LX1745CPW Microsemi Analog Mixed Signal Group, LX1745CPW Datasheet

LX1745CPW

Manufacturer Part Number

LX1745CPW

Description

IC LED DRVR WT/CLR BCKLT 20TSSOP

Manufacturer

Microsemi Analog Mixed Signal Group

Type

Backlight, White LED, Color LEDr

Datasheet

1.LX1745CPW.pdf (16 pages)

Specifications of LX1745CPW

Constant Current

Yes

Topology

PWM, Step-Up (Boost)

Number Of Outputs

Internal Driver

Both

Type - Primary

Backlight

Type - Secondary

Color, White LED

Voltage - Supply

1.6 V ~ 6 V

Voltage - Output

25V

Mounting Type

Surface Mount

Package / Case

20-TSSOP

Operating Temperature

-40°C ~ 85°C

Current - Output / Channel

100mA

Internal Switch(s)

Yes

Efficiency

90%

Lead Free Status / RoHS Status

Lead free / RoHS Compliant

Frequency

Current page: 1 of 16
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Rev. 1.2, 2006-02-27

efficiency step-up boost regulator for

driving white or color LEDs in LCD

lighting applications while supplying the

necessary LCD bias voltages with an

additional two integrated boost converters.

featuring

topology (that decreases output voltage

ripple), the LX1745 minimizes system cost

and condenses layout area making it ideal

for PDA, smart-phone, and digital camera

applications.

implemented using an internal N-Channel

MOSFET for LCD Bias generation, the

LED driver utilizes an external N-Channel

MOSFET in order to maintain maximum

efficiency along with flexible power

requirements..

optimized for portable systems with a

shutdown current of less than 1µA. The

input voltage range of 1.6V to 6.0 allows

for a wide selection of system battery

voltages

IMPORTANT: For the most current data, consult MICROSEMI’s website:

The LX1745 is a compact high

Designed for maximum efficiency and

While the LCD Bias generation is

The LX1745’s control circuitry is

LCD1

LCD2

= V

to 25V

and

- V

to 25V

BAT

psuedo-hysteretic

LCD

= 1.6V to 6.0V

11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570

start-up

D E S C R I P T I O N

PFM

SW1

FB1

SW2

REF

FB2

GND

SHDN2

1206 Case Size

LX1745

47μH

guaranteed at a V

sustained operation as low as 1.1V.

easily programmed using one external

current sense resistor in series with the

LEDs. In this configuration, LED current

provides a feedback signal to the FB pin,

maintaining constant current regardless of

varying

Depending on the MOSFET selected, the

LX1745 is capable of achieving an LED

drive in excess of 1.0W.

adjustment of the LED drive current (0% to

100% full range dimming) and the LCD

Bias output voltages (up to ±15% typ)

through separate IC interfaces.

interface has an internal RC filter allowing

designers to make these adjustments via a

direct PWM input signal or an analog

reference signal.

amplitude is easily accommodated using a

single external resistor.

profile 20-Pin TSSOP.

Note: Available in Tape & Reel. Append the letters “TR”

to the part number. (i.e. LX1745CPW-TR)

LSHDN

SHDN1

ADJ2

ADJ1

DRV

SRC

OVP

BRT

LFB

The maximum LED drive current is

The LX1745 provides simple dynamic

The LX1745 is available in the low-

-40 to 85

P R O D U C T H I G H L I G H T

P A C K A G E O R D E R I N F O

Integrated Products Division

ON OFF

(°C)

LED

Microsemi

http://www.microsemi.com

forward

LED

4.7μF

RoHS Compliant / Pb-free

= 20mA to 0mA

Triple Output Boost – LED Driver / LCD Bias

Further, any PWM

equal to 1.6V with

Transition DC: 0442

LX1745CPW

15Ω

SET

Plastic TSSOP

20-Pin

voltage

Each

RODUCTION

LX1745 Evaluation Board

> 90% Maximum Efficiency

Low Quiescent Supply Current

Externally Programmable Peak

Inductor Current Limit For

Maximum Efficiency

Logic Controlled Shutdown

< 1µA Shutdown Current

Dynamic Output LED Current

and Two LCD Bias Voltage

Adjustments Via Analog

Reference Or Direct PWM

Input

20-Pin TSSOP Package

Pagers

Smart Phones

PDAs

Handheld Computers

General LCD Bias Applications

LED Driver

K E Y F E A T U R E S

ATASHEET

A P P L I C A T I O N S

LX1745

Page 1

Related parts for LX1745CPW

LX1745CPW Summary of contents

Page 1

... Plastic TSSOP PW 20-Pin T (°C) A RoHS Compliant / Pb-free Transition DC: 0442 - LX1745CPW Note: Available in Tape & Reel. Append the letters “TR” to the part number. (i.e. LX1745CPW-TR) Microsemi Integrated Products Division LX1745 P D RODUCTION ATASHEET > 90% Maximum Efficiency Low Quiescent Supply Current Externally Programmable Peak ...

Page 2

Supply Input Voltage ...........................................................................-0. Feedback Input Voltage (V ) ...............................................-0. FBx Shutdown Input ...

Page 3

TM Name Unregulated IC Supply Voltage Input – Input range from +1.6V to 6.0V. Bypass with a 1μF or greater capacitor IN for operation below 2.0V. DRV LED MOSFET Gate Driver – Connects to an external N-Channel MOSFET. SRC LED ...

Page 4

TM Unless otherwise specified, the following specifications apply over the operating ambient temperature 0°C otherwise noted and the following test conditions: V Parameter LED DRIVER LFB Threshold Voltage LFB Input Bias Current BRT Input Voltage Range BRT Input Bias Current ...

Page 5

TM LFB Reference Logic BRT 50pF 2.5MΩ IN OVP REF Reference Logic ADJx 50pF 2.5MΩ Voltage Reference Reference Logic ADJx 50pF 2.5MΩ Copyright © 2000 Rev. 1.2, 2006-02-27 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570 ® Triple ...

Page 6

1.6V to 6.0V BAT - V LCD 25V LCD1 IN R (Feedforward Capacitor 25V LCD2 IN Figure 2 – LED Driver with Full-Range Dimming plus LCD ...

Page 7

UNCTIONAL ESCRIPTION The LX1745 is a triple output Pulse Frequency Modulated (PFM) boost converter that is optimized for large step-up voltage applications like LCD biasing and LED drive. Operating in a pseudo-hysteretic mode with a fixed switch ...

Page 8

TM less than 100kHz, an external filter capacitor will be needed (Figure 5). The value of C based on the PWM frequency and R following equation PWM ⋅ π ⋅ PWM where << ...

Page 9

TM negative voltage transition that is greater than the output voltage OWER OSFET ELECTION The LX1745 can source up to 100mA of gate current. An logic level N-channel MOSFET with a low turn on threshold voltage, low ...

Page 10

TM N LCD B G EGATIVE IAS ENERATION For applications that require it, a negative bias can be easily generated using an inductorless charge pump consisting of only four additional discrete components (Figure 8 OUT D ...

Page 11

TM Input/Output Name Range VIN GND 0V ADJ1 0 to VIN-100mV ADJ2 SHDN 0 to VIN SHDN1 SHDN2 VLCD1 ≤25V -VLCD ≥-25V VLCD2 ≤25V VOUT ≤25V FDBK 0 to VIN BRT 0 to 350mV REF 1.19V Typ. ...

Page 12

... RESISTOR, 1.25M, 1/16W, 0805 R9, R10, R11 RESISTOR, 10K, 1/16W, 0805 R12, R13 RESISTOR, 100K, 1/16W, 0805 U1 Microsemi LX1745CPW BOOST CONTROLLER Notes 1. Use these locations to insert additional input and/or output capacitance. Copyright © 2000 Rev. 1.2, 2006-02-27 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570 ® ...

Page 13

TM L1 Vin 1 47.0uH C1 1 GND spare 4.7uF 6.3V FDV303N R9 R10 R11 10K 10K 10K L2 1 ADJ1 SHDN1 1 SHDN SHDN2 CR3 22V VLCD2 1 UPS5819 ...

Page 14

0.5 1 Adjustment Signal Voltage (VADJx) Figure 12 – Output Voltage Vs. Adjustment Signal Threshold Note: The ...

Page 15

TM PW 20-Pin Thin Small Shrink Outline Package (TSSOP SEATING PLANE * Lead Coplanarity Note: Dimensions do not include mold flash or protrusions; these shall not exceed 0.155mm(.006”) on any side. Lead dimension shall not include solder coverage. ...

Page 16

TM PRODUCTION DATA – Information contained in this document is proprietary to Microsemi and is current as of publication date. This document may not be modified in any way without the express written consent of Microsemi. Product processing does not ...

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