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LTC4000

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CSN (Pin 19/Pin 15): Charge Current Sense Negative Input

and Battery Ideal Diode Cathode. Connect a sense resistor

between this pin and the CSP pin. The LTC4000 senses

the voltage across this sense resistor and regulates it to

a voltage equal to 1/20th (typical) of the voltage set at the

CL pin. The maximum regulated sense voltage is 50mV.

The CSN pin is also the cathode input of the battery ideal

diode driver (the anode input is the BAT pin). Tie this pin

to the CSP pin if no charge current limit is desired. Refer to

the Applications Information section for complete details.
CSP (Pin 20/Pin 16): Charge Current Sense Positive Input

and Input Ideal Diode Cathode. Connect a sense resis-

tor between this pin and the CSN pin for charge current

sensing and regulation. This input should be tied to CSN

to disable the charge current regulation function. This

pin is also the cathode of the input ideal diode driver (the

anode is the IID pin).
OFB (Pin 21/Pin 17): Output Feedback Voltage Pin. This

pin is a high impedance input pin used to sense the output

voltage level. In regulation, the output voltage loop sets the

voltage on this feedback pin to 1.193V. Connect this pin

to the center node of a resistor divider between the CSP

pin and the FBG pin to set the output voltage when battery

charging is terminated and all the output load current is

provided from the input. The output voltage can then be

obtained as follows:

OUT

OFB2

OFB1

OFB2

• 1.193V

When charging a heavily discharged battery (such that V

OFB

< V

OUT(INST_ON)

), the battery PowerPath PMOS connected

to BGATE is regulated to set the voltage on this feedback

pin to 0.974V (approximately 86% of the battery float

voltage). The instant-on output voltage is then as follows:

OUT(INST _ ON)

OFB2

OFB1

OFB2

• 0.974V

IGATE (Pin 22/Pin 18): Input PMOS Gate Drive Output. The

IGATE pin drives the external PMOS to behave as an ideal

diode from the IID pin (anode) to the CSP pin (cathode)

when the voltage at the IN pin is within its operating range

(3V to 60V). To ensure that the input PMOS is turned off

when the IN pin voltage is not within its operating range,

connect a 10M resistor from this pin to the CSP pin.
IID (Pin 23/Pin 19): Input Ideal Diode Anode. This pin is

the anode of the input ideal diode driver (the cathode is

the CSP pin).
ITH (Pin 24/Pin 20): High Impedance Control Voltage Pin.

When any of the regulation loops (input current, charge

current, battery float voltage or the output voltage) indicate

that its limit is reached, the ITH pin will sink current (up to

1mA) to regulate that particular loop at the limit. In many

applications, this ITH pin is connected to the control/

compensation node of a DC/DC converter. Without any

external pull-up, the operating voltage range on this pin

is GND to 2.5V. With an external pull-up, the voltage on

this pin can be pulled up to 6V. Note that the impedance

connected to this pin affects the overall loop gain. For

details, refer to the Applications Information section.
CC (Pin 25/Pin 21): Converter Compensation Pin. Connect

an R-C network from this pin to the ITH pin to provide a

suitable loop compensation for the converter used. Refer

to the Applications Information section for discussion and

procedure on choosing an appropriate R-C network for a

particular DC/DC converter.
CLN (Pin 26/Pin 22): Input Current Sense Negative Input.

Connect a sense resistor between this pin and the IN pin.

The LTC4000 senses the voltage across this sense resis-

tor and regulates it to a voltage equal to 1/20th (typical)

of the voltage set at the IL pin. Tie this pin to the IN pin if

no input current limit is desired. Refer to the Applications

Information section for complete details.
IN (Pin 27/Pin 23): Input Supply Voltage: 3V to 60V.

Supplies power to the internal circuitry and the BIAS pin.

Connect the power source to the downstream system

and the battery charger to this pin. This pin is also the

positive sense pin for the input current limit. Connect a

sense resistor between this pin and the CLN pin. Tie this

pin to CLN if no input current limit is desired. A local 0.1µF

bypass capacitor to ground is recommended on this pin.

pin FuncTions

(QFN/SSOP)

Содержание LTC4000

Страница 1: ...ogy and the Linear logo are registered trademarks and PowerPath is a trademark of Linear Technology Corporation All other trademarks are the property of their respective owners 48V to 10 8V at 10A Buck Converter Charger for Three LiFePO4 Cells Applications n Complete High Performance Battery Charger When Paired with a DC DC Converter n Wide Input and Output Voltage Range 3V to 60V n Input Ideal Di...

Страница 2: ...9 10 11 12 13 14 TOP VIEW GN PACKAGE 28 LEAD PLASTIC SSOP 28 27 26 25 24 23 22 21 20 19 18 17 16 15 ENC IBMON CX CL TMR GND FLT CHRG BIAS NTC FBG BFB BAT BGATE IL IIMON RST VM GND IN CLN CC ITH IID IGATE OFB CSP CSN TJMAX 125 C θJA 80 C W θJC 25 C W Pin Configuration Order Information LEAD FREE FINISH TAPE AND REEL PART MARKING PACKAGE DESCRIPTION TEMPERATURE RANGE LTC4000EUFD PBF LTC4000EUFD TRPB...

Страница 3: ..._REG l 96 9 97 6 98 3 VRECHRG HYS Recharge Battery Threshold Voltage Hysteresis of VBFB_REG 0 5 VOUT INST_ON Instant On Battery Voltage Threshold of VBFB_REG l 82 86 90 VLOBAT Falling Low Battery Threshold Voltage of VBFB_REG l 65 68 71 VLOBAT HYS Low Battery Threshold Voltage Hysteresis of VBFB_REG 3 Current Regulation Ratio of Monitored Current Voltage to Sense Voltage VIN CLN 50mV VIIMON VIN CL...

Страница 4: ... 45 50 55 RNTC OPEN NTC Open Circuit Input Resistance 300 kΩ Voltage Monitoring and Open Drain Status Pins VVM TH VM Input Falling Threshold l 1 176 1 193 1 204 V VVM HYS VM Input Hysteresis 40 mV VM Input Current VVM 1 2V 0 1 µA IRST CHRG FLT LKG Open Drain Status Pins Leakage Current VPIN 60V 1 µA VRST CHRG FLT VOL Open Drain Status Pins Voltage Output Low IPIN 1mA l 0 4 V Input PowerPath Contro...

Страница 5: ...E VCSN 1 5V VCSN VBAT VOFB VOUT INST_ON and Charging in Progress or VCSN VBAT and Not Charging 0 3 μA Battery Gate Turn On Current VBGATE VBAT 1 5V VCSN VBAT VOFB VOUT INST_ON and Charging in Progress or VCSN VBAT 20mV 0 3 μA IBGATE FASTOFF Battery Gate Fast Turn Off Current VCSN VBAT 0 1V and Not Charging VBGATE VCSN 3V 0 5 mA IBGATE FASTON Battery Gate Fast Turn On Current VCSN VBAT 0 2V VBGATE ...

Страница 6: ... 1 14 1 10 100 20 4000 G03 140 40 60 80 20 0 40 120 VOFB_REG VBFB_REG VVM TH TEMPERATURE C 60 V IIMON V IBMON V 1 015 1 010 0 995 1 000 0 990 1 005 0 985 100 20 4000 G06 140 40 60 80 20 0 40 120 TEMPERATURE C 60 PERCENT OF V BFB_REG 100 85 95 90 65 75 80 70 60 100 20 4000 G04 140 40 60 80 20 0 40 120 VLOBAT VRECHRG RISE VOUT INST_ON TEMPERATURE C 60 I IL I CL µA 45 0 47 5 52 5 50 0 55 0 100 20 400...

Страница 7: ...D TEMPERATURE C 60 V IID CSP V BAT CSN mV 14 6 10 12 8 4 2 0 100 20 4000 G12 140 40 60 80 20 0 40 120 VIID VBAT 60V VIID VBAT 3V VIID VBAT 15V TEMPERATURE C 60 V IID CSP V BAT CSN mV 120 0 60 90 30 30 60 90 100 20 4000 G13 140 40 60 80 20 0 40 120 VIID VBAT 15V TEMPERATURE C 60 V IGATE ON V BGATE ON V 15 0 12 5 13 5 14 5 14 0 13 0 12 0 11 5 11 0 100 20 4000 G14 140 40 60 80 20 0 40 120 VIID VBAT 1...

Страница 8: ... pins Leave the pin open for the maximum input current limit of 50mV RIS ENC Pin 5 Pin 1 Enable Charging Pin High impedance digital input pin Pull this pin above 1 5V to enable charg ing and below 0 5V to disable charging Leaving this pin open causes the internal 2µA pull up current to pull the pin to 2 5V typical IBMON Pin6 Pin2 BatteryChargeCurrentMonitor The voltage on this pin is 20 times typi...

Страница 9: ...mBIAStoNTC Thevoltagelevelonthispindetermines if the battery temperature is safe for charging The charge current and charge timer are suspended if the thermistor indicatesatemperaturethatisunsafeforcharging Oncethe temperaturereturnstothesaferegion chargingresumes Leave the pin open or connected to a capacitor to disable the temperature qualified charging function FBG Pin 15 Pin 11 Feedback Ground...

Страница 10: ... at the IN pin is within its operating range 3V to 60V To ensure that the input PMOS is turned off when the IN pin voltage is not within its operating range connect a 10M resistor from this pin to the CSP pin IID Pin 23 Pin 19 Input Ideal Diode Anode This pin is the anode of the input ideal diode driver the cathode is the CSP pin ITH Pin 24 Pin 20 High Impedance Control Voltage Pin When any of the...

Страница 11: ... FBG BAT CX ITH RST CLN CC IID 60k ROFB2 ROFB1 RBFB2 RBFB1 RIS DC DC CONVERTER IN CIID VM BIAS TMR FLT CHRG CIN CCLN CL CBAT CTMR RVM1 RVM2 CIBMON 4000 BD ENC GND IBMON OUT CSP RCX R3 1V BIAS 50µA BIAS 2µA BIAS 5µA 50µA RIL CIIMON IIMON IL IN A8 gm 0 33m A9 gm 0 33m A11 0 974V gm BFB A6 1 136V A10 1 193V CP5 1 109V CP6 0 771V CP2 BIAS 5µA 10mV A5 60k 8mV CBIAS OSCILLATOR LOGIC CP3 CP4 TOO HOT NTC ...

Страница 12: ...4000 is charging an over discharged dead or short faulted battery The state of the ENC pin determines whether charging is enabled When ENC is grounded charging is disabled and thebatteryfloatvoltageloopisdisabled Chargingisenabled when the ENC pin is left floating or pulled high 1 5V The LTC4000 offers several user configurable battery charge termination schemes The TMR pin can be config uredforei...

Страница 13: ...smaximized Once the float voltage is achieved the battery float volt age regulation loop takes over from the charge current regulation loop and initiates constant voltage charging In constantvoltagecharging chargecurrentslowlydeclines Charge termination can be configured with the TMR pin in several ways If the TMR pin is tied to the BIAS pin C X termination is selected In this case charging is ter...

Страница 14: ...BFB BAT FBG CC TO DC DC 4000 FO4 RC RBFB2 RBFB1 A6 CC 1 193V ITH LTC4000 OFB CSP FBG CC TO DC DC 4000 FO5 RC ROFB2 ROFB1 A7 Battery Voltage Regulation Oncethefloatvoltageisreached thebatteryvoltageregu lation loop takes over from the charge current regulation loop Figure 4 The float voltage level is programmed using the feedback resistor divider between the BAT pin and the FBG pin with the center ...

Страница 15: ...ro If the LTC4000 is charging in the constant voltage mode and the charge termination timer is enabled the timer pauses until the thermistor indicates a return to a valid temperature If the battery charger is in the trickle charge mode and the bad battery detection timer is enabled the bad battery timer pauses until the thermistor indicates a return to a valid temperature Input UVLO and Voltage Mo...

Страница 16: ...eincreaseinthisforwardvoltageiscalculatedaccording to the following formula VIID CSP REG VGSON 20k RIGATE where VGSON is the source to gate voltage required to achieve the desired ON resistance of the external PMOS and RIGATE is the external pull up resistor from the IGATE Applications Information pin to the CSP pin Therefore for a 10M RIGATE resistor andassuminga10VVGSON theadditionalforwardvolta...

Страница 17: ... the internal reference of 1V WhentheoutputcurrentwaveformoftheDC DCconverter orthesystemloadcurrentisnoisy itisrecommendedthat a capacitor is connected to the CSP pin CCSP This is to Applications Information reduce the AC content of the current through the sense resistor RCS Where the highest accuracy is important pick the value of CCSP such that the AC content is less than or equal to 50 of the ...

Страница 18: ...ins When the voltage at BFB is higher than the recharge threshold 97 6 offloat theC Xcomparatorisenabled In order to ensure proper C X termination coming out of a paused charging condition connect a capacitor on the CX pin according to the following formula CCX 100CBGATE where CBGATE is the total capacitance connected to the BGATE pin Forexample atypicalcapacitanceof1nFrequiresacapaci tor greater ...

Страница 19: ...can be calculated as follows PINST _ON 0 86 VFLOAT VBAT ICLIM where ICLIM is the full scale charge current limit For example when charging a 3 cell Lithium Ion battery with a programmed full charged current of 1A the float voltage is 12 6V the bad battery voltage level is 8 55V and the instant on voltage level is 10 8V During instant on operation and in the trickle charge mode the worst case maxim...

Страница 20: ...pends on the same resistors ROFB1 and ROFB2 that set VOUT As noted before this means that the output voltage regulation level is always 122 5 of the instant on voltage The higher the programmed value of VOUT INST_ON the larger the operating region when the charger PMOS is driven in the linear region where it is less efficient If ROFB1 and ROFB2 are set to be equal to RBFB1 and RBFB2 respectively t...

Страница 21: ...Desensitizing Resistor RD NTC RESISTOR THERMALLY COUPLED WITH BATTERY PACK R3 RNTC NTC BIAS BAT LTC4000 4000 F09 CBIAS NTC RESISTOR THERMALLY COUPLED WITH BATTERY PACK R3 RNTC NTC BIAS BAT LTC4000 RD 4000 F10 CBIAS Battery Temperature Qualified Charging To use the battery temperature qualified charging feature connect an NTC thermistor RNTC between the NTC pin and the GND pin and a bias resistor R...

Страница 22: ...can be calculated using a similar method as described above keeping in mind that the threshold at the NTC pin is always 75 and 35 of VBIAS LeavingtheNTCpinfloatingorconnectingittoacapacitor disables all NTC functionality The FLT and CHRG Indicator Pins The FLT and CHRG pins in the LTC4000 provide status indicators Table 2 summarizes the mapping of the pin states to the part status Table 2 FLT and ...

Страница 23: ...between the CC pin and the ITH pin is shown here Each of the loops has slightly different dynamics due to differencesinthefeedbacksignalpath Theanalyticdescrip tion of each of the loops is included in the Appendix sec tion In most situations an alternative empirical approach to compensation as described here is more practical CC ITH LTC4000 CC 4000 F11 RC A4 A7 gm4 7 0 2m A10 gm10 0 1m RO4 7 RO10 ...

Страница 24: ...ing waveform with no distortion Oscilloscope and generator connections should be made exactly as shown in Figure 12 to prevent ground loop er rors The oscilloscope is synced by connecting the chan nel B probe to the generator output with the ground clip of the second probe connected to exactly the same place as channel A ground The standard 50Ω BNC sync output of the generator should not be used b...

Страница 25: ...chosen for RC and CC should be checked under all conditions of input voltage and load current The simplest way of accomplishing this is to apply load currents of minimum maximum and several points in between At each load current input voltage is varied from minimum to maximum while observing the settling waveform Iflargetemperaturevariationsareexpectedforthesystem stability checks should also be d...

Страница 26: ...pin is clamped at 1V with an accurate internal reference Therefore the charge current limit is set at 10A according to the following formula ICLIM MAX 0 050V RCS 0 050V 5mΩ 10A The trickle charge current level is consequently set at 1 25A according to the following formula ICLIM TRKL 0 25µA 24 9kΩ 5mΩ 1 25A The battery float voltage is set at 10 8V according to the following formula RBFB1 10 8 1 1...

Страница 27: ...d PMOS over temperature detection circuit included in Figure 7 may needtobeincluded Forthecompleteapplicationcircuit please refer to Figure 25 The range of valid temperature for charging is set at 1 5 C to 41 5 C by picking a 10k Vishay Curve 2 NTC thermistor that is thermally coupled to the battery and connecting this in series with a regular 10k resistor to the BIAS pin For compensation the proc...

Страница 28: ... Regulated to VOUT INST_ON with CC 22nF RC 10k for a 100mA Charge Current Step Figure 18 Transient Response of Charge Current Regulation Loop Observed at IBMON When VOFB is Regulated to VOUT INST_ON with CC 22nF RC 20k for a 100mA Charge Current Step 5ms DIV 20 V IBMON mV 5mV DIV 15 10 5 0 5 10 15 10 5 15 4000 F17 25 20 0 10 5 15 5ms DIV 20 V IBMON mV 5mV DIV 15 10 5 0 5 10 15 10 5 15 4000 F18 25 ...

Страница 29: ...ion For accurate current sensing the sense lines from RIS and RCS Figure 19 must be Kelvined back all the way to the sense resistors terminals The two sense lines of eachresistormustalsoberoutedclosetogetherandaway from noise sources to minimize error Furthermore cur rent filtering capacitors should be placed strategically to ensure that very little AC current is flowing through these sense resist...

Страница 30: ... current into the ITH pin and its value can be approximated as gm10 IITH 5µA 50mV The higher the value of gm10 the smaller the lower limit of the value of RC would be This lower limit is to prevent the presence of the right half plane zero Eventhoughalltheloopssharethistransferfunctionfrom the error amplifier input to the ITH pin each of the loops has a slightly different dynamic due to difference...

Страница 31: ...Voltage Regulation Loop The battery float voltage regulation loop is very similar to theoutputfloatvoltageregulationloop Insteadofobserv ing the voltage at the OFB pin the battery float voltage regulation loop observes the voltage at the BFB pin One significant difference is that while the value of RL in the output voltage loop can vary significantly the output resistance of the battery float volt...

Страница 32: ...ITH pin driving the external DC DC converter to regulate the input current across the sense resistor RCS Due to the presence of the instant on feature description ofthechargecurrentregulationloophastobedividedinto twoseparateoperatingregions Theseregionsofoperation depend on whether the voltage on the OFB pin is higher or lower than the instant on threshold VOUT INST_ON The Battery Charge Current ...

Страница 33: ...refore the linear model of the PFET has to be included in the analysis of the charge current regulation loop The detail of this loop is shown in Figure 24 Figure 24 Simplified Linear Model of the Charge Current Regulation Loop with the External Charging PFET Linearly Regulated The simplified loop transmission is LCC2 s gm5 RC 1 gm10 CCs 1 CCs 20RCS R2 CIBMONs 1 R1 R2 CIBMONs 1 RL RfIDC RL 1 RL PRf...

Страница 34: ...35DP 47nF 5mΩ VOUT 12V 15A VIN 15V TO 60V 10A MAX BSC123NO8NS3 BAS521 1N4148 B160 0 1µF WÜRTH ELEKTRONIC 74435561100 10µH 133k CSN CSP BGATE IGATE BAT OFB FBG BFB NTC CX LTC4000 ITH BIAS CC IID 1M 5mΩ 3mΩ LT3845A SENSE BURST_EN SENSE 33µF 3 RST CLN IN SW BG BOOST VCC ENC VFB VC SHDN CSS fSET CHRG FLT VM IIMON IBMON 22 1k CL IL TMR GND BIAS BIAS 1µF 1 10M 100k 10nF 10nF BZX84C3VO 24 9k 1µF 0 1µF 40...

Страница 35: ...1002J 22nF 10mΩ VOUT 22V 5A VIN 6V TO 18V 15A MAX BSC027N04 BAS140W Si7135DP BSC027N04 107k CSN CSP BGATE IGATE BAT OFB FBG BFB NTC CX LTC4000 ITH CC IID 1 87M 232k 3 3mΩ LTC3786 VBIAS VFB 22µF 5 150µF SW BG TG ITH GND SENSE SENSE FREQ SS RST CLN IN ENC CHRG FLT VM IIMON IBMON 22 1k CL TMR IL GND BIAS 22 1k 1µF 383k 100k 12 1k 10nF 10nF 1µF 4000 F26 BOOST 22µF 4 150µF INTVCC PLLINMODE RUN PGOOD 4 ...

Страница 36: ...V 2 5A SiA923EDJ 115k CSN CSP BGATE IGATE BAT OFB FBG BFB NTC CX LTC4000 IID CLN IN VM 309k RST ITH ENC CHRG FLT CC 22 1k CL TMR IL GND BIAS 22 1k 1µF 4000 F27 SiA923EDJ 25mΩ 100nF IIMON 10nF IBMON 10nF 10k 1µF 24 9k 1 5k 13 6k 3 01k BAS516 BAS516 MMBTA42 PDZ6 8B 6 8V PDS1040 47nF 100k 150k V OUT V OUT V CC 0 04Ω GATE FDC2512 ISENSE RUN SSFLT ITH OC FB GND SYNC V CC V IN 18V TO 72V LTC3805 5 FS 15...

Страница 37: ...NOT EXCEED 0 15mm ON ANY SIDE 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 NOTE 6 0 40 0 10 27 28 1 2 BOTTOM VIEW EXPOSED PAD 3 50 REF 0 75 0 05 R 0 115 TYP R 0 05 TYP PIN 1 NOTCH R 0 20 OR 0 35 45 CHAMFER 0 25 0 05 0 50 BSC 0 200 REF 0 00 0 05 UFD28 QFN 0506 REV B RECOMMENDED SOLDER PAD PITCH AND DIMENSIO...

Страница 38: ...ECOMMENDED SOLDER PAD LAYOUT 150 165 0250 BSC 0165 0015 045 005 DIMENSION DOES NOT INCLUDE MOLD FLASH MOLD FLASH SHALL NOT EXCEED 0 006 0 152mm PER SIDE DIMENSION DOES NOT INCLUDE INTERLEAD FLASH INTERLEAD FLASH SHALL NOT EXCEED 0 010 0 254mm PER SIDE INCHES MILLIMETERS NOTE 1 CONTROLLING DIMENSION INCHES 2 DIMENSIONS ARE IN 3 DRAWING NOT TO SCALE 4 PIN 1 CAN BE BEVEL EDGE OR A DIMPLE GN Package 2...

Страница 39: ...cs section Updated the ENC pin text in the Pin Functions section Updated the Block Diagram Updated Figures 14 and 25 1 3 4 5 8 11 26 34 B 6 13 Added Common Mode Range spec to CLN CSP and CSN Revised Ratio of Monitored Current Voltage to Sense Voltage min Revised VBFB_REG Battery Feedback Voltage min Revised VOFB_REG Output Feedback Voltage min Revised Voltage Monitoring Input Falling Threshold min...

Страница 40: ...iciency Multi Chemistry Battery Charger with PowerPath Control Similar to LTC4009 Adding PowerPath Control LT3741 High Power Constant Current Constant Voltage Step Down Controller Thermally Enhanced 4mm 4mm QFN and 20 Pin TSSOP Figure 28 6V to 36VIN to 14 4V at 4 5A Buck Boost Converter 4 Cell LiFePO4 Battery Charger with 2 9h Timer Termination and 0 45A Trickle Charge Current 1 37M 14 7k 26 7k 10...

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