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LTC3559/LTC3559-1

3559fb

TYPICAL APPLICATION

FEATURES

APPLICATIONS

DESCRIPTION

Linear USB Battery Charger

with Dual Buck Regulators

The LTC

3559/LTC3559-1 are USB battery chargers with

dual high efﬁ ciency buck regulators. The parts are ideally

suited to power single-cell Li-Ion/Polymer based handheld

applications needing multiple supply rails.

Battery charge current is programmed via the PROG pin

and the HPWR pin, with capability up to 950mA at the BAT

pin. The battery charger has an NTC input for temperature

qualiﬁ ed charging. The CHRG pin allows battery status to

be monitored continuously during the charging process.

An internal timer controls charger termination.

Each monolithic synchronous buck regulator provides up

to 400mA of output current while operating at efﬁ ciencies

greater than 90% over the entire Li-Ion/Polymer range.

A MODE pin provides the ﬂ exibility to place both buck

regulators in a power saving Burst Mode

operation or a

low noise pulse skip mode.

The LTC3559/LTC3559-1 are offered in a low proﬁ le ther-

mally enhanced 16-lead (3mm × 3mm) QFN package.

USB Charger Plus Dual Buck Regulators

Battery Charger

Standalone USB Charger

Up to 950mA Charge Current Programmable via

Single Resistor

HPWR Input Selects 20% or 100% of Programmed

Charge Current

NTC Input for Temperature Qualiﬁ ed Charging

Internal Timer Termination

Bad Battery Detection

CHRG Indicates C/10 or Timeout

Buck Regulators

400mA Output Current

2.25MHz Constant Frequency Operation

Zero Current in Shutdown

Low Noise Pulse Skip Operation or Power Saving

Burst Mode Operation

Low No-Load Quiescent Current: 35μA

Available in a Low Proﬁ le Thermally Enhanced

16-Lead 3mm × 3mm QFN Package

SD/Flash-Based MP3 Players

Low Power Handheld Applications

NTC

CHRG

PROG

SUSP

HPWR

EN1

4.7μH

2.2μF

10μF

309k

655k

649k

324k

10μF

22pF

UP TO 500mA

LTC3559

GND

EXPOSED

PAD

1μF

4.7μH

1.74k

EN2

MODE

BAT

USB (4.3V TO 5.5V)

OR AC ADAPTOR

DIGITAL

CONTROL

SW1

FB1

SW2

FB2

2.5V

400mA

SINGLE

Li-lon CELL

(2.7V TO 4.2V)

1.2V

400mA

3559 TA01

L, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.

All other trademarks are the property of their respective owners.

Summary of content (24 pages)

PAGE 1
LTC3559/LTC3559-1 Linear USB Battery Charger with Dual Buck Regulators DESCRIPTION FEATURES Battery Charger n Standalone USB Charger n Up to 950mA Charge Current Programmable via Single Resistor n HPWR Input Selects 20% or 100% of Programmed Charge Current n NTC Input for Temperature Qualiﬁed Charging n Internal Timer Termination n Bad Battery Detection n CHRG Indicates C/10 or Timeout Buck Regulators n 400mA Output Current n 2.
PAGE 2
LTC3559/LTC3559-1 ABSOLUTE MAXIMUM RATINGS PIN CONFIGURATION (Note 1) NTC PROG CHRG VCC TOP VIEW 16 15 14 13 GND 1 12 HPWR BAT 2 11 SUSP 17 MODE 3 10 FB2 FB1 4 6 7 8 EN1 PVIN SW2 9 5 SW1 VCC (Transient); t < 1ms and Duty Cycle < 1%....................... –0.3V to 7V VCC (Static) .................................................. –0.3V to 6V BAT, CHRG, SUSP ........................................ –0.3V to 6V HPWR, NTC, PROG ....... –0.3V to Max (VCC, BAT) + 0.3V PROG Pin Current ......
PAGE 3
LTC3559/LTC3559-1 ELECTRICAL CHARACTERISTICS The l denotes speciﬁcations that apply over the full operating temperature range, otherwise speciﬁcations are at TA = 25°C. SYMBOL ΔVDUVLO VPROG hPROG ITRKL VTRKL ΔVTRKL ΔVRECHRG tRECHRG tTERM tBADBAT hC/10 tC/10 RON(CHG) TLIM PARAMETER Differential Undervoltage Lockout Hysteresis PROG Pin Servo Voltage CONDITIONS BAT = 4.05V (LTC3559) BAT = 3.
PAGE 4
LTC3559/LTC3559-1 ELECTRICAL CHARACTERISTICS The l denotes speciﬁcations that apply over the full operating temperature range, otherwise speciﬁcations are at TA = 25°C. SYMBOL VFB IFB DMAX RPMOS PARAMETER Feedback Voltage FB Input Current Maximum Duty Cycle RDS(ON) of PMOS CONDITIONS RNMOS RDS(ON) of NMOS ISW = –150mA RSW(PD) SW Pull-Down in Shutdown l FB1, FB2 = 0.
PAGE 5
LTC3559/LTC3559-1 TYPICAL PERFORMANCE CHARACTERISTICS Battery Charge Current vs Supply Voltage 500 500 VCC = 5V 495 HPWR = 5V 490 RPROG = 1.74k 485 EN1 = EN2 = 0V 470 465 460 450 400 400 350 350 300 300 IBAT (mA) IBAT (mA) 475 500 HPWR = 5V VCC = 5V RPROG = 1.74k 450 480 IBAT (mA) Battery Charge Current vs Ambient Temperature in Thermal Regulation Battery Charge Current vs Battery Voltage (LTC3559) 250 200 HPWR = 0V 100 450 445 50 440 0 4.3 4.4 4.5 4.6 4.7 4.8 4.9 5.0 5.1 5.2 5.
PAGE 6
LTC3559/LTC3559-1 TYPICAL PERFORMANCE CHARACTERISTICS CHRG Pin Output Low Voltage vs Temperature 120 CHRG Pin I-V Curve 70 VCC = 5V ICHRG = 5mA VCC = 5V BAT = 3.8V 60 1.5 50 ICHRG (mA) 100 VCHRG (mV) Timer Accuracy vs Supply Voltage 2.0 PERCENT ERROR (%) 140 80 60 40 30 40 20 20 10 0 –55 –35 25 5 45 –15 TEMPERATURE (°C) 65 1 2 4 3 CHRG (V) BAT (V) 4 3 2 CHRG (V) 1 0 –1 65 4.9 VCC (V) 5.3 5.1 VCC = 5V RPROG = 0.845k HPWR = 5V VFB = 0.82V 45 40 PVIN = 4.2V 35 PVIN = 2.
PAGE 7
LTC3559/LTC3559-1 TYPICAL PERFORMANCE CHARACTERISTICS Buck Regulator PMOS RDS(0N) vs Temperature (LTC3559) Buck Regulator Enable Thresholds vs Temperature PVIN = 3.8V 1100 1300 1200 1200 1100 1100 1000 1000 RDS(ON) (mΩ) VEN (mV) 1000 1300 900 800 RISING 700 900 PVIN = 2.7V 800 PVIN = 4.2V 700 FALLING 600 500 500 400 –55 –35 –15 400 –55 –35 –15 100 400 –55 –35 –15 5 25 45 65 85 105 125 TEMPERATURE (°C) 3559 G24 Buck Regulator Load Regulation 2.
PAGE 8
LTC3559/LTC3559-1 TYPICAL PERFORMANCE CHARACTERISTICS Buck Regulator Pulse Skip Mode Operation Buck Regulator Start-Up Transient VOUT 500mV/DIV VOUT 20mV/DIV (AC) INDUCTOR CURRENT IL = 200mA/DIV SW 2V/DIV INDUCTOR CURRENT IL = 50mA/DIV EN 2V/DIV 3559 G33 PVIN = 3.8V 50μs/DIV PULSE SKIP MODE LOAD = 6Ω PVIN = 3.
PAGE 9
LTC3559/LTC3559-1 PIN FUNCTIONS GND (Pin 1): Ground, Connect to Exposed Pad (Pin 17). BAT (Pin 2): Charge Current Output. Provides charge current to the battery and regulates ﬁnal ﬂoat voltage to 4.2V (LTC3559) or 4.1V (LTC3559-1). MODE (Pin 3): MODE Pin for Buck Regulators. When held high, both regulators are in Burst Mode operation. When held low both regulators operate in pulse skip mode. This pin is a high impedance input; do not ﬂoat. FB1 (Pin 4): Buck 1 Feedback Voltage Pin.
PAGE 10
LTC3559/LTC3559-1 BLOCK DIAGRAM 16 VCC BAT BODY MAXER VIN 1x 800x BAT – 12 11 + 15 CHRG HPWR CA LOGIC TA SUSP TDIE PROG NTCA 13 BATTERY CHARGER PVIN 5 9 4 14 NTC NTC REF 3 2 7 MODE EN1 UNDERVOLTAGE LOCKOUT EN2 EN VFB FB1 OT DIE TEMPERATURE TDIE 0.8V – + MODE CLK VC Gm CONTROL LOGIC SW1 6 BUCK REGULATOR 1 10 FB2 BANDGAP VREF OSCILLATOR 2.25MHz CLK EN VFB 0.
PAGE 11
LTC3559/LTC3559-1 OPERATION The LTC3559/LTC3559-1 are linear battery chargers with dual monolithic synchronous buck regulators. The buck regulators are internally compensated and need no external compensation components. The battery charger employs a constant- current/constantvoltage charging algorithm and is capable of charging a single Li-Ion battery at charging currents up to 950mA. The user can program the maximum charging current available at the BAT pin via a single PROG resistor.
PAGE 12
LTC3559/LTC3559-1 APPLICATIONS INFORMATION Suspend Mode The battery charger can also be disabled by pulling the SUSP pin above 1.2V. In suspend mode, the battery drain current is reduced to 1.5μA and the input current is reduced to 8.5μA. Charge Cycle Overview When a battery charge cycle begins, the battery charger ﬁrst determines if the battery is deeply discharged. If the battery voltage is below VTRKL, typically 2.
PAGE 13
LTC3559/LTC3559-1 APPLICATIONS INFORMATION In any mode, the actual battery current can be determined by monitoring the PROG pin voltage and using the following equation: IBAT = PROG • 800 RPROG Thermal Regulation To prevent thermal damage to the IC or surrounding components, an internal thermal feedback loop will automatically decrease the programmed charge current if the die temperature rises to approximately 115°C.
PAGE 14
LTC3559/LTC3559-1 APPLICATIONS INFORMATION NTC Thermistor The battery temperature is measured by placing a negative temperature coefﬁcient (NTC) thermistor close to the battery pack. The NTC circuitry is shown in Figure 3. To use this feature, connect the NTC thermistor, RNTC, between the NTC pin and ground, and a bias resistor, RNOM, from VCC to NTC. RNOM should be a 1% resistor with a value equal to the value of the chosen NTC thermistor at 25°C (R25).
PAGE 15
LTC3559/LTC3559-1 APPLICATIONS INFORMATION Alternate NTC Thermistors and Biasing In the explanation below, the following notation is used. The battery charger provides temperature qualiﬁed charging if a grounded thermistor and a bias resistor are connected to the NTC pin.
PAGE 16
LTC3559/LTC3559-1 APPLICATIONS INFORMATION Solving these equations for RNTC|COLD and RNTC|HOT results in the following: RNTC|HOT = 0.536 • RNOM and RNTC|COLD = 3.25 • RNOM By setting RNOM equal to R25, the above equations result in rHOT = 0.536 and rCOLD = 3.25. Referencing these ratios to the Vishay Resistance-Temperature Curve 1 chart gives a hot trip point of about 40°C and a cold trip point of about 0°C. The difference between the hot and cold trip points is approximately 40°C.
PAGE 17
LTC3559/LTC3559-1 APPLICATIONS INFORMATION Power Dissipation The conditions that cause the LTC3559/LTC3559-1 to reduce charge current through thermal feedback can be approximated by considering the power dissipated in the IC. For high charge currents, the LTC3559/LTC3559-1 power dissipation is approximately: PD = ( VCC – VBAT ) • IBAT where PD is the power dissipated, VCC is the input supply voltage, VBAT is the battery voltage, and IBAT is the charge current.
PAGE 18
LTC3559/LTC3559-1 APPLICATIONS INFORMATION Average, rather than instantaneous, battery current may be of interest to the user. For example, if a switching power supply operating in low-current mode is connected in parallel with the battery, the average current being pulled out of the BAT pin is typically of more interest than the instantaneous current pulses. In such a case, a simple RC ﬁlter can be used on the PROG pin to measure the average battery current as shown in Figure 6.
PAGE 19
LTC3559/LTC3559-1 APPLICATIONS INFORMATION most applications. Experimentation with capacitor sizes between 2pF and 22pF may yield improved transient response if so desired by the user. Buck Switching Regulator Operating Modes The step-down switching regulators include two possible operating modes to meet the noise/power needs of a variety of applications. In pulse skip mode, an internal latch is set at the start of every cycle, which turns on the main P-channel MOSFET switch.
PAGE 20
LTC3559/LTC3559-1 APPLICATIONS INFORMATION leakage pulled to ground through a 10k resistor on the switch (SW1 or SW2) pin when in shutdown. Buck Switching Regulator Dropout Operation It is possible for a step-down switching regulator’s input voltage to approach its programmed output voltage (e.g., a battery voltage of 3.4V with a programmed output voltage of 3.3V). When this happens, the PMOS switch duty cycle increases until it is turned on continuously at 100%.
PAGE 21
LTC3559/LTC3559-1 APPLICATIONS INFORMATION Table 2 Recommended Inductors INDUCTOR TYPE L (μH) MAX IDC(A) MAX DCR(Ω) SIZE IN MM (L × W × H) MANUFACTURER DB318C 4.7 3.3 4.7 3.3 4.7 3.3 1.07 1.20 0.79 0.90 1.15 1.37 0.1 0.07 0.24 0.20 0.13* 0.105* 3.8 × 3.8 × 1.8 3.8 × 3.8 × 1.8 3.6 × 3.6 × 1.2 3.6 × 3.6 × 1.2 3.0 × 2.8 × 1.2 3.0 × 2.8 × 1.2 Toko www.toko.com 4.7 3.3 4.7 3.3 4.7 0.9 1.1 0.5 0.6 0.75 0.11 0.085 0.17 0.123 0.19 4 × 4 × 1.8 4 × 4 × 1.8 3.2 × 3.2 × 1.2 3.2 × 3.2 × 1.2 4.9 × 4.
PAGE 22
LTC3559/LTC3559-1 TYPICAL APPLICATIONS The Output Voltage of a Buck Regulator Is Programmed for 3.3V. When BAT Voltage Approaches 3.3V, the Regulator Operates in Dropout and the Output Voltage Will Be BAT – (ILOAD • 0.6). An LED at CHRG Gives a Visual Indication of the Battery Charger State. A 3-Resistor Bias Network for NTC Sets Hot and Cold Trip Points at Approximately 55°C and 0°C UP TO 950mA ADAPTER 4.5V TO 5.5V VCC 510Ω BAT 1μF 110k + PVIN 2.2μF NTC SINGLE Li-lon CELL 2.7V TO 4.2V (LTC3559) 2.
PAGE 23
LTC3559/LTC3559-1 TYPICAL APPLICATIONS The Battery Can be Charged with Up to 950mA of Charge Current. Buck Regulator 2 Is Enabled Only After VOUT1 Is Up to Approximately 0.7V. This Provides a Sequencing Function Which May Be Desirable in Applications Where a Microprocessor Needs to Be Powered Up Before Peripherals. CHRG Interfaces to a Microprocessor Which Decodes the Battery Charger State UP TO 950mA ADAPTER 4.5V TO 5.5V VCC BAT 1μF 100k + PVIN 2.
PAGE 24
LTC3559/LTC3559-1 RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LTC3550 Dual Input USB/AC Adapter Li-Ion Battery Charger with Adjustable Output 600mA Buck Converter Synchronous Buck Converter, Efﬁciency: 93%, Adjustable Output at 600mA, Charge Current: 950mA Programmable, USB Compatible, Automatic Input Power Detection and Selection LTC3552 Standalone Linear Li-Ion Battery Charger with Adjustable Synchronous Buck Converter, Efﬁciency: >90%, Adjustable Outputs at Output Dual Synchronous Buck Converte