LM3350 National Semiconductor, LM3350 Datasheet - Page 6

• Manufacturer Part Number: LM3350
• Description: Switched Capacitor Voltage Converter
• Manufacturer: National Semiconductor

Typical Application Circuits
DS100002-13
FIGURE 2. Step-Up Converter
DS100002-14
FIGURE 3. Step-Down Converter
Layout Information
LAYOUT CONSIDERATIONS
The LM3350’s high switching frequency (800 kHz) makes a good layout important. Figure 4 illustrates a typical layout. It is im-
portant to keep the distance short between the four capacitors and the IC. Wide traces and grounding are also recommended.
These steps will minimize trace inductance and high frequency ringing. Of the four capacitors, C
and C
have the highest
high
low
value of di/dt. It is therefore most important to keep them close to the IC. The ground lead that C
and C
share should also
high
low
be kept wide and short.
The location of the diode (D1) used in the step-up configuration is not critical. This diode is only used during the initial turn on of
the IC. D1 is not needed in step-down applications.
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