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LTC3450

3450fa

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

All other trademarks are the property of their respective owners.

FEATURES

DESCRIPTIO

APPLICATIO S

TYPICAL APPLICATIO

The LTC

3450 is a complete power converter solution for

small thin film transistor (TFT) liquid crystal display (LCD)

panels. The device operates from a single Lithium-Ion cell,

2- to 3-cell alkaline input or any voltage source between

1.5V and 4.6V.

The synchronous boost converter generates a low noise,

high efficiency 5.1V, 10mA supply. Internal charge pumps

are used to generate 10V, 15V, and –5V, –10V or –15V.

Output sequencing is controlled internally to insure proper

initialization of the LCD panel.

A master shutdown input reduces quiescent current to

<2µA and quickly discharges each output for rapid turn off

of the LCD panel. The LTC3450 is offered in a low profile

(0.75mm), 3mm × 3mm 16-pin QFN package, minimizing

the solution profile and footprint.

■

Cellular Handsets with Color Display

■

Handheld Instruments

■

PDA

■

Generates Three Voltages:

5.1V at 10mA

– 5V, –10V, or –15V at 500µA

10V or 15V at 500µA

■

Better than 90% Efficiency

■

Low Output Ripple: Less than 5mV

P-P

■

Complete 1mm Component Profile Solution

■

Controlled Power-Up Sequence: AV

■

All Outputs Disconnected and Actively Discharged in

Shutdown

■

Low Noise Fixed Frequency Operation

■

Frequency Reduction Input for High Efficiency in

Blank Mode

■

Ultralow Quiescent Current: 75µA (Typ) in Scan Mode

■

Available in a 3mm × 3mm 16-Pin QFN Package

Triple Output Power Supply

for Small TFT-LCD Displays

0.1µF

2.2µF

1.5V TO

4.6V

5.1V/10mA

VGH (3 × AV

)

15V/500µA

VGL

–10V/500µA

3450 TA01

0.1µF

–

0.1µF

–

V2X

V3X

INV

SHDN

MODE

SW V

OUT

NEG

LTC3450

GND

123

OFF ON

BLANK SCAN

47µH

2.2µF

0.47µF

0.1µF

–

5.1V, –10V, 15V Triple Output TFT-LCD Supply

Efficiency vs V

(V)

1.5

EFFICIENCY (%)

100

3.0 4.0

3450 TA01b

2.0 2.5

3.5 4.5 5.0

100µH

47µH

5mA LOAD

Summary of content (12 pages)

PAGE 1
LTC3450 Triple Output Power Supply for Small TFT-LCD Displays U FEATURES DESCRIPTIO ■ The LTC®3450 is a complete power converter solution for small thin film transistor (TFT) liquid crystal display (LCD) panels. The device operates from a single Lithium-Ion cell, 2- to 3-cell alkaline input or any voltage source between 1.5V and 4.6V. ■ ■ ■ ■ ■ ■ ■ ■ ■ Generates Three Voltages: 5.
PAGE 2
LTC3450 U W W W ABSOLUTE AXI U RATI GS U W U PACKAGE/ORDER I FOR ATIO (Note 1) (Referred to GND) ORDER PART NUMBER C2– C2+ VINV V3X TOP VIEW VIN, SW.......................................................... – 0.3 to 7V SHDN, MODE ................................................. – 0.3 to 7V VOUT .......................................................................... – 0.3 to 5.5V VNEG ........................................................................ –17V to 0.
PAGE 3
LTC3450 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 = 5.2V unless otherwise noted. PARAMETER CONDITIONS V3X Output Voltage Load on V3X = 100µA V2X Efficiency Load on V2X = 100µA, (Note 2) 90 V3X Efficiency Load on V3X = 100µA, (Note 2) 80 % Output Impedance V2X, V3X Flying Capacitors = 0.
PAGE 4
LTC3450 U W TYPICAL PERFOR A CE CHARACTERISTICS AVDD Efficiency vs VIN AVDD Efficiency vs VIN 100 100 L = 100µH L = 47µH 10mA 95 95 EFFICIENCY (%) EFFICIENCY (%) 5mA 90 2mA 85 80 10mA 90 5mA 85 2mA 80 75 75 70 (TA = 25°C unless otherwise noted) 70 1.5 2.0 2.5 3.0 3.5 VIN (V) 4.0 4.5 5.0 1.5 2.0 2.5 3.0 3.5 VIN (V) 4.5 4.0 3450 G03 3450 G02 No Load VIN Current in Blank Mode AVDD vs VIN and Load No Load VIN Current in Scan Mode 100 90 800 5.16 700 5.
PAGE 5
LTC3450 U W TYPICAL PERFOR A CE CHARACTERISTICS AVDD Ripple Voltage AVDD Load = 5mA AVDD Transient Response AVDD 100mV/DIV (AC) AVDD 5mV/DIV (AC) AVDD LOAD 5mA 5mA/DIV 1mA VIN = 3.6V C2 = 2.2µF 1µs/DIV 3450 G10 VIN = 3.6V C2 = 2.2µF 100µs/DIV 3450 G11 AVDD Turn-On Showing Inrush Current Limiting AVDD, VGL, VGH Turn-On and Turn-Off Sequence INDUCTOR CURRENT 100mA/DIV VGH 0 10V/DIV 0 AVDD 5V/DIV AVDD 2V/DIV 0 VGL 5V/DIV 0 VIN = 3.6V C2 = 2.2µF 2ms/DIV 3450 G12 VIN = 3.
PAGE 6
LTC3450 U U U PI FU CTIO S C3+ (Pin 1): Charge Pump Inverter Flying Capacitor Positive Node. The charge pump inverter flying capacitor is connected between C3+ and C3 –. The voltage on C3+ will alternate between GND and VINV at an approximate 50% duty cycle while the inverting charge pump is operating. Use a 10nF or larger X5R type ceramic capacitor for best results. SW (Pin 8): Switch Pin. Connect the inductor between SW and VIN.
PAGE 7
LTC3450 U U U PI FU CTIO S V3X (Pin 15): Charge Pump Tripler Output. This output is 15.3V (nom) at no load and is capable of delivering up to 500µA to a load. V3X should be bypassed to GND with a 0.1µF X5R type ceramic capacitor. Connecting VINV to 5V or 10V will generate –5V or –10V respectively on VNEG. See Applications section for –15V generation. Exposed Pad (Pin 17): The exposed pad must be connected to VNEG (Pin 3) on the PCB. Do not connect the exposed pad to GND.
PAGE 8
LTC3450 U OPERATIO The LTC3450 is a highly integrated power converter intended for small TFT-LCD display modules. A fixed frequency, synchronous PWM boost regulator generates a low noise 5.1V, 10mA bias at greater than 90% efficiency from an input voltage of 1.5V to 4.6V. Three charge pump converters use the 5.1V output to generate 10V, 15V and –5V, –10V or –15V at load currents up to 500µA. Each converter is frequency synchronized to the main 550kHz (nominal) boost converter.
PAGE 9
LTC3450 U U W U APPLICATIO S I FOR ATIO Inductor Selection Soft-Start Inductors in the range of 47µH to 100µH with saturation current (ISAT) ratings of at least 150mA are recommended for use with the LTC3450. Ferrite core materials are strongly recommended for their superior high frequency performance characteristics. A bobbin or toroid type core will reduce radiated noise. Inductors meeting these requirements are listed in Table 1.
PAGE 10
LTC3450 U U W U APPLICATIO S I FOR ATIO V3X JUMPER VNEG MODE SHDN VOUT VIN GND NOTE: QFN PACKAGE EXPOSED PAD IS CONNECTED TO THE VNEG PIN. DO NOT CONNECT EXPOSED PAD TO GROUND 3450 F03 Figure 3. Suggested Layout U TYPICAL APPLICATIO 5.1V, –15V, 15V Triple Output TFT-LCD Supply VIN 1.5V TO 4.6V L1 47µH C1 2.2µF BLANK SCAN 8 6 4 7 SW VIN VOUT 11 C1 + 10 C1 – MODE V2X LTC3450 OFF ON 5 SHDN 9 14 C2 – 13 GND VINV VNEG C3 – C3 + 3 2 AVDD 5.1V/10mA CF1 0.
PAGE 11
LTC3450 U PACKAGE DESCRIPTIO UD Package 16-Lead Plastic QFN (3mm × 3mm) (Reference LTC DWG # 05-08-1691) 0.70 ±0.05 3.50 ± 0.05 1.45 ± 0.05 2.10 ± 0.05 (4 SIDES) PACKAGE OUTLINE 0.25 ±0.05 0.50 BSC RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS 3.00 ± 0.10 (4 SIDES) BOTTOM VIEW—EXPOSED PAD 0.23 TYP R = 0.115 (4 SIDES) TYP 15 16 0.75 ± 0.05 PIN 1 TOP MARK (NOTE 6) 0.40 ± 0.10 1 1.45 ± 0.10 (4-SIDES) 2 (UD) QFN 0603 0.200 REF 0.00 – 0.05 NOTE: 1.
PAGE 12
LTC3450 U TYPICAL APPLICATIO 5.1V, – 5V, 15V Triple Output TFT-LCD Supply VIN 1.5V TO 4.6V L1 47µH 8 C1 2.2µF 6 BLANK SCAN 4 7 SW VIN VOUT 11 C1 + 10 C1 – MODE V2X LTC3450 OFF ON 5 SHDN 9 14 C2 – 13 GND VINV VNEG C3 – C3 + 3 2 AVDD 5.1V/10mA CF1 0.1µF 12 C2 + V3X C2 2.2µF CF2 0.1µF 15 C4 0.47µF VGH (3 × AVDD) 15V/500µA 16 C6 0.1µF 1 C5 0.1µF CF3 0.1µF VGL –5V/500µA L1: SUMIDA CMD4D08-470 3450 TA03 RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LT1310 1.5A ISW, 4.