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I'm using an MIC2251 (MIC2251-1YD5-TR) in a design to boost a lithium battery (3.6V-4.1V) to 5.4V for powering a small camera peripheral that requires a typical draw of 80mA. I expect that the worse case current supplied needs to be about 2x 80mA due to efficiency and the switched voltage boost. I followed the reference design from Figure 5-1 on page 10.

I'm using the recommended capacitances and inductance values of 10uF on input (C1), Cff of 2.2 uF, and L = 10 uH or 4.7uH. My R1 is 910k and R2 is 270k. Output voltage with a load resistance of 1k Ohm is as expected at Vout = 1.24(R1/R2 + 1) = 1.24*(3.37+1) = 5.42V. As this load is increased output voltage drops to 5.2 at load of 462 Ohm, 4.99V at load of 231 Ohm.

I've tested the following inductors: Sumida CDRH2D18/LDNP-4R7NC 4.7 uH with Isat of 630mA Bourns SRN3030HA-4R7Y 4.7uH with Isat 2.4A Bourns SRN3030HA-100M 10uH with Isat 1.6A

R1 is Yageo RC0805JR-07910KL 910k ohm R2 is Yageo RC0805JR-07270KL 270k ohm Cinput is Samsung CL21A106KOQNNNG Cff is Samsung CL21B225KPFNNNE Diode is Diodes Inc 1N5819HW-7-F

The reference design show a boosted output of 15V at 100mA from a Li-ion cell so I believe my application is well within the capabilities of the regulator. I suspect the inductor may be the limiting factor, but for a light load the saturation seems sufficient? Can you help me to understand which component of element might be giving me problems and suggest a replacement?

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    \$\begingroup\$ Show us a pic of your layout too. \$\endgroup\$
    – brhans
    Commented Mar 11, 2023 at 4:19
  • \$\begingroup\$ @brhans, added my layout too \$\endgroup\$
    – user220456
    Commented Mar 11, 2023 at 4:45
  • \$\begingroup\$ @brhans, should I change my value of R1 to 100k as suggested in the table 5.1 on page 10? \$\endgroup\$
    – user220456
    Commented Mar 11, 2023 at 10:12
  • \$\begingroup\$ Some junctions on your schematic have dots to indicate a positive connection but, some don't and therefore cannot be assumed to be connected. Looking at the wire entering on the left to C4, it's clear you haven't used a sensible grid size and, in fact, you may have grid snap turned off <-- this can create a significant connectivity problem. \$\endgroup\$
    – Andy aka
    Commented Mar 11, 2023 at 10:59
  • \$\begingroup\$ Yes, you should follow the manufacturer's guidance there unless you have a good reason not to. \$\endgroup\$
    – brhans
    Commented Mar 11, 2023 at 13:58

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