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While the SIC462ED is the best option for price and efficiency, the beast of a chip has 30 pins

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. Based on simplicity and efficiency, the TPS54560B is chosen instead.

Datasheet

Typical Application Circuit

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• V_{in_max} = 55V, V_out = 5V, I_out= 5A, K_ind = ΔI_L/I_out = 0.3 (recommended by datasheet), and f_sw= 400kHz

• This gives Using the equation above, L_min = 7.6uH. Choose the next standard value of 8.2uH. The saturation current of the inductor should be greater than the switch current limit of 7.5A

https://www.digikey.ca/en/products/detail/würth-elektronik/7443330820/2175573

Output Capacitor

• Datasheet recommends C_out > 62.5uF to account for transient load response

• Use 3x 47uF 10V caps to get C_out = 90uF at 5V DC bias, which is safely above the minimum 62.5uF

• https://www.digikey.ca/en/products/detail/murata-electronics/GRM32EC81A476KE19L/2548451

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Catch Diode

• Reverse voltage rating must be > V_{in_max} = 55V

• Current rating must be > max inductor current = 5.8A

• Use schottky diode since it has lower forward voltage, resulting in higher converter efficiency

https://www.digikey.ca/en/products/detail/diodes-incorporated/PDS760-13/776756

Input Capacitor

• As per datasheet, C_in > 3uF and should be X5R or X7R rated for at least V_{in_max} = 55V

• Use 4x 2.2uF 100V, which provides 3.4uF at 55V DC bias

• Samsung caps were chosen over Murata as the Murata option was 3x more expensive

https://www.digikey.ca/en/products/detail/samsung-electro-mechanics/CL32B225KCJZW6E/7320552

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Bootstrap Capacitor

• 0.1uF 10V X5R capacitor is needed

https://www.digikey.ca/en/products/detail/murata-electronics/GCJ188R71E104KA12D/7363221

Undervoltage Lockout Setpoint Resistors

• For the converter to start supplying when V_in > 6.5V and stop supplying when V_in < 5V, R_UVLO1 = 441K and R_UVLO2 = 90.9K

https://www.digikey.ca/en/products/detail/yageo/RC0603FR-07442KL/727243

https://www.digikey.ca/en/products/detail/yageo/RC0603FR-0790K9L/727424

Output Voltage & Feedback Resistors

• For 5V output, R_LS = 10.2K and R_HS = 53.6K

https://www.digikey.ca/en/products/detail/yageo/RC0603FR-0710K2L/726883

https://www.digikey.ca/en/products/detail/yageo/AC0603FR-0753K6L/5896188

Compensation

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=1768Hz

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=707kHz

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=35.35kHz

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=18.8kHz

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=16.08K

Use standard value 16K:

https://www.digikey.ca/en/products/detail/yageo/RC0603JR-0716KL/726721

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=5626pF

Use standard value 5600pF:

https://www.digikey.ca/en/products/detail/murata-electronics/GRM1885C1H562JA01D/4421635

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=49.7pF

Use standard value 51pF:

https://www.digikey.ca/en/products/detail/murata-electronics/GRM1885C2A510JA01D/586986

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12V Buck

Requirements

• Steps down 18-55V to 12V

• The 12V rail is only used to power the vtx, which has a 500mA current draw. Ideally, the current limit of the buck converter should be closer to 750mA to be safe

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