Datasheet

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LT3463/LT3463A

3463f

Dual Micropower

DC/DC Converters

with Schottky Diodes

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

CCD Bias Supply (15V, –8V)

Efficiency and Power Loss

The LT

3463/LT3463A are dual micropower DC/DC con-

verters with internal Schottky diodes in a 10-lead 3mm ×

3mm

DFN package. Negative and positive LT3463 con-

verters have a 250mA current limit. The LT3463A positive

converter also has a 250mA limit, while the negative

converter has a 400mA limit. Both devices have an input

voltage range of 2.4V to 15V, making them ideal for a wide

variety of applications. Each converter features a quies-

cent current of only 20µA, which drops to under 1µA in

shutdown. A current limited, fixed off-time control scheme

conserves operating current, resulting in high efficiency

over a broad range of load current. The 42V switch enables

high voltage outputs up to ±40V to be easily generated

without the use of costly transformers. The low 300ns off-

time permits the use of tiny, low profile inductors and

capacitors to minimize footprint and cost in space-con-

scious portable applications.

■

Generates Well-Regulated Positive and

Negative Outputs

■

Low Quiescent Current:

A (per Converter) in Active Mode

A in Shutdown Mode

■

Internal 42V Power Switches

■

Internal 42V Schottky Diodes

■

Low V

CESAT

Switch: 180mV at 150mA

■

Input Voltage Range: 2.4V to 15V

■

High Output Voltages: Up to ±40V

■

Low Profile (0.8mm) 3mm x 3mm DFN Package

■

CCD Bias

■

LCD Bias

■

Handheld Computers

■

Digital Cameras

DESCRIPTIO

FEATURES

APPLICATIO S

TYPICAL APPLICATIO

REF

OUT1

15V

10mA

OUT2

–8V

50mA

SW1

FB2

LT3463A

10µH

SHDN2

2.2µF

2.7V

TO 5V

3463 TA01a

GND SW2 D2

1µF

4.7µF

FB1SHDN1

1M 10pF

154k

90.9k

4.7µF

10µH

LOAD CURRENT (mA)

0.1

EFFICIENCY (%)

POWER LOSS (mW)

1 10 100

3463 TA01b

–8V LOSS

160

200

240

120

= 3.6V

15V EFFICIENCY

–8V EFFICIENCY

15V LOSS

Summary of content (8 pages)

PAGE 1
LT3463/LT3463A Dual Micropower DC/DC Converters with Schottky Diodes U FEATURES ■ ■ ■ ■ ■ ■ ■ ■ DESCRIPTIO The LT®3463/LT3463A are dual micropower DC/DC converters with internal Schottky diodes in a 10-lead 3mm × 3mm DFN package. Negative and positive LT3463 converters have a 250mA current limit. The LT3463A positive converter also has a 250mA limit, while the negative converter has a 400mA limit. Both devices have an input voltage range of 2.
PAGE 2
LT3463/LT3463A U W W W ABSOLUTE AXI U RATI GS U W U PACKAGE/ORDER I FOR ATIO (Note 1) VIN, SHDN1, SHDN2 Voltage ................................... 15V SW1, SW2, VOUT1 Voltage ....................................... 42V D2 Voltage ............................................................. –42V FB1, FB2 Voltage Range .............................. –0.3V to 2V Junction Temperature ........................................... 125°C Operating Ambient Temperature Range (Note 2) ........................
PAGE 3
LT3463/LT3463A U W TYPICAL PERFOR A CE CHARACTERISTICS VCESAT and VDIODE Voltage 900 VREF and VFB1 Voltage FOR BOTH SWITCHERS VFB2 Voltage 1.27 10 1.26 8 600 VREF 1.25 500 400 VFB1 1.24 300 200 6 4 2 1.23 ISWITCH = 150mA 0 –50 –25 0 25 50 75 100 1.
PAGE 4
LT3463/LT3463A U U U PI FU CTIO S SHDN1 (Pin 9): Shutdown Pin for Switcher 1. Pull this pin above 1.5V to enable Switcher 1. Pull below 0.3V to turn it off. Do not leave this pin floating. GND (Pin 11): Exposed Pad. Solder this exposed pad directly to the local ground plane. This pad must be electrically connected for proper operation. FB1 (Pin 10): Feedback Pin for Switcher 1. Set the output voltage by selecting values for R1 and R2.
PAGE 5
LT3463/LT3463A U U W U APPLICATIO S I FOR ATIO Choosing an Inductor Several recommended inductors that work well with the LT3463 are listed in Table 1, although 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. Many different sizes and shapes are available. Use the equations and recommendations in the next few sections to find the correct inductance value for your design. Table 1.
PAGE 6
LT3463/LT3463A U U W U APPLICATIO S I FOR ATIO output voltages from a high input voltage source will often exceed the 50V maximum switch rating. For instance, a 12V to – 40V converter using the inverting topology would generate 52V on the SW pin, exceeding its maximum rating. For this application, an inverting charge pump is the best topology. The formula below calculates the approximate inductor value to be used for an inverting charge pump regulator using the LT3463.
PAGE 7
LT3463/LT3463A U TYPICAL APPLICATIO Dual Output ±20V Converter VIN 2.7V TO 5V L1 10µH C1 1µF 3 2 9 SHDN1 FB1 LT3463 8 SHDN2 GND R2 1M 1 SW1 VOUT1 VIN VREF FB2 SW2 D2 4 5 11 C4 0.1µF L2 10µH VOUT1 20V 9mA R1 66.5k 10 C2 0.47µF 7 6 R3 61.9k R4 1M D1 VOUT2 –20V 9mA C3 0.47µF 3463 TA02 U PACKAGE DESCRIPTIO DD Package 10-Lead Plastic DFN (3mm × 3mm) (Reference LTC DWG # 05-08-1699) R = 0.115 TYP 6 0.38 ± 0.10 10 0.675 ±0.05 3.50 ±0.05 1.65 ±0.05 2.15 ±0.05 (2 SIDES) 3.
PAGE 8
LT3463/LT3463A U TYPICAL APPLICATIO CCD Bias Supply VIN 2.7V TO 5V L1 10µH C1 4.7µF 3 VIN 9 2 FB1 LT3463A 8 SHDN2 GND 11 R2 1M 1 SW1 VOUT1 SHDN1 VREF FB2 SW2 10 R1 90.9k C2 2.2µF 7 6 R3 154k D2 4 L2 10µH VOUT1 15V 10mA 5 C4 1µF D1 C1: TAIYO YUDEN JMK212BJ475MG C2: TAIYO YUDEN EMK316BJ225ML C3: TAIYO YUDEN LMK316BJ475ML C4: TAIYO YUDEN EMK212BJ105MG C5: AVX 06035A100KAT2A D1: DIODES, INC B0540W L1, L2: MURATA LQH32CN100K53 Typical Waveforms for 15V Output C5 10pF R4 1M C3 4.