applicaTions current monitoring with …

1 LT870518705ffFor more information applicaTion FeaTuresDescripTion80V VIN and VOUT Synchronous 4-Switch buck - boost DC/DC ControllerThe LT 8705 is a high performance buck - boost switch-ing regulator controller that operates from input voltages above, below or equal to the output voltage. The part has integrated input current , input voltage, output current and output voltage feedback loops. With a wide to 80V input and to 80V output range, the LT8705 is compatible with most solar, automotive, telecom and battery-powered systems. The LT8705 includes servo pins to indicate which feedback loops are active. The MODE pin selects among Burst Mode operation, discontinuous or continuous conduction mode at light loads. Additional features include a LDO, a synchronizable fixed operating frequency, onboard gate drivers, adjustable UVLO, along with input and output current monitoring with programmable maximum , LT, LT C, LT M, Linear Technology, Burst Mode, Module and the Linear logo are registered trademarks of Linear Technology Corporation.

2 All other trademarks are the property of their respective owners. nSingle Inductor Allows VIN Above, Below, or Equal to Regulated VOUT nVIN Range (Need EXTVCC > ) to 80V nVOUT Range: to 80V nQuad N-Channel MOSFET Gate Drivers nSynchronous Rectification: Up to 98% Efficiency nInput and Output current Monitor Pins nSynchronizable Fixed Frequency: 100kHz to 400kHz nIntegrated Input current , Input Voltage, Output Cur-rent and Output Voltage Feedback Loops nClock Output Usable To Monitor Die Temperature nAvailable in 38-Lead (5mm 7mm) QFN and TSSOP Packages with the TSSOP Modified for Improved High Voltage Operation nHigh Voltage buck - boost Converters nInput or Output current Limited ConvertersTelecom Voltage Stabilizer8705 FTODIODETODIODEM2M1 222 F 4M4M3 21nF1nFSW1 BG1 CSPCSNLT8705 GND BG2 SW2 BOOST2 VOUT48V5 AVIN36V F1 F10k392k220 F F 64 F2 22 210m +220 F 2+TOBOOST2100k10 10 VIN (V)30 EFFICIENCY (%)POWER LOSS (W)9095708705 TA01b8580040506080 VOUT = 48 VILOAD = 2A100654321 Efficiency and Power LossLT870528705ffFor more information conFiguraTionabsoluTe MaxiMuM raTingsVCSP-VCSN, VCSPIN-VCSNIN, to , CLKOUT, CSP, CSN Voltage.

3 To 3 VVC Voltage (Note 2) .. to , LDO33, FBOUT Voltage .. to 5 VIMON_IN, IMON_OUT Voltage .. to 5 VSYNC Voltage .. to INTVCC, GATEVCC Voltage .. to 7 VVBOOST1-VSW1, VBOOST2-VSW2 .. to 7 VSWEN, MODE Voltage .. to 7 VSRVO_FBIN, SRVO_FBOUT Voltage .. to 30 VSRVO_IIN, SRVO_IOUT Voltage .. to 30 VFBIN, SHDN Voltage .. to 30V(Note 1)CSNIN, CSPIN, CSPOUT, CSNOUT Voltage .. to 80 VVIN, EXTVCC Voltage .. to 80 VSW1, SW2 Voltage ..81V (Note 7)BOOST1, BOOST2 Voltage .. to 87 VBG1, BG2, TG1, TG2 ..(Note 6)Operating Junction Temper atur e Range LT8705E (Notes 3, 8) .. 40 C to 125 C LT8705I (Notes 3, 8) .. 40 C to 125 C LT8705H (Notes 3, 8).. 40 C to 150 C LT8705MP (Notes 3, 8) .. 55 C to 150 CStorage Temper atur e Range .. 65 C to 150 C Lead Temper atur e (Soldering, 10 sec) FE Package ..300 C13141516 TOP VIEW39 GNDUHF PACKAGE38-LEAD (5mm 7mm) PLASTIC QFN1718193837363534333224252627282930318 7654321 SHDNCSNCSPLDO33 FBINFBOUTIMON_OUTVCSSCLKOUTSYNCRTCSPOUTC SNOUTEXTVCCSRVO_FBOUTSRVO_IOUTSRVO_IINSR VO_FBINNCBOOST1TG1SW1 NCIMON_INMODESWENINTVCCVINCSPINCSNINGNDB G1 GATEVCCBG2 BOOST2TG2SW2232221209101112 TJMAX = 125 C, JA = 34 C/W EXPOSED PAD (PIN 39) IS GND, MUST BE SOLDERED TO PCB12345678910111213141516171819 TOP VIEWFE PACKAGEVARIATION.

4 FE38(31)38-LEAD PLASTIC TSSOP38373634323028262422212039 GNDINTVCCMODEIMON_INSHDNCSNCSPLDO33 FBINFBOUTIMON_OUTVCSSCLKOUTSYNCRTGNDBG1 GATEVCCBG2 VINCSPINCSNINCSPOUTCSNOUTEXTVCCBOOST1TG1 SW1SW2TG2 BOOST2 TJMAX = 125 C, JA = 25 C/W EXPOSED PAD (PIN 39) IS GND, MUST BE SOLDERED TO PCBLT870538705ffFor more information characTerisTicsPARAMETERCONDITIONSMINTYP MAXUNITSV oltage Supplies and RegulatorsVIN Operating Voltage RangeEXTVCC = 0V EXTVCC = 80V VVIN Quiescent CurrentNot Switching, VEXTVCC = Quiescent current in ShutdownVSHDN = 0V01 AEXTVCC Switchover VoltageIINTVCC = 20mA, VEXTVCC Switchover current LimitMaximum current Draw from INTVCC and LDO33 Pins Combined. Regulated from VIN or EXTVCC (12V) INTVCC = INTVCC = l l 90 28 127 42 165 55 mA mAINTVCC VoltageRegulated from VIN, IINTVCC = 20mA Regulated from EXTVCC (12V), IINTVCC = 20mAl VINTVCC Load RegulationIINTVCC = 0mA to 50mA , GATEVCC Undervoltage LockoutINTVCC Falling, GATEVCC Connected to , GATEVCC Undervoltage Lockout HysteresisGATEVCC Connected to INTVCC160mVINTVCC Regulator Dropout VoltageVIN-VINTVCC, IINTVCC = 20mA245mVLDO33 Pin Voltage5mA from LDO33 Pin Load RegulationILDO33 = to 5mA 1%LDO33 Pin current Pin Undervoltage LockoutLDO33 Pin Undervoltage Lockout Hysteresis35mVSwitching Regulator ControlMaximum current Sense Threshold (VCSP VCSN) boost Mode, Minimum M3 Switch Duty Cycle (LT8705E, LT8705I) (LT8705H, LT8705MP)

5 L l 102 100 117 117 132 134 mV mVMaximum current Sense Threshold (VCSN VCSP) buck Mode, Minimum M2 Switch Duty Cycle (LT8705E, LT8705I) (LT8705H, LT8705MP) l l 69 67 86 86 102 104 mV mV The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25 C. VIN = 12V, SHDN = 3V unless otherwise noted. (Note 3)orDer inForMaTionLEAD FREE FINISHTAPE AND REELPART MARKING*PACKAGE DESCRIPTIONTEMPERATURE RANGELT8705 EUHF#PBFLT8705 EUHF#TRPBF870538-Lead (5mm 7mm) Plastic QFN 40 C to 125 CLT8705 IUHF#PBFLT8705 IUHF#TRPBF870538-Lead (5mm 7mm) Plastic QFN 40 C to 125 CLT8705 EFE#PBFLT8705 EFE#TRPBFLT8705FE38-Lead Plastic TSSOP 40 C to 125 CLT8705 IFE#PBFLT8705 IFE#TRPBFLT8705FE38-Lead Plastic TSSOP 40 C to 125 CLT8705 HFE#PBFLT8705 HFE#TRPBFLT8705FE38-Lead Plastic TSSOP 40 C to 150 CLT8705 MPFE#PBFLT8705 MPFE#TRPBFLT8705FE38-Lead Plastic TSSOP 55 C to 150 CConsult LT C Marketing for parts specified with wider operating temperature ranges.

6 *The temperature grade is identified by a label on the shipping more information on lead free part marking, go to: For more information on tape and reel specifications, go to: more information from VC to Maximum current Sense Voltage (VCSP-VCSN) (A5 in the Block Diagram) boost Mode buck Mode150 150mV/V mV/VSHDN Input Voltage High SHDN Rising to Enable the Input Voltage High Hysteresis50mVSHDN Input Voltage LowDevice Disabled, Low Quiescent current (LT8705E, LT8705I) (LT8705H, LT8705MP) l l V VSHDN Pin Bias CurrentVSHDN = 3V VSHDN = 12V0 111 22 A ASWEN Rising Threshold Voltage (Note 5) Threshold Voltage Hysteresis (Note 5)22mVMODE Pin Forced Continuous Mode Pin Burst Mode Pin Discontinuous Mode Charging CurrentVSS = ASoft-Start Discharge CurrentVSS = AVoltage Regulator Loops (Refer to Block Diagram to Locate Amplifiers)Regulation Voltage for FBOUTVC = (LT8705E, LT8705I) VC = (LT8705H, LT8705MP)l VRegulation Voltage for FBINVC = (LT8705E, LT8705I)

7 VC = (LT8705H, LT8705MP)l VLine Regulation for FBOUT and FBIN Error Amp Reference VoltageVIN = 12V to 80V; Not Pin Bias CurrentCurrent Out of Pin15nAFBOUT Error Amp EA4 gm315 mhoFBOUT Error Amp EA4 Voltage Gain220V/VFBIN Pin Bias CurrentCurrent Out of Pin10nAFBIN Error Amp EA3 gm130 mhoFBIN Error Amp EA3 Voltage Gain90V/VSRVO_FBIN Activation Threshold (Note 5)(VFBIN Falling) (Regulation Voltage for FBIN), VFBOUT = VIMON_IN = VIMON_OUT = 0V567289mVSRVO_FBIN Activation Threshold Hysteresis (Note 5)VFBOUT = VIMON_IN = VIMON_OUT = 0V33mVSRVO_FBOUT Activation Threshold (Note 5)(VFBOUT Rising) (Regulation Voltage for FBOUT), VFBIN = 3V, VIMON_IN = VIMON_OUT = 0V 37 29 21mVSRVO_FBOUT Activation Threshold Hysteresis (Note 5)VFBIN = 3V, VIMON_IN = 0V, VIMON_OUT = 0V15mVSRVO_FBIN, SRVO_FBOUT Low Voltage (Note 5)I = 100 Al110330mVSRVO_FBIN, SRVO_FBOUT Leakage current (Note 5)

8 VSRVO_FBIN = VSRVO_FBOUT = ACurrent Regulation Loops (Refer to Block Diagram to Locate Amplifiers)Regulation Voltages for IMON_IN and IMON_OUTVC = Regulation for IMON_IN and IMON_OUT Error Amp Reference VoltageVIN = 12V to 80V; Not , CSNIN Bias CurrentBOOST Capacitor Charge Control Block Not Active ICSPIN + ICSNIN, VCSPIN = VCSNIN = 12V 31 AelecTrical characTerisTics The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25 C. VIN = 12V, SHDN = 3V unless otherwise noted. (Note 3)LT870558705ffFor more information , CSNIN Common Mode Operating Voltage , CSNIN Differential Operating Voltage Rangel 100100mVVCSPIN-CSNIN to IMON_IN Amplifier A7 gmVCSPIN VCSNIN = 50mV, VCSPIN = (All Grades) (LT8705E, LT8705I) (LT8705H, LT8705MP) l l 1 1 1 mmho mmho mmhoIMON_IN Maximum Output Currentl100 AIMON_IN Overvoltage Error Amp EA2 gm185 mhoIMON_IN Error Amp EA2 Voltage Gain130V/VCSPOUT, CSNOUT Bias CurrentBOOST Capacitor Charge Control Block Not Active ICSPOUT + ICSNOUT, VCSPOUT = VCSNOUT = 12V ICSPOUT + ICSNOUT, VCSPOUT = VCSNOUT = 45 4 A ACSPOUT, CSNOUT Common Mode Operating Voltage Rangel080 VCSPOUT, CSNOUT Differential Mode Operating Voltage Rangel 100100mVVCSPOUT-CSNOUT to IMON_OUT Amplifier A6 gmVCSPOUT VCSNOUT = 50mV, VCSPOUT = (All Grades) (LT8705E, LT8705I)

9 (LT8705H, LT8705MP) VCSPOUT VCSNOUT = 5mV, VCSPOUT = (All Grades) (LT8705E, LT8705I) (LT8705H, LT8705MP) l l l l 1 1 1 1 1 1 mmho mmho mmho mmho mmho mmhoIMON_OUT Maximum Output Currentl100 AIMON_OUT Overvoltage Error Amp EA1 gm185 mhoIMON_OUT Error Amp EA1 Voltage Gain130V/VSRVO_IIN Activation Threshold (Note 5)(VIMON_IN Rising) (Regulation Voltage for IMON_IN), VFBIN = 3V, VFBOUT = 0V, VIMON_OUT = 0V 60 49 37mVSRVO_IIN Activation Threshold Hysteresis (Note 5)VFBIN = 3V, VFBOUT = 0V, VIMON_OUT = 0V22mVSRVO_IOUT Activation Threshold (Note 5)(VIMON_OUT Rising) (Regulation Voltage for IMON_OUT), VFBIN = 3V, VFBOUT = 0V, VIMON_IN = 0V 62 51 39mVSRVO_IOUT Activation Threshold Hysteresis (Note 5)VFBIN = 3V, VFBOUT = 0V, VIMON_IN = 0V22mVSRVO_IIN, SRVO_IOUT Low Voltage (Note 5)I = 100 Al110330mVSRVO_IIN, SRVO_IOUT Leakage current (Note 5)VSRVO_IIN = VSRVO_IOUT = ANMOS Gate DriversTG1, TG2 Rise TimeCLOAD = 3300pF (Note 4)20nsTG1, TG2 Fall TimeCLOAD = 3300pF (Note 4)20nsBG1, BG2 Rise TimeCLOAD = 3300pF (Note 4)20nsBG1, BG2 Fall TimeCLOAD = 3300pF (Note 4)20nsTG1 Off to BG1 On DelayCLOAD = 3300pF Each Driver100nsBG1 Off to TG1 On DelayCLOAD = 3300pF Each Driver80nsTG2 Off to BG2 On DelayCLOAD = 3300pF Each Driver100nselecTrical characTerisTics The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25 C.

10 VIN = 12V, SHDN = 3V unless otherwise noted. (Note 2)LT870568705ffFor more information 1: Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. Exposure to any Absolute Maximum Rating condition for extended periods may affect device reliability and 2: Do not force voltage on the VC 3: The LT8705E is guaranteed to meet performance specifications from 0 C to 125 C junction temperature. Specifications over the 40 C to 125 C operating junction temperature range are assured by design, characterization and correlation with statistical process controls. The LT8705I is guaranteed over the full 40 C to 125 C junction temperature range. The LT8705H is guaranteed over the full 40 C to 150 C operating junction temperature range. The LT8705MP is guaranteed over the full 55 C to 150 C operating junction temperature range.