LX1662CD Ver la hoja de datos (PDF) - Microsemi Corporation
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LX1662CD Datasheet PDF : 15 Pages
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PRODUCT DATABOOK 1996/1997
LX1662/62A, LX1663/63A
SINGLE-CHIP PROGRAMMABLE PWM CONTROLLERS WITH 5-BIT DAC
PRODUCTION DATA SHEET
Ref
C2
C1
C8
C3
C5
L1
L2
Q1
Q2
R1
U1
Total
BILL OF MATERIALS
LX1662 Bill of Materials (Refer to Product Highlight)
Description
Part Number / Manufacturer
1500µF, 6.3V capacitor
1500µF, 6.3V capacitor
680pF
0.1µF
1µF, 16V
5µF Inductor
1µF Inductor
MOSFET
MOSFET
2.5mΩ Sense Resistor (PCB trace)
Controller IC
MV-GX Sanyo
MV-GX Sanyo
SMD Cap
SMD Cap
SMD Ceramic
HM0096832 BI
IRL3102 International Rectifier or equivalent
IRL3303 International Rectifier or equivalent
LX1662CD Linfinity
Qty.
2
4
1
1
1
1
1
1
1
1
1
15
USING THE LX1662/63 DEVICES
The LX1662/63 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:
CT =
(1
-
V
OUT
/V )
IN
*
I
DIS
fS (1.52 - 0.29* VOUT)
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 (f )
S
can be approximated as follows:
CT = 0.621 *
IDIS
f
S
Choosing a 680pF capacitor will result in an operating
frequency of 183kHz at V = 2.8V. When a 12V power input
OUT
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. 1.2a, 11/04
11
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