ZXLD1370_11 DIODES [Diodes Incorporated], ZXLD1370_11 Datasheet - Page 23

• 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
Applications Information
PWM OUTPUT CURRENT CONTROL & DIMMING
The ZXLD1370 has a dedicated PWM dimming input that allows a wide dimming frequency range from 100Hz to 1kHz with
up to 1000:1 resolution; however higher dimming frequencies can be used – at the expense of dimming dynamic range and
accuracy.
Typically, for a PWM frequency of 1kHz, the error on the current linearity is lower than 5%; in particular the accuracy is
better than 1% for PWM from 5% to 100%. This is shown in the graph below:
For a PWM frequency of 100Hz, the error on the current linearity is lower than 2.5%; it becomes negligible for PWM greater
than 5%. This is shown in the graph below:
The PWM pin is designed to be driven by both 3.3V and 5V logic levels. It can be driven also by an open drain/collector
transistor. In this case the designer can either use the internal pull-up network or an external pull-up network in order to
speed-up PWM transitions, as shown in the Boost/ Buck-Boost section.
1500.00
1250.00
1000.00
1500.00
1250.00
1000.00
750.00
500.00
250.00
750.00
500.00
250.00
0.00
0.00
Figure 28: LED current linearity and accuracy with PWM dimming at 100Hz
Figure 27: LED current linearity and accuracy with PWM dimming at 1kHz
0
0
10
10
(Continued)
Buck m ode - L=33uH - Rs = 150m Ω - PW M @ 100Hz
Buck m ode - L=33uH - Rs = 150m Ω - PW M @ 1kHz
20
20
30
30
www.diodes.com
40
40
PWM @ 100Hz
PWM @ 1kHz
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PWM
PWM
50
50
60
60
Error
Error
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70
Diodes Incorporated
A Product Line of
80
80
90
90
100
100
10%
9%
8%
7%
6%
5%
4%
3%
2%
1%
0%
10%
9%
8%
7%
6%
5%
4%
3%
2%
1%
0%
© Diodes Incorporated
ZXLD1370
February 2011