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Table Of Contents

LT3495/LT3495B/

LT3495-1/LT3495B-1

3495b1b1fa

TYPICAL APPLICATION

FEATURES

APPLICATIONS

DESCRIPTION

650mA/350mA Micropower

Low Noise Boost Converter

with Output Disconnect

The LT

3495/LT3495B/LT3495-1/LT3495B-1 are low noise

boost converters with integrated power switch, feedback

resistor and output disconnect circuitry. The parts control

power delivery by varying both the peak inductor current

and switch off-time. This novel* control scheme results

in low output voltage ripple as well as high efﬁciency

over a wide load range. For the LT3495/LT3495-1, the

off-time of the switch is not allowed to exceed a ﬁxed

level, guaranteeing the switching frequency stays above

the audio band for the entire load range. The parts feature

a high performance NPN power switch with a 650mA

and 350mA current limit for the LT3495/LT3495B and

LT3495-1/LT3495B-1 respectively. The quiescent current

is a low 60µA, which is further reduced to less than 0.1µA

in shutdown. The internal disconnect circuitry allows the

output voltage to be isolated from the input during shut-

down. An auxiliary reference input (CTRL pin) overrides

the internal 1.235V feedback reference with any lower

value allowing full control of the output voltage during

operation. The LT3495 series are available in a tiny 10-lead

3mm × 2mm DFN package.

OLED Power Supply from One Li-Ion Cell

Low Quiescent Current

60µA in Active Mode

0.1µA in Shutdown Mode

Low Noise Control Scheme (Switching Frequency

Always Stays Above Audible Range for LT3495/-1)

Integrated Power NPN:

650mA Current Limit (LT3495/B)

350mA Current Limit (LT3495-1/B-1)

Integrated Output Disconnect

Integrated Output Dimming

Wide input range: 2.5V to 16V

Wide output range: Up to 40V

Integrated feedback resistor

Tiny 10-Lead 3mm × 2mm DFN Package

OLED Power

Low Noise Power

MP3 Player

Output Voltage Ripple

vs Load Current

Efﬁciency vs Load Current

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

All other trademarks are the property of their respective owners. *Patent pending.

LOAD CURRENT (mA)

0.1

OUT

PEAK-TO-PEAK RIPPLE (mV)

3495 TA01b

10010

1.0µF 0603

CAPACITOR AT V

OUT

2.2µF 1206

CAPACITOR AT V

OUT

SW CAP

SHDN

CTRL

OUT

GND

909k

3495 TA01a

LT3495

4.7µF

1µF

10µH

2.2µF

ONE

Li-Ion

CELL

OUT

16V

70mA

LOAD CURRENT (mA)

EFFICIENCY (%)

POWER LOSS (mW)

3495 TA01c

400

320

160

240

0.1 10 1001

= 3.6V

LOAD FROM CAP

LOAD FROM V

OUT

Summary of content (16 pages)

PAGE 1
LT3495/LT3495B/ LT3495-1/LT3495B-1 650mA/350mA Micropower Low Noise Boost Converter with Output Disconnect FEATURES n n n n n n n n n DESCRIPTION Low Quiescent Current 60µA in Active Mode 0.1µA in Shutdown Mode Low Noise Control Scheme (Switching Frequency Always Stays Above Audible Range for LT3495/-1) Integrated Power NPN: 650mA Current Limit (LT3495/B) 350mA Current Limit (LT3495-1/B-1) Integrated Output Disconnect Integrated Output Dimming Wide input range: 2.
PAGE 2
LT3495/LT3495B/ LT3495-1/LT3495B-1 ABSOLUTE MAXIMUM RATINGS PIN CONFIGURATION (Note 1) VCC Voltage................................................................16V SW Voltage................................................................40V CAP Voltage...............................................................40V VOUT Voltage..............................................................40V SHDN Voltage............................................................10V CTRL Voltage.....................
PAGE 3
LT3495/LT3495B/ LT3495-1/LT3495B-1 ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VCC = 3V, VSHDN = VCC, unless otherwise noted.
PAGE 4
LT3495/LT3495B/ LT3495-1/LT3495B-1 TYPICAL PERFORMANCE CHARACTERISTICS Output Voltage vs Temperature Minimum Switching Frequency 50 0.25 0.00 –0.25 –0.50 –0.
PAGE 5
LT3495/LT3495B/ LT3495-1/LT3495B-1 TYPICAL PERFORMANCE CHARACTERISTICS LT3495 Switching Waveform at 10mA LT3495 Switching Waveform at No Load VOUT VOLTAGE 10mV/DIV AC COUPLED VOUT VOLTAGE 50mV/DIV AC COUPLED SW VOLTAGE 10V/DIV SW VOLTAGE 10V/DIV INDUCTOR CURRENT 100mA/DIV INDUCTOR CURRENT 500mA/DIV VCC = 3.6V VOUT = 16V 10µs/DIV VCC = 3.
PAGE 6
LT3495/LT3495B/ LT3495-1/LT3495B-1 TYPICAL PERFORMANCE CHARACTERISTICS 0.30 600 0.25 500 PMOS CURRENT (mA) OUTPUT VOLTAGE CHANGE (%) Line Regulation 0.20 0.15 0.10 Output Disconnect PMOS Current vs CAP to VOUT Voltage Difference 400 AFTER START-UP 300 200 IN START-UP 100 0.05 0 TA = 25°C unless otherwise noted.
PAGE 7
LT3495/LT3495B/ LT3495-1/LT3495B-1 PIN FUNCTIONS GND (Pins 1, 2): Ground. Tie directly to local ground plane. achieve the desired output voltage, choose R1 according to the following formula: VCC (Pin 3): Input Supply Pin. Must be locally bypassed. R1 = 76 • (VOUT/1.235 – 1)kΩ VOUT (Pin 7): Drain of Output Disconnect PMOS. Place a bypass capacitor from this pin to GND. See Applications information. CTRL (Pin 4): Dimming Pin. If not used, tie CTRL to 1.5V or higher. If in use, drive CTRL below 1.
PAGE 8
LT3495/LT3495B/ LT3495-1/LT3495B-1 OPERATION The LT3495 series utilizes a variable peak current, variable off-time control scheme to provide high efficiency over a wide range of output current. The operation of the part can be better understood by referring to the Block Diagram. The part senses the output voltage by monitoring the voltage on the FB pin. The user sets the desired output voltage by choosing the value of the external top feedback resistor.
PAGE 9
LT3495/LT3495B/ LT3495-1/LT3495B-1 APPLICATIONS INFORMATION Inductor Selection Several inductors that work well with the LT3495/LT3495B are listed in Table 2 and those for the LT3495-1/LT3495B-1 are listed in Table 3. These tables are not complete, and there are many other manufacturers and devices that can be used. Consult each manufacturer for more detailed information and for their entire selection of related parts, as many different sizes and shapes are available. Inductors with a value of 3.
PAGE 10
LT3495/LT3495B/ LT3495-1/LT3495B-1 APPLICATIONS INFORMATION Setting Output Voltage and the Auxiliary Reference Input The LT3495 series is equipped with both an internal 1.235V reference and an auxiliary reference input. This allows the user to select between using the built-in reference and supplying an external reference voltage. The voltage at the CTRL pin can be adjusted while the chip is operating to alter the output voltage for purposes such as display dimming or contrast adjustment.
PAGE 11
LT3495/LT3495B/ LT3495-1/LT3495B-1 APPLICATIONS INFORMATION Maximum Output Load Current Inrush Current The maximum output current of a particular LT3495 series circuit is a function of several circuit variables.
PAGE 12
LT3495/LT3495B/ LT3495-1/LT3495B-1 APPLICATIONS INFORMATION can be set by the value of RCTRL and CCTRL. The following expression can be used to design the soft-start time: Also be aware of the thermal dissipation in the PMOS at all times. In addition, if the input voltage is more than 8V, the PMOS will turn on during shutdown, resulting in the output voltage no longer being blocked from the input. Under this condition, the output voltage will be about 8V lower than the input voltage.
PAGE 13
LT3495/LT3495B/ LT3495-1/LT3495B-1 TYPICAL APPLICATIONS L1 10µH C1 4.7µF 90 CAP VOUT OUTPUT 16V 70mA R1 909k LT3495 TURN ON/OFF SHDN FB VOUT DIMMING CTRL GND C3 1µF 400 VIN = 3.6V LOAD FROM CAP 80 3495 F07a C1: 4.7µF, 6.3V, X5R, 0603 C2: 2.2µF, 25V, X5R, 0805 C3: 1µF, 25V, X5R, 0603 D1: DIODES INC. B0540WS-7 L1: COILCRAFT LPS4018-103MLB 320 LOAD FROM VOUT 70 240 60 160 50 80 40 0.1 POWER LOSS (mW) SW VCC C2 2.
PAGE 14
LT3495/LT3495B/ LT3495-1/LT3495B-1 TYPICAL APPLICATIONS One Li-Ion Cell Input Boost Converter with the LT3495-1/LT3495B-1 L1 10µH SW CAP VCC VOUT OUTPUT 16V 30mA TURN ON/OFF SHDN FB VOUT DIMMING CTRL GND 909k LOAD FROM CAP 80 C2 1µF LT3495B-1/ LT3495-1 250 VIN = 3.6V C3 1µF 200 70 150 LOAD FROM VOUT 60 100 50 50 POWER LOSS (mW) C1 2.2µF D1 EFFICIENCY (%) ONE LI-ION CELL Efficiency vs Load Current 90 3495 F09a 40 0.1 C1: 2.2µF, 6.
PAGE 15
LT3495/LT3495B/ LT3495-1/LT3495B-1 TYPICAL APPLICATIONS Wide Input Range SEPIC Converter with 5V Output C2 1µF INPUT 2.6V TO 12V SW VCC VOUT LT3495B TURN ON/OFF SHDN FB VOUT DIMMING CTRL GND 232k 1000 80 C3 10µF L2 10µH CAP 1200 VCC = 3.3V VOUT = 5V 200mA, VIN = 3.3V, 300mA, VIN = 5V, 500mA, VIN = 8V 800 70 600 60 400 50 3495 TA03a 200 40 0.1 C1: 2.
PAGE 16
LT3495/LT3495B/ LT3495-1/LT3495B-1 TYPICAL APPLICATION Adjustable High Voltage Power Supply Doesn’t Need a Transformer Output vs CTRL 150 DANGER HIGH VOLTAGE! OPERATION BY HIGH VOLTAGE TRAINED PERSONNEL ONLY 3.3V TO 8V INPUT L1 22µH C6 1µF D5 C1 4.7µF D1 SW CAP VCC VOUT SHDN VOUT DIMMING CTRL D2 C1: 4.7µF, 16V, X5R, 0805 C2-C7: 1µF, 50V, X5R, 0805 D1-D5: DIODE INC.