Datasheet

ManualsBrandsLINEAR TECHNOLOGY ManualsPMICsPMIC - battery management Charge management VRLA, LiFePO4, Li-Ion, Li-Po, NiCd, NiMH DFN

LT3652

3652fd

TYPICAL APPLICATION

DESCRIPTION

Power Tracking 2A Battery

Charger for Solar Power

The LT

3652 is a complete monolithic step-down bat-

tery charger that operates over a 4.95V to 32V input

voltage range. The LT3652 provides a constant-current/

constant-voltage charge characteristic, with maximum

charge current externally programmable up to 2A. The

charger employs a 3.3V ﬂ oat voltage feedback reference,

so any desired battery ﬂ oat voltage up to 14.4V can be

programmed with a resistor divider.

The LT3652 employs an input voltage regulation loop, which

reduces charge current if the input voltage falls below a

programmed level, set with a resistor divider. When the

LT3652 is powered by a solar panel, the input regulation

loop is used to maintain the panel at peak output power.

The LT3652 can be conﬁ gured to terminate charging

when charge current falls below 1/10 of the programmed

maximum (C/10). Once charging is terminated, the LT3652

enters a low-current (85μA) standby mode. An auto-re-

charge feature starts a new charging cycle if the battery

voltage falls 2.5% below the programmed ﬂ oat voltage.

The LT3652 also contains a programmable safety timer,

used to terminate charging after a desired time is reached.

This allows top-off charging at currents less than C/10.

2A Solar Panel Power Manager With 7.2V LiFePO

Battery

and 17V Peak Power Tracking

FEATURES

APPLICATIONS

Input Supply Voltage Regulation Loop for Peak

Power Tracking in (MPPT) Solar Applications

Wide Input Voltage Range: 4.95V to 32V (40V Abs Max)

Programmable Charge Rate Up to 2A

User Selectable Termination: C/10 or On-Board

Termination Timer

Resistor Programmable Float Voltage Up to 14.4V

Accommodates Li-Ion/Polymer, LiFePO

SLA Chemistries

No V

Blocking Diode Required for Battery

Voltages ≤ 4.2V

1MHz Fixed Frequency

0.5% Float Voltage Reference Accuracy

5% Charge Current Accuracy

2.5% C/10 Detection Accuracy

Binary-Coded Open-Collector Status Pins

3mm × 3mm DFN12 or MSOP-12 Packages

Solar Powered Applications

Remote Monitoring Stations

LiFePO

(Lithium Phosphate) Applications

Portable Handheld Instruments

12V to 24V Automotive Systems

Solar Panel Input Voltage

Regulation, Tracks Max Power

Point to Greater Than 98%

SOLAR PANEL INPUT

(<40V OC VOLTAGE)

IN_REG

BOOST

SENSE

BAT

NTC

TIMER

CMSH3-40MA

SYSTEM LOAD

1μF

542k

459k

3652 TA01a

10k

B = 3380

2-CELL LiFePO

(2 × 3.6V) BATTERY PACK

10μF

CMSH1-40MA

10μF

10μH

0.05

LT3652

530k

100k

SHDN

CHRG

FAULT

CMSH3-40MA

CHARGER OUTPUT CURRENT (A)

0.2

INPUT REGULATION VOLTAGE (V)

0.6

1.2

3652 TA01b

0.4

0.8

1.61.4

21.8

100% TO 98% PEAK POWER

98% TO 95% PEAK POWER

= 25°C

L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear

Technology Corporation. All other trademarks are the property of their respective owners.

Summary of content (26 pages)

PAGE 1
LT3652 Power Tracking 2A Battery Charger for Solar Power FEATURES DESCRIPTION n The LT®3652 is a complete monolithic step-down battery charger that operates over a 4.95V to 32V input voltage range. The LT3652 provides a constant-current/ constant-voltage charge characteristic, with maximum charge current externally programmable up to 2A. The charger employs a 3.3V ﬂoat voltage feedback reference, so any desired battery ﬂoat voltage up to 14.4V can be programmed with a resistor divider.
PAGE 2
LT3652 ABSOLUTE MAXIMUM RATINGS (Note 1) Voltages: VIN ........................................................................40V VIN_REG, SHDN, CHRG, FAULT ............ VIN + 0.5V, 40V SW ........................................................................40V SW-VIN.................................................................4.5V BOOST ...................................................SW+10V, 50V BAT, SENSE ...........................................................15V BAT-SENSE ...............
PAGE 3
LT3652 ELECTRICAL CHARACTERISTICS The l denotes the speciﬁcations which apply over the full operating temperature range, otherwise speciﬁcations are at TA = 25°C. VIN = 20V, Boost – SW = 4V, SHDN = 2V, VFB = 3.3V, CTIMER = 0.68μF. SYMBOL PARAMETER CONDITIONS MIN VIN VIN Operating Range VIN Start Voltage VBAT = 4.2 (Notes 3, 4) VBAT = 4.2 (Note 4) l l 4.95 7.
PAGE 4
LT3652 ELECTRICAL CHARACTERISTICS The l denotes the speciﬁcations which apply over the full operating temperature range, otherwise speciﬁcations are at TA = 25°C. VIN = 20V, Boost – SW = 4V, SHDN = 2V, VFB = 3.3V, CTIMER = 0.68μF. SYMBOL PARAMETER tTIMER Full Charge Cycle Timeout CONDITIONS MIN l DC Duty Cycle Range –10 min 10 1 Continuous Operation Note 1: Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device.
PAGE 5
LT3652 TYPICAL PERFORMANCE CHARACTERISTICS VIN_REG Threshold vs Temperature: ICHG at 50% TJ = 25°C, unless otherwise noted. VIN Standby Mode Current vs Temperature VFB Reference Voltage vs Temperature 2.720 100 3.304 2.715 95 2.710 IVIN CURRENT (μA) VFB (FLT) 2.700 3.300 2.695 3.298 2.690 2.
PAGE 6
LT3652 TYPICAL PERFORMANCE CHARACTERISTICS Thermal Foldback – Maximum Charge Current (VSENSE –VBAT ) vs Temperature Maximum Charge Current (VSENSE –VBAT ) vs Temperature 101.0 100 100 VSENSE(DC) (mV) 100.4 100.2 100.0 99.8 99.6 99.4 80 80 VSENSE(DC) (mV) 100.6 VSENSE(DC) (mV) Maximum Charge Current (VSENSE –VBAT ) vs VIN_REG Voltage 120 VFB = 3V 100.8 TA = 25°C, unless otherwise noted. 60 40 60 40 20 20 99.2 99.
PAGE 7
LT3652 PIN FUNCTIONS VIN (Pin 1): Charger Input Supply. VIN operating range is 4.95V to 32V. VIN must be 3.3V greater than the programmed output battery ﬂoat voltage (VBAT(FLT)) for reliable start-up. (VIN – VBAT(FLT)) ≥ 0.75V is the minimum operating voltage, provided (VBOOST – VSW) ≥ 2V. IVIN ~ 85μA after charge termination. VIN_REG (Pin 2): Input Voltage Regulation Reference. Maximum charge current is reduced when this pin is below 2.7V.
PAGE 8
LT3652 PIN FUNCTIONS 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 1.36 (T < 0°C) or below 0.29V (T > 40°C), charging is disabled and the CHRG and FAULT pins are both pulled low.
PAGE 9
LT3652 BLOCK DIAGRAM + – 125°C TDIE STANDBY UVLO + – OVLO 4.6V – + VIN_REG 2.7V BOOST + – VIN 35V + – R LATCH S Q 0.2V TIMER + – 10mΩ 30mV OSC 1MHz + – TIMER OSC. SW VC – SENSE RS BAT C-EA STANDBY + RIPPLE COUNTER COUNT RESET RS OFFSET – COUNT + 0.3V RESET ENABLE V-EA + COUNT ITH 10 × RS MODE (TIMER OR C/10) CHRG VFB – CONTROL LOGIC TERMINATE FAULT STATUS – + C/10 0.1V 1V PRECONDITION – + 0.15V NTC VINT 2.7V + – – + – + x2.25 2.3V SHDN STANDBY 1.
PAGE 10
LT3652 APPLICATIONS INFORMATION Overview LT3652 is a complete monolithic, mid-power, multi-chemistry buck battery charger, addressing high input voltage applications with solutions that require a minimum of external components. The IC uses a 1MHz constant frequency, average-current mode step-down architecture. The LT3652 incorporates a 2A switch that is driven by a bootstrapped supply to maximize efficiency during charging cycles.
PAGE 11
LT3652 APPLICATIONS INFORMATION The ITH error voltage corresponds linearly to average current 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.
PAGE 12
LT3652 APPLICATIONS INFORMATION 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)1/2, where ICHG(MAX) is the maximum average charge current (100mV/RSENSE). The above relation has a maximum at VIN = 2 • VBAT, where: BOOST Supply The BOOST bootstrapped supply rail drives the internal switch and facilitates saturation of the switch transistor.
PAGE 13
LT3652 APPLICATIONS INFORMATION SW LT3652 BOOST SENSE BAT 3652 F02 Figure 2. Zener Diode Reduces Refresh Voltage for BOOST Pin VIN / BOOST Start-Up Requirement The LT3652 operates with a VIN range of 4.95V to 32V, however, a start-up voltage requirement exists due to the nature of the non-synchronous step-down switcher topology used for the charger. If there is no BOOST supply available, the internal switch requires (VIN – VSW) ≥ 3.3V to reliably operate.
PAGE 14
LT3652 APPLICATIONS INFORMATION forward voltage yields the lowest power loss and highest efficiency. The rectifier diode must be rated to withstand reverse voltages greater than the maximum VIN voltage. SWITCHED INDUCTOR VALUE (μH) 16 14 12 The minimum average diode current rating (IDIODE(MAX)) is calculated with maximum output current (ICHG(MAX)), maximum operational VIN, and output at the precondition threshold (VBAT(PRE), or 0.
PAGE 15
LT3652 APPLICATIONS INFORMATION Using a resistor divider with an equivalent input resistance at the VFB pin of 250k compensates for input bias current error. Required resistor values to program desired VBAT(FLT) follow the equations: RFB1 = (VBAT(FLT) • 2.5 • 105) / 3.3 (Ω) RFB2 = (R1 • (2.5 • 105)) / (R1- (2.5 • 105)) (Ω) The charge function operates to achieve the final float voltage of 3.3V on the VFB pin.
PAGE 16
LT3652 APPLICATIONS INFORMATION cleaning measures should be implemented to prevent board contamination, and low-leakage solder flux is recommended. Input Supply Voltage Regulation The LT3652 contains a voltage monitor pin that enables programming a minimum operational voltage. Connecting a resistor divider from VIN to the VIN_REG pin enables programming of minimum input supply voltage, typically used to program the peak power voltage for a solar panel.
PAGE 17
LT3652 APPLICATIONS INFORMATION simple solution for tracking that characteristic can be implemented using an LM234 3-terminal temperature sensor. This creates an easily programmable, linear temperature dependent characteristic. In the circuit shown in figure 8, VIN RSET = 1k LM234 V+ RIN1 R V– As the temperature coefficient for VMP is similar to that of VOC, the specified temperature coefficient for VOC (TC) of –78mV/°C and the specified peak power voltage (VMP(25°C)) of 17.
PAGE 18
LT3652 APPLICATIONS INFORMATION or –19.8mV/°C. Using the feedback network shown in Figure 9, with the desired temperature coefficient (TC) and 25°C float voltage (VFLOAT(25°C)) specified, and using a convenient value of 2.4k for RSET , necessary resistor values follow the relations: RFB1 = –RSET • (TC • 4405) = –2.4k • (–0.0198 • 4405) = 210k RFB2 = RFB1 / ({[VFLOAT(25°C) + RFB1 • (0.
PAGE 19
LT3652 APPLICATIONS INFORMATION Status Pins The LT3652 reports charger status through two open collector outputs, the CHRG and FAULT pins. These pins can accept voltages as high as VIN, and can sink up to 10mA when enabled. The CHRG pin indicates that the charger is delivering current at greater that a C/10 rate, or 1/10th of the programmed maximum charge current. The FAULT pin signals bad battery and NTC faults.
PAGE 20
LT3652 APPLICATIONS INFORMATION full-charge float voltage. If a charge cycle is not successful at EOC, the timer cycle resets and charging continues for another full timer cycle. When VBAT drops below 97.5% of the full-charge float voltage, whether by battery loading or replacement of the battery, the charger automatically reengages and starts charging.
PAGE 21
LT3652 APPLICATIONS INFORMATION 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 LT3652 will suspend charging and enter standby mode until the excessive temperature condition is relieved. Layout Considerations The LT3652 switch node has rise and fall times that are typically less than 10nS to maximize conversion efficiency.
PAGE 22
LT3652 TYPICAL APPLICATIONS 2-Cell Li-Ion Charger (8.3V at 2A) With 3 Hour Timer Termination Powered by Inexpensive 12V at 1A Unregulated Wall Adapter; VIN_REG Loop Servos Maximum Charge Current to Prevent AC Adapter Output from Drooping Lower than 12V MBRS340 AC ADAPTER INPUT 12V AT 1A SH-DC121000 D3 VIN SW LT3652 VIN_REG 330k 47k SHDN 1μF 10k CHRG 51k 10k 10μF 1μF 1N914 BOOST VISHAY 1HLP-2525CZ8R2M11 8.2μH MBRS340 0.
PAGE 23
LT3652 PACKAGE DESCRIPTION Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings. DD Package 12-Lead Plastic DFN (3mm w 3mm) (Reference LTC DWG # 05-08-1725 Rev A) 0.70 ±0.05 3.50 ±0.05 2.10 ±0.05 2.38 ±0.05 1.65 ±0.05 PACKAGE OUTLINE 0.25 ±0.05 0.45 BSC 2.25 REF RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS APPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED 3.00 ±0.10 (4 SIDES) R = 0.115 TYP 7 0.40 ±0.10 12 2.38 ±0.10 1.65 ±0.10 PIN 1 NOTCH R = 0.20 OR 0.
PAGE 24
LT3652 PACKAGE DESCRIPTION Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings. MSE Package 12-Lead Plastic MSOP, Exposed Die Pad (Reference LTC DWG # 05-08-1666 Rev F) BOTTOM VIEW OF EXPOSED PAD OPTION 2.845 t0.102 (.112 t.004) 5.23 (.206) MIN 2.845 t0.102 (.112 t.004) 0.889 t0.127 (.035 t.005) 6 1 1.651 t0.102 (.065 t.004) 1.651 t0.102 3.20 – 3.45 (.065 t.004) (.126 – .136) 12 0.65 0.42 t0.038 (.0256) (.0165 t.
PAGE 25
LT3652 REVISION HISTORY (Revision history begins at Rev B) REV DATE DESCRIPTION PAGE NUMBER B 2/10 Add MSOP-12 Package C 5/10 Corrected SHDN Pin Labels D 12/12 Removed reference to Nickel cell charging capability Added new Battery Bias Current curve 1, 2, 24 3, 4 1 6 3652fd Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use.
PAGE 26
LT3652 TYPICAL APPLICATION 1A Solar Panel Powered 3-Stage 12V Lead-Acid Fast/Float Charger; 1A Charger Fast Charges with CC/CV Characteristics Up to 14.4V; When Charge Current Falls to 0.1A Charger Switches to 13.5V Float Charge Mode; Charger Re-Initiates 14.4V Fast Charge Mode if Battery Voltage Falls Below 13.2V and Trickle Charges at 0.