ZLED7520ZI1R ZMDI, ZLED7520ZI1R Datasheet - Page 19

• Manufacturer Part Number: ZLED7520ZI1R
• Description: LED Lighting Drivers LED driver
• Manufacturer: ZMDI

Specifications of ZLED7520ZI1R

• Rohs: yes
• Input Voltage: 6 V to 40 V
• Operating Frequency: 1 MHz
• Maximum Supply Current: 600 uA
• Output Current: 0.75 A
• Maximum Operating Temperature: + 105 C
• Mounting Style: SMD/SMT
• Package / Case: DFN-5
• Minimum Operating Temperature: - 40 C
• Power Dissipation: 500 mW

The inductance value has an equivalent effect on t
the same reason, the inductance has no influence on the duty cycle, for which the relationship of the summed
LED forward voltages n * V
factor in the on time, variations in the input voltage affect the switching frequency and duty cycle.
To achieve optimum performance, duty cycles close to 0.5 at the nominal average supply voltage are preferable
for improving the temperature stability of the output current.
Equations (5), (6), (7), and (8) provide an example of calculating t
D
and R
Example:
For the L1 inductor, use a coil with a continuous current rating higher than the required mean output current and a
saturation current that exceeds the peak output current by 30% to 50% for robustness against transient con-
ditions; e.g., during start-up.
3.3.3
The bypass capacitor C1 has two functions: maintaining operating voltage and bypassing the current ripple of the
switching converter. In general low ESR capacitors must be used.
If the circuit is supplied by rectified line voltage, C1 must provide enough charge to maintain the ZLED7x20’s
minimum operating voltage as well as the forward voltage of the LED string to keep the application working even
if the rectified supply voltage periodically drops below these values. A rough estimate for the minimum capacity
needed can be calculated with equation (9).
LX
D
t
t
f
Data Sheet
August 12, 2011
LX
ON
OFF
LX
when using a 220µH inductor for L1 and V
ZLED7520
High Current 40V LED Driver with Internal Switch
LX
=0.27 .
12
t
ON
V
3
V
Bypass Capacitor C1
LED
V
4 .
IN
1
V
t
3
OFF
4 .
3
12
. 0
V
4 .
© 2011 Zentrum Mikroelektronik Dresden AG — Rev. 1.2
All rights reserved. The material contained herein may not be reproduced, adapted, merged, translated, stored, or used without
the prior written consent of the copyright owner. The information furnished in this publication is subject to changes without notice.
36
V
V
220
220
. 2
. 0
V
64
333
t
H
ON
H
. 0
s
F
A
*
*
t
333
1
to the input voltage V
0
ON
*
0
3 .
. 5
3 .
t
0
OFF
56
*
3 .
A
*
. 0
. 0
*
333
s
333
. 0
. 2
. 0
30
A
121
64
26
A
. 2
8 .
s
64
kHz
. 0
IN
. 0
. 5
26
=12V, Rs = 0.30 , r
s
27
56
IN
ON
is a reasonable approximation. Because the input voltage is a
s
and t
. 5
. 2
0
3 .
64
56
OFF
s
s
and therefore affects the switching frequency. For
ON
L
, t
=0.26 , V
OFF
, operating frequency f
LED
=3.4V, I
AVG
=333mA, V
LX
, and duty cycle
(5)
(6)
(7)
(8)
19 of 27
D
=0.36V,