LM3530UME-25A/NOPB National Semiconductor, LM3530UME-25A/NOPB Datasheet - Page 37

• Manufacturer Part Number: LM3530UME-25A/NOPB
• Description: IC LED DRVR PRGRAM I2C 10LED SMD
• Manufacturer: National Semiconductor
• Series: PowerWise®r

Specifications of LM3530UME-25A/NOPB

• Topology: PWM, Step-Up (Boost)
• Number Of Outputs: 1
• Internal Driver: Yes
• Type - Primary: Backlight
• Type - Secondary: White LED
• Frequency: 500kHz
• Voltage - Supply: 2.7 V ~ 5.5 V
• Mounting Type: Surface Mount
• Package / Case: 12-XFBGA
• Operating Temperature: -40°C ~ 85°C
• Current - Output / Channel: Adjustable
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Voltage - Output: -
• Other names: LM3530UME-25A/NOPBTR

The following lists the main (layout sensitive) areas of the
LM3530 in order of decreasing importance:
Output Capacitor
•
•
Schottky Diode
•
•
Inductor
•
Input Capacitor
•
•
Schottky Cathode to C
C
SW Pin to Schottky Anode
Schottky Cathode to
SW Node PCB capacitance to other traces
CIN+ to IN pin
CIN- to GND
OUT
- to GND
FIGURE 26. LM3530's Boost Converter Showing Pulsed Voltage at SW (High dV/dt) and
COUT
OUT
+
+
Current Through Schottky and C
37
Output Capacitor Placement
The output capacitor is in the path of the inductor current dis-
charge path. As a result C
0 to I
turns on. Any inductance along this series path from the cath-
ode of the diode through C
GND pin will contribute to voltage spikes (V
dt) at SW and OUT which can potentially over-voltage the SW
pin, or feed through to GND. To avoid this, C
connected as close as possible to the Cathode of the Schottky
diode and C
the LM3530's GND bump. The best placement for C
the same layer as the LM3530 so as to avoid any vias that
can add excessive series inductance (see
29, and
PEAK
OUT
Figure
each time the switch turns off and the Schottky diode
(High dI/dt)
OUT
30).
- must be connected as close as possible to
OUT
OUT
sees a high current step from
and back into the LM3530's
Figure
SPIKE
OUT
www.national.com
= L
+ must be
300866100
28,
OUT
P_
Figure
× dI/
is on