LT3650-4.1

LT3650-4.1/LT3650-4.2 - High Voltage 2 Amp Monolithic Li-Ion Battery Charger

Document overview

• Manufacturer or author: Linear Technology Corporation
• PDF pages: 22

Technical content

LT3650-4.1/LT3650-4.2 36504142fc Typical applicaTion The LT®3650 is a complete monolithic single-cell Li-Ion/ Polymer battery charger that operates over a 4.75V to 32V input voltage range (7.5V minimum start-up voltage). The LT3650 provides a constant-current/constant-voltage charge characteristic, with maximum charge current externally programmable up to 2A, set using an external current sense resistor. A precondition feature trickle- charges a low voltage battery, and bad-battery detection provides a signal and suspends charging if a battery does not respond to preconditioning. The LT3650 can be configured to terminate charging when charge current falls to C/10, or one-tenth the programmed maximum current. Once charging is terminated, the LT3650 enters a low current (85µA) standby mode. An auto-restart feature starts a new charging cycle if the battery voltage drops 2.5% from the float voltage, or if a new battery is inserted into a charging system. The LT3650 contains a user-programmable internal safety timer (typically set to a three hour full cycle time). The IC can be configured to use this internal timer if a time-based termination scheme is desired in which charging can con- tinue below C/10 until a desired time is reached. The LT3650 is available in a low profile (0.75mm) 3mm × 3mm 12-pin DFN and 12-pin MSOP packages.

FeaTures

applicaTions

DescripTion

Monolithic Li-Ion Battery Charger 7.5V to 32V Single-Cell Li-Ion 2A Charger n Wide Input Voltage Range: 4.75V to 32V (40V Absolute Maximum) n Programmable Charge Current Up to 2A n User-Selectable Termination: C/10 or Onboard T ermination Timer n Dynamic Charge Rate Programming/Soft-Start Pin n Programmable Input Current Limit n No VIN Blocking Diode Required n 1MHz Fixed Frequency n Average Current Mode Control n 0.5% Float Voltage Accuracy n 5% Charge Current Accuracy n 2.5% C/10 Detection Accuracy n NTC Resistor Temperature Monitor n Auto-Recharge at 97.5% Float Voltage n Auto-Precondition at <70% Float Voltage n Bad-Battery Detection with Auto-Reset n Binary Coded Open-Collector Status Pins n 3mm × 3mm DFN-12 or MSOP-12 Package n Industrial Handheld Instruments n 12V to 24V Automotive and Heavy Equipment n Desktop Cradle Chargers n Notebook Computers

3650 TA01a

7.5V to 32V CLP RNG/SS BOOST SENSE BAT NTC TIMER CMPSH1-4 CMSH3-40MA 1µF10µF 6.8µH 0.05/uni03A9 10µF L T3650-4.2 Li-ION BATTERY SHDN CHRG FAULT VBAT and Efficiency vs IBAT SPELL CHECK COMPLETED IBAT (A) VBAT (V) EFFICIENCY (%) 100

365042 TA01b

4.15 4.20 4.10 4.05 0.5 1 1.5 2 VBAT VIN = 12V VIN = 20V L, LT, LT C, LT M, Linear Technology, PowerPath and the Linear logo are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners.

LT3650-4.1/LT3650-4.2 36504142fc absoluTe MaxiMuM raTings SHD SW B W + 10V, 50V (Note 1) orDer inForMaTion LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE LT3650EDD-4.1#PBF LT3650EDD-4.1#TRPBF LFGQ 12-Lead Plastic DFN (3mm × 3mm) –40°C to 85°C LT3650IDD-4.1#PBF LT3650IDD-4.1#TRPBF LFGQ 12-Lead Plastic DFN (3mm × 3mm) –40°C to 85°C LT3650EDD-4.2#PBF LT3650EDD-4.2#TRPBF LDDS 12-Lead Plastic DFN (3mm × 3mm) –40°C to 85°C LT3650IDD-4.2#PBF LT3650IDD-4.2#TRPBF LDDS 12-Lead Plastic DFN (3mm × 3mm) –40°C to 85°C LT3650EMSE-4.1#PBF LT3650EMSE-4.1#TRPBF 365041 12-Lead Plastic MSOP –40°C to 85°C LT3650IMSE-4.1#PBF LT3650IMSE-4.1#TRPBF 365041 12-Lead Plastic MSOP –40°C to 85°C LT3650EMSE-4.2#PBF LT3650EMSE-4.2#TRPBF 365042 12-Lead Plastic MSOP –40°C to 85°C LT3650IMSE-4.2#PBF LT3650IMSE-4.2#TRPBF 365042 12-Lead Plastic MSOP –40°C to 85°C Consult LT C Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.Consult LT C Marketing for information on nonstandard lead based finish parts. For more information on lead free part marking, go to: http://www.linear.com/leadfree/ For more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/ Operating Junction Temperature Range 0°C to 125°C 5°C to 15 0° C Lead Temperature (Soldering, 10 sec) 0°C TOP VIEW DD PACKAGE 12-LEAD (3mm × 3mm) PLASTIC DFN 133 1 SW BOOST SENSE BAT NTC RNG/SS V IN CLP SHDN CHRG FAUL T TIMER 6 7 TJMAX = 125°C, θJA = 43°C/W, θJC = 3°C/W EXPOSED PAD (PIN 13) IS GND, MUST BE SOLDERED TO PCB V IN CLP SHDN CHRG FAULT TIMER SW BOOST SENSE BAT NTC RNG/SS TOP VIEW MSE PACKAGE 12-LEAD PLASTIC MSOP TJMAX = 125°C, θJA = 43°C/W, θJC = 3°C/W EXPOSED PAD (PIN 13) IS GND, MUST BE SOLDERED TO PCB pin conFiguraTion

LT3650-4.1/LT3650-4.2 36504142fc SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS LT3650 VIN VIN Operating Range VIN Start Voltage (Note 3) l l 4.75 32 7.5 V V VIN(OVLO) OVLO Threshold OVLO Hysteresis V IN Rising l 32 35 40 V V VIN(UVLO) UVLO Threshold UVLO Hysteresis V IN Rising l 4.6 0.2 4.75 V V V BAT(F LT) Battery Float Voltage LT3650-4.1 l 4.08 4.06 4.1 4.12 4.14 V V LT3650-4.2 l 4.18 4.16 4.2 4.22 4.24 V V RECHRG Recharge Battery Threshold Threshold Voltage Relative to VBAT(F LT) –100 mV VBAT(PRE) Battery Precondition Threshold Voltage V BAT Rising 2.9 V VBAT(PREHYST) Battery Precondition Threshold Hysteresis 90 mV I VIN Operating Input Supply Current CC/CV Mode, I SW = 0 Standby Mode Shutdown (SHDN = 0) l 2.5 3.5 mA µA µA I BOOST BOOST Supply Current Switch-On, ISW = 0 2.5V < V(BOOST – SW) < 4.5V mA IBOOST/ISW BOOST Switch Drive ISW = 2A 30 mA/A VSW(ON) Switch-On Voltage Drop VIN – VSW, ISW = 2A 350 mV ISW(MAX) Switch Current Limit l 2.5 A VSENSE(PRE) Precondition Current Sense Voltage V SENSE – VBAT VBAT = 2.5 15 mV VCLP(DC) CLP Threshold Voltage VCLP – VIN; VSENSE – VBAT = 50mV l 37.5 50 62.5 mV ICLP CLP Input Bias Current 200 nA VSENSE(DC) Maximum Current Sense Voltage V SENSE – VBAT; VBAT = 3.5V, VRNG/SS = 1.2V l 95 100 105 mV VSENSE(C/10) C/10 T rigger Sense Voltage l 7.5 10 12.5 mV IBAT BAT Input Bias Current Charging Terminated l 0.1 1 µA ISENSE SENSE Input Bias Current Charging Terminated l 0.1 1 µA IREVERSE Charger Reverse Current: I BAT + ISENSE + ISW VIN = 0V; BAT = SENSE = SW = VBAT(F LT) 1 µA VNTC(H) NTC Range Limit (High) VNTC Rising l 1.25 1.36 1.45 V VNTC(L) NTC Range Limit (Low) VNTC Falling l 0.27 0.29 0.315 V VNTC(HYST) NTC Threshold Hysteresis % of Threshold 20 % RNTC(DIS) NTC Disable Impedance Minimum External Impedance to GND l 250 500 kΩ INTC NTC Bias Current VNTC = 0.8V l 47.5 50 52.5 µA IRNG/SS IRNG/SS Bias Current l 45 50 55 µA VRNG/SS/ VSENSE Current Limit Programming: V RNG/SS/VSENSE(MAX) VRNG/SS = 0.5 l 8.5 10 11.5 V/V VSHDN Shutdown Threshold Rising l 1.17 1.20 1.23 V VSHDN(HYST) Shutdown Hysteresis 120 mV ISHDN SHDN Input Bias Current –10 nA elecTrical characTerisTics The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at VIN = 20V, BOOST-SW = 4V, SHDN = 2V, SENSE = BAT = VBAT(F LT), CTIMER = 0.68µF.

LT3650-4.1/LT3650-4.2 36504142fc TEMPERATURE (°C) –50 IVIN CURRENT (µA) 100 0 50 75

365042 G02

–25 25 100 VRNG/SS ICHG(MAX) (%) 100 0.4 0.8 1.0

365042 G03

0.2 0.6 1.2 TEMPERATURE (°C) –50 ∆VBAT(FLT) (%) 0 50 75

3650 G01

0.1 0.05 –0.05 –0.1 –25 25 100 125 Typical perForMance characTerisTics Battery Float Voltage vs Temperature VIN Standby Mode Current vs Temperature Maximum Charge Current vs IRNG/SS Voltage, ICHG(MAX) as a Percentage of Programmed IMAX TA = 25°C, unless otherwise noted. Note 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 lifetime. Note 2: The LT3650E is guaranteed to meet performance specifications from 0°C to 85°C. Specifications over the –40°C to 85°C operating temperature range are assured by design, characterization and correlation with statistical process controls. The LT3650I specifications are guaranteed over the full –40°C to 85°C temperature range. High junction temperatures degrade operating lifetimes. Note 3: V IN voltages below the start threshold are only supported if (VBOOST – VSW) > 2V. elecTrical characTerisTics The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at VIN = 20V, BOOST-SW = 4V, SHDN = 2V, SENSE = BAT = VBAT(F LT), CTIMER = 0.68µF. SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS VCHRG, VFAUL T Status Low Voltage 10mA Load l 0.4 V ITIMER Charge/Discharge Current 25 µA VTIMER(DIS) Timer Disable Threshold l 0.1 0.25 V tTIMER Full Charge Cycle Timeout 3 hr Precondition Timeout 22.5 min Timer Accuracy l –10 10 % fO Operating Frequency l 0.9 1 1.1 MHz DC Duty Cycle Range Continuous Operation l 15 90 %

LT3650-4.1/LT3650-4.2 36504142fc VBAT (V) –0.4 IBAT (mA) 0.0 0.4 0.8 2.2 1.6 1 2 2.5 2.0 1.2 –0.2 0.2 0.6 1.0 1.8 1.4 0.5 1.5 3 3.5 4 4.5

365042 G11

LT3650-4.2 ISW (A) ISW/IBOOST 1.6

365042 G04

TEMPERATURE (°C) –50 320 SWITCH FORWARD DROP (mV) 340 360 380 480 420 0 50 75

365042 G05

–25 25 100 125 ISW = 2A Switch Drive (ISW/IBOOST) vs ISW Switch Forward Drop (VIN – VSW) vs Temperature TEMPERATURE (°C) –50 99.0 VSENSE – VBAT (mV) 99.2 99.6 99.8 100.0 101.0 100.4 0 50 75

365042 G09

99.4 100.6 100.8 100.2 –25 25 100 125 VBAT = 3.5V TEMPERATURE (°C) –50 VSENSE – VBAT (mV) 0 50 75

365042 G07

–25 25 100 125 TEMPERATURE (°C) VSENSE – VBAT (mV) 100 120 45 65 85 105 12535 13525 55 75 95 115

365042 G10

Typical perForMance characTerisTics IMAX Current Limit (VSENSE – VBAT) vs Temperature C/10 Threshold (VSENSE – VBAT) vs Temperature CC/CV Charging; SENSE Pin Bias Current vs VSENSE Thermal Foldback – IMAX Current Limit (VSENSE – VBAT) vs Temperature TEMPERATURE (°C) –50 49.0 VCLP – VIN (mV) 49.2 49.6 49.8 50.0 51.0 50.4 0 50 75

365042 G08

49.4 50.6 50.8 50.2 –25 25 100 125 CLP Input Limit Threshold (VCLP – VIN) vs Temperature, ICHG at 50% CC/CV Charging; BAT Pin Bias Current vs VBAT Battery Bias Current with Charger Disabled (I BAT + ISENSE + IBOOST + ISW) VSENSE (V) –350 ISENSE (µA) –250 –150 –50 100 1 2 2.5 –300 –200 –100 0.5 1.5 3 3.5 4 4.5

365042 G06

LT3650-4.2 TA = 25°C, unless otherwise noted. VIN = 20V, VSHDN = 0V VIN FLOATING VBAT (V) BATTERY CURRENT (µA) 2.0 4.5 5.0 1.0 2.0 3.0 1.0 3.5 1.5 4.0 0.5 3.0 2.5

365042 G12

LT3650-4.1/LT3650-4.2 36504142fc pin FuncTions VIN (Pin 1): Charger Input Supply. VIN pin operating range is 4.75V to 32V. V IN ≥ 7.5V or (V BOOST – V SW) > 2V is required for start-up. IVIN = 85µA after charge termination. CLP (Pin 2): System Current Limit Input. System current levels can be monitored by connecting the input power supply to the CLP pin and connecting a sense resistor from the CLP pin to the VIN pin. Additional system load is drawn from the VIN pin connection, and maximum system load is achieved when VCLP – VVIN = 50mV. The LT3650 servos the maximum charge current required to maintain programmed maximum system current. If this function is not desired, connect the CLP pin to the V IN pin (see the Applications Information section). SHDN (Pin 3): Precision Threshold Shutdown Pin. The enable threshold is 1.225V (rising), with 120mV of input hysteresis. When in shutdown mode, all charging functions are disabled. The precision threshold allows use of the SHDN pin to incorporate UVLO functions. If the SHDN pin is pulled below 0.4V, the IC enters a low current shutdown mode where the VIN pin current is reduced to 15µA. Typi- cal SHDN pin input bias current is 10nA. If the shutdown function is not desired, connect the pin to the VIN pin. CHRG (Pin 4): Open-Collector Charger Status Output; typically pulled up through a resistor to a reference volt- age. This status pin can be pulled up to voltages as high as VIN when disabled, and can sink currents up to 10mA when enabled. During a battery charging cycle, CHRG is pulled low. When the charge cycle is terminated, the CHRG pin becomes high impedance. If the internal timer is used for termination, the pin stays low during the charging cycle until the charge current drops below a C/10 rate, or ICHG(MAX)/10. A temperature fault also causes this pin to be pulled low (see the Applications Information section). FAUL T (Pin 5): Open-Collector Fault Status Output; typi- cally pulled up through a resistor to a reference voltage. This status pin can be pulled up to voltages as high as VIN when disabled, and can sink currents up to 10mA when enabled. This pin indicates charge cycle fault conditions during a battery charging cycle. A temperature fault causes this pin to be pulled low. If the internal timer is used for termination, a bad-battery fault also causes this pin to be pulled low. If no fault conditions exist, the FAUL T pin remains high impedance (see the Applications Informa- tion section). TIMER (Pin 6): End-Of-Cycle Timer Programming Pin. If a timer-based charge termination is desired, connect a capacitor from this pin to ground. Full charge end-of- cycle time (in hours) is programmed with this capacitor following the equation: tEOC = CTIMER • 4.4 • 106 A bad-battery fault is generated if the battery does not reach the precondition threshold voltage within one-eighth of tEOC, or: tPRE = CTIMER • 5.5 • 105 A 0.68µF capacitor is typically used, which generates a timer EOC at three hours, and a precondition limit time of 22.5 minutes. If a timer-based termination is not desired, the timer function is disabled by connecting the TIMER pin to ground. With the timer function disabled, charging terminates when the charge current drops below a C/10 rate, or ICHG(MAX)/10. RNG/SS (Pin 7): Charge Current Programming Pin. This pin allows a dynamic adjustment of the maximum charge current, and can be used to employ a soft-start function. Maximum charge current is adjusted by setting the volt- age on this pin, such that the maximum desired voltage across the inductor current sense resistor (VSENSE – VBAT) is 0.1 • VRNG/SS, so the maximum charge current reduces to: VRNG/SS • ICHG(MAX) This pin has an effective range from 0V to 1V. 50µA is sourced from this pin, so the maximum charge current can be programmed by connecting a resistor (R RNG/SS) from RNG/SS to ground, such that the voltage dropped across the resistor is equivalent to the desired program- ming voltage, or: VRNG/SS = 50µA • RRNG/SS Soft-start functionality can be implemented by con- necting a capacitor (C RNG/SS) from RNG/SS to ground, such that the time required to charge the capacitor to 1V

LT3650-4.1/LT3650-4.2 36504142fc (full charge current) is the desired soft-start interval (tSS). For no RRNG/SS, this capacitor value follows the relation: CRNG/SS = 50µA • tSS The RNG/SS pin is pulled low during fault conditions, allowing graceful recovery from faults should soft-start functionality be implemented. Both the soft-start capaci- tor and the programming resistor can be implemented in parallel. All C/10 monitoring functions are disabled while VRNG/SS is below 0.1V to accommodate long soft-start intervals. RNG/SS voltage can also be manipulated using an active device, employing a pull-down transistor to disable charge current or to dynamically servo maximum charge current. Manipulation of the RNG/SS pin with active devices that have low impedance pull-up capability is not allowed (see the Applications Information section). NTC (Pin 8): Battery Temperature Monitor Pin. This pin is the input to the NTC (negative temperature coefficient) thermistor temperature monitoring circuit. This function is enabled by connecting a 10kΩ, B = 3380 NTC thermistor from the NTC pin to ground. The pin sources 50µA, and monitors the voltage across the 10kΩ thermistor. When the voltage on this pin is above 1.36V (T < 0°C) or below 0.29V (T > 40°C), charging is disabled and the CHRG and FAUL T pins are both pulled low. If internal timer termina- tion is being used, the timer is paused, suspending the charging cycle. Charging resumes when the voltage on NTC returns to within the 0.29V to 1.36V active region. There is approximately 5°C of temperature hysteresis associated with each of the temperature thresholds. The temperature monitoring function remains enabled while thermistor resistance to ground is less than 250kΩ, so if this function is not desired, leave the NTC pin unconnected. BAT (Pin 9): Battery Voltage Monitor Pin. Connect 10µF decoupling capacitance (C BAT) from this pin to ground. Depending on application requirements, larger value de- coupling capacitors may be required (see the Application Information section). The charge function operates to achieve the final float voltage at this pin. The auto-restart feature initiates a new charging cycle when the voltage at the BAT pin falls 2.5% below this float voltage. Once the charge cycle is terminated, the input bias current of the BAT pin is reduced to <0.1µA, to minimize battery discharge while the charger remains connected. SENSE (Pin 10): Charge Current Sense Pin. Connect the more positive voltage end of the inductor sense resistor (RSENSE) to the SENSE pin and the other end to the BAT pin. The voltage across this resistor sets the average charge current. The maximum average charge current (IMAX) corresponds to 100mV across the sense resistor. This resistor can be set to program maximum charge currents as high as 2A. The sense resistor value follows the relation: RSENSE = 0.1V IMAX Once the charge cycle is terminated, the input bias cur- rent of the SENSE pin is reduced to <0.1µA, to minimize battery discharge while the charger remains connected. BOOST (Pin 11): Bootstrapped Supply Rail for Switch Drive. This pin facilitates saturation of the switch transistor. Connect a 1µF or greater capacitor from the BOOST pin to the SW pin. Operating range of this pin is 0V to 4.5V, referenced to the SW pin. The voltage on the decoupling capacitor is refreshed through a rectifying diode, with the anode connected to either the battery output voltage or an external source, and the cathode connected to the BOOST pin. SW (Pin 12): Switch Output Pin. This pin is the output of the charger switch, and corresponds to the emitter of the switch transistor. When enabled, the switch shorts the SW pin to the V IN supply. The drive circuitry for this switch is bootstrapped above the V IN supply using the BOOST supply pin, allowing saturation of the switch for maximum efficiency. The effective on-resistance of the boosted switch is 0.175Ω. SGND (Pin 13): Ground Reference and Backside Exposed Lead Frame Thermal Connection. Solder the exposed lead frame to the PCB ground plane. pin FuncTions

LT3650-4.1/LT3650-4.2 36504142fc block DiagraM 365042 BD TIMER 10m/uni03A9 35V 0.1V OFFSET 2.9V 1.2V 4.6V RESET ENABLE COUNT RESET C/10 PRECONDITION 1.36V 0.29V 46µA CLP BOOST VIN SW SENSE BAT RNG/SS NTC VINT 2.7V 1.3V SSRESET 1V 0.15V 1.2V 4.2V* 4.1V** TERMINATE * VBAT(FL T): 4.2V FOR L T3650-4.2, 4.1V FOR L T3650-4.1 ** VBAT(FL T) – ∆VRECHRG: 4.1V FOR L T3650-4.2, 4.0 FOR L T3650-4.1 50µA 0.7V CONTROL LOGIC RIPPLE COUNTER STATUS TIMER OSC. NTC 0.2V 125°C COUNT COUNT OSC 1MHz LATCH RS RS C-EA 50µA 30mV x2.25 10 × RS 0.3V VC TDIE ITH MODE (TIMER OR C/10) TERMINATE R Q S SSRESET 50mV UVLO OVLO FAULT CHRG STANDBY SHDN V-EA STANDBY STANDBY

LT3650-4.1/LT3650-4.2 36504142fc operaTion OVERVIEW LT3650 is a complete monolithic, mid-power, Li-Ion battery charger, addressing high input voltage applications with solutions that use a minimum of external components. The IC uses a 1MHz constant-frequency, average current mode step-down architecture. Internal reverse-voltage protection allows direct connection to the input supply without a blocking diode. The LT3650 incorporates a 2A switch that is driven by a bootstrapped supply to maximize efficiency during charging cycles. A wide input range allows the operation to full charge from 5V ±5% to 32V. A precision threshold shutdown pin allows incorporation of UVLO functionality using a simple resistor divider. The IC can also be put into a low current shutdown mode, in which the input supply bias is reduced to only 15µA. The LT3650 incorporates several degrees of charge current control freedom. The overall maximum charge current is set using an external inductor current sense resistor. A maximum charge current programming pin allows dynamic manipulation of the battery charge current. The LT3650 also incorporates a system input supply current limit control feature that servos the battery charge current to accommodate overall system load requirements. The LT3650 automatically enters a battery precondi- tion mode if the sensed battery voltage is very low. In this mode, the charge current is reduced to 15% of the programmed maximum, as set by the inductor sense resistor, RSENSE. Once the battery voltage climbs above the internally set precondition threshold of 2.9V, the IC automatically increases the maximum charge current to the full programmed value. The LT3650 can use a charge current based C/10 termina- tion scheme, which ends a charge cycle when the battery charge current falls to one-tenth the programmed maxi- mum charge current. The LT3650 also contains an internal charge cycle control timer, for timer-based termination. When using the internal timer, the IC combines C/10 detec- tion with a programmable time constraint, during which the charging cycle can continue beyond the C/10 level to top-off a battery. The charge cycle terminates when a specific time elapses, typically three hours. When the timer-based scheme is used, the IC also supports bad- battery detection, which triggers a system fault if a battery stays in precondition mode for more than one-eighth of the total programmed charge cycle time. Once charging is terminated and the LT3650 is not actively charging, the IC automatically enters a low current standby mode in which supply bias currents are reduced to 85µA. If the battery voltage drops 2.5% from the full charge float voltage, the LT3650 engages an automatic charge cycle restart. The IC also automati- cally restarts a new charge cycle after a bad-battery fault once the failed battery is removed and replaced with another battery. The LT3650 contains provisions for a battery temperature monitoring circuit. This feature monitors battery tem- perature by using a thermistor during the charging cycle, suspends charging, and signals a fault condition if the battery temperature moves outside a safe charging range. The LT3650 contains two digital open-collector outputs, which provide charger status and signal fault conditions. These binary coded pins signal battery charging, standby or shutdown modes, battery temperature faults and bad- battery faults. General Operation (See Block Diagram) The LT3650 uses average current mode control architec- ture, such that the IC servos directly to average charge current. The LT3650 senses charger output voltage via the BAT pin. The difference between the voltage on this pin and an internal float voltage reference is integrated by the voltage error amplifier (V-EA). This amplifier generates an error voltage on its output (ITH), which corresponds to the average current sensed across the inductor cur- rent sense resistor, RSENSE, which is connected between the SENSE and BAT pins. The ITH voltage is then divided down by a factor of 10, and imposed on the input of the current error amplifier (C-EA). The difference between this imposed voltage and the current sense resistor voltage is integrated, with the resulting voltage ( VC) used as a threshold that is compared against an internally gener- ated ramp. The output of this comparison controls the charger’s switch.

LT3650-4.1/LT3650-4.2 36504142fc operaTion The ITH error voltage corresponds linearly to average cur- rent sensed across the inductor current sense resistor, allowing maximum charge current control by limiting the effective voltage range of ITH. A clamp limits this voltage to 1V which, in turn, limits the current sense voltage to 100mV. This sets the maximum charge current, or the current delivered while the charger is operating in constant-current (CC) mode, which corresponds to 100mV across RSENSE. This maximum charge current level can also be manipu- lated through the RNG/SS pin (see the RNG/SS: Dynamic Charge Current Adjust and RNG/SS: Soft-Start sections). If the voltage on the BAT pin is below V BAT(PRE), the LT3650 engages precondition mode. During the precondition inter- val, the charger continues to operate in constant-current mode, but the maximum charge current is reduced to 15% of the maximum programmed value as set by RSENSE. When the charger output voltage on the BAT pin approaches the float voltage (V BAT(F LT)), the charger transitions into constant-voltage (CV) mode, and charge current is reduced from the maximum value. As this occurs, the ITH voltage falls from the limit clamp and ser vos to lower voltages. The IC monitors the I TH voltage as it is reduced, and detection of the C/10 charge current is achieved when ITH = 0.1V. If the charger is configured for C/10 termina- tion, this threshold is used to terminate the charge cycle. Once the charge cycle is terminated, the CHRG status pin becomes high impedance and the charger enters low current standby mode. The LT3650 contains an internal charge cycle timer that terminates a successful charge cycle after a programmed amount of time. This timer is typically programmed to achieve end-of-cycle (EOC) in three hours, but can be configured for any amount of time by setting an appropriate timing capacitor value (CTIMER). When timer termination is used, the charge cycle does not terminate after C/10 is achieved. Because the CHRG status pin responds to the C/10 current level, the IC will indicate a fully charged battery status, but the charger will continue to source low currents into the battery until the programmed EOC time has elapsed, at which time the charge cycle will terminate. At EOC, when the charging cycle terminates, if the battery did not achieve at least 97.5% of the full float voltage, charging is deemed unsuccessful. The LT3650 will then re-initiate, and charging will continue for another full timer cycle. Use of the timer function also enables bad-battery detec- tion. This fault condition is achieved if the battery does not respond to preconditioning and the charger remains in (or enters) precondition mode after one-eighth of the programmed charge cycle time. A bad-battery fault halts the charging cycle, the CHRG status pin goes high imped- ance and the FAUL T pin is pulled low. When the LT3650 terminates a charging cycle, whether through C/10 detection or by reaching timer EOC, the average current mode analog loop remains active but the internal float voltage reference is reduced by 2.5%. Because the voltage on a successfully charged battery is at the full float voltage, the voltage error amp detects an overvoltage condition and rails low. When the voltage er- ror amp output drops below 0.3V, the IC enters standby mode, where most of the internal circuitry is disabled, and the V IN bias current is reduced to 85µA. When the voltage on the BAT pin drops below the reduced float reference level, the output of the voltage error amp will climb, at which point the IC comes out of standby mode and a new charging cycle is initiated.

LT3650-4.1/LT3650-4.2 36504142fc VIN Input Supply The LT3650 is biased directly from the charger input supply through the VIN pin. This supply provides large switched currents, so a high quality, low ESR decoupling capacitor is recommended to minimize voltage glitches on VIN. The VIN decoupling capacitor (CVIN) absorbs all input switching ripple current in the charger, so it must have an adequate ripple current rating. RMS ripple current (ICVIN(RMS)) is: ICVIN(RMS) ICHG(MAX) • VBAT VIN  • VIN VBAT −1 which has a maximum at VIN = 2 • VBAT, where: ICVIN(RMS) = ICHG(MAX)/2 The simple worst-case of 1/2 • ICHG(MAX) is commonly used for design. Bulk capacitance is a function of desired input ripple volt- age (∆VIN), and follows the relation: CIN(BULK) =IMAX • VBAT / VIN ∆VIN  µF( ) 10µF is typically adequate for most charger applications. BOOST Supply The BOOST bootstrapped supply rail drives the internal switch and facilitates saturation of switch transistor. Oper- ating range of the BOOST pin is 0V to 4.5V, as referenced to the SW pin. Connect a 1µF or greater capacitor from the BOOST pin to the SW pin. The voltage on the decoupling capacitor is refreshed through a diode, with the anode connected to/from either the battery output voltage or an external source, and the cathode connected to the BOOST pin. Rate the diode av- erage current greater than 0.1A, and its reverse voltages greater than V IN(MAX). VIN / BOOST Start-Up Requirement The LT3650 operates with a V IN range of 4.75V to 32V, however, a start-up voltage requirement exists due to the nature of the nonsynchronous step-down switcher topol- ogy used for the charger. If there is no BOOST supply available, the internal switch requires (V IN – VSW) > 3V to operate. This requirement does not exist if the BOOST supply is available and (VBOOST – VSW) > 2V. When an LT3650 charger is not switching, the SW pin is at the same potential as the battery, which can be as high as V BAT(F LT). For reliable start-up, the V IN supply must be at least 3V above the SW pin. The minimum start-up specification of VIN at or above 7.5V provides ample margin to satisfy this requirement. Once switching begins, the BOOST supply capacitor gets charged such that (VBOOST – VSW) > 2V, and the VIN requirement no longer applies. In low VIN applications, the BOOST supply can be powered by an external source for start-up, eliminating the V IN start-up requirement. VBAT Output Decoupling An LT3650 charger output requires bypass capacitance connected from the BAT pin to ground (CBAT). A 10µF ce- ramic capacitor is required for all applications. In systems where the battery can be disconnected from the charger output, additional bypass capacitance may be desired for visual indication of a no-battery condition (see the Status Pins section). If it is desired to operate a system load from the LT3650 charger output when the battery is disconnected, additional bypass capacitance is required. In this type of application with the charger being used as a DC/DC converter, exces- sive ripple and/or low amplitude oscillations can occur without additional output bulk capacitance. For these ap- plications, place a 100µF low ESR nonceramic capacitor (chip tantalum or organic semiconductor capacitors such as Sanyo OS-CONs or POSCAPs) from BAT to ground, in parallel with the 10µF ceramic bypass capacitor. This additional bypass capacitance may also be required in systems where the battery is connected to the charger through long wires. The voltage rating on CBAT must meet or exceed the battery float voltage. applicaTions inForMaTion

where IMAX(AVG) is the maximum average charge current. volt-second product is not being exceeded by your design. Figure 1. Programming Maximum Charge Current Using RSENSE

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Figure 2. 2A Charger Switched Inductor Value Figure 3. 1.3A Charger Switched Inductor Value LT3650 charger is the ripple current created in that inductor.

• 1− VBAT +VF VIN(MAX) +VF (µH) In the previous relation, ∆I MAX is the normalized ripple current, V IN(MAX) as the maximum operational voltage, and VF is the forward voltage of the rectifying Schottky diode. Ripple current is typically set within a range of 25%

forward voltage, reverse voltage, and maximum current. than the maximum VIN voltage. current exceeds the programmed maximum value. tem limit, for example, would use a 33mΩ sense resistor. the need for external filter elements. Figure 4. RCLP Sets the Input Supply Current Limit

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Figure 5. CLP Limit: Charger Current vs

no effect on the maximum charge current. sense voltage of 50mV, RNG/SS would be set to 0.5V. exceed the 2.5V absolute maximum voltage on the pin. from these faults is possible. Figure 6. Using the RNG/SS Pin for Digital Figure 7. Driving the RNG/SS Pin with a Figure 8. Using the RNG/SS Pin for Soft-Start

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the charger is not actively charging. continues for another full timer cycle. Table 1. Status Pins State Table due to cycling between termination and recharge events. tenth the maximum current, as programmed with RSENSE.

LT3650-4.1/LT3650-4.2 36504142fc Preconditioning and Bad-Battery Fault An LT3650 charger has a precondition mode, in which charge current is limited to 15% of the programmed IMAX, as set by RSENSE. The precondition current corresponds to 15mV across RSENSE. Precondition mode is engaged while the voltage on the BAT pin is below the precondition threshold (VBAT(PRE)). Once the BAT voltage rises above the precondition threshold, normal full-current charging can commence. The LT3650 incorporates 3% of threshold hysteresis to prevent mode glitching. When the internal timer is used for termination, bad-battery detection is engaged. This fault detection feature is designed to identify failed cells. A bad-battery fault is triggered when the voltage on BAT remains below the precondition threshold for greater than one-eighth of a full timer cycle (one-eighth EOC). A bad-battery fault is also triggered if a normally charging battery re-enters precondition mode after one-eighth EOC. When a bad-battery fault is triggered, the charging cycle is suspended, so the CHRG status pin becomes high impedance. The FAUL T pin is pulled low to signal a fault detection. The RNG/SS pin is also pulled low during this fault, to accommodate a graceful restart, in the event that a soft-start function is incorporated (see the RNG/SS: Soft-Start section). Cycling the charger’s power or SHDN function initiates a new charging cycle, but an LT3650 charger does not require a reset. Once a bad-battery fault is detected, a new timer charging cycle initiates when the BAT pin exceeds the precondition threshold voltage. During a bad-battery fault, 0.5mA is sourced from the charger; removing the failed battery allows the charger output voltage to rise and initiate a charge cycle reset. As such, removing a bad bat- tery resets the LT3650, so a new charging cycle is started by connecting another battery to the charger output. Battery Temperature Fault: NTC The LT3650 can accommodate battery temperature moni- toring by using an NTC (negative temperature coefficient) thermistor close to the battery pack. The temperature monitoring function is enabled by connecting a 10kΩ, B = 3380 NTC thermistor from the NTC pin to ground. If the NTC function is not desired, leave the pin unconnected. The NTC pin sources 50µA, and monitors the voltage dropped across the 10kΩ thermistor. When the voltage on this pin is above 1.36V (0°C) or below 0.29V (40°C), the battery temperature is out of range, and the LT3650 triggers an NTC fault. The NTC fault condition remains until the voltage on the NTC pin corresponds to a temperature within the 0°C to 40°C range. Both hot and cold thresholds incorporate hysteresis that corresponds to 5°C. If higher operational charging temperatures are desired, the temperature range can be expanded by adding se- ries resistance to the 10k NTC resistor. Adding a 0.91k resistor will increase the effective temperature threshold to 45°C. During an NTC fault, charging is halted and both status pins are pulled low. If timer termination is enabled, the timer count is suspended and held until the fault condition is relieved. The RNG/SS pin is also pulled low during this fault, to accommodate a graceful restart in the event that a soft-start function is being incorporated (see the RNG/ SS: Soft-Start section). Thermal Foldback The LT3650 contains a thermal foldback protection feature that reduces maximum charger output current if the IC junction temperature approaches 125°C. In most cases, on-chip temperatures servo such that any overtempera- ture conditions are relieved with only slight reductions in maximum charger current. In some cases, the thermal foldback protection feature can reduce charger currents below the C/10 threshold. In applications that use C/10 termination (TIMER = 0V), the LT3650 will suspend charging and enter standby mode until the overtemperature condition is relieved. applicaTions inForMaTion

typically less than 10ns to maximize conversion efficiency. also help to avoid voltage stress from inductive ringing. switching noise with ground is recommended. the output bypass capacitor (CBAT). Figure 9. Component Orientation Isolates High Current Paths From Sensitive Nodes

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LT3650-4.1/LT3650-4.2 36504142fc Typical applicaTions 5V to 32V 1.5A Charger with Three Hour EOC Termination. The LTC1515 Provides Boost Start-Up Requirement. Status Pins Use LED Indicators 12V to 32V 2A Charger with Three Hour EOC Termination and Removable Battery Pack. The RNG/SS Pin Is Used to Reduce the Maximum Charger Current if 12V < VIN < 20V; Input UVLO = 10V. NTC Range Is Extended to +45C. The Charger Can Supply Loads Up to the Maximum Charger Current with No Battery Connected

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(9.1V) 1µF 6.8µH 0.05/uni03A9 SYSTEM LOAD L T3650 10µF 36k 0.68µF 0.91k SHDN CHRG FAULT 0.1µF CMSH3-40MA 10µF 100µF B = 3380 10k

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0.5 10 14 12 16 VIN 18 22 20 32 2.0 1.5 1.0 MAXIMUM CHARGE CURRENT (A) RNG/SS Pin Foldback: ICHG(MAX) vs VIN

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C1– VIN CLP RNG/SS BOOST SENSE BAT NTC TIMER 1N4148 0.068/uni03A9 1N4148 2N3904 B240A INPUT SUPPL Y 5V TO 32V 1µF10µF 20k 10µF 100k 10µH 0.1µF L T3650 SHDN CHRG FAULT GND 0.1µF L TC1515 SHDN POR FB 5.1k 10µF 0.68µF 10µF B = 3380 10k 100k 5.1k BZX84C6V2L (6.2V) 10k10k

LT3650-4.1/LT3650-4.2 36504142fc 3.00 ±0.10 (4 SIDES) NOTE: 1. DRAWING IS NOT A JEDEC PACKAGE OUTLINE 2. DRAWING NOT TO SCALE 3. ALL DIMENSIONS ARE IN MILLIMETERS 4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE 5. EXPOSED PAD AND TIE BARS SHALL BE SOLDER PLATED 6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON THE TOP AND BOTTOM OF PACKAGE 0.40 ±0.10 BOTTOM VIEW—EXPOSED PAD 1.65 ±0.10 0.75 ±0.05 R = 0.115 TYP 127 PIN 1 TOP MARK (SEE NOTE 6)

0.200 REF

0.00 – 0.05 (DD12) DFN 0106 REV A RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS APPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED 0.23 ±0.05 0.25 ±0.05

2.25 REF

2.38 ±0.05 0.70 ±0.05 3.50 ±0.05 PACKAGE OUTLINE PIN 1 NOTCH R = 0.20 OR 0.25 × 45° CHAMFER 2.38 ±0.10

0.45 BSC

12-Lead Plastic DFN (3mm × 3mm) (Reference LTC DWG # 05-08-1725 Rev A) package DescripTion Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings.

LT3650-4.1/LT3650-4.2 36504142fc package DescripTion MSOP (MSE12) 0911 REV F 0.53 ±0.152 (.021 ±.006) SEATING PLANE 0.18 (.007) 1.10 (.043) MAX 0.22 –/uni00A00.38 (.009 – .015) TYP 0.86 (.034) REF 0.650 (.0256) BSC 12 11 10 9 8 7 DETAIL “B” 1 6 NOTE: 1. DIMENSIONS IN MILLIMETER/(INCH) 2. DRAWING NOT TO SCALE 3. DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS. MOLD FLASH, PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.152mm (.006") PER SIDE 4. DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS. INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.152mm (.006") PER SIDE 5. LEAD COPLANARITY (BOTTOM OF LEADS AFTER FORMING) SHALL BE 0.102mm (.004") MAX 6. EXPOSED PAD DIMENSION DOES INCLUDE MOLD FLASH. MOLD FLASH ON E-PAD SHALL NOT EXCEED 0.254mm (.010") PER SIDE. 0.254 (.010) 0° – 6° TYP DETAIL “A” DETAIL “A” GAUGE PLANE RECOMMENDED SOLDER PAD LAYOUT BOTTOM VIEW OF EXPOSED PAD OPTION 2.845 ±0.102 (.112 ±.004) 4.039 ±0.102 (.159 ±.004) (NOTE 3) 1.651 ±0.102 (.065 ±.004) 1.651 ±0.102 (.065 ±.004) 0.1016 ±0.0508 (.004 ±.002) 1 2 3 4 5 6 3.00 ±0.102 (.118 ±.004) (NOTE 4) 0.406 ±0.076 (.016 ±.003) REF 4.90 ±0.152 (.193 ±.006) DETAIL “B” CORNER TAIL IS PART OF THE LEADFRAME FEATURE. FOR REFERENCE ONL Y NO MEASUREMENT PURPOSE

0.12 REF

0.35 REF 5.23 (.206) MIN 3.20 – 3.45 (.126 – .136) 0.889 ±0.127 (.035 ±.005) 0.42 ±0.038 (.0165 ±.0015) TYP 0.65 (.0256) BSC 12-Lead Plastic MSOP, Exposed Die Pad (Reference LTC DWG # 05-08-1666 Rev F) Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings.

LT3650-4.1/LT3650-4.2 36504142fc Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representa- tion that the interconnection of its circuits as described herein will not infringe on existing patent rights.

revision hisTory

REV DATE DESCRIPTION PAGE NUMBER C 12/12 Added new Battery Bias Current curve 5 (Revision history begins at Rev C)

LT3650-4.1/LT3650-4.2 36504142fc Linear Technology Corporation 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com © LINEAR TECHNOLOGY CORPORATION 2009 LT 1212 REV C • PRINTED IN USA relaTeD parTs Typical applicaTion PART NUMBER DESCRIPTION COMMENTS LT1511 3A Constant-Current/Constant-Voltage Battery Charger High Efficiency, Minimum External Components to Fast Charge Lithium, NIMH and NiCd Batteries, 24-Lead SO Package LT1513 SEPIC Constant or Programmable Current/ Constant-Voltage Battery Charger Charger Input Voltage May Be Higher, Equal to or Lower Than Battery Voltage, 500kHz Switching Frequency, DD-Pak and TO-220 Packages LT1571 1.5A Switching Charger 1- or 2-Cell Li-Ion, 500kHz or 200kHz Switching Frequency, Termination Flag, 16- and 28-Lead SSOP Packages LT1769 2A Switching Charger Constant-Current/Constant-Voltage Switching Regulator, Input Current Limiting Maximizes Charge Current, 20-Lead TSSOP and 28-Lead SSOP Packages LT3650-8.2/ LT3650-8.4 Monolithic 2A Switch Mode Nonsynchronous 2-Cell Li-Ion Battery Charger Standalone, 9V ≤ V IN ≤ 32V (40V Abs Max), 1MHz, 2A Programmable Charge Current, Timer or C/10 Termination, Small and Few External Components, LT3650-8.2 for 2 × 4.1V Float Voltage Batteries, LT3650-8.4 for 2 × 4.2V Float Voltage Batteries, 3mm × 3mm LTC4001/ LTC4001-1 Monolithic 2A Switch Mode Synchronous Li-Ion Battery Charger Standalone, 4V ≤ V IN ≤ 5.5V (6V Abs Max, 7V Transient), 1.5MHz, Synchronous Rectification Efficiency >90%, Adjustable Timer Termination, Small and Few External Components, LTC4001-1 for 4.1V Float Voltage Batteries, 4mm × 4mm QFN-16 Package LTC4002 Standalone Li-Ion Switch Mode Battery Charger Complete Charger for 1- or 2-Cell Li-Ion Batteries, Onboard T imer Termination, Up to 4A Charge Current, 10-Lead DFN and SO-8 Packages LTC4006 Small, High Efficiency, Fixed Voltage Li-Ion Battery Charger with Termination Complete Charger for 2-, 3- or 4-Cell Li-Ion Batteries, AC Adapter Current Limit and Thermistor Sensor, 16-Lead Narrow SSOP Package LTC4007 High Efficiency, Programmable Voltage Battery Charger with Termination Complete Charger for 3- or 4-Cell Li-Ion Batteries, AC Adapter Current Limit, Thermistor Sensor and Indicator Outputs, 24-Lead SSOP Package LTC4008 4A, High Efficiency, Multi-Chemistry Battery Charger Complete Charger for 2- to 6-Cell Li-Ion Batteries or 4- to 18-Cell Nickel Batteries, Up to 96% Efficiency, 20-Lead SSOP Package LTC4009/ LTC4009-1/ LTC4009-2 4A, High Efficiency, Multi-Chemistry Battery Charger Constant-Current/Constant-Voltage Switching Regulator Charger, Resistor Voltage/ Current Programming, AC Adapter Current Limit and Thermistor Sensor and Indicator Outputs 1- to 4-Cell Li, Up to 18-Cell Ni, SLA and Supercap Compatible; 4mm × 4mm 4.2V Float Voltage Li-Ion Cells. 10V to 32V 1.5A Charger with C/10 Termination and 1A Input Supply Limit. Status Pins Use LED Indicators

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1µF 10µH 0.068Ω L T3650 10µF 0.1µF INPUT SUPPL Y 10V TO 32V AT 1A 10µF 47k 0.05/uni03A9 SHDN CHRG FAULT 10k 330k 10k B = 3380 10k