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LTC3530

3530fb

Wide Input Voltage

Synchronous Buck-Boost

DC/DC Converter

The LTC

3530 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 lithium-ion, two-cell

alkaline or NiMH applications where the output voltage is

within the battery voltage range.

The LTC3530 is pin compatible with the LTC3440 buck-

boost DC/DC converter but adds programmable automatic

Burst Mode operation and extends the V

OUT

range to

1.8V. Switching frequencies up to 2MHz are programmed

with an external resistor. Automatic Burst Mode operation

allows the user to program the load current threshold for

Burst Mode operation using a single resistor from the

BURST pin to GND.

Other features include 1μA shutdown, short circuit pro-

tection, programmable soft-start control, current limit

and thermal shutdown. The LTC3530 is available in a

thermally enhanced 10-lead (3mm × 3mm) DFN or MSOP

package.

MP3 Players

Handheld Instruments

Digital Cameras

Smart Phones

Portable GPS Units

Miniature Hard Disk Drive Power

Regulated Output with Input Voltages Above, Below

or Equal to the Output

1.8V to 5.5V Input and 1.8V to 5.25V Output Range

250mA Continuous Output Current from 1.8V V

600mA Continuous/1A Peak Output Current from

Li-Ion

Single Inductor

Synchronous Rectiﬁ cation: Up to 96% Efﬁ ciency

Programmable Automatic Burst Mode

Operation

Output Disconnect in Shutdown

Pin Compatible with the LTC3440

Programmable Frequency from 300kHz to 2MHz

<1μA Shutdown Current

Small Thermally Enhanced 10-Lead (3mm × 3mm)

DFN and 10-Lead MS Packages

Efﬁ ciency

SW1

SHDN/SS

SW2

OUT

BURST

LTC3530

10μF

1.8V TO 5.5V

22μF

OUT

3.3V AT

250mA

576k

0.01μF

10k

560pF

3530 TA01a

4.7μH

33.2k

100k

GND

ONOFF

33pF

15k

LOAD CURRENT (mA)

EFFICIENCY (%)

100

0.1 10 100 100

3350 TA01b

= 2.0V

= 4.2V

= 3.6V

Burst Mode V

= 3.6V

TYPICAL APPLICATION

FEATURES

APPLICATIONS

DESCRIPTION

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

All other trademarks are the property of their respective owners. Patents Pending.

Summary of content (16 pages)

PAGE 1
LTC3530 Wide Input Voltage Synchronous Buck-Boost DC/DC Converter DESCRIPTION FEATURES n n n n n n n n n n n n Regulated Output with Input Voltages Above, Below or Equal to the Output 1.8V to 5.5V Input and 1.8V to 5.25V Output Range 250mA Continuous Output Current from 1.
PAGE 2
LTC3530 ABSOLUTE MAXIMUM RATINGS (Note 1) VIN, VOUT Voltage ......................................... –0.3V to 6V SW1, SW2 Voltage DC............................................................ –0.3V to 6V Pulsed < 100ns ........................................ –0.3V to 7V VC, RT, FB, SHDN/SS, BURST Voltage .......... –0.3V to 6V Operating Temperature (Note 2)............... –40°C to 85°C Maximum Junction Temperature (Note 4)............. 125°C Storage Temperature Range...................
PAGE 3
LTC3530 ELECTRICAL CHARACTERISTICS The l denotes the speciﬁcations which apply over the full operating temperature range, otherwise speciﬁcations are at TA = 25°C. VIN = VOUT = 3.6V, RT = 33.2k, unless otherwise noted. PARAMETER CONDITIONS NMOS Switch Leakage MIN TYP MAX Switches B and C 0.1 5 μA PMOS Switch Leakage Switches A and D 0.1 10 μA NMOS Switch On Resistance Switches B and C 0.21 Ω PMOS Switch On Resistance Switches A and D 0.
PAGE 4
LTC3530 TYPICAL PERFORMANCE CHARACTERISTICS Automatic Burst Mode Threshold vs RBURST 1.84 80 1.82 LEAVE Burst Mode OPERATION 60 50 40 30 ENTER Burst Mode OPERATION 20 Average Input Current Limit vs Temperature 5% 4% 1.78 1.76 1.74 125 175 225 275 325 375 425 475 500 RBURST (kΩ) 1% 0% –1% –2% –4% 1.70 –45 –25 –5 0 2% –3% 1.72 10 VIN = VOUT = 3.3V 3% 1.
PAGE 5
LTC3530 TYPICAL PERFORMANCE CHARACTERISTICS Load Transient Response in Auto Burst Mode Operation, No Load to 500mA Load Transient Response in Fixed Frequency Mode, No Load to 300mA VOUT 100mV/DIV VOUT 100mV/DIV LOAD 0.25A/DIV LOAD 0.25A/DIV 100μs/DIV VIN = 3.6V VOUT = 3.3V COUT = 22μF, X5R CERAMIC TA = 25°C, unless otherwise speciﬁed. 3530 G13 Typical Burst Mode Waveforms VOUT 50mV/DIV INDUCTOR CURRENT 0.25A/DIV 3530 G14 100μs/DIV VIN = 3.6V VOUT = 3.
PAGE 6
LTC3530 PIN FUNCTIONS FB (Pin 9): Feedback Pin. Connect resistor divider tap here. The output voltage can be adjusted from 1.8V to 5.25V. The feedback reference is typically 1.215V. GND (Pin 5): Ground for the IC. VOUT (Pin 6): Output of the Synchronous Rectiﬁer. A ﬁlter capacitor is placed from VOUT to GND. A ceramic bypass capacitor is recommended as close to the VOUT and GND pins as possible. R1 VOUT = 1.215V • 1+ R2 VIN (Pin 7): Input Supply Voltage. Internal VCC for the IC.
PAGE 7
LTC3530 OPERATION The LTC3530 provides high efﬁciency, low noise power for a wide variety of handheld electronic devices. The LTC proprietary topology allows input voltages above, below or equal to the output voltage by properly phasing the output switches. The error amp output voltage on VC determines the output duty cycle of the switches. Since VC is a ﬁltered signal, it provides rejection of frequencies from well below the switching frequency.
PAGE 8
LTC3530 OPERATION Depending on the control voltage, the IC will operate in either buck, buck/boost or boost mode. The VCI voltage is a level shifted voltage from the output of the error amp (VC). The four power switches are properly phased so the transfer between operating modes is continuous, smooth and transparent to the user. When VIN approaches VOUT the buck/boost region is reached where the conduction time of the four switch region is typically 150ns.
PAGE 9
LTC3530 OPERATION The efﬁciency below 1mA becomes dominated primarily by the quiescent current. The Burst Mode operation efﬁciency is given by: EFFICIENCY •ILOAD 40μA +ILOAD where η is typically 90% during Burst Mode operation. Automatic Burst Mode Operation Control Burst Mode operation can be automatic or manually controlled with a single pin. In automatic mode, the IC will enter Burst Mode operation at light load and return to ﬁxed frequency operation at heavier loads.
PAGE 10
LTC3530 OPERATION where f = operating frequency, Hz VIN SHDN/SS ΔIL = maximum allowable inductor ripple current, A VCI VIN(MIN) = minimum input voltage, V VC VIN(MAX) = maximum input voltage, V VOUT = output voltage, V 3530 F05 IOUT(MAX) = maximum output load current Figure 3. Soft-Start The soft-start function is combined with shutdown. When the SHDN/SS pin is brought above 1V typical, the IC is enabled but the EA duty cycle is clamped from VC.
PAGE 11
LTC3530 APPLICATIONS INFORMATION The output capacitance is usually many times larger than the minimum value in order to handle the transient response requirements of the converter. For 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.
PAGE 12
LTC3530 APPLICATIONS INFORMATION where f = switching frequency in MHz. Therefore frequency selection is a compromise between the optimal efﬁciency and the smallest solution size. Closing the Feedback Loop The LTC3530 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 13
LTC3530 TYPICAL APPLICATIONS 1MHz Li-Ion to 3.3V at 500mA Converter with Manual Mode Control L1 3.3μH 2.7V TO 4.2V SW1 VIN LTC3530 RSS 1M CIN 10μF RT CSS RT 0.01μF 33.2k VOUT 3.3V 500mA VOUT R1 1M FB SHDN/SS Li-Ion SW2 VC BURST RZ 10k GND BURST FIXED FREQ CP1 560pF RFF 15k CZ1 33pF COUT 22μF R2 576k CIN: TAIYO YUDEN JMK212BJ106MG COUT: TAIYO YUDEN JMK325BJ226MM L1: TDK RLF7030T-3R3M4R 3530 TA02 1MHz Li-Ion to 3.
PAGE 14
LTC3530 TYPICAL APPLICATIONS High Efﬁciency Li-Ion Powered Constant Current Lumiled Driver L1 3.3μH SW1 SW2 VIN VOUT SD/SS OFF ON CIN 10μF FB VC CP1 1nF LHXL-PW01 R2 100k GND RT 44.2k R3 95.3k 12,810 (R1+R2+R3+R4) ILED = R1 • R3 COUT 4.7μF R4 100k BURST RT R2 = R1/1.5 ILED = 500mA D1 LTC3530 CBURST 470pF R1 301k 3530 TA04a VIN 2.2V TO 4.2V CIN = TAIYO YUDEN JMK212BJ106MG COUT = TAIYO YUDEN JMK325BJ475MM D1 = BAT54 Lumiled Driver Efﬁciency vs LED Current 100 98 VIN = 3.
PAGE 15
LTC3530 PACKAGE DESCRIPTION DD Package 10-Lead Plastic DFN (3mm × 3mm) (Reference LTC DWG # 05-08-1695) R = 0.115 TYP 6 0.38 ± 0.10 10 0.675 ±0.05 3.50 ±0.05 2.15 ±0.05 1.65 ±0.05 (2 SIDES) 1.65 ± 0.10 (2 SIDES) 3.00 ±0.10 (4 SIDES) PIN 1 TOP MARK (SEE NOTE 6) (DD10) DFN 1103 5 0.25 ± 0.05 0.50 BSC 2.38 ± 0.05 (2 SIDES) 0.25 ± 0.05 0.50 BSC 0.75 ±0.05 0.200 REF PACKAGE OUTLINE 1 2.38 ± 0.10 (2 SIDES) 0.00 – 0.05 BOTTOM VIEW—EXPOSED PAD RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS NOTE: 4.
PAGE 16
LTC3530 TYPICAL APPLICATION USB to 5V Converter with Output Disconnect L1 10μH 1nF 2Ω D2** USB 4.35V TO 5.25V R4 1M 4 SW1 SW2 LTC3530 6 7 VIN VOUT 2 C3 * 0.1μF 1 SHDN/SS FB BURST VC RT GND *0 = Burst Mode OPERATION 1 = FIXED FREQUENCY ** LOCATE COMPONENTS AS CLOSE TO IC AS POSSIBLE 33pF R1 1M 15k 9 10 5 RT = 1MHz f 33.2k OSC SD VOUT 5VIN – 435mA MAX 4.