How can the output ripple of an LM2621 boost converter be reduced?
First confirm that the circuit components were selected using instructions in the datasheet, and the PCB layout follows the datasheet guidelines. If the output ripple voltage is too large, for example 500mV on a 5V output, there are a few more things to check: (1) Check the circuit grounding and lead lengths: If the objectionable ripple occurs at the switching frequency (measure 200kHz per the datasheet typical application circuit), then make sure that the negative terminals of C1, C2, Icpin1 and the output return terminal are located closely together. Output should be taken from the terminals of C2. Don”t use more than one measurement grounding point. (2) Add “bead” to reduce diode ringing: Some high frequency noise (10 to 25MHz) may be generated in the diode when it is switched off. If the objectionable noise occurs synchronous to turn-off in the switching cycle, a small bead on the diode lead may reduce it. (3) Check timing capacitor, CF1 connections: If the objectionable ripple oc
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