ZXLD1374_11 DIODES [Diodes Incorporated], ZXLD1374_11 Datasheet - Page 24

• Manufacturer Part Number: ZXLD1374_11
• Description: 60V HIGH ACCURACY 1.5A BUCK/BOOST/BUCK-BOOST
• Manufacturer: DIODES [Diodes Incorporated]

ZXLD1374
Document number: DS35032 Rev. 2 - 2
Applications Information
Boost and Buck-boost
Ceramic capacitors with X7R dielectric are the best choice due to their high ripple current rating, long lifetime, and
performance over the voltage and temperature ranges.
BOOTSTRAP CIRCUIT
In Boost and Buck-boost modes with input voltages below 12V to fully enhance the internal power switch it is required to use
a bootstrap network as shown in figure 40.
The bootstrap circuit is realized by adding a reservoir capacitor, C8, current limiting resistor R13 (=100Ω) and a blocking
diode D2 (DFSL160). During the power switch turn-on C8 needs to be able to supply approximately 10mA current.
A capacitor of 1µF (C8) provides a reasonable trade-off between VAUX supply needs and LED current accuracy. At start-up
the VAUX pin requires only a few mA of current from the LED current. In normal operation the current taken from the LED
current to supply VAUX will be negligible.
INPUT CAPACITOR
The input capacitor and minimum RMS current for the output capacitor can be calculated knowing the input voltage ripple
ΔV
Buck
Boost
Buck-boost
IN-PP
as follows:
Use D = D
C
C
use D=0.5 as worst case
C
IN
IN
IN
Input capacitor
=
=
=
8
f
f x
SW
f
D
SW
MAX
x
Δ
SW
D
1 (
I
COIL
x
I x
x
−
as worst case
Δ
Δ
x
D
LED
V
Figure 40: Bootstrap circuit for low voltage operations
V
Δ
)
IN
IN
I x
V
−
−
PP
IN
LED
−
(Continued)
PP
PP
−
PP
60V HIGH ACCURACY 1.5A BUCK/BOOST/BUCK-BOOST
I
COUTPUT
www.diodes.com
−
RMS
24 of 37
=
LED DRIVER CONVERTER WITH AEC-Q100
I
LED
1
D
−
MAX
D
MAX
I
CIN
Use D = D
I
Minimum RMS current
Diodes Incorporated
CIN
use D=0.5 as worst case
A Product Line of
−
I
CIN
−
RMS
RMS
−
RMS
MAX
=
=
I
LED
I
LED
as worst case
=
L I
x
x
−
12
Dx
PP
1 (
1 (
D
−
−
D
D
)
© Diodes Incorporated
)
ZXLD1374
March 2011