ZXLD1374_11 DIODES [Diodes Incorporated], ZXLD1374_11 Datasheet - Page 17

• 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
When the ADJ pin is directly connected to the REF pin, this becomes:
Note that the average LED current for a Boost or Buck-boost converter is always less than the average sense resistor
current. For the ZXLD1374, the recommended potential divider ratio is given by:
It is possible to use a different combination of GI pin voltages and sense resistor values to set the LED current.
In general the design procedure to follow is:
Calculate the maximum duty-cycle as:
Buck mode
Boost mode
Buck-boost mode
Set the appropriate GI
If the potential divider ratio is greater than 0.64, the device detects that Buck-mode operation is desired and the output
current will deviate from the desired value.
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-
-
-
-
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Define input conditions in terms of V
Set output conditions in terms of LED current and the number of LEDs
Define controller topology – Buck, Boost or Buck-boost
Set RGI1 as:
Calculate RGI2 as:
Calculate the sense resistor as:
RATIO
according to the circuit duty and the max switch current admissible limitations
(Continued)
60V HIGH ACCURACY 1.5A BUCK/BOOST/BUCK-BOOST
GI
IN
RATIO
and I
R
0
s
2 .
=
IN
D
D
R
≤
D
=
MAX
MAX
R
s
(R
www.diodes.com
MAX
R (
10
V
GI
=
V
GI
ADJ
GI
GI
k
2
R
1
Ω
(R
1
17 of 37
R
=
=
≈
=
GI
+
+
GI
≤
GI
V
V
1
R
=
LED DRIVER CONVERTER WITH AEC-Q100
1
V
1
R
V
LEDS
LEDS
R
D
−
R
1
IN
GI
LEDs
GI
GI
(R
D
MAX
GI
+
MIN
2
) 2
MAX
1
V
V
)
R
GI
1
LEDS
LEDS
≤
≤
GI
225
R
1
+
−
I
200
LED
. 0
GI
+
) 2
V
V
x
mV
50
IN
R
IN
1
225
k
R
GI
I
Ω
LED
MIN
MIN
GI
) 2
mV
1
≤
Diodes Incorporated
1
−
A Product Line of
D
MAX
© Diodes Incorporated
ZXLD1374
March 2011