MAX16812 Datasheet, PDF (18/21 Pages) Maxim Integrated Products – Integrated High-Voltage LED Driver with Analog and PWM Dimming Control

Integrated High-Voltage LED Driver
with Analog and PWM Dimming Control
Layout Recommendations
Typically, there are two sources of noise emission in a
switching power supply: high di/dt loops and high dv/dt
surfaces. For example, traces that carry the drain cur-
rent often form high di/dt loops. Similarly, the drain of
the internal MOSFET connected to the LX pin presents
a dv/dt source. Keep all PCB traces carrying switching
currents as short as possible to minimize current loops.
Use ground planes for best results.
Careful PCB layout is critical to achieve low switching
losses and clean, stable operation. Use a multilayer
board whenever possible for better noise immunity and
power dissipation. Follow these guidelines for good
PCB layout:
• Use a large copper plane under the MAX16812
package. Ensure that all heat-dissipating compo-
nents have adequate cooling. Connect the exposed
pad of the device to the ground plane.
• Isolate the power components and high-current
paths from sensitive analog circuitry.
• Keep the high-current paths short, especially at the
ground terminals. This practice is essential for stable,
jitter-free operation. Keep switching loops short.
• Connect AGND and SGND to a ground plane.
Ensure a low-impedance connection between all
ground points.
• Keep the power traces and load connections short.
This practice is essential for high efficiency. Use
thick copper PCBs to enhance full-load efficiency.
• Ensure that the feedback connection to FB is short
and direct.
• Route high-speed switching nodes away from the
sensitive analog areas.
• To prevent discharge of the compensation capaci-
tors, C_COMP1 and C_COMP2, during the off-time of
the dimming cycle, ensure that the PCB area close
to these components has extremely low leakage.
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