ML4863CS Micro Linear, ML4863CS Datasheet - Page 7

• Manufacturer Part Number: ML4863CS
• Description: High Efficiency Flyback Controller
• Manufacturer: Micro Linear

DESIGN CONSIDERATIONS
DESIGN PROCEDURE
A typical design can be implemented by using the
following procedure.
1.
As a general design rule, the output ripple should be kept
below 100mV to ensure stability.
2.
3a.
3b.
3c.
3d.
4a.
4b.
5.
I
R
C I
L PEAK
ESR
V
=
OUT
Specify the application by defining:
The maximum input voltage (V
The mainimum input voltage (V
The maximum output current (I
The maximum output ripple ( V
Select a sense resistor, R
Determine the inductance required for the
optimum output ripple using equation 2.
Determine the minimum inductor current rating
required. The peak inductor current is calculated
using the following formula:
Specify the inductor's DC winding resistance. A
good rule of thumb is to allow 5m , or less, of
resistance per µH of inductance. For minimum
core loss, choose a high frequency core material
such as Kool-Mu, ferrite, or MPP.
Specify the coupled inductor's turns ratio:
Calculate the minimum output capacitance
required using:
Establish the maximum allowable ESR for the
ouput capacitor:
As a final design check, evaluate the system
stability (no compensation, single pole response)
by using the following equation:
where R
used.
OUT MAX
<
=
D
235
(
V
R
(
OUT
6 10
SENSE
150
mV
SENSE
Np : Ns = 1:1
)
™
™
mV

 
R
+
6
V
SENSE
)
V
OUT
and L
IN MAX
!
(
R
V
+
OUT
SENSE
P
V
)
are the actual values to be
IN MAX
™
L
(
SENSE
( .
P
25 10
(
V
)
™
OUT
L
, using equation 1.
™
P
IN(MAX)
OUT(MAX)
IN(MIN)
OUT
. 25 10
-
6
D
)
V
V
™
IN MIN
)
OUT
(
)
)
-
)
6
)
)
"
$ #
(4)
(5)
(6)
(7)
See Table 1 for suggested component manufacturers.
DESIGN EXAMPLE
1.
2.
3a.
3b.
Component Manufacturer
Sense
Resistors
Inductors
Capacitors
MOSFETs
R
R
L
I
L PEAK
P
SENSE
SENSE
Specify the application by defining:
V
V
I
Select the sense resistor, R
Determine the inductance required using
equation 2.
Determine the minimum inductor current rating
required.
(
OUT(MAX)
25 10
V
IN(MAX)
IN(MIN)
OUT
= 138m
120
Dale
IRC
Coilcraft
AVX
National
Coiltronics
Dale
Sprague
Motorola
Siliconix
235
5 4
Table 1. Component Suppliers
4
= 100mV
m
mV
= 4V
= 6V
6
= 500mA
)

 
150
500
6 0 12
6
120m
18 10
mV
mA
( .
.
25 10
LRC Series
WSL Series
R4999
OCTA-PAC Series [phone]
LPE-6562 Series [phone]
LPT-4545 series
TPS series
593D Series
NDS94XX
NDS99XX
MMDF Series
MMSF Series
Littlefoot Series [phone]
= 18µH
Number
20 6 0 5
–6
Part
SENSE
6
4
)
V
2 79
, using Equation 1:
.
.
[phone]
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[phone]
[phone]
[phone]
[phone]
[phone]
A
ML4863
0 85
.
Phone
(1a)
(2a)
(4a)
7