Rainbow Electronics MAX608 - Manual (Page 11)

Feed-Forward Capacitor
When adjusting the output voltage, it may be necessary
to parallel a 47pF to 220pF capacitor across R2, as
shown in Figures 2 and 3. Choose the lowest capacitor
value that insures stability; high capacitance values
may degrade line regulation.
__________Applications Information
Starting Up Under Load
The Typical Operating Characteristics show the Start-Up
Voltage vs. Load Current graphs for 5V and 12V output
voltages. These graphs depend on the type of power
switch used. The MAX608 is not designed to start up
under full load with low input voltages.
Layout Considerations
Due to high current levels and fast switching wave-
forms, which radiate noise, proper PC board layout is
essential. Protect sensitive analog grounds by using a
star ground configuration. Minimize ground noise by
connecting GND, the input bypass capacitor ground
lead, and the output filter capacitor ground lead to a
single point (star ground configuration). Also, minimize
lead lengths to reduce stray capacitance, trace resis-
tance, and radiated noise. Place input bypass capaci-
tor C2 as close as possible to OUT and GND.
If an external resistor divider is used (Figures 2 and
3), the trace from FB to the resistors must be
extremely short.
MAX608
5V or Adjustable, Low-Voltage,
Step-Up DC-DC Controller
______________________________________________________________________________________ 11
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