XRP7410EVB Exar Corporation, XRP7410EVB Datasheet - Page 10

• Manufacturer Part Number: XRP7410EVB
• Description: Power Management Modules & Development Tools Eval Board for XRP7410 Series
• Manufacturer: Exar Corporation

Specifications of XRP7410EVB

• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Where Vin is converter input voltage and Vo is
converter output voltage. Since voltage across
Rset is small, Vo approximately equals Vf (for
a string of series connected LEDs Vo equals
total Vf)
ΔI
30% of Io)
Inductor Isat and Irms must allow sufficient
safeguard over output current Io. As a rule of
thumb these parameters should be 50%
higher than Io. Where high efficiency is
required a low DCR inductor should be used.
I
Select the input capacitor for capacitance and
ripple current rating. Use the capacitances
listed in the table 1 as a starting point and if
needed increase Cin.
Calculate the ripple current requirement from:
Where
© 2009 Exar Corporation
NPUT CAPACITOR SELECTION
L
is inductor current ripple (nominally set to
0.71 to 1.2
D =
Equ.4:
I
<0.7
>1.2
O
Equ.3:
(A)
Vin
Vo
Table 1: Cin Selection
Irip
L
=
=
Vo
Io
Vin
×
×
×
(
Vin
D
f
×
×
−
5
5
Cin (µF)
1 ( D
Δ
Vo
2 x 4.7
0
0
I
−
2.2
4.7
L
0
0
)
m
m
)
A
A
2
2
9
9
V
V
10/13
N
N
o
o
n
n
Ceramic capacitors are recommended for input
filtering due to their low Equivalent Series
Resistance
inductance (ESL) and small form factor.
S
Select the Schottky D1 for Voltage rating VR
and current rating If. Recommended schottky
diode
applications is 30V and 40V respectively.
Current rating can be calculated from:
Note that in applications where duty cycle is
low,
percentage of converter losses. In order to
improve the efficiency in these applications
choose a Schottky that meets the calculated
current rating and has a lower Vf.
F
R2 is part of XRP7603 loop compensation
network. Use a 30k R2 for Vin of 20V and
larger. Use R2 of 60K for Vin less than 20V.
C
This is the decoupling capacitor for the power
supply for the internal driver. Use a 0.1uF and
place as closely to VDR and SVIN pins as
possible.
-
-
S
S
EEDBACK RESISTOR
CHOTTKY RECTIFIER SELECTION
APACITOR
y
y
n
n
c
c
Schottky
.
.
voltage
B
B
Equ.5 :
u
u
C5
c
c
k
k
(ESR),
H
H
rating
losses
i
i
g
If
g
h
h
≥ 1
RFB
P
P
o
o
for
Equivalent
comprise
−
w
w
Vin
Vo
e
e
r
r
12V
×
X
L
L
X
Io
E
E
R
R
D
D
P
and
P
a
Rev. 1.0.0
D
D
7
7
r
r
Series
6
6
larger
i
i
v
v
0
0
24V
e
e
3
3
r
r