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LTC3675/LTC3675-1

36751fc

For more information www.linear.com/LTC3675

Typical applicaTion

DescripTion

7-Channel Configurable

High Power PMIC

The LT C

3675/LTC3675-1 are a digitally programmable

high efficiency multioutput power supplies plus dual

string LED driver ICs optimized for high power single cell

Li-Ion/Polymer applications. The DC/DCs consist of four

synchronous buck converters (1A/1A/500mA/500mA), one

synchronous boost DC/DC (1A), and one buck-boost DC/

DC (1A) all powered from a 2.7V to 5.5V input. The 40V

LED driver can regulate up to 25mA of current through

two LED strings with up to 10 LEDs each. The LED driver

may also be configured as a general purpose high voltage

boost converter.

DC/DC enables, output voltages, switch slew rates and

operating modes may all be independently programmed

over I

C or used in standalone mode via simple I/O and

power-up defaults. The buck DC/DCs may be used indepen-

dently or paralleled to achieve higher output currents with

a shared inductor. LED enable, 60dB brightness control

and up/down gradation are programmed using I

C. Alarm

levels for low V

and high die temperature may also be

programmed via I

C with a maskable interrupt output to

monitor DC/DC and system faults.

Pushbutton

ON/OFF/RESET control and a power-on reset

output provide flexible and reliable power-up sequencing.

The LTC3675/LTC3675-1 are available in a low profile

(0.75mm), thermally enhanced 44-lead 4mm × 7mm

QFN package.

FeaTures

applicaTions

Four Monolithic Synchronous Buck DC/DCs

(1A/1A/500mA/500mA)

Buck DC/DCs Can Be Paralleled to Deliver Up to

2× Current with a Single Inductor

Independent 1A Boost and 1A Buck-Boost DC/DCs

Dual String I

C Controlled 40V LED Driver

C Programmable Output Voltage, Operating

Mode, and Switch Node Slew Rate for All DC/DCs

C Read Back of DC/DC, LED Driver, Fault Status

C Slave Address Options: LTC3675 = 0001001X,

LTC3675-1 = 0110100X

Maskable Interrupts to Report DC/DC, V

and Die

Temperature Faults

Pushbutton ON/OFF/RESET

Always-On 25mA LDO

Low Quiescent Current: 16µA (All DC/DCs Off)

4mm × 7mm × 0.75mm 44-Lead QFN Package

High Power (5W to 10W) Single Cell Li-Ion/Polymer

Applications

Portable Industrial Applications, Handy Terminals,

Portable Instruments

Multioutput Low Voltage Power Supplies

L, LT, LT C , LT M , Linear Technology, the Linear logo and Burst Mode are registered trademarks

of Linear Technology Corporation and Hot Swap is a trademark of Linear Technology Corporation.

All other trademarks are the property of their respective owners.

LTC3675/

LTC3675-1

EXPOSED PAD

0.01µF

PUSH BUTTON

DIGITAL

CONTROL

2.7V TO 5.5V

•

EN1

EN2

EN3

EN4

ENBB

IRQB

RSTB

WAKE

PBSTAT

ONB

SW1

SW2

SW3

SW4

SW5

VOUT5

SWAB6

SWCD6

VOUT6

LDO_OUT

SW7

LED1

LED2

0.425V TO V

, 1A MAX

0.425V TO V

, 1A MAX

0.425V TO V

, 500mA MAX

0.425V TO V

, 500mA MAX

TO 5.35V, 1A MAX

2.65V TO 5.25V, 1A MAX

0.8V TO V

, 25mA MAX

36751 TA01

•

UP TO 10 LEDS

PER STRING

Summary of content (38 pages)

PAGE 1
LTC3675/LTC3675-1 7-Channel Configurable High Power PMIC Features n n n n n n n n n n n n Description Four Monolithic Synchronous Buck DC/DCs (1A/1A/500mA/500mA) Buck DC/DCs Can Be Paralleled to Deliver Up to 2× Current with a Single Inductor Independent 1A Boost and 1A Buck-Boost DC/DCs Dual String I2C Controlled 40V LED Driver I2C Programmable Output Voltage, Operating Mode, and Switch Node Slew Rate for All DC/DCs I2C Read Back of DC/DC, LED Driver, Fault Status I2C Slave Address Options: LTC3675
PAGE 2
LTC3675/LTC3675-1 Table of Contents Features............................................................................................................................. 1 Applications........................................................................................................................ 1 Typical Application................................................................................................................ 1 Description............................................................
PAGE 3
LTC3675/LTC3675-1 Absolute Maximum Ratings Pin Configuration (Note 1) 44 SWCD6 43 SDA 42 VOUT6 41 DVCC 40 VIN 39 SCL 38 SWAB6 TOP VIEW EN1 1 FB1 2 FB2 3 EN2 4 SW1 5 VIN 6 VIN 7 SW2 8 SW3 9 VIN 10 SW4 11 EN3 12 EN4 13 FB4 14 FB3 15 45 GND 37 ENBB 36 FB6 35 FB5 34 VIN 33 VOUT5 32 SW5 31 VIN 30 LDO_OUT 29 LDOFB 28 ONB 27 LED_FS 26 WAKE 25 PBSTAT 24 IRQB 23 RSTB LED_0V 16 LED1 17 SW7 18 SW7 19 SW7 20 LED2 21 CT 22 VIN, VOUT5, VOUT6 , FB1-6, LED_OV, EN1-4, ENBB, LED_ FS, CT, WAKE, PBSTAT, IRQB, RSTB, ONB
PAGE 4
LTC3675/LTC3675-1 Electrical Characteristics The l denotes the specifications which apply over the full operating junction temperature range, otherwise specifications are at TA = 25°C. VIN = 3.6V. (Note 2) SYMBOL PARAMETER VIN Input Supply Range l 2.7 VIN_FALLING Falling Undervoltage Threshold l 2.35 VIN_RISING Rising Undervoltage Threshold l 2.45 VIN_WARN Falling Undervoltage Warning Threshold VIN_HYS CONDITIONS MIN TYP MAX UNITS 5.5 V 2.45 2.55 V 2.55 2.
PAGE 5
LTC3675/LTC3675-1 Electrical Characteristics The l denotes the specifications which apply over the full operating junction temperature range, otherwise specifications are at TA = 25°C. VIN = 3.6V.
PAGE 6
LTC3675/LTC3675-1 Electrical Characteristics The l denotes the specifications which apply over the full operating junction temperature range, otherwise specifications are at TA = 25°C. VIN = 3.6V. (Note 2) SYMBOL PARAMETER CONDITIONS IFB6 Feedback Leakage Current VFB6 = 0.
PAGE 7
LTC3675/LTC3675-1 Electrical Characteristics The l denotes the specifications which apply over the full operating junction temperature range, otherwise specifications are at TA = 25°C. VIN = 3.6V. (Note 2) SYMBOL PARAMETER CONDITIONS MIN TYP MAX tBUF Bus Free Time Between Stop and Start Condition 1.3 µs tHD_SDA Hold Time After Repeated Start Condition 0.6 µs tSU_STA Repeated Start Condition Set-Up Time 0.6 µs tSU_STO Stop Condition Set-Up Time 0.
PAGE 8
LTC3675/LTC3675-1 Typical Performance Characteristics Undervoltage Threshold vs Temperature Input Supply Current vs Temperature 2.70 2.55 2.50 VIN_FALLING 2.45 40 2.40 35 2.35 30 2.30 25 VIN = 3.6V VIN = 5.5V 20 15 36751 G01 420 EN FALLING 500 80 405 EN RISING 400 EN FALLING 395 390 400 –55 –35 –15 380 –55 –35 –15 60 50 40 0 5 25 45 65 85 105 125 TEMPERATURE (°C) 1.220 90 1.216 80 1.212 70 1.208 60 1.
PAGE 9
LTC3675/LTC3675-1 Typical Performance Characteristics 1A Buck Regulators, Transient Response (Pulse-Skipping Mode) TA = 25°C, unless otherwise noted. 1A Buck Regulators, No Load Start-Up Transient (Pulse-Skipping Mode) 1A Buck Regulators, Transient Response (Burst Mode Operation) VIN = 3.
PAGE 10
LTC3675/LTC3675-1 Typical Performance Characteristics 500mA Buck Regulators Transient Response (Pulse-Skipping Mode) TA = 25°C, unless otherwise noted. 500mA Buck Regulators No Load Start-Up Transient (Pulse-Skipping Mode) 500mA Buck Regulators Transient Response (Burst Mode Operation) VIN = 3.6V VOUT3 100mV/DIV AC-COUPLED VOUT3 100mV/DIV AC-COUPLED INDUCTOR CURRENT 100mA/DIV INDUCTOR CURRENT 100mA/DIV 500mA Buck Regulators, VOUT3 vs Temperature PULSE-SKIPPING MODE, LOAD = 250mA 1.0 1.45 0.9 1.
PAGE 11
LTC3675/LTC3675-1 Typical Performance Characteristics Boost Regulator Transient Response (PWM Mode) Boost Regulator, Line Regulation 5.020 5.016 PWM MODE VOUT5 100mV/DIV AC-COUPLED 5.012 VOUT5 (V) 5.008 LOAD = 500mA 5.004 5.000 LOAD = 100mA 4.996 INDUCTOR CURRENT 200mA/DIV 4.992 4.988 200µs/DIV 4.984 4.980 2.7 3.1 3.5 3.9 4.3 VIN (V) 4.7 5.1 36751 G29 LOAD STEP = 100mA to 600mA VIN = 3.6V, VOUT5 = 5V 5.
PAGE 12
LTC3675/LTC3675-1 Typical Performance Characteristics 100 Buck-Boost Regulator, Load Regulation Buck-Boost Regulator, Efficiency vs Load 3.35 90 3.33 70 VIN = 3.6V VIN = 2.7V 60 3.32 VOUT6 (V) EFFICIENCY (%) 80 VIN = 5.5V 50 40 30 VIN = 4.2V 3.31 3.30 VIN = 2.7V 3.29 VIN = 3.6V 3.28 20 Burst Mode OPERATION 3.27 10 PWM MODE 3.26 0 PWM MODE 3.34 1 10 100 LOAD CURRENT (mA) 3.
PAGE 13
LTC3675/LTC3675-1 Typical Performance Characteristics PWM MODE, LOAD = 500mA 3.38 2.90 0.60 2.85 0.55 3.36 2.80 3.34 2.75 VIN = 5.5V 3.32 3.30 IFWD6 (A) VIN = 3.6V 3.28 VIN = 2.7V 3.26 0.40 2.70 VIN = 2.7V VIN = 3.6V 2.65 2.60 2.50 3.22 2.45 3.20 –55 –35 –15 2.40 –55 –35 –15 VIN = 4.2V LED Driver, Forward Current Limit vs Temperature 2.05 2.00 VIN = 2.7V 70 1.95 60 IFWD6 (A) 40 50 40 1.85 20 20 1.
PAGE 14
LTC3675/LTC3675-1 Pin Functions EN1 (Pin 1): Buck Regulator 1 Enable Input. Active high. This pin is a high impedance input; do not float. EN4 (Pin 13): Buck Regulator 4 Enable Input. Active high. This pin is a high impedance input; do not float. FB1 (Pin 2): Buck Regulator 1 Feedback Pin. Receives feedback by a resistor divider connected across the output. FB4 (Pin 14): Buck Regulator 4 Feedback Pin. Receives feedback by a resistor divider connected across the output.
PAGE 15
LTC3675/LTC3675-1 Pin Functions WAKE (Pin 26): Open Drain Output. When the ONB pin is pressed and released, the signal is debounced and the WAKE signal is held HIGH for a minimum time period that is scaled by the CT capacitor. FB5 (Pin 35): Boost Regulator Feedback Pin. Receives feedback by a resistor divider connected across the output. LED_FS (Pin 27): A resistor connected from this pin to GND programs full-scale LED current. ENBB (Pin 37): Buck-Boost Regulator Enable Input. Active high.
PAGE 16
LTC3675/LTC3675-1 Block Diagram 34 VIN VIN 33 VOUT5 BOOST REGULATOR VIN 6 SW1 5 FB1 2 EN1 32 SW5 35 FB5 BUCK-BOOST REGULATOR 40 VIN BUCK REGULATOR 1 1A 42 VOUT6 A D 1 MODULATION CONTROL MASTER/SLAVE LINES 38 SWAB6 B 44 SWCD6 C VIN 7 SW2 8 FB2 3 EN2 4 BUCK REGULATOR 2 1A 36 FB6 VIN REF, CLK 37 ENBB 17 LED1 MASTER/SLAVE LINES SW3 9 FB3 15 BANDGAP, OSCILLATOR, UV, OT 18,19, 20 LED DRIVER BUCK REGULATOR 3 500mA LDO EN3 12 VIN 10 21 LED2 MODULATION CONTROL – + FB4 14
PAGE 17
LTC3675/LTC3675-1 Operation The LTC3675/LTC3675-1 have six monolithic synchronous switching regulators and a dual string boost LED driver and is designed to operate from a single Li-Ion battery. All of the switching regulators and the LED driver are internally compensated and need only external feedback resistors for regulation. The switching regulators also offer two operating modes: Burst Mode operation for higher efficiency at light loads and pulse-skipping/PWM mode.
PAGE 18
LTC3675/LTC3675-1 Operation regulator 1 is the master. The feedback network connected to the FB1 pin programs the output voltage to 1.2V. The FB2 pin is tied to VIN, which configures buck regulator 2 as the slave. The SW1 and SW2 pins must be tied together. The register contents of the master program the combined buck regulator’s behavior and the register contents of the slave are ignored. The slave buck control circuitry draws no current.
PAGE 19
LTC3675/LTC3675-1 Operation The gradation circuit will then ramp the current to the programmed value at a rate determined by the gradation rate bits. Once the LED driver reaches this value it will regulate that current until programmed otherwise. If a new value is programmed in the LED brightness register, the LED driver’s current will ramp up or down at the programmed rate until that current is reached. To disable the LED driver, a code of zero is programmed in the LED DAC register.
PAGE 20
LTC3675/LTC3675-1 Operation ONB 5 sec WAKE (TIED TO EN1) PBSTAT (Hi-Z) SEQUENCE UP SEQUENCE DOWN BUCKS 1–4 RSTB 36751 F02a t3 (BUCK REGULATOR’S ENABLE IS NOT REINFORCED BY I2C BEFORE t3) t1 t2 Figure 2a. Power-Up Using WAKE (Sequenced Power-Up, Figure 7) ONB 5 sec WAKE PBSTAT SEQUENCE UP BUCKS 1–4 RSTB 36751 F02b t1 t2 t3 t4 t5 (BUCK REGULATOR 1 IS ENABLED VIA I2C, BEFORE t3) Figure 2b.
PAGE 21
LTC3675/LTC3675-1 Operation Power-Up and Power-Down via Enable Pin or I2C code of 64h will result in a LED current of 19.6mA and a full-scale setting of FFh will result in an LED current of 50mA. The 2xFS mode is only intended for use when the output voltage is below 20V. With the LTC3675/LTC3675-1 in its off state, a regulator can be enabled either via its enable pin or I2C. In Figure 2c, buck regulator 1 is enabled via its enable pin at time t1.
PAGE 22
LTC3675/LTC3675-1 Operation I2C Start and Stop Conditions I2C Slave Address A bus master signals the beginning of communications by transmitting a START condition. A START condition is generated by transitioning SDA from high to low while SCL is high. The master may transmit either the slave write or the slave read address. Once data is written to the LTC3675/LTC3675-1, the master may transmit a STOP condition which commands the LTC3675/LTC3675-1 to act upon its new command set.
PAGE 23
LTC3675/LTC3675-1 Operation Table 1. Summary of I2C Sub-Addresses and Byte Formats.
PAGE 24
LTC3675/LTC3675-1 Operation RSTB MASK REGISTER VIN EXTERNAL PULL-UP RESISTOR RSTB OTHER UNMASKED PGOOD OUTPUTS VOUT AND1 REGULATOR UNMASKED PGOOD OUTPUTS VIN PGOOD 92% OF PROGRAMMED VOUT – COMPARATOR + AND2 EXTERNAL PULL-UP RESISTOR UNMASKED ERROR OTHER UNMASKED ERRORS IRQB SET CLRINT CLR LATCHED STATUS REGISTER IRQB MASK REGISTER REAL TIME STATUS REGISTER 36751 F04 Figure 4. Simplified Schematic Showing RSTB and IRQB Signal Path is acknowledged by the LTC3675/LTC3675-1.
PAGE 25
LTC3675/LTC3675-1 Operation and undervoltage flags. The undervoltage and overtemperature faults cannot be masked. A fault that causes the IRQB pin to be pulled low is latched. When the fault condition is cleared, the IRQB pin is still maintained in its low state. The user needs to clear the interrupt by using a CLRINT command. On start-up, all PGOOD outputs are unmasked and a poweron reset will cause RSTB to be pulled low. Once all enabled regulators have their output PGOOD for 200ms typical (CT = 0.
PAGE 26
LTC3675/LTC3675-1 Applications Information Buck Regulators Switching Regulator Output Voltage and Feedback Network All four buck regulators are designed to be used with 2.2µH inductors. Tables 4 and 5 show the recommended inductors for the 500mA and 1A buck regulators. The output voltage of the switching regulators is programmed by a resistor divider connected from the switching regulator’s output to its feedback pin and is given by VOUT = VFB (1 + R2/R1) as shown in Figure 5.
PAGE 27
LTC3675/LTC3675-1 Applications Information The input supply needs to be decoupled with a 10µF capacitor while the output needs to be decoupled with two 22µF capacitors. Refer to Capacitor Selection in the Applications Information section for details on selecting a proper capacitor. a 47µF capacitor for a 2A combined buck regulator and 22µF for a 1A combined buck regulator. Refer to “Capacitor Selection” in the Applications Information section for details on selecting a proper capacitor.
PAGE 28
LTC3675/LTC3675-1 Applications Information Optional capacitor CFF is not needed and may compromise loop stability. To ensure loop stability, feedback resistor R1 in Figure 5 should be no greater than 105kΩ. Optional capacitor CFF is not needed and may compromise loop stability. Buck-Boost Regulator LED Driver The buck-boost regulator is an internally compensated voltage mode regulator that is designed to be used with a 2.2µH inductor. Recommended inductors are listed in the Table 8.
PAGE 29
LTC3675/LTC3675-1 Applications Information Table 13. LED Driver Regulator Program Register 1 Bit Format Bit7 x Unused Bit6 Bit5 Mode1 Mode0 Mode1 = Mode0 = 0 is default; both LED pins are regulated. Mode1 = 0 Mode0 = 1; Only LED1 is regulated. (Single string application). Mode1 = 1 Mode0 = 0; LED driver is configured as a high voltage boost regulator. Mode1 = Mode0 = 1; Both LED pins are regulated, but boost is not powered up. In this mode an external voltage is needed to drive the LED’s.
PAGE 30
LTC3675/LTC3675-1 Applications Information Choosing the CT Capacitor The CT capacitor may be used to program the timing parameters associated with the pushbutton. For a given CT capacitor the timing parameters may be calculated as below. CT is in units of µF.
PAGE 31
LTC3675/LTC3675-1 Applications Information Status Byte Read Back When either the RSTB or IRQB pin is pulled low, it indicates to the user that a fault condition has occurred. To find out the exact nature of the fault, the user can read the status registers. There are two status registers. One register provides real time fault condition reporting while a second register latches data when an interrupt has occurred. Figure 4 shows the operation of the real time and latched status registers.
PAGE 32
LTC3675/LTC3675-1 Applications Information connect directly to the ground plane of the part. These capacitors provide the AC current to the internal power MOSFETs and their drivers. It’s important to minimize inductance from these capacitors to the VIN pins of the LTC3675/LTC3675-1. 4. The switching power traces connecting SW1, SW2, SW3, SW4, SW5, SWAB6, SWCD6 and SW7 to their respective inductors should be minimized to reduce radiated EMI and parasitic coupling.
PAGE 33
LTC3675/LTC3675-1 Typical Applications Li-Ion CELL 2.7V TO 4.2V VIN VIN 2.2µF 1.2V 25mA LDO_OUT 10µF SW1 10µF 2.2µH 324k 22µF 324k LDOFB FB1 649k 649k VIN VIN 10µF 2.2µH 2.2µH SW2 SW5 VOUT5 5V, 1A 22µF 22µF 22µF FB5 200k 2.5V 1A 10µF FB2 309k LTC3675/ LTC3675-1 2.2µH VIN 2.2µH SWAB6 SWCD6 VOUT6 10µF 22µF 655k 1.05M 3.3V, 1A 1.2V 1A SW3 322k 590k FB3 FB6 10µF 1.8V 500mA 10µF 475k 105k 2.2µH SW4 DVCC I2C CONTROL 10µF 511k 1µF FB4 1.
PAGE 34
LTC3675/LTC3675-1 Typical Applications Li-Ion CELL 2.7V TO 4.2V VIN 2.2µF 1.2V 25mA VIN 10µF 2.2µH LDO_OUT 10µF 324k 649k 10µF 1.2V 1A SW1 324k LDOFB FB1 VIN VIN 22µF 649k 10µF 2.2µH 2.2µH 5V, 1A 22µF 22µF 22µF SW5 VOUT5 655k 200k 2.2µH 309k LTC3675/ LTC3675-1 10µF VIN 2.2µH SWAB6 SWCD6 VOUT6 3.3V, 1A 22µF FB2 1.05M FB5 2.5V 1A SW2 SW3 590k 332k 10µF 1.8V 500mA 10µF FB3 FB6 475k 105k 2.2µH SW4 DVCC I2C CONTROL 511k 1µF 10µF 1.
PAGE 35
LTC3675/LTC3675-1 Typical Applications Li-Ion CELL 2.7V TO 4.2V VIN VIN 2.2µF 10µF 1.2V 25mA LDO_OUT 10µF 324k SW1 LDOFB 2.2µH SW2 649k 655k 2.2µH VIN SW5 VOUT5 22µF 10µF FB2 1.05M FB5 200k LTC3675/ LTC3675-1 VIN 10µF 2.2µH 2.2µH SWAB6 SWCD6 VOUT6 3.3V, 1A 10µF 22µF 309k 10µF 22µF 22µF FB1 VIN 5V, 1A 22µF 2.5V 2A SW3 22µF 332k 324k SW4 FB6 1.
PAGE 36
LTC3675/LTC3675-1 Package Description Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings. UFF Package Variation: UFF44MA 44-Lead Plastic QFN (4mm × 7mm) (Reference LTC DWG # 05-08-1762 Rev A) 1.48 ±0.05 0.70 ±0.05 4.50 ±0.05 3.10 ±0.05 2.40 REF 1.70 ±0.05 2.56 ±0.05 2.02 ±0.05 2.76 ±0.05 2.64 ±0.05 0.98 ±0.05 PACKAGE OUTLINE 0.20 ±0.05 5.60 REF 6.10 ±0.05 7.50 ±0.05 0.
PAGE 37
LTC3675/LTC3675-1 Revision History REV DATE A 4/12 DESCRIPTION PAGE NUMBER Clarified PGood Threshold Voltage spec, added Min/Max 7 Modified pin function descriptions for RSTB and IRQB 14 Changed figure reference in I2C Interface section 21 Modified PGood Comparator Polarity Figure 4 24 Modified Programming the RSTB and IRQB Mask Registers section 30 Modified Status Byte Read Back section Modified application circuit VIN caps B 10/12 Added part number LTC3675-1 Added new I2C address C 3/1
PAGE 38
LTC3675/LTC3675-1 Typical Application Li-Ion CELL 2.7V TO 4.2V VIN VIN 2.2µF 1.2V 25mA LDO_OUT 10µF SW1 10µF 2.2µH 324k 22µF 324k LDOFB FB1 649k 649k VIN VIN 10µF 2.2µH 2.2µH SW2 SW5 VOUT5 5V, 1A 22µF 22µF 22µF FB5 200k 309k LTC3675/ LTC3675-1 2.2µH VIN 2.2µH SWAB6 SWCD6 VOUT6 10µF 22µF 655k 10µF 2.5V 1A FB2 1.05M 3.3V, 1A 1.2V 1A SW3 332k 590k FB3 FB6 10µF 1.8V 500mA 10µF 475k 105k 2.2µH SW4 DVCC 10µF 511k 1µF I2C CONTROL FB4 1.