ZXLD1370_11 DIODES [Diodes Incorporated], ZXLD1370_11 Datasheet - Page 15

• Manufacturer Part Number: ZXLD1370_11
• Description: 60V HIGH ACCURACY BUCK/BOOST/BUCK-BOOST LED DRIVER CONTROLLER
• Manufacturer: DIODES [Diodes Incorporated]

ZXLD1370
Document number: DS32165 Rev. 3 - 2
This will result in:
Table 1 shows typical resistor values used to determine GI
Applications Information
Table 1
Recommended inductor values for the ZXLD1370 are in the range 22 μH to 100 μH. The chosen coil should have a
saturation current higher than the peak sensed current and a continuous current rating above the required mean sensed
current by at least 50%.
The inductor value should be chosen to maintain operating duty cycle and switch 'on'/'off' times within the recommended
limits over the supply voltage and load current range.
The frequency compensation mechanism inside the chip tends to keep the frequency within the range 300kHz – 400kHz in
most of the operating conditions. Nonetheless, the controller allows for higher frequencies when either the number of LEDs
or the input voltage increases.
The graphs below can be used to select a recommended inductor to maintain the ZXLD1370 switching frequency within a
predetermined range when used in different topologies.
Buck inductor selection:
INDUCTOR/FREQUENCY SELECTION
GI ratio
0.25
0.35
0.45
0.2
0.3
0.4
0.5
R
R
GI
s
2
=
=
(R
R
100kΩ
GI
GI
30kΩ
33kΩ
39kΩ
30kΩ
51kΩ
30kΩ
RGI1
1
R
1
(
Figure 19. 1.5A Buck mode inductor selection for target frequency of 400 kHz
+
GI
15
13
11
V
V
9
7
5
3
1
R
1
ADJ
GI
0
GI
2
)
−
225
) 1
L=10uH
I
LED
=
110
mV
10
(Continued)
k
120kΩ
100kΩ
150kΩ
=
91kΩ
56kΩ
62kΩ
30kΩ
Ω
RG2
L=22uH
150
ZXLD1370 Buck Mode 1.5A Minimum Recommended Inductor
m
Ω
20
Target Switching frequency - 400kHz
L=33uH
www.diodes.com
Supply Voltage (V)
RATIO
15 of 35
30
with E24 series resistors
40
Diodes Incorporated
A Product Line of
L=47uH
50
60
© Diodes Incorporated
ZXLD1370
February 2011