irs2540 International Rectifier Corp., irs2540 Datasheet - Page 11

• Manufacturer Part Number: irs2540
• Description: Led Buck Regulator Control Ic -
• Manufacturer: International Rectifier Corp.

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The addition of the C
energy that can be stored in the output stage, which
also means it can supply current for an increased
period of time. Therefore by slowing down the di/dt
transients in the load, the frequency is effectively
decreased.
With the C
longer identical to that seen in the load.
inductor current will still have a perfectly triangular
shape, where as the load will see the same basic
trend in the current, but all sharp corners will be
rounded with all peaks significantly reduced, as can
be seen in Fig. 15
V CC Supply
Since the IRS245(0,1) is rated for 200 V (or 600 V),
V
supply resistor to V
extremely high power losses. For higher voltage
applications an alternate V
the micro-power start-up and a resistor feed-back
BUS
400
350
300
250
200
150
100
1000
50
100
0
10
can reach values of this magnitude. If only a
0
30
Fig. 14 I
Fig. 13 I
OUT
50
10
out
out
capacitor, the inductor current is no
= 350 mA, V
= 350 mA, V
70
Capacitance (uF)
20
BUS
OUT
90
is used, it will experience
out
out
CC
Vin (V)
increases the amount of
30
= 16.8 V, L = 470 µH
= 16.8 V, L = 470 µH
supply scheme utilizing
110
130
40
150
50
170
0uF
4.7uF
10uF
22uF
33uF
47uF
40V
100V
160V
The
from the output needs to be implemented, as seen in
Fig. 16.
The resistance between V
be large enough to minimize the current sourced
directly from the input voltage line; value should be
on the order of hundreds of k . Through the supply
resistor, a current will flow to charge the V
capacitor. Once the capacitor is charged up to the
V
start-up regime and begins to operate, activating the
LO and HO outputs. After the first few cycles of
switching, the resistor connected between the output
and V
current for the IC.
output to the supply should be carefully designed
according to its power rating.
CCUV+
Fig. 15 I
ENN
COM
VBUS
threshold, the IRS254(0,1) enters the micro
CC
out
will take over and source all necessary
RS
P
Icc
= 350 mA, V
Fig. 16 Alternate Supply Diagram
RS
VCC
COM
2
ENN
IFB
2
|
10
1
2
3
4
V
(
10
mA
out
IRS254(0,1)(S)PbF
10
mA
in

C
mA
= 100 V, V
15
)
out
The resistor connecting the
2
8
7
6
5
6 .
RS
= 33 µF
VB
HO
VS
LO
V
BUS
2
d
and V
out
P
RS
= 16.85 V, L = 470 µH,
2
_
CC
Rated
supply should
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CC