ZXLD1371QESTTC Diodes Inc. / Zetex, ZXLD1371QESTTC Datasheet - Page 33

• Manufacturer Part Number: ZXLD1371QESTTC
• Description: MOSFET LED Controller TSSOP TSSOP-16EP T&R 2.5K
• Manufacturer: Diodes Inc. / Zetex

Specifications of ZXLD1371QESTTC

• Rohs: yes

ZXLD1371
Document number: DS35436 Rev. 1 - 2
Applications Information
PWM Output Current Control & Dimming
The ZXLD1371 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 and as such doesn’t require open collector/drain
drive. It can also be driven 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
Figure 11. LED Current Linearity and Accuracy with PWM Dimming at 100Hz
Figure 10. LED Current Linearity and Accuracy with PWM Dimming at 1kHz
750.00
500.00
250.00
0.00
0.00
0
0
10
10
(cont.)
Buck m ode - L=33uH - Rs = 150m Ω - PW M @ 1kHz
Buck m ode - L=33uH - Rs = 150m Ω - PW M @ 100Hz
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
70
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
February 2012
ZXLD1371