal hardware response for the delay time specified by bits...

Page 97: ...by Asserting ALERT Unless Masked This command has one data byte MFR_OT_FAULT_RESPONSE The MFR_OT_FAULT_RESPONSE command instructs the device on what action to take in response to an internal overtempe...

Page 98: ...shuts down immediately disables the output and responds according to the retry setting in bits 5 3 11 Not supported Writing this value will generate a CML fault 5 3 Retry setting 000 110 The LTC3882...

Page 99: ...MBALERT_MASK Default Setting Refer Also to Figure 2 STATUS RESISTER ALERT Mask Value MASKED BITS STATUS_VOUT 0x00 None STATUS_IOUT 0x00 None STATUS_TEMPERATURE 0x00 None STATUS_CML 0x00 None STATUS_IN...

Page 100: ...xceeded 3 Reserved 2 IOUT_OC_FAULT_LIMIT exceeded 1 VOUT_UV_FAULT_LIMIT exceeded 0 VOUT_OV_FAULT_LIMIT exceeded This command has two data bytes MFR_FAULT_RESPONSE The MFR_FAULT_RESPONSE command instru...

Page 101: ...well as peak values of these quantities are stored in a continuously updated buffer in RAM The operation is similar to a strip chart recorder When a fault occurs the contents are written into EEPROM...

Page 102: ...STORE_USER_ALL is executed immediately and MFR_FAULT_LOG_STORE is executed after the IC temperature drops below 125 C Refer to Table 4 for details of fault log contents Using any command that writes d...

Page 103: ...D DATA FORMAT UNITS NVM DEFAULT VALUE MFR_ID 0x99 Manufacturer identification R String N ASC LTC MFR_MODEL 0x9A LTC model number R String N ASC LTC3882 1 MFR_SERIAL 0x9E Device serial number R Block N...

Page 104: ...4 7 F V CC 25 C17 1 F V DD25 V DD25 22 C16 2 2 F V DD33 V CC V DD25 V DD33 24 C8 100nF C4 47 F VINSNS 4 R5 1 V OUT0_CFG ASEL1 ASEL0 V OUT1_CFG FREQ_CFG PHAS_CFG I AVG1 I AVG0 R14 1 37k R35 5 76k R34 2...

Page 105: ...F C124 1 0 F C117 100 F 2 C120 470 F 3 C107 2 2 F COMP1 CSB CSB C110 47 F R21 100k C111 22 F V INB V INA 7V 4 V IN V CC V DD25 V DD25 V DD33 V DD25 V DD33 VINSNS CSA CSA PWMA PWM0 PWMB PWM1 V OUT 1 5...

Page 106: ...DE IF PRESENT 5 EXPOSED PAD SHALL BE SOLDER PLATED 6 SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON THE TOP AND BOTTOM OF PACKAGE PIN 1 TOP MARK SEE NOTE 6 PIN 1 NOTCH R 0 45 OR 0 35 45 CHAMFER...

Page 107: ...r its use nor for any infringements of patents or other rights of third parties that may result from its use Specifications subject to change without notice No license is granted by implication or oth...

Page 108: ...gital Power Supply Manager with EEPROM Controls and Monitors Four Outputs 16 Bit ADC Differential Inputs with Fault Logging LTC3774 Dual Multiphase Current Mode Synchronous Controller for Sub Milliohm...

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