add LTM4638/LTM4626/LTM4657: Analog Devices 20VIN, 15A/12A/8A Step-Down DC/DC uModule Regulator, BGA-49

This are 3 pin-compatible Step-Down DC/DC uModule Regulators from Analog Devices in a 6.25x6.25mm 7x7 BGA-49

Datasheets:

• 15A Version: https://www.analog.com/media/en/technical-documentation/data-sheets/ltm4638.pdf
• 12A Version: https://www.analog.com/media/en/technical-documentation/data-sheets/ltm4626.pdf
• 8A Version: https://www.analog.com/media/en/technical-documentation/data-sheets/ltm4657.pdf

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