Rainbow Electronics MAX1730 - Manual (Page 8)

MAX1730
50mA Regulated Step-Down Charge Pump
for 1.8V or 1.9V Logic
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Shutdown
The MAX1730 features an active-low shutdown pin
(SHDN) to decrease supply current to below 5µA.
When in shutdown, the output disconnects from the
input and OUT goes to high impedance.
Capacitor Selection
The input capacitor provides the charge pump with a low-
impedance supply. For most applications, a 1µF ceramic
capacitor is adequate. Lower-value capacitors and those
with higher ESR may be inadequate for proper operation
and may result in lower output current capability and
higher output ripple.
To reduce the output voltage ripple, the value of the
output capacitor should exceed that of the flying
capacitors (C1 + C2) by 10:1 or more. Values for C1
and C2 between 0.22µF and 0.47µF are recommended
for most applications. Use ceramic capacitors to
increase maximum output current and improve efficiency.
Layout Considerations
The MAX1730’s high-frequency operation demands
careful layout. All components should be placed as
close to the IC as possible, with priority going to CIN,
C1, and C2. Traces should be kept short, wide, and as
straight as possible. Connect PGND and GND together
with a low-impedance ground plane.
Chip Information
TRANSISTOR COUNT: 2295
Package Information
10LUMAX.EPS
Note: The MAX1730 does not have an exposed pad.