Datasheet

ManualsBrandsLINEAR TECHNOLOGY ManualsPMICsPMIC - power management - special purpose QFN 28 (4x4)

LTC3557/LTC3557-1

35571fc

TYPICAL APPLICATION

FEATURES

APPLICATIONS

DESCRIPTION

USB Power Manager with

Li-Ion Charger and Three

Step-Down Regulators

The LTC

3557/LTC3557-1 is a highly integrated power

management and battery charger IC for single cell Li-Ion/

Polymer battery applications. It includes a PowerPath

manager with automatic load prioritization, a battery

charger, an ideal diode and numerous internal protection

features. Designed speciﬁ cally for USB applications, the

LTC3557/LTC3557-1 power manager automatically limits

input current to a maximum of either 100mA or 500mA

for USB applications or 1A for wall adapter powered

applications. Battery charge current is automatically

reduced such that the sum of the load current and the

charge current does not exceed the programmed input

current limit. The LTC3557/LTC3557-1 also includes three

adjustable synchronous step-down switching regulators

and a high voltage buck regulator output controller with

Bat-Track that allows efﬁ cient charging from supplies as

high as 38V. The LTC3557/LTC3557-1 is available in a low

proﬁ le 4mm × 4mm × 0.75mm 28-pin QFN package.

■

Seamless Transition Between Input Power Sources:

Li-Ion Battery, USB, 5V Wall Adapter or High

Voltage Buck Regulator with Bat-Track

■

200mΩ Internal Ideal Diode Plus Optional External

Ideal Diode Controller Provides Low Loss Power

Path When Input Current is Limited or Unavailable

■

Triple Adjustable High Efﬁ ciency Step-Down

Switching Regulators (600mA, 400mA, 400mA I

OUT

)

■

Pin Selectable Burst Mode

Operation

■

Full Featured Li-Ion/Polymer Battery Charger

■

1.5A Maximum Charge Current with Thermal Limiting

■

Battery Float Voltage:

4.2V (LTC3557)

4.1V (LTC3557-1)

■

Low Proﬁ le 4mm × 4mm 28-Pin QFN Package

■

HDD-Based MP3 Players

■

PDA, PMP, PND/GPS

■

USB-Based Handheld Products

100mA/500mA

1000mA

HV SUPPLY

8V TO 38V

(TRANSIENTS

TO 60V)

USB OR

5V ADAPTER

CHARGE

RST

CC/CV

CHARGER

ALWAYS ON LDO

LTC3557/LTC3557-1

TRIPLE HIGH EFFICIENCY

STEP-DOWN

SWITCHING REGULATORS

HIGH VOLTAGE

BUCK DC/DC

3.3V/25mA

SINGLE CELL

Li-Ion

OUT

0.8V to 3.6V/600mA

0.8V to 3.6V/400mA

NTC

35571 TA01a

, LT, LTC, LTM and Burst Mode are registered trademarks of Linear Technology

Corporation. Bat-Track and PowerPath are trademarks of Linear Technology Corporation.

All other trademarks are the property of their respective owners.

Protected b

U.S. Patents

includin

6522118

6700364. Other

atents

endin

LOAD

(mA)

600

500

400

300

200

100

–100

300 500

35571 TA01b

100 200

400 600

CURRENT (mA)

LOAD

BAT

(CHARGING)

BAT

(DISCHARGING)

WALL = 0V

PROG

= 2k

CLPROG

= 2k

Input and Battery Current vs Load Current

Summary of content (28 pages)

PAGE 1
LTC3557/LTC3557-1 USB Power Manager with Li-Ion Charger and Three Step-Down Regulators FEATURES ■ ■ ■ ■ ■ ■ ■ ■ DESCRIPTION Seamless Transition Between Input Power Sources: Li-Ion Battery, USB, 5V Wall Adapter or High Voltage Buck Regulator with Bat-TrackTM 200mΩ Internal Ideal Diode Plus Optional External Ideal Diode Controller Provides Low Loss Power Path When Input Current is Limited or Unavailable Triple Adjustable High Efﬁciency Step-Down Switching Regulators (600mA, 400mA, 400mA IOUT) Pin Select
PAGE 2
LTC3557/LTC3557-1 ABSOLUTE MAXIMUM RATINGS PIN CONFIGURATION BAT VOUT VBUS ACPR VC CLPROG TOP VIEW 28 27 26 25 24 23 22 ILIM0 1 21 GATE ILIM1 2 20 PROG WALL 3 19 NTC LDO3V3 4 SW1 5 18 VNTC 17 SW3 VIN1 6 16 VIN2 FB1 7 15 SW2 RST2 FB2 FB3 EN3 9 10 11 12 13 14 EN2 8 EN1 29 MODE VBUS, VOUT, VIN1, VIN2 t < 1ms and Duty Cycle < 1% .................. −0.3V to 7V Steady State ............................................. −0.3V to 6V BAT, NTC, CHRG, WALL, VC, MODE, FB1, FB2, FB3, RST2 ..
PAGE 3
LTC3557/LTC3557-1 POWER MANAGER ELECTRICAL CHARACTERISTICS The ● denotes the speciﬁcations which apply over the full operating temperature range, otherwise speciﬁcations are at TA = 25°C. VBUS = 5V, VBAT = 3.8V, ILIM0 = ILIM1 = 5V, WALL = EN1 = EN2 = EN3 = 0V, RPROG = 2k, RCLPROG = 2.1k.
PAGE 4
LTC3557/LTC3557-1 POWER MANAGER ELECTRICAL CHARACTERISTICS The ● denotes the speciﬁcations which apply over the full operating temperature range, otherwise speciﬁcations are at TA = 25°C. VBUS = 5V, VBAT = 3.8V, ILIM0 = ILIM1 = 5V, WALL = EN1 = EN2 = EN3 = 0V, RPROG = 2k, RCLPROG = 2.1k. SYMBOL PARAMETER CONDITIONS MIN TYP MAX ACPR Pin Output High Voltage ACPR Pin Output Low Voltage IACPR = 1mA IACPR = 1mA VOUT − 0.3 VOUT 0 0.
PAGE 5
LTC3557/LTC3557-1 SWITCHING REGULATOR ELECTRICAL CHARACTERISTICS The ● denotes the speciﬁcations which apply over the full operating temperature range, otherwise speciﬁcations are at TA = 25°C. VOUT = VIN1 = VIN2 = 3.8V, MODE = EN1 = EN2 = EN3 = 0V. SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS Step-Down Switching Regulator 2 IVIN2 ILIM2 Pulse-Skip Mode Input Current (Note 10) IOUT = 0, EN2 = 3.8V, MODE = 0V 220 μA Burst Mode Input Current (Note 10) IOUT = 0, EN2 = MODE = 3.
PAGE 6
LTC3557/LTC3557-1 TYPICAL PERFORMANCE CHARACTERISTICS Input Supply Current vs Temperature 0.7 Input Supply Current vs Temperature (Suspend Mode) 0.10 VBUS = 5V 1x MODE 0.20 VBUS = 5V 0.18 3 BUCKS ENABLED 2 BUCKS ENABLED 0.16 0.08 0.6 0.14 0.5 0.06 IVBUS (mA) IVBUS (mA) Battery Drain Current vs Temperature 0.4 IBAT (mA) 0.8 TA = 25°C unless otherwise speciﬁed 0.04 0.3 0.12 0.10 0.08 1 BUCK ENABLED 0.06 0.2 0.04 0.02 0.1 0.
PAGE 7
LTC3557/LTC3557-1 TYPICAL PERFORMANCE CHARACTERISTICS TA = 25°C unless otherwise speciﬁed Forward Voltage vs Ideal Diode Current (with Si2333DS External FET) Forward Voltage vs Ideal Diode Current (No External FET) IBAT vs VBAT 600 0.25 500 40 VBUS = 0V TA = 25°C 0.20 30 VBAT = 3.6V VFWD (mV) VBAT = 4.2V 0.15 VFWD (V) IBAT (mA) 400 300 0.10 200 0 2.0 2.4 2.8 3.2 3.6 VBAT (V) 25 20 15 10 VBUS = 5V 10x MODE RPROG = 2k RCLPROG = 2k 100 VBAT = 3.8V VBUS = 0V TA = 25°C 35 VBAT = 3.
PAGE 8
LTC3557/LTC3557-1 TYPICAL PERFORMANCE CHARACTERISTICS Oscillator Frequency vs Temperature Step-Down Switching Regulator 1 3.3V Output Efﬁciency vs IOUT1 2.5 100 Burst Mode 90 OPERATION 90 VIN = 3.8V 80 80 2.2 VIN = 5V 70 70 2.1 2.0 1.9 VIN = 2.9V 1.8 EFFICIENCY (%) 2.3 EFFICIENCY (%) 60 50 PULSE SKIP 40 30 VIN = 2.7V Burst Mode OPERATION 60 50 PULSE SKIP 40 30 1.7 20 VOUT1 = 3.3V 20 VOUT2 = 1.2V 1.6 10 VIN1 = 3.8V VIN1 = 5V 10 VIN2 = 3.8V VIN2 = 5V 1.
PAGE 9
LTC3557/LTC3557-1 TYPICAL PERFORMANCE CHARACTERISTICS 600mA Step-Down Switching Regulator Feedback Voltage vs Output Current 0.85 0.84 0.84 0.83 0.83 0.81 Burst Mode OPERATION 0.82 FEEDBACK (V) FEEDBACK (V) 400mA Step-Down Switching Regulator Feedback Voltage vs Output Current 0.85 0.82 0.80 0.79 PULSE SKIP 0.79 0.78 0.77 0.75 0.1 1 10 100 OUTPUT CURRENT (mA) 1000 VOUT2 50mV/DIV(AC) Burst Mode OPERATION VOUT1 1V/DIV 0.80 0.77 3.8V 5V Step-Down Switching Regulator Start-Up Waveform 0.
PAGE 10
LTC3557/LTC3557-1 PIN FUNCTIONS VIN2 (Pin 16): Power Input for Step-Down Switching Regulators 2 and 3. This pin will generally be connected to VOUT. SW3 (Pin 17): Power Transmission (Switch) Pin for Step-Down Switching Regulator 3. VNTC (Pin 18): Output Bias Voltage for NTC. A resistor from this pin to the NTC pin will bias the NTC thermistor. NTC (Pin 19): The NTC pin connects to a battery’s thermistor to determine if the battery is too hot or too cold to charge.
PAGE 11
LTC3557/LTC3557-1 BLOCK DIAGRAM 3 25 26 ACPR WALL VC WALL DETECT 24 27 VC CONTROL VBUS VOUT INPUT CURRENT LIMIT CLPROG CC/CV CHARGER + – IDEAL DIODE – + GATE PROG 3.3V LDO 19 VNTC NTC BATTERY TEMP MONITOR OSC 21 15mV BAT 18 23 LDO3V3 VIN1 22 20 4 6 600mA, 2.25MHz BUCK REGULATOR REF SW1 CHRG 5 28 CHARGE STATUS EN FB1 MODE VIN2 ILIM0 1 ILIM1 2 9 10 11 8 14 ILIM LOGIC OSC SW2 EN3 EN LOGIC 16 400mA, 2.
PAGE 12
LTC3557/LTC3557-1 OPERATION Introduction The LTC3557/LTC3557-1 is a highly integrated power management IC that includes a PowerPath controller, battery charger, an ideal diode, an always-on LDO, three synchronous step-down switching regulators as well as a buck regulator VC controller. Designed speciﬁcally for USB applications, the PowerPath controller incorporates a precision input current limit which communicates with the battery charger to ensure that input current never violates the USB speciﬁcations.
PAGE 13
LTC3557/LTC3557-1 OPERATION The LTC3557/LTC3557-1 includes three 2.25MHz constant frequency current mode step-down switching regulators providing 400mA, 400mA and 600mA each. All stepdown switching regulators can be programmed for a minimum output voltage of 0.8V and can be used to power a microcontroller core, microcontroller I/O, memory or other logic circuitry.
PAGE 14
LTC3557/LTC3557-1 OPERATION by the battery via the ideal diodes. The ideal diodes are fast enough to keep VOUT from dropping with just the recommended output capacitor. The ideal diode consists of a precision ampliﬁer that enables an on-chip P-channel MOSFET whenever the voltage at VOUT is approximately 15mV (VFWD) below the voltage at BAT. The resistance of the internal ideal diode is approximately 200mΩ. If this is sufﬁcient for the application, then no external components are necessary.
PAGE 15
LTC3557/LTC3557-1 OPERATION Battery Charger The LTC3557/LTC3557-1 includes a constant current/constant voltage battery charger with automatic recharge, automatic termination by safety timer, low voltage trickle charging, bad cell detection and thermistor sensor input for out of temperature charge pausing. 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 16
LTC3557/LTC3557-1 OPERATION or high ambient thermal conditions and allows the user to push the limits of the power handling capability with a given circuit board design without risk of damaging the LTC3557/LTC3557-1 or external components. The beneﬁt of the LTC3557/LTC3557-1 thermal regulation loop is that charge current can be set according to actual conditions rather than worst-case conditions with the assurance that the battery charger will automatically reduce the current in worst-case conditions.
PAGE 17
LTC3557/LTC3557-1 OPERATION 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 8. To use this feature connect the NTC thermistor, RNTC, between the NTC pin and ground and a bias resistor, RNOM, from VNTC 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 18
LTC3557/LTC3557-1 OPERATION Step-Down Switching Regulator RST2 Operation The RST2 pin is an open-drain output used to indicate that step-down switching regulator 2 has been enabled and has reached its ﬁnal voltage. A 230ms delay is included from the time switching regulator 2 reaches 92% of its regulation value to allow a system controller ample time to reset itself.
PAGE 19
LTC3557/LTC3557-1 OPERATION Step-down 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 20
LTC3557/LTC3557-1 OPERATION The inductor value also has an effect on Burst Mode operation. Lower inductor values will cause Burst Mode switching frequency to increase. Table 3 shows several inductors that work well with the step-down switching regulators. These inductors offer a good compromise in current rating, DCR and physical size. Consult each manufacturer for detailed information on their entire selection of inductors.
PAGE 21
LTC3557/LTC3557-1 APPLICATIONS INFORMATION External HV Buck Control Through the VC Pin compensation components are required on the VC node. The voltage at the VOUT pin is regulated to the larger of (BAT + 300mV) or 3.6V as shown in Figures 6 and 7. The feedback network of the high voltage regulator should be set to generate an output voltage higher than 4.4V (be sure to include the output voltage tolerance of the buck regulator).
PAGE 22
LTC3557/LTC3557-1 APPLICATIONS INFORMATION 3 HVIN 8V TO 36V 68nF 1μF 150k 4 VIN BOOST 1N4148 1 LT3505 2 SW SHDN BZT52C16T 0.1μF 6.8μH MBRM140 49.9k 10μF 806k 20k 6 RT GND 5, 9 LT3505 HIGH VOLTAGE BUCK CIRCUITRY FB VC 10.0k 7 8 Si2333DS 26 3 UP TO 1.2A VOUT 25 VC WALL ACPR 23 VOUT 21 LTC3557 LTC3557-1 GATE 22 BAT COUT Si2333DS (OPT) + BAT Li-Ion 35571 F05 Figure 5. LT3505 Buck Control Using VC (2.
PAGE 23
LTC3557/LTC3557-1 APPLICATIONS INFORMATION Alternate NTC Thermistors and Biasing The LTC3557/LTC3557-1 provides temperature qualiﬁed charging if a grounded thermistor and a bias resistor are connected to NTC. By using a bias resistor whose value is equal to the room temperature resistance of the thermistor (R25) the upper and lower temperatures are pre-programmed to approximately 40°C and 0°C, respectively (assuming a Vishay “Curve 1” thermistor).
PAGE 24
LTC3557/LTC3557-1 APPLICATIONS INFORMATION From the Vishay Curve 1 R-T characteristics, rHOT is 0.2488 at 60°C. Using the above equation, RNOM should be set to 46.4k. With this value of RNOM, the cold trip point is about 16°C. Notice that the span is now 44°C rather than the previous 40°C. This is due to the decrease in “temperature gain” of the thermistor as absolute temperature increases.
PAGE 25
LTC3557/LTC3557-1 APPLICATIONS INFORMATION no additional capacitance on the PROG pin, the battery charger is stable with program resistor values as high as 25k. However, additional capacitance on this node reduces the maximum allowed program resistor. The pole frequency at the PROG pin should be kept above 100kHz.
PAGE 26
LTC3557/LTC3557-1 APPLICATIONS INFORMATION If an external buck switching regulator controlled by the LTC3557/LTC3557-1 VC pin is used instead of a 5V wall adapter we see a signiﬁcant reduction in power dissipated by the LTC3557/LTC3557-1. This is because the external buck switching regulator will drive the PowerPath output (VOUT) to about 3.6V with the battery at 3.3V. If you go through the example above and substitute 3.6V for VOUT we see that thermal regulation does not kick in until about 93°C.
PAGE 27
LTC3557/LTC3557-1 TYPICAL APPLICATION HVIN 8V TO 38V (TRANSIENTS TO 60V) 4 4.7μF 68nF 150k 5 10 40.2k NC NC 6 7 VIN BOOST 0.47μF LT3480 RUN/SS OPTIONAL HIGH VOLTAGE BUCK INPUT 2 SW 3 RT 6.8μH DFLS240L SYNC BD FB PG GND 499k 22μF 1 100k 8 VC 11 9 Si2333DS 26 USB OR 5V WALL ADAPTER 24 25 3 VC WALL ACPR VOUT VBUS 10μF BVIN1 2.1k 27 2k 20 100k 18 19 100k NTC CLPROG BVIN2 PROG CHRG GATE BAT VNTC NTC LDO3V3 VOUT 10μF 23 2.2μF 6 510Ω 2.
PAGE 28
LTC3557/LTC3557-1 PACKAGE DESCRIPTION UF Package 28-Lead Plastic QFN (4mm × 4mm) (Reference LTC DWG # 05-08-1721 Rev A) PIN 1 NOTCH R = 0.20 TYP OR 0.35 s 45o CHAMFER BOTTOM VIEW—EXPOSED PAD 4.00 p 0.10 (4 SIDES) 0.70 p 0.05 0.75 p 0.05 R = 0.05 TYP R = 0.115 TYP 27 28 0.40 p 0.05 PIN 1 TOP MARK (NOTE 6) 1 2 2.64 p 0.10 (4-SIDES) PACKAGE OUTLINE 0.20 p 0.05 0.40 BSC (UF28) QFN 0106 REVA 0.200 REF 0.00 – 0.05 0.20 p 0.05 0.