AMS1302 AMS [Advanced Monolithic Systems Ltd], AMS1302 Datasheet - Page 7

• Manufacturer Part Number: AMS1302
• Description: Output up to 24V Internal MOSFET with high switch current up to 3A
• Manufacturer: AMS [Advanced Monolithic Systems Ltd]

A
Output Voltage Setting
Referring to Typical Application Circuits, the output voltage of the switching regulator (V
with Equation (1).
Feedback Loop Design
Referring to the Typical Application Circuits. The selection of R1 and R2 based on the trade-off between
quiescent current consumption and interference immunity is stated below:
For applications without standby or suspend modes, lower values of R1 and R2 are preferred. For
applications concerning the current consumption in standby or suspend modes, the higher values of R1
and R2 are needed. Such high impedance feedback loop is sensitive to any interference, which requires
careful PCB layout and avoid any interference, especially to FB pin. To improve the system stability, a
proper value capacitor between FB pin and GND pin is suggested. An empirical suggestion is around
22pF.
PCB Layout Guide
PCB Layout shall follow these guidelines for better system stability:
A
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p
p
Follow Equation (1)
Higher R reduces the quiescent current (Path current = 1.212V/R2), however resistors beyond
5MW are not Recommended.
Lower R gives better noise immunity, and is less sensitive to interference, layout parasitics, FB
node leakage, and improper probing to FB pin.
A full GND plane without gap break.
VDD to GND noise bypass - Short and wide connection for the 20-100uF capacitor between Pin 5
and Pin 1.
VIN to GND noise bypass - Add a 10uF capacitor close to L1 inductor, when V
voltage source.
Minimized FB node copper area and keep far away from noise sources.
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Advanced Monolithic Systems http://www.ams-semitech.com
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AMS1302
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