Datasheet

ManualsBrandsLINEAR TECHNOLOGY ManualsPMICsPMIC - DC/DC voltage regulator Converter, Boost QFN 16 EP

LTC3523/LTC3523-2

3523fb

TYPICAL APPLICATION

FEATURES

APPLICATIONS

DESCRIPTION

Synchronous 600mA Step-Up

and 400mA Step-Down

DC/DC Converters

The LTC

3523/LTC3523-2 combine a 600mA step-up

DC/DC converter with a 400mA synchronous step-down

DC/DC converter in a tiny 3mm × 3mm package. The

1.2MHz/2.4MHz switching frequencies minimize the

solution footprint while maintaining high efﬁ ciency. Both

converters feature soft-start and internal compensation,

simplifying the design.

Both the step-up and step-down converters are current

mode controlled and utilize an internal synchronous rec-

tiﬁ er for high efﬁ ciency. The step-up supports 0% duty

cycle operation and the step-down converter supports

100% duty cycle operation to extend battery run time.

If the MODE pin is held high, both converters automati-

cally transition between Burst Mode operation and PWM

operation improving light load efﬁ ciency. Fixed, low noise

1.2MHz/2.4MHz PWM operation is selected when MODE

is grounded.

The LTC3523/LTC3523-2 provide a sub-3μA shutdown

mode, overtemperature shutdown and current limit pro-

tection on both converters. The LTC3523/LTC3523-2 are

housed in a 16-lead 3mm × 3mm × 0.75mm QFN package.

LTC3523 Efﬁ ciency and Power

Loss vs Load Current

Dual High Efﬁ ciency DC/DC Converters:

Step-Up (V

OUT

= 1.8V to 5.25V, I

= 600mA)

Step-Down (V

OUT

= 0.615V to 5.5V, I

OUT

= 400mA)

1.8V to 5.5V Input Voltage Range

Up to 94% Efﬁ ciency

Pin Selectable Burst Mode

Operation

45μA Quiescent Current in Burst Mode Operation

1.2MHz (LTC3523) or 2.4MHz (LTC3523-2)

Switching Frequency

Independent Power Good Indicator Outputs

Integrated Soft-Start

Thermal and Overcurrent Protection

<3μA Quiescent Current in Shutdown

Small 16-Lead 3mm × 3mm × 0.75mm QFN Package

Digital Cameras

Medical Instruments

Industrial Handhelds

GPS Navigators

IN1

SW1 SW2

FB2

MODE

PGOOD2

SHDN2

FB1

PGOOD1

SHDN1

OUT

10pF

10μF

OUT2

STEP-DOWN

OUTPUT

1.2V

200mA

511k

3523 TA01a

634k

365k

4.7μH

IN2

LTC3523

BAT

GND1 GND2 GND3

47μF

2-CELL

ALKALINE

1.8V TO 3.2V

OUT1

STEP-UP

OUTPUT

3.3V

200mA

10μF

OFF ON OFF ON

LOAD CURRENT (mA)

EFFICIENCY (%)

POWER LOSS (mW)

100

0.1 10 100 1000

3523 TA01b

1000

100

0.1

STEP-UP

STEP-DOWN

= 2.4V

OUT1

= 3.3V

OUT2

= 1.2V

OSC

= 1.2MHz

EFFICIENCY

P0WER LOSS

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

All other trademarks are the property of their respective owners.

Summary of content (16 pages)

PAGE 1
LTC3523/LTC3523-2 Synchronous 600mA Step-Up and 400mA Step-Down DC/DC Converters FEATURES DESCRIPTION n The LTC®3523/LTC3523-2 combine a 600mA step-up DC/DC converter with a 400mA synchronous step-down DC/DC converter in a tiny 3mm × 3mm package. The 1.2MHz/2.4MHz switching frequencies minimize the solution footprint while maintaining high efﬁciency. Both converters feature soft-start and internal compensation, simplifying the design.
PAGE 2
LTC3523/LTC3523-2 ABSOLUTE MAXIMUM RATINGS PIN CONFIGURATION (Note 1) VIN1, VIN2, VBAT, VOUT Voltages .................... –0.3V to 6V SHDN1, PGOOD1, PGOOD2, FB1 Voltages .. –0.3V to 6V SHDN2, FB2, MODE Voltages ...... –0.3V to (VIN2 + 0.3V) SW1 Voltage DC.............................................................. 0.3V to 6V Pulse < 100ns .......................................... –0.3V to 7V SW2 Voltage Pulse < 100ns ......... –0.3V to (VIN2 + 0.3V) Operating Temperature Range (Notes 2, 3) ..........
PAGE 3
LTC3523/LTC3523-2 ELECTRICAL CHARACTERISTICS The l denotes the speciﬁcations which apply over the full operating temperature range, otherwise speciﬁcations are at TA = 25°C. VIN1 = VIN2 = VBAT = 2.4V, VOUT = 3.3V, unless otherwise speciﬁed. PARAMETER CONDITIONS MODE Leakage Current VMODE = 5.5V MIN Soft-Start Time TYP MAX 0.01 1 500 UNITS μA μs Step-Up Converter Input Voltage Range Output Voltage Adjust Range (Note 6) l 1.8 5.25 V l 1.8 5.25 V l 1.16 1.20 1.
PAGE 4
LTC3523/LTC3523-2 TYPICAL PERFORMANCE CHARACTERISTICS (TA = 25°C unless otherwise noted) Normalized FBx Reference vs Temperature Normalized Oscillator Frequency vs Temperature 1.00125 NORMALIZED FBx VOLTAGE (V) NORMALIZED FREQUENCY (Hz) 1.05 1.00000 0.99875 0.99750 0.99625 0.99500 –45 –25 15 35 55 –5 TEMPERATURE (°C) 75 VOUT_BST 2V/DIV IL_BST 200mA/DIV SHDN1 2V/DIV 1.00 VOUT = 3.3V VIN = 2.4V COUT = 10μF L1 = 4.7μH 0.
PAGE 5
LTC3523/LTC3523-2 TYPICAL PERFORMANCE CHARACTERISTICS (TA = 25°C unless otherwise noted) Step-Up No-Load Input Current vs VIN 1.3 500 1.2 450 1.0 PMOS 0.9 NMOS 0.8 0.7 Mode Transition Response VOUT_BST 50mV/DIV 400 1.1 INPUT CURRENT (μA) NORMALIZED RDS(ON) (Ω) Normalized RDS(ON) vs Temperature VOUT = 5V 350 VOUT_BCK 20mV/DIV 300 MODE 2V/DIV 250 200 VOUT = 3.3V 150 VOUT1 = 3.3V 200μs/DIV VOUT2 = 1.2V VIN = 2.4V IOUT1 = 20mA IOUT2 = 25mA COUT1 = COUT2 = 10μF L1 = L2 = 4.7μH 100 0.6 0.
PAGE 6
LTC3523/LTC3523-2 PIN FUNCTIONS SW1 (Pin 5): Step-Up Converter Switch Pin. Connect the inductor between SW1 and VIN1. Keep these PCB trace lengths as short and wide as possible to reduce EMI and voltage overshoot. If the inductor current falls to zero or SHDN1 is low, an internal 150Ω anti-ringing resistor is connected from SW1 to VIN1 to minimize EMI. GND1 (Pin 6): Step-Up Converter Power Ground. Connect this pin to the ground plane. GND2 (Pin 7): Step-Down Converter Power Ground.
PAGE 7
LTC3523/LTC3523-2 BLOCK DIAGRAM L1 4.7μH + 16 CIN 47μF 2 SHUTDOWN AND VBIAS 5 VIN1 SHDN1 SW1 BULK CONTROL SIGNALS VOUT ANTI-RING SHDN OSC + – CURRENT SENSE PWM/ILIM COMP MODE + ILIM REF CC1 + CC2 RZ FB1 R1 FB1 + – COUT 10μF 1 R2 1.2V SLP 1.2V –9% STEP-UP OSC OSCILLATOR 15 MODE START-UP SOFT-START AND THERM REG PGOOD1 – + IZERO COMP gm ERROR AMPLIFIER SLOPE COMPENSATION 3 VOUT STEP-UP 1.8V TO 5.25V 4 PWM LOGIC AND DRIVERS MODE –+– VBAT 0.6V 1.
PAGE 8
LTC3523/LTC3523-2 OPERATION The LTC3523 and LTC3523-2 are synchronous step-up and step-down converters housed in a 16-pin QFN package. Operating from inputs down to 1.8V, the devices feature ﬁxed frequency, current mode PWM control for exceptional line and load regulation and transient response. With low RDS(ON) and internal MOSFET switches, the devices maintain high efﬁciency over a wide range of load current. Operation can be best understood by referring to the Block Diagram.
PAGE 9
LTC3523/LTC3523-2 OPERATION Step-Up Anti-Ringing Control The anti-ring circuitry connects a resistor across the inductor to prevent high frequency ringing on the SW1 pin during discontinuous current mode operation. The ringing of the resonant circuit formed by L and CSW (capacitance on SW pin) is low energy, but can cause EMI radiation.
PAGE 10
LTC3523/LTC3523-2 APPLICATIONS INFORMATION frequency ferrite core inductor materials reduce frequency dependent power losses compared to cheaper powdered iron types, improving efﬁciency. The inductor should have low ESR (series resistance of the windings) to reduce the I2R power losses, and must be able to handle the peak inductor current without saturating. Molded chokes and some chip inductors usually do not have enough core to support the peak inductor currents of 1000mA seen on the LTC3523/LTC3523-2.
PAGE 11
LTC3523/LTC3523-2 APPLICATIONS INFORMATION will increase loop bandwidth resulting in a faster transient response. Maximum capacitance values will produce lower ripple. Table 3 shows a list of several ceramic capacitor manufacturers. Consult the manufacturers directly for detailed information on their entire selection of ceramic parts. Table 2. Step-Down Output Capacitor Range vs Programmed Output Voltage VOUT MINIMUM CAPACITANCE (μF) MAXIMUM CAPACITANCE (μF) 0.8 8.4 33.6 1.2 5.6 22.4 1.5 4.5 17.
PAGE 12
LTC3523/LTC3523-2 APPLICATIONS INFORMATION DUAL BUCK-BOOST AND STEP-UP CONVERTER OPERATION into the step-down’s SHDN2 pin. Note that the overall 3.3V converter efﬁciency is the product of the individual efﬁciencies. The LTC3523/LTC3523-2 can be operated in a cascaded conﬁguration as shown in Figure 2, allowing buck-boost and step-up converter operation. Supply rail sequencing is achieved by feeding the step-up converter PGOOD1 VIN 1.8V TO 5.25V 4.
PAGE 13
LTC3523/LTC3523-2 TYPICAL APPLICATIONS Power Sequence Operation VIN 1.8V TO 3.2V 2-CELL ALKALINE + 4.7μF 4.7μH VIN1 VOUT1 STEP-UP OUTPUT 3.3V 200mA VIN2 VBAT 4.7μH SW1 SW2 VOUT FB2 10pF 4.7μF 634k FB1 PGOOD1 365k LTC3523 MODE 511k 10μF VOUT2 STEP-DOWN OUTPUT 1.
PAGE 14
LTC3523/LTC3523-2 TYPICAL APPLICATIONS Li-Ion to 5V/150mA, 2.5V/200mA VIN 2.5V TO 4.2V Li-Ion + 4.7μF 10μH VIN1 VOUT1 STEP-UP OUTPUT 5V 150mA VIN2 VBAT 4.7μH SW1 SW2 VOUT FB2 10pF 10μF FB1 768k PGOOD1 SHDN1 243k LTC3523 MODE VIN 768k 10μF VOUT2 STEP-DOWN OUTPUT 2.5V 200mA 243k PGOOD2 SHDN2 GND1 GND2 GND3 OFF ON OFF ON 3523 TA03 Efﬁciency and Power Loss vs Load Current 1000 100 EFFICIENCY 90 100 70 60 P0WER LOSS 50 40 10 VIN = 3.6V VOUT1 = 5V VOUT2 = 2.5V fOSC = 1.
PAGE 15
LTC3523/LTC3523-2 PACKAGE DESCRIPTION UD Package 16-Lead Plastic QFN (3mm × 3mm) (Reference LTC DWG # 05-08-1691) 0.70 p0.05 3.50 p 0.05 1.45 p 0.05 2.10 p 0.05 (4 SIDES) PACKAGE OUTLINE 0.25 p0.05 0.50 BSC RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS 3.00 p 0.10 (4 SIDES) BOTTOM VIEW—EXPOSED PAD PIN 1 NOTCH R = 0.20 TYP OR 0.25 s 45o CHAMFER R = 0.115 TYP 0.75 p 0.05 15 16 PIN 1 TOP MARK (NOTE 6) 0.40 p 0.10 1 1.45 p 0.10 (4-SIDES) 2 (UD16) QFN 0904 0.200 REF 0.00 – 0.05 NOTE: 1.
PAGE 16
LTC3523/LTC3523-2 RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LTC3400/LTC3400B 600mA (ISW), 1.2MHz, Synchronous Step-Up DC/DC Converters 92% Efﬁciency, VIN: 0.85V to 5V, VOUT(MAX) = 5V, IQ = 19μA/300μA, ISD < 1μA, ThinSOTTM Package LTC3401 1A (ISW), 3MHz, Synchronous Step-Up DC/DC Converter 97% Efﬁciency, VIN: 0.85V to 5V, VOUT(MAX) = 5.5V, IQ = 38μA, ISD < 1μA, 10-Pin MS Package LTC3402 2A (ISW), 3MHz, Synchronous Step-Up DC/DC Converter 97% Efﬁciency, VIN: 0.85V to 5V, VOUT(MAX) = 5.