LM3532TMX-40ANOPB National Semiconductor Corporation, LM3532TMX-40ANOPB Datasheet - Page 38

• Manufacturer Part Number: LM3532TMX-40ANOPB
• Description: High Efficiency White Led Driver With Programmable Ambient Light Sensing Capability And I2c-compatible Interface
• Manufacturer: National Semiconductor Corporation

www.national.com
LAYOUT GUIDELINES
The LM3532 contains an inductive boost converter which
sees a high switched voltage (up to 40V) at the SW pin, and
a step current (up to 1A) through the Schottky diode and out-
put capacitor each switching cycle. The high switching volt-
age can create interference into nearby nodes due to electric
field coupling (I = CdV/dt). The large step current through the
The following lists the main (layout sensitive) areas of the
LM3532 in order of decreasing importance:
Output Capacitor
•
•
Schottky Diode
•
•
Schottky Cathode to COUT+
COUT− to GND
SW Pin to Schottky Anode
Schottky Cathode to COUT+
FIGURE 16. LM3532's Boost Converter Showing Pulsed Voltage at SW (High dV/dt) and
Current Through Schottky and COUT (High dI/dt)
38
diode, and the output capacitor can cause a large voltage
spike at the SW pin and the OVP pin due to parasitic induc-
tance in the step current conducting path (V = LdI/dt). Board
layout guidelines are geared towards minimizing this electric
field coupling and conducted noise.
two noise generating components.
Inductor
•
Input Capacitor
•
•
SW Node PCB capacitance to other traces
CIN+ to IN pin
CIN− to GND
Figure 16
highlights these
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