Datasheet

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LTC3562

3562fa

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

All other trademarks are the property of their respective owners.

FEATURES

APPLICATIONS

DESCRIPTION

C Quad Synchronous

Step-Down DC/DC Regulator

2 × 600mA, 2 × 400mA

The LTC

3562 is a quad high efﬁ ciency monolithic syn-

chronous step-down regulator with an I

C interface. Two

regulators are externally adjustable and can have their

feedback voltages programmed between 425mV and

800mV in 25mV steps (Type A). The other two regulators

are ﬁ xed output regulators whose output voltages can be

programmed between 600mV and 3.775V in 25mV steps

(Type B). All four regulators operate independently and

can be put into pulse skip, LDO, Burst Mode operation,

or forced Burst Mode operation through I

C control. The

Type-A regulators have separate RUN pins that can be

enabled if I

C control is unavailable.

The 2.85V to 5.5V input voltage range makes the LTC3562

ideally suited for single Li-Ion battery-powered applica-

tions. At low output load conditions, the regulators can

be switched into LDO, Burst Mode operation, or forced

Burst Mode operation, extending battery life in portable

systems. The quiescent current drops to under 100μA

with all regulators in LDO mode, and under 0.1μA when

all regulators are shut down.

Switching frequency is internally set to 2.25MHz, allowing

the use of small surface mount inductors and capacitors.

All regulators are internally compensated. The LTC3562 is

available in a low proﬁ le 3mm × 3mm QFN package.

High Efﬁ ciency Quad Step-Down Converter with I

Four Independent I

C Controllable Step-Down

Regulators (2 × 600mA, 2 × 400mA)

Two I

C Programmable Feedback Voltage

Regulators (R600A, R400A): V

425mV to 800mV

Two I

C Programmable Output Voltage Regulators

(R600B, R400B): V

OUT

600mV to 3.775V

Programmable Modes: Pulse Skip, LDO, Burst Mode,

Forced Burst Mode Operation

Quiescent Current < 100μA (All Regulators Enabled

in LDO Mode)

Fixed 2.25MHz Switching Frequency (Pulse Skip

Mode)

Slew Limiting Reduces Switching Noise

Power-On Reset Output for Regulator R600A

Small, Thermally Enhanced, 20-Lead 3mm × 3mm

QFN Package

Miscellaneous Handheld Applications with Multiple

Supply Rails

Personal Information Appliances

Wireless and DSL Modems

Digital Still Cameras

MP3 Players

Portable Instruments

R600x Burst Mode Efﬁ ciency

and Power Loss vs Load Current

TYPICAL APPLICATION

SW400A

SDA

SCL

POR

100k

10pF

3.3

μH4.7μH

634k

μF

FB400A

RUN400A

SW400B

POR600A

SCL SDA DV

SW600A

FB600A

RUN600A

SW600B

OUT400B OUT600B

PGND AGND

LTC3562

OUT

400A

1.5V

400mA

Li-Ion/Polymer

3.4V TO 4.2V

MICROPROCESSOR

3562 TA01

10μF

475k

536k

10pF10

μF

499k

4.7μH

OUT

400B

1.2V

400mA

μF

3.3μH

OUT

600B

3.3V

600mA

OUT

600A

1.8V

600mA

μF

LOAD CURRENT (mA)

0.01

EFFICIENCY (%)

POWER LOSS (mW)

0.1 1 10010 1000

100

1000

0.1

10000

3562 TA01b

= 3.8V

OUT

= 3.3V

OUT

= 1.2V

OUT

= 3.3V

OUT

2.5V

OUT

= 1.2V,

1.8V, 2.5V

OUT

1.8V

Summary of content (20 pages)

PAGE 1
LTC3562 I2C Quad Synchronous Step-Down DC/DC Regulator 2 × 600mA, 2 × 400mA DESCRIPTION FEATURES n n n n n n n n n Four Independent I2C Controllable Step-Down Regulators (2 × 600mA, 2 × 400mA) Two I2C Programmable Feedback Voltage Regulators (R600A, R400A): VFB 425mV to 800mV Two I2C Programmable Output Voltage Regulators (R600B, R400B): VOUT 600mV to 3.775V Programmable Modes: Pulse Skip, LDO, Burst Mode,® Forced Burst Mode Operation Quiescent Current < 100μA (All Regulators Enabled in LDO Mode) Fixed 2.
PAGE 2
LTC3562 ABSOLUTE MAXIMUM RATINGS PIN CONFIGURATION (Notes 1, 2) RUN400A RUN600A DVCC SCL SDA TOP VIEW 20 19 18 17 16 15 POR600A AGND 1 14 FB600A FB400A 2 13 OUT600B 21 OUT400B 3 12 SW600B SW400B 4 11 PGND 7 8 9 10 VIN VIN SW600A 6 VIN PGND 5 SW400A VIN ............................................................... –0.3V to 6V RUN600A ...................................... –0.3V to (VIN + 0.3V) RUN400A ...................................... –0.3V to (VIN + 0.3V) FBx ...............
PAGE 3
LTC3562 ELECTRICAL CHARACTERISTICS The l denotes the speciﬁcations which apply over the full operating temperature range, otherwise speciﬁcations are at TA = 25°C, VIN = 3.8V, unless otherwise noted. PARAMETER CONDITIONS MIN TYP MAX UNITS I2C Port l DVCC Operating Voltage DVCC Operating Current 1.5 DVCC = 1.8V, Serial Port Idle DVCC UVLO Threshold Voltage V 1 μA 1 VIL SDA, SCL (Low Level Input Voltage) V 0.3 • DVCC VIH SDA, SCL (High Level Input Voltage) VOL SDA (Digital Output Low) 5.
PAGE 4
LTC3562 ELECTRICAL CHARACTERISTICS The l denotes the speciﬁcations which apply over the full operating temperature range, otherwise speciﬁcations are at TA = 25°C, VIN = 3.8V, VOUTx = 1.5V, unless otherwise noted. PARAMETER CONDITIONS MIN TYP MAX UNITS Pulse Skip Mode 600 800 1000 mA Regulators R400A, R400B PMOS Switch Current Limit PMOS RDS(ON) 0.5 Ω NMOS RDS(ON) 0.
PAGE 5
LTC3562 TYPICAL PERFORMANCE CHARACTERISTICS Efﬁciency vs Load Current FORCED Burst Mode OPERATION 80 Burst Mode 70 OPERATION 600mA BUCKS 50 40 PULSE SKIP 60 20 VIN = 3.8V VOUT = 1.2V 1 10 IOUT (mA) 100 Burst Mode OPERATION 40 20 10 PULSE SKIP 50 30 0.1 80 600mA BUCKS 70 30 0 0.01 100 VIN = 3.8V VOUT = 1.8V EFFICIENCY (%) EFFICIENCY (%) 600mA BUCKS PULSE SKIP Burst Mode OPERATION 40 0.1 1 10 IOUT (mA) 100 1 10 IOUT (mA) 100 1000 100 VOUT = 1.2V 80 70 70 60 50 40 20 0.
PAGE 6
LTC3562 TYPICAL PERFORMANCE CHARACTERISTICS R600A Feedback Voltage vs Temperature Output Voltage vs Load Current (B Version) 1.220 2.5 0.808 2.4 VIN = 5.5V 0.806 2.3 VIN = 3V 0.804 2.2 0.802 0.800 0.798 0.796 VIN = 3.8V VIN = 2.7V 2.1 2.0 1.9 0.794 1.7 1.6 0.790 –50 –25 25 50 0 TEMPERATURE (°C) 75 1.190 –25 25 50 0 TEMPERATURE (°C) 75 6 IOUT = 0mA VOUT = 1.
PAGE 7
LTC3562 PIN FUNCTIONS AGND (Pin 1): Analog Ground Pin. All small-signal components should connect to this ground, which in turn connects to PGND at one point. FB400A (Pin 2): Feedback Pin for R400A. When the control loop is complete, this pin servos to 1 of 16 possible set-points based on the programmed value from the I2C serial port (see Table 4). OUT400B (Pin 3): Output Voltage Feedback Pin for R400B.
PAGE 8
LTC3562 BLOCK DIAGRAM 17 18 20 19 DVCC SDA SCL DVCC SDA 16 RUN600A I 2C EN 1 SCL MODE DATA 2 VIN 7, 8, 9 RUN400A 4 1 R600A 7 4 D/A REF600A EN 0.425V-0.8V SW600A 10 REF MODE FB FB600A 14 R400A 4 D/A REF400A EN 0.425V-0.8V SW400A MODE FB FB400A 1 6 REF 2 R600B AGND 1 EN 0.6V SW600B 12 REF OUT600B MODE 13 FB 7 R400B 1 EN 0.
PAGE 9
LTC3562 OPERATION Introduction The LTC3562 is a highly integrated power management IC that contains four I2C controllable, monolithic, high efﬁciency step-down regulators. Two regulators provide up to 600mA of output current and the other two regulators produce up to 400mA. All four regulators are 2.25MHz, constant-frequency, current mode switching regulators that can be independently controlled through I2C. All regulators are internally compensated eliminating the need for external compensation components.
PAGE 10
LTC3562 OPERATION VOUT Adjustable (Type-B) Regulators Unlike the Type-A regulators, the two Type-B regulators do not require an external resistor divider network to program its output voltage. Regulators R600B and R400B have feedback resistor networks internal to the chip whose values can be adjusted through I2C control. These internal feedback resistors can be conﬁgured such that the output voltages can be programmed directly. The output voltages can be programmed from 600mV to 3.775V in 25mV increments.
PAGE 11
LTC3562 OPERATION the output capacitor is charged to a voltage slightly higher than the regulation point. The step-down converter then goes into sleep mode, during which the output capacitor provides the load current. In sleep mode, most of the regulator’s circuitry is powered down, helping conserve battery power and increase efﬁciency. When the output voltage drops below a predetermined value, the switching regulator circuitry is powered on and another burst cycle begins.
PAGE 12
LTC3562 OPERATION I2C Interface Acknowledge The LTC3562 may communicate with a host (master) using the standard I2C 2-wire interface. The Timing Diagram in Figure 4 shows the timing relationship of the signals on the bus. The two bus lines, SDA and SCL, must be high when the bus is not in use. External pull-up resistors or current sources, such as the LTC1694 SMBus Accelerator, are required on these lines. The LTC3562 is a receive-only (slave) device.
PAGE 13
LTC3562 OPERATION SUB-ADDRESS ADDRESS DATA BYTE WR 1 1 0 0 1 0 1 0 SDA 1 1 0 0 1 0 1 0 SCL 1 2 3 4 5 6 7 8 A7 A6 A5 A4 A3 A2 A1 A0 B7 B6 B5 B4 B3 B2 B1 B0 ACK A7 A6 A5 A4 A3 A2 A1 A0 ACK 7 6 5 4 3 2 1 0 ACK 9 1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8 9 START STOP 9 3562 F03 Figure 3.
PAGE 14
LTC3562 OPERATION If a Type-A regulator is being programmed, then bits B3 through B0 program the DAC that controls the regulator’s feedback servo voltage. This 4-bit sequence programs the feedback voltage from 425mV to 800mV in 25mV increments (Table 4). Bits B6 through B4 are not used when programming a Type-A regulator. will ignore this stop condition and will not respond until a new start condition, correct address, new set of data and stop condition are transmitted.
PAGE 15
LTC3562 OPERATION Table 5. Type-B Regulator Base Output Voltage Programming Table 3. Regulator Operating Modes A1 A0 B6 B5 B4 B3 B2 TYPE-B REGULATOR BASE OUTPUT VOLTAGE 0 0 0 0 0 0.600 0 0 0 0 1 0.700 0 0 0 1 0 0.800 0 0 0 1 1 0.900 0 0 1 0 0 1.000 0 0 1 0 1 1.100 0 0 1 1 0 1.200 REGULATOR MODE 0 0 Pulse Skip Mode 0 1 LDO Mode 1 0 Forced Burst Mode Operation 1 1 Burst Mode Operation Table 4.
PAGE 16
LTC3562 APPLICATIONS INFORMATION Inductor Selection Many different sizes and shapes of inductors are available from numerous manufacturers. Choosing the right inductor from such a large selection of devices can be overwhelming, but following a few basic guidelines will make the selection process much simpler. The step-down converters are designed to work with inductors in the range of 2.2μH to 10μH. For most applications a 4.
PAGE 17
LTC3562 APPLICATIONS INFORMATION very thin (<1mm tall) ceramic capacitors ideal for use in height-restricted designs. Table 8 shows a list of several ceramic capacitor manufacturers. Table 8. Recommended Ceramic Capacitor Manufacturers AVX www.avxcorp.com Murata www.murata.com Taiyo Yuden www.t-yuden.com Vishay Siliconix www.vishay.com TDK www.tdk.
PAGE 18
LTC3562 TYPICAL APPLICATION Quad Step-Down Converter with Push Button Control and Power Sequencing 100k C5 10μF Li-Ion BATTERY 3.4V TO 4.2V SDA VIN VOUT 600B 3.3V 600mA VOUT 400B 1.2V 400mA L3 3.3μH SCL DVCC LTC3562 SW600B C3 10μF OUT600B R5 100k R1 634k FB600A L4 4.7μH C4 10μF POR600A SW600A L1 3.3μH RUN600A VOUT 600A 1.8V 600mA C6 10pF C1 10μF POR SCL SDA VCC CORE VCC I/O MICROPROCESSOR SW400B OUT400B R2 499k RUN400A VOUT 400A 2.5V 400mA L2 4.
PAGE 19
LTC3562 PACKAGE DESCRIPTION UD Package 20-Lead Plastic QFN (3mm × 3mm) (Reference LTC DWG # 05-08-1720 Rev Ø) 0.70 ±0.05 3.50 ± 0.05 (4 SIDES) 1.65 ± 0.05 2.10 ± 0.05 PACKAGE OUTLINE 0.20 ±0.05 0.40 BSC RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS APPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED 3.00 ± 0.10 (4 SIDES) BOTTOM VIEW—EXPOSED PAD R = 0.115 TYP 0.75 ± 0.05 R = 0.05 TYP PIN 1 TOP MARK (NOTE 6) PIN 1 NOTCH R = 0.20 TYP OR 0.25 × 45° CHAMFER 19 20 0.40 ± 0.10 1 2 1.65 ± 0.
PAGE 20
LTC3562 RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LTC3406/ LTC3406B 600mA IOUT, 1.5MHz, Synchronous Step-Down DC/DC Converter 96% Efﬁciency, VIN(MIN) = 2.5V, VIN(MAX) = 5.5V, VOUT(MIN) = 0.6V, IQ = 20μA, ISD < 1μA, ThinSOT™ Package LTC3407/ LTC3407-2 Dual 600mA/800mA IOUT, 1.5MHz/2.25MHz, Synchronous Step-Down DC/DC Converter 95% Efﬁciency, VIN(MIN) = 2.5V, VIN(MAX) = 5.5V, VOUT(MIN) = 0.6V, IQ = 40μA, ISD < 1μA, MS10E and DFN Packages LTC3410/ LTC3410B 300mA IOUT, 2.