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LTC4098-3.6

409836f

USB Compatible Switching

Power Manager/LiFePO

Charger

with Overvoltage Protection

The LTC

4098-3.6 is a high efﬁciency USB PowerPath

controller and full-featured LiFePO

battery charger. It seam-

lessly manages power distribution from multiple sources

including USB, wall adapter, automotive, Firewire or other

high voltage DC/DC converters, and a LiFePO

battery.

The LTC4098-3.6 charge algorithm is optimized for LiFePO

by implementing a 1-hour ﬂoat voltage termination timer

and a 0°C to 60°C NTC-based charge qualiﬁcation range.

Furthermore, completely discharged batteries are charged

at the full programmed charge current.

The LTC4098-3.6’s switching regulator can automatically

limit its input current for USB compatibility. For automo-

tive and other high voltage applications, the LTC4098-3.6

interfaces with an external switching regulator. Both the

USB input and the auxiliary input controller feature Bat-

Track optimized charging to provide maximum power to

the application and reduced heat in high power density ap-

plications with input supplies from 5V to as high as 38V.

An overvoltage protection circuit guards the LTC4098-3.6

from high voltage damage on the VBUS pin with just two

external components.

The LTC4098-3.6 is available in a 20-lead 3mm × 4mm ×

0.75mm QFN surface mount package.

High Peak Power Battery-Powered Equipment

Backup Applications

High Reliability Handhelds

Switching Regulator with Bat-Track

Adaptive

Output Control Makes Optimal Use of Limited

Power Available from USB Port to Charge Battery

and Power Application

Charge Control Algorithm Speciﬁcally Designed

for LiFePO

(Lithium Iron Phosphate)

Overvoltage Protection Guards Against Damage

Bat-Track External Step-Down Switching Regulator

Control Maximizes Efﬁciency from Automotive,

Firewire and Other High Voltage Input Sources

180mΩ Internal Ideal Diode Plus External Ideal Diode

Controller Seamlessly Provide Low Loss PowerPath

When Input Power Is Limited or Unavailable

Preset 3.6V Charge Voltage with 0.5% Accuracy

Instant-On Operation with Discharged Battery

700mA Maximum Load Current from USB Port

2A Maximum Input Current from Internal Switching

Regulator

1.5A Maximum Charge Current with Thermal Limiting

20-Lead 3mm × 4mm × 0.75mm QFN Package

High Efﬁciency USB Compatible LiFePO

Battery Charger with Overvoltage Protection

BUS

10µF

0.1µF 3.01k 500Ω

10µF

3.3µH

6.04k

5V/USB

TO µC

SYSTEM

LOAD

409836 TA01a

CLPROG PROG

LTC4098-3.6

GND

BATSENS

OVGATE

OVSENS

D0-D2

BAT

OUT

LiFePO

Reduced Power Dissipation

vs Linear Battery Charger

BATTERY VOLTAGE (V)

2.70

POWER DISSIPATION (W)

0.5

1.0

1.5

2.0

3.0

2.85

3.00 3.15 3.30

409836 TA01b

3.45 3.60

2.5

= 5V

PROG = 500Ω

CHRG

= 1.1A

10x MODE

SWITCHING

BATTERY

CHARGER

LINEAR BATTERY

CHARGER

ADDITIONAL POWER

AVAILABLE FOR CHARGING

TYPICAL APPLICATION

FEATURES

APPLICATIONS

DESCRIPTION

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

Bat Track and PowerPath are trademarks of Linear Technology Corporation. All other trademarks

are the property of their respective owners.

Summary of content (32 pages)

PAGE 1
LTC4098-3.
PAGE 2
LTC4098-3.6 PIN CONFIGURATION VBUS, WALL (Transient) t < 1ms, Duty Cycle < 1%........................................... –0.3V to 7V VBUS, WALL (Static), BAT, BATSENS, CHRG, NTC,.................................................. –0.3V to 6V D0, D1, D2..........–0.3V to Max (VBUS, VOUT, BAT) + 0.3V IOVSENS..................................................................±10mA ICLPROG.....................................................................3mA IPROG................................................
PAGE 3
LTC4098-3.6 ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C (Note 2). VBUS = 5V, BAT = 3.3V, RCLPROG = 3.01k, unless otherwise noted. SYMBOL PARAMETER CONDITIONS IVOUT VOUT Current Available Before Discharging Battery 1x Mode 5x Mode 10x Mode Low Power Suspend Mode High Power Suspend Mode MIN TYP 135 659 1231 0.32 2.
PAGE 4
LTC4098-3.6 ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C (Note 2). VBUS = 5V, BAT = 3.3V, RCLPROG = 3.01k, unless otherwise noted. SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS tTERM Safety Timer Termination Period Timer Starts When BAT = VFLOAT 0.85 1 1.15 Hour tBADBAT Bad Battery Termination Time BAT < VTRKL 0.43 0.5 0.
PAGE 5
LTC4098-3.6 TYPICAL PERFORMANCE CHARACTERISTICS Ideal Diode Resistance vs Battery Voltage Ideal Diode V-I Characteristics DIODE RESISTANCE (Ω) INTERNAL IDEAL DIODE ONLY 0.2 0.15 0.10 0.05 0 0.04 0.12 0.16 0.08 FORWARD VOLTAGE (V) 0 2.7 0.20 409836 G01 VOUT Voltage vs VOUT Current (Battery Charger Disabled) 4.00 BAT = 3.6V 3.75 BAT = 3.3V 3.50 VBUS = 5V 5x USB SETTING 0 550 2.7 4.2 200 600 400 OUTPUT CURRENT (mA) 3.3 3.
PAGE 6
LTC4098-3.6 TYPICAL PERFORMANCE CHARACTERISTICS Battery Drain Current vs Battery Voltage 30 IVOUT = 0µA 25 Battery Charging Efficiency vs Battery Voltage with No External Load (PBAT/PVBUS) PowerPath Switching Regulator Efficiency vs Output Current 100 VBUS = 0V 100 BAT = 3.3V 5x, 10x MODE 90 10 60 3.0 3.3 BATTERY VOLTAGE (V) 40 0.01 3.6 3.75 OUTPUT VOLTAGE (V) VBUS CURRENT (µA) 2.5 20 3.60 3.45 SUSPEND LOW 4 VBUS VOLTAGE (V) 3 5 3.00 6 0.
PAGE 7
LTC4098-3.6 TYPICAL PERFORMANCE CHARACTERISTICS Low Battery (Instant-On, Charger Disabled) Output Voltage vs Temperature Oscillator Frequency vs Temperature 3.54 3.52 –15 35 60 10 TEMPERATURE (°C) 85 110 20 17 2.30 QUIESCENT CURRENT (mA) OSCILLATOR FREQUENCY (MHz) 3.56 2.25 2.20 2.15 2.
PAGE 8
LTC4098-3.6 TYPICAL PERFORMANCE CHARACTERISTICS OVP Protection Waveform TA = 25°C, unless otherwise noted. OVP Reconnection Waveform VBUS 5V/DIV VBUS 5V/DIV OVGATE 5V/DIV OVGATE 5V/DIV OVP INPUT VOLTAGE 10V TO 5V STEP 5V/DIV OVP INPUT VOLTAGE 5V TO 10V STEP 5V/DIV 409836 G26 500µs/DIV OVSENS Quiescent Current vs Temperature Rising Overvoltage Threshold vs Temperature 12 OVSENS CONNECTED TO INPUT THROUGH 10 6.04k RESISTOR 33 31 OVGATE VOLTAGE (V) 6.275 35 6.270 6.265 6.
PAGE 9
LTC4098-3.6 PIN FUNCTIONS OVSENS (Pin 1): Overvoltage Protection Sense Input. OVSENS should be connected through a 6.04k resistor to the input power connector and the drain of an external N-channel MOSFET pass transistor. When the voltage on this pin exceeds a preset level, the OVGATE pin will be pulled to GND to disable the pass transistor and protect downstream circuitry. If overvoltage protection is not desired, connect OVSENS to GND. OVGATE (Pin 2): Overvoltage Protection Gate Output.
PAGE 10
LTC4098-3.6 PIN FUNCTIONS majority of the portable product should be powered from VOUT . The LTC4098-3.6 will partition the available power between the external load on VOUT and the internal battery charger. Priority is given to the external load and any extra power is used to charge the battery. An ideal diode from BAT to VOUT ensures that VOUT is powered even if the load exceeds the allotted power from VBUS or if the VBUS power source is removed.
PAGE 11
TO USB OR WALL ADPAPTER T NTC 5 4 3 13 0.1V NTC NTCBIAS 1.188V CLPROG ISWITCH /N ILDO /M VBUS OVGATE + – + – + – 2 + – 1 AVERAGE INPUT CURRENT LIMIT CONTROLLER NTC ENABLE OVERTEMP UNDERTEMP VOUT + – SUSPEND LDO 100mV ×2 OVERVOLTAGE PROTECTION – + NTC FAULT OSC 3.8V Q D0 15 D1 16 LOGIC D2 17 NONOVERLAP AND DRIVE LOGIC AVERAGE OUTPUT VOLTAGE LIMIT CONTROLLER PWM R S +– 6V 20 + + – + – OVSENS VC GND 9 3.5V GND 21 +– 0.
PAGE 12
LTC4098-3.6 OPERATION Introduction The LTC4098-3.6 is a high efficiency power management and LiFePO4 charger solution designed to make optimal use of the power available from a variety of sources, while minimizing power dissipation and easing thermal budgeting constraints. The innovative PowerPath architecture ensures that the application is powered immediately after external voltage is applied, even with a completely dead battery, by prioritizing power to the application over the battery. The LTC4098-3.
PAGE 13
FROM USB OR WALL ADAPTER 3 13 2 1 CLPROG VBUS OVGATE 1.188V ISWITCH /N ×2 +– PWM AND GATE DRIVE AVERAGE INPUT CURRENT LIMIT CONTROLLER + – OVERVOLTAGE PROTECTION 20 VC 3.5V +– 0.4V CONSTANT-CURRENT CONSTANT-VOLTAGE BATTERY CHARGER VOUT ISENSE SW 18 4.3V WALL 15mV OmV IDEAL DIODE + – Bat-Track HV CONTROL VOUT 3.6V BAT + 0.4V Figure 1.
PAGE 14
LTC4098-3.6 OPERATION The input current limit is programmed by various combinations of the D0, D1 and D2 pins as shown in Table 1. The switching input regulator can also be deactivated (USB suspend). The average input current will be limited by the CLPROG programming resistor according to the following expression: IVBUS = IVBUSQ + VCLPROG • (hCLPROG + 1) RCLPROG where IVBUSQ is the quiescent current of the LTC4098‑3.
PAGE 15
LTC4098-3.6 OPERATION For very low battery voltages, the battery charger acts like a load and, due to limited input power, its current will tend to pull VOUT below the 3.5V instant-on voltage. To prevent VOUT from falling below this level, an undervoltage circuit automatically detects that VOUT is falling and reduces the battery charge current as needed. This reduction ensures that load current and voltage are always prioritized while allowing as much battery charge current as possible.
PAGE 16
LTC4098-3.6 OPERATION With the same assumptions as previously stated, the total battery charger efficiency is approximately 78%. This example works out to just over 1W of power dissipation, or almost 50% less heat. The charge pump output on OVGATE has limited output drive capability. Care must be taken to avoid leakage on this pin, as it may adversely affect operation. See the Typical Applications section for complete circuits using the LT3653 and LT3480 with Bat-Track control.
PAGE 17
LTC4098-3.6 OPERATION transistor may be added from BAT to VOUT. The IDGATE pin of the LTC4098-3.6 drives the gate of the external P-channel MOSFET transistor for automatic ideal diode control. The source of the external P-channel MOSFET should be connected to VOUT and the drain should be connected to BAT. Capable of driving a 1nF load, the IDGATE pin can control an external P-channel MOSFET transistor having an on-resistance of 30mΩ or lower.
PAGE 18
LTC4098-3.6 OPERATION by monitoring the PROG pin voltage and using the following equation: IBAT = VPROG • 1030 RPROG In many cases, the actual battery charge current, IBAT, will be lower than the programmed current, ICHG, due to limited input power available and prioritization to the system load drawn from VOUT. Charge Status Indication The CHRG pin indicates the status of the battery charger.
PAGE 19
LTC4098-3.6 OPERATION NTC Thermistor Thermal Regulation The battery temperature is measured by placing a negative temperature coefficient (NTC) thermistor close to the battery pack. The NTC circuitry is shown in the Block Diagram. To prevent thermal damage to the LTC4098-3.6 or surrounding components, an internal thermal feedback loop will automatically decrease the programmed charge current if the die temperature rises to approximately 110°C. Thermal regulation protects the LTC4098-3.
PAGE 20
LTC4098-3.6 OPERATION POWER ON/ ENABLE CHARGER CLEAR EVENT TIMER ASSERT CHRG LOW NTC OUT OF RANGE YES INHIBIT CHARGING NO PAUSE EVENT TIMER BAT < 2.85V BATTERY STATE BAT > VFLOAT – ε 2.
PAGE 21
LTC4098-3.6 APPLICATIONS INFORMATION CLPROG Resistor and Capacitor VBUS and VOUT Bypass Capacitors As described in the Bat-Track Input Current Limited Step Down Switching Regulator section, the resistor on the CLPROG pin determines the average input current limit in each of the five current limit modes. The input current will be comprised of two components, the current that is used to drive VOUT and the quiescent current of the switching regulator.
PAGE 22
LTC4098-3.6 APPLICATIONS INFORMATION Multilayer ceramic chip capacitors typically have exceptional ESR performance. MLCCs combined with a tight board layout and an unbroken ground plane will yield very good performance and low EMI emissions. There are several types of ceramic capacitors available each having considerably different characteristics. For example, X7R ceramic capacitors have the best voltage and temperature stability.
PAGE 23
LTC4098-3.6 APPLICATIONS INFORMATION Reverse Voltage Protection The LTC4098-3.6 can also be easily protected against the application of reverse voltage, as shown in Figure 8. D1 and R1 are necessary to limit the maximum VGS seen by MP1 during positive overvoltage events. D1’s breakdown voltage must be safely below MP1’s BVGS. The circuit shown in Figure 8 offers forward voltage protection up to MN1’s BVDSS and reverse voltage protection up to MP1’s BVDSS.
PAGE 24
LTC4098-3.6 APPLICATIONS INFORMATION Solving these equations for RNTC|COLD and RNTC|HOT results in the following: RNTC|HOT = 0.25 • RNOM and RNTC|COLD = 3.26 • RNOM By setting RNOM equal to R25, the previous equations result in aHOT = 0.25 and aCOLD = 3.26. Referencing these ratios to the Vishay Resistance-Temperature curve 1 chart gives a hot trip point of about 60°C and a cold trip point of about 0°C. The difference between the hot and cold trip points is approximately 60°C.
PAGE 25
LTC4098-3.6 APPLICATIONS INFORMATION are linked. Therefore, only one of the two trip points can be chosen, the other is determined by the default ratios designed in the IC. Consider an example where a 70°C hot trip point is desired. From the Vishay curve 1 R-T characteristics, aHOT is 0.1753 at 70°C. Using the previous equation, RNOM should be set to 70.4k. With this value of RNOM, the cold trip point is 7°C. Notice that the span is now 63°C rather than the previous 60°C.
PAGE 26
LTC4098-3.6 APPLICATIONS INFORMATION Board Layout Considerations The exposed pad on the backside of the LTC4098-3.6 package must be securely soldered to the PC board ground. This is the primary ground pin in the package and it serves as the return path for both the control circuitry and the synchronous rectifier. Furthermore, due to its high frequency switching circuitry, it is imperative that the input capacitor, inductor, and output capacitor be as close to the LTC4098-3.
PAGE 27
LTC4098-3.6 TYPICAL APPLICATIONS High Efficiency USB/2A Automotive Battery Charger with Overvoltage Protection and Low Battery Start-Up 4 AUTOMOTIVE, FIREWIRE, ETC. C1 C7 4.7µF 68nF R10 40.2k R11 150k 5 10 C6 0.47µF 2 VIN BOOST 3 SW LT3480 RUN/SS PG VC 7 C4 22µF BD GND 9 R9 R8 499k 100k D3 8 FB RT L2 10µH 11 1 M1 L1 3.3µH M3 USB 13 C2 10µF 0805 2 R3 6.
PAGE 28
LTC4098-3.6 TYPICAL APPLICATIONS USB/Wall Adapter Battery Charger with Dual Overvoltage Protection, Reverse-Voltage Protection and Low Battery Start-Up M1 5V WALL ADAPTER M3 C1 10µF 0805 D3 R1 M5 R2 L1 3.3µH D4 13 USB M2 C2 10µF 0805 M4 D1 D2 R3 6.
PAGE 29
LTC4098-3.6 TYPICAL APPLICATIONS Low Component Count USB and Automotive High Efficiency Power Manager 1 AUTOMOTIVE, FIREWIRE, ETC. C1 4.7µF 7 BOOST VIN SW 4 R1 27.4k ILIM C3 10µF 0805 2 1 TO µC TO µC 3 D1 VC VBUS ISENSE 5 VOUT HVOK 3 2 20 18 VC L2 3.3µH 19 8 4 5 SYSTEM LOAD 14 WALL ACPR SW OVGATE VOUT OVSENS IDGATE LTC4098-3.6 15-17 L1 4.7µH 6 GND 13 8 LT3653 9 USB WALL ADAPTER C2 0.1µF 10V BAT 12 10 11 D0-D2 CHRG NTCBIAS NTC CLPROG C4 0.
PAGE 30
LTC4098-3.6 TYPICAL APPLICATIONS High Efficiency USB Automotive Battery Charger with Overvoltage Protection and Low Battery Start-Up 1 AUTOMOTIVE, FIREWIRE, ETC. C1 4.7µF 50V BOOST VIN SW 4 R2 27.4k M2 13 R4 6.04k TO µC 1 3 15-17 8 TO µC 4 M1: VISHAY-SILICONIX Si2333CDS M2: ON SEMICONDUCTOR NTLJS4114N R6: VISHAY-DALE NTHS0603N011-N1003F R5 100k T R6 100k 5 L1 4.7µH D2 6 GND C3 10µF 0805 2 C2 0.
PAGE 31
LTC4098-3.6 PACKAGE DESCRIPTION UDC Package 20-Lead Plastic QFN (3mm × 4mm) (Reference LTC DWG # 05-08-1742 Rev Ø) 0.70 ±0.05 3.50 ± 0.05 2.10 ± 0.05 2.65 ± 0.05 1.50 REF 1.65 ± 0.05 PACKAGE OUTLINE 0.25 ±0.05 0.50 BSC 2.50 REF 3.10 ± 0.05 4.50 ± 0.05 RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS APPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED 3.00 ± 0.10 0.75 ± 0.05 1.50 REF 19 R = 0.05 TYP PIN 1 NOTCH R = 0.20 OR 0.25 × 45° CHAMFER 20 0.40 ± 0.10 1 PIN 1 TOP MARK (NOTE 6) 4.00 ± 0.10 2 2.
PAGE 32
LTC4098-3.6 TYPICAL APPLICATION 1.5A Standalone LiFeP04 Charger L1 3.3µH 13 WALL ADAPTER C1 10µF 0805 2 1 15 R1 2k ON OFF 8 17 16 20 VBUS VC 18 19 WALL ACPR 14 SW OVGATE VOUT OVSENS IDGATE D0 BAT LTC4098-3.6 BATSENS CHRG NTCBIAS D2 D1 NTC CLPROG C2 0.