LX1665A Ver la hoja de datos (PDF) - Microsemi Corporation

Número de pieza

componentes Descripción

Lista de partido

LX1665A

DUAL OUTPUT PWM CONTROLLERS WITH 5-BIT DAC

Microsemi Corporation 

Ref

C1

C2

C7, C9

C3

C4

C8

C5

L1

L2

Q1

Q2

Q3

R5, R6

R1

U1

Total

PRODUCT DATABOOK 1996/1997

LX1664/1664A, LX1665/65A

DUAL OUTPUT PWM CONTROLLERS WITH 5-BIT DAC

PRODUCTION DATA SHEET

BILL OF MATERIALS

LX1665 Bill of Materials (Refer to Product Highlight)

Description

Part Number / Manufacturer

1500µF, 6.3V capacitor

1500µF, 6.3V capacitor

330µF, Electrolytic

0.1µF

390pF

680pF

1µF, 16V

2.5µH Inductor

1µH Inductor

MOSFET

MOSFET

MOSFET

Resistor (See Table 6 for values)

2.5mΩ Sense Resistor

Controller IC

MV-GX Sanyo

MV-GX Sanyo

MV-GX Sanyo

SMD Cap

SMD Cap

SMD Cap

SMD Ceramic

HM0096832 BI or equivalent

IRL3102 International Rectifier or equivalent

IRL3303 International Rectifier or equivalent

IRLZ44 International Rectifier or equivalent

SMD Resistor

IRC OARS-1 or PCB trace

LX1665CDW Linfinity

Qty.

4

2

2

1

1

1

1

1

1

1

1

1

2

1

1

21

USING THE LX1664/65 DEVICES

The LX1664/65 devices are very easy to design with, requiring

only a few simple calculations to implement a given design. The

following procedures and considerations should provide effec-

tive operation for virtually all applications. Refer to the Appli-

cation Information section for component reference designa-

tors.

TIMING CAPACITOR SELECTION

The frequency of operation of the LX166x is a function of duty

cycle and OFF-time. The OFF-time is proportional to the timing

capacitor (which is shown as C8 in all application schematics in

this data sheet), and is modulated to minimize frequency

variations with duty cycle. The frequency is constant, during

steady-state operation, due to the modulation of the OFF-time.

The timing capacitor (C ) should be selected using the

T

following equation:

(1 - VOUT /VIN ) * IDIS

C=

T

f

S

(1.52

-

0.29

*

V

OUT

)

Where IDIS is fixed at 200µA and fS is the switching frequency

(recommended to be around 200kHz for optimal operation and

component selection).

When using a 5V input voltage, the switching frequency (fS)

can be approximated as follows:

I

DIS

C

T

=

0.621

*

f

S

Choosing a 680pF capacitor will result in an operating

frequency of 183kHz at VOUT = 2.8V. When a 12V power input

is used, he capacitor value must be changed (the optimal timing

capacitor for 12V input will be in the range of 1000-1500pF).

L OUTPUT INDUCTOR SELECTION

1

The inductance value chosen determines the ripple current

present at the output of the power supply. Size the inductance

to allow a nominal ±10% swing above and below the nominal DC

load

current,

using

the

equation

L

=

V

L

*

∆T/∆I,

where

∆T

is

the

OFF-time, VL is the voltage across the inductor during the OFF-

time, and ∆I is peak-to-peak ripple current in the inductor. Be

sure to select a high-frequency core material which can handle

the DC current, such as 3C8, which is sized for the correct power

level. Typical inductance values can range from 2 to 10µH.

Note that ripple current will increase with a smaller inductor.

Exceeding the ripple current rating of the capacitors could cause

reliability problems.

Copyright © 1999

Rev. 1.2 11/99

11

Share Link: