Diodes ZXLD1356/ ZXLD1356Q - Manual (Page 23)

ZXLD1356/ ZXLD1356Q
Document number: DS33470 Rev. 4 - 2
23 of 29
www.diodes.com
October 2012
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ZXLD1356/ ZXLD1356Q
A Product Line of
Diodes Incorporated
Application Information
(cont.)
Inductor Selection (cont.)
Minimum Recommended Inductor
2% Accuracy, <60°C Case Temperature
0 10 20 30 40 50 60
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
N
um
be
r
of
LE
D
s
Supply Voltage (V)
Legend
68uH
100uH
150uH
220uH
Figure 3. ZXLD1356 Minimum Recommended Inductor
Diode Selection
For maximum efficiency and performance, the rectifier (D1) should be a fast low capacitance Schottky diode* with low reverse leakage at the
maximum operating voltage and temperature.
They also provide better efficiency than silicon diodes, due to a combination of lower forward voltage and reduced recovery time.
It is important to select parts with a peak current rating above the peak coil current and a continuous current rating higher than the maximum
output load current. It is very important to consider the reverse leakage of the diode when operating above 85°C. Excess leakage will increase
the power dissipation in the device and if close to the load may create a thermal runaway condition.
The higher forward voltage and overshoot due to reverse recovery time in silicon diodes will increase the peak voltage on the LX output. If a
silicon diode is used, care should be taken to ensure that the total voltage appearing on the LX pin including supply ripple, does not exceed the
specified maximum value.
*A suitable Schottky diode would be B1100B (Diodes Inc).