Rainbow Electronics MAX1745 - Manual (Page 13)

MAX1744/MAX1745
High-Voltage, Step-Down DC-DC
Controller in µMAX
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ripple at IN, caused by the circuit’s switching action.
Use a low-ESR capacitor. Two smaller-value low-ESR
capacitors can be connected in parallel if necessary.
Choose input capacitors with working voltage ratings
higher than the maximum input voltage.
Place a surface-mount ceramic capacitor very close to
IN and GND. This capacitor bypasses the MAX1744/
MAX1745, minimizing the effects of spikes and ringing
on the power source (IN).
Bypass REF with 0.1µF. This capacitor should be
placed within 0.2 inches (5mm) of the IC, next to REF,
with a direct trace to GND.
Layout Considerations
High-frequency switching regulators are sensitive to PC
board layout. Poor layout introduces switching noise into
the current and voltage feedback signals and may
degrade performance. The current-sense resistor must
be placed within 0.2 inches (5mm) of the controller IC,
directly between OUT and CS. Place voltage feedback
resistors (MAX1745) next to the FB pin (no more than
0.2in) rather than near the output. Place the 0.47µF input
bypass capacitor within 0.2in (5mm) of IN.
Refer to the MAX1744 Evaluation Kit manual for a two-
layer PC board example.
Chip Information
TRANSISTOR COUNT: 645
High-Voltage, Step-Down DC-DC
Controller in µMAX