Switch to AP3441LSHE-7B

[jackpot51]

All of the work is constrained to the area shown here:

• U4 and U17 changed to AP3441LSHE-7B
• U17 moved left to increase contact with VCC area on pin 7
• C32, C34, C35, C48, C49, C50 changed to 22uF
• Add 22pF capacitors C68 and C69
• R14 and R15 moved to the front
• Ground vias done in new ground pad of U4 and U17
• VCC fill area increased to cover pins 3 and 7 of U4 and U17
• RESET rerouted to minimize fill cuts
• CL_SEL nudged to the left to provide room for RESET via on U4
• Other minor routing changes in that area
• Revision updated to 1.2

I tried really hard to minimize fill cuts. I need help checking that I have done ground vias properly on U4 and U17, that the VCC area is sufficient for expected power, and anything else that would be affected by modifying that area. I don't see any high speed traces that have changed, or fills underneath them. So most of my concern is with power stability.

[dlharmon]

I expect this will perform as desired.

C68 and C69 would probably be better as 220 pF. This would provide the same transfer function for the feedback network as in Table 1 of the AP3441 data sheet. Alternately, the resistor values could be increased by a factor of 10 to match the data sheet. Realistically, it should work fine with 22 pF or even no part populated.

Pin 3 of the AP3441 is the power input to the switch, pin 7 is just an enable. Input capacitor placement could be closer to pin 3. I expect it to work properly given the wide plane area and thin dielectric to the ground plane. EMI may be slightly increased over optimal capacitor placement.