Datasheet

ManualsBrandsLINEAR TECHNOLOGY ManualsPMICsPMIC - DC/DC voltage regulator Converter/amplifier DFN 14

LTC3533

3533f

TYPICAL APPLICATION

FEATURES

APPLICATIONS

DESCRIPTION

2A Wide Input Voltage

Synchronous Buck-Boost

DC/DC Converter

The LTC

3533 is a wide V

range, highly efﬁ cient, ﬁ xed

frequency, buck-boost DC/DC converter that operates

from input voltages above, below or equal to the output

voltage. The topology incorporated in the IC provides a

continuous transfer function through all operating modes,

making the product ideal for single cell lithium-ion/polymer

or multi-cell alkaline/NiMH applications where the output

voltage is within the input voltage range.

The LTC3533 features programmable Burst Mode opera-

tion, extended V

and V

OUT

ranges down to 1.8V, and

increased output current. Switching frequencies up to

2MHz are programmed with an external resistor. The Burst

Mode threshold is programmed with a single resistor from

the BURST pin to GND.

Other features include 1µA shutdown current, short

circuit protection, programmable soft-start, current limit

and thermal shutdown. The LTC3533 is housed in the

thermally enhanced 14-lead (3mm × 4mm × 0.75mm)

DFN package.

Efﬁ ciency

■

Regulated Output with Input Voltages Above,

Below or Equal to the Output

■

1.8V to 5.5V (Input) and 5.25V (Output)

Voltage Range

■

0.8A Continuous Output Current: V

> 1.8V

■

2A Continuous Output Current: V

> 3V

■

Single Inductor

■

Synchronous Rectiﬁ cation: Up to 96% Efﬁ ciency

■

Programmable Burst Mode

Operation: I

= 40µA

■

Output Disconnect in Shutdown

■

Programmable Frequency from 300kHz to 2MHz

■

<1µA Shutdown Current

■

Small Thermally Enhanced 14-Lead (3mm × 4mm ×

0.75mm) DFN package

■

GSM Modems

■

Handheld Instruments

■

Digital Cameras

■

Smart Phones

■

Media Players

■

Miniature Hard Disk Drive Power

SW1

RUN/SS

SW2

OUT

LTC3533

10µF

2.4V TO 4.2V

340k 6.49k

100µF

47pF

OUT

3.3V

1.5A

200k

0.1µF

107k

330pF

4.7pF

3533 TA01

2.2µH

33.2k 200k

PGNDSGND

ONOFF

BURST

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

Corporation. All other trademarks are the property of their respective owners.

OUTPUT CURRENT (mA)

0.1

EFFICIENCY (%)

1 10 100 1000 10000

3533 TA01b

100

Burst Mode

OPERATION

= 3.9V

= 2.2V

= 2.9V

Summary of content (16 pages)

PAGE 1
LTC3533 2A Wide Input Voltage Synchronous Buck-Boost DC/DC Converter DESCRIPTION FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ Regulated Output with Input Voltages Above, Below or Equal to the Output 1.8V to 5.5V (Input) and 5.25V (Output) Voltage Range 0.8A Continuous Output Current: VIN > 1.
PAGE 2
LTC3533 ABSOLUTE MAXIMUM RATINGS PACKAGE/ORDER INFORMATION (Note 1) TOP VIEW VIN, PVIN Voltages ...........................................–0.3 to 6V VOUT, PVOUT Voltages ......................................–0.3 to 6V SW1, SW2 Voltages DC...............................................................–0.3 to 6V Pulsed < 100ns ...........................................–0.3 to 7V VC, FB, RUN/SS, BURST Voltages ..................–0.3 to 6 V Operating Temperature Range (Note 2) ...
PAGE 3
LTC3533 ELECTRICAL CHARACTERISTICS The ● denotes the speciﬁcations which apply over the full operating temperature range, otherwise speciﬁcations are at TA = 25°C. VIN = 3.6V, VOUT = 3.3V, unless otherwise noted. PARAMETER CONDITIONS Frequency Accuracy RT = 33.2k ● MIN TYP MAX 0.7 1 1.3 UNITS MHz Error Amp AVOL 80 dB Error Amp Source Current –20 µA Error Amp Sink Current 250 µA 1 V Burst Threshold Burst Input Current VBURST = 5.5V, VIN = 5.
PAGE 4
LTC3533 TYPICAL PERFORMANCE CHARACTERISTICS Quiescent Current vs VIN (Fixed Frequency Mode) 3.0 1.5 MHz 2.5 1.0 MHz 1.5 0.5 MHz 1.0 NO SWITCHING 50 5 45 4 40 3 CURRENT LIMIT CHANGE (%) VIN QUIESCENT CURRENT (µA) VIN QUIESCENT CURRENT (mA) 2.0 MHz 2.0 35 30 25 20 15 10 2 1 0 –1 –2 –3 0.5 5 –4 0.0 2.5 0 –5 –55 –35 –15 3.0 3.5 4.0 VIN (V) 4.5 5.0 2.5 5.5 3.0 3.5 4.0 VIN (V) 4.5 5.0 5.
PAGE 5
LTC3533 TYPICAL PERFORMANCE CHARACTERISTICS TA = 25°C, unless otherwise speciﬁed. Switch Pins Entering Buck-Boost Mode Switch Pins in Buck-Boost Mode SW1 2V/DIV SW1 2V/DIV Output Ripple at 1A Load VIN = 2.7V VIN = 3.3V SW2 2V/DIV SW2 2V/DIV 50ns/DIV VIN = 3.3V VOUT = 3.3V AT 500mA VIN = 4.2V 3533 G10 50ns/DIV 3533 G11 1µs/DIV VOUT = 3.3V, 20mV/DIV COUT = 100µF CERAMIC 3533 G12 VIN = 4.2V VOUT = 3.3V AT 500mA Load Transient Response in Fixed Frequency Mode, No Load to 1.
PAGE 6
LTC3533 PIN FUNCTIONS RT (Pin 1): Programs the Frequency of the Internal Oscillator. Connect a resistor from RT to ground. f(kHz) = 33,170/RT (kΩ) BURST (Pin 2): Used to set the Automatic Burst Mode Threshold. Connect a resistor and capacitor in parallel from this pin to ground. See the Applications Information section for component value selection. For manual control, ground the pin to force Burst Mode operation, connect to VIN to force ﬁxed frequency PWM mode. SGND (Pin 3): Signal ground for the IC.
PAGE 7
LTC3533 BLOCK DIAGRAM SW2 SW1 VOUT SW D SW B GATE DRIVERS AND ANTI-CROSS CONDUCTION –0.5A SW C – SW A + VIN 1.8V TO 5.5V ISENSE AMP REVERSE CURRENT LIMIT R1 + + SUPPLY CURRENT LIMIT + ERROR AMP + – UVLO + RT PWM LOGIC AND OUTPUT PHASING CLAMP PWM COMPARATORS VC + – – 1.6V FB – – 4.5A 1.
PAGE 8
LTC3533 OPERATION Error Ampliﬁer The error ampliﬁer is a voltage mode ampliﬁer. The loop compensation components are conﬁgured around the ampliﬁer (from FB to VC) to obtain stability of the converter. For improved bandwidth, an additional RC feed-forward network can be placed across the upper feedback divider resistor. The voltage on the RUN/SS pin clamps the error ampliﬁer output, VC, to provide a soft-start function.
PAGE 9
LTC3533 OPERATION D4SW = (150ns • f) • 100 % where f = operating frequency, Hz. Beyond this point the “four switch,” or buck/boost region is reached. Buck/Boost or Four Switch (VIN ~ VOUT) When the control voltage, VC, is above voltage V2, switch pair AD remain on for duty cycle DMAX_BUCK, and switch pair AC begins to phase in. As switch pair AC phases in, switch pair BD phases out accordingly.
PAGE 10
LTC3533 OPERATION For automatic operation a ﬁlter capacitor must also be connected from BURST to ground. The equation for the minimum capacitor value is: CBURST(MIN) ≥ COUT • VOUT 60, 000 where CBURST(MIN) and COUT are in µF. In the event that a load transient causes FB to drop by more than 4% from the regulation value while in Burst Mode operation, the LTC3533 will immediately switch to ﬁxed frequency mode and an internal pull-up will be momentarily applied to BURST, rapidly charging CBURST.
PAGE 11
LTC3533 APPLICATIONS INFORMATION COMPONENT SELECTION where f = switching frequency, Hz ∆IL = maximum allowable inductor ripple current 1 RT VC 14 2 BURST FB 13 VIN(MAX) = maximum input voltage 3 SGND RUN/SS 12 VOUT = output voltage 4 SW1 PVIN 11 5 PGND VIN 10 6 PGND PVOUT 9 VIN(MIN) = minimum input voltage VIN VOUT 7 SW2 8 VOUT GND MULTIPLE VIAS 3533 F04 Figure 4. Recommended Component Placement. Traces Carrying High Current Should be Short and Wide.
PAGE 12
LTC3533 APPLICATIONS INFORMATION requirements of the converter. As a rule of thumb, the ratio of the operating frequency to the unity-gain bandwidth of the converter is the amount the output capacitance will have to increase from the above calculations in order to maintain the desired transient response. to provide the conduction path to the output. Note that Burst Mode operation is inhibited at output voltages below 1V typical.
PAGE 13
LTC3533 APPLICATIONS INFORMATION Closing the Feedback Loop The LTC3533 incorporates voltage mode PWM control. The control to output gain varies with operation region (buck, boost, buck/boost), but is usually no greater than 15.
PAGE 14
LTC3533 TYPICAL APPLICATIONS High Efﬁciency, High Current LED Driver 3.3µH 11 VIN 3V TO 4.2V 10 4 7 SW1 SW2 PVIN PVOUT VIN VOUT 9 ILED = 1A 8 4.7µF LTC3533 OFF ON 12 RUN/SS FB 13 1nF 1 10µF RT VC BURST 14 SGND PGND 44.2k 3 5 100k 2 47pF 95.3k 6 100k 301k 3533 TA02 1MHz Li-Ion to 3.6V at 2A, Pulsed, with Manual Mode Control 6.8µH 11 VIN 3V TO 4.2V 10 4 7 SW1 SW2 PVIN PVOUT VIN VOUT 9 VOUT 3.6V AT 2A 8 388k 220pF LTC3533 OFF ON 12 1 10µF 64.
PAGE 15
LTC3533 PACKAGE DESCRIPTION DE Package 14-Lead Plastic DFN (4mm × 3mm) (Reference LTC DWG # 05-08-1708 Rev A) 0.70 ±0.05 3.60 ±0.05 1.70 ±0.05 2.20 ±0.05 (2 SIDES) PACKAGE OUTLINE 0.25 ± 0.05 0.50 BSC 3.30 ±0.05 (2 SIDES) RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS R = 0.115 TYP 4.00 ±0.10 (2 SIDES) R = 0.05 TYP 3.00 ±0.10 (2 SIDES) 8 0.40 ± 0.10 14 1.70 ± 0.05 (2 SIDES) PIN 1 NOTCH R = 0.20 OR 0.35 × 45° CHAMFER PIN 1 TOP MARK (SEE NOTE 6) (DE14) DFN 0905 REV A 7 0.200 REF 1 0.25 ± 0.05 0.
PAGE 16
LTC3533 RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LTC3400/LT3400B 600mA (ISW), 1.2MHz Synchronous Step-Up DC/DC Converter VIN: 0.85V to 5V, VOUT(MAX) = 5V, IQ = 19µA/300µA, ISD < 1µA, ThinSOT Package LTC3401/LT3402 1A/2A (ISW), 3MHz Synchronous Step-Up DC/DC Converter VIN: 0.5V to 5V, VOUT(MAX) = 6V, IQ = 38mA, ISD < 1µA, MS Package LTC3405/LTC3405A 300mA (IOUT), 1.5MHz Synchronous Step-Up DC/DC Converter VIN: 2.7V to 6V, VOUT(MIN) = 0.