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Demonstration circuit 2949A is a 40V 4-Switch Buck-Boost Controller configured for automotive USB-C PD charging applications supporting up to 45W output power capability featuring the LT8253A. LT8253A powers devices connected through the USB-C port at voltages between 3.3V and 16V at up to 3A when VIN is between 9V and 18V. DC2949A will run down to 6V at its input with reduced output power capability and can operate through up to 36V input transient conditions. DC2949A runs at 2MHz switching frequency and features spread spectrum frequency modulation (SSFM) for reduced EMI.
The LT8253A has an operating input voltage range of 4V to 40V. LT8253A can regulate an output as a boost, a buck, or a 4-switch buck-boost controller. LT8253A has an adjustable switching frequency between 600kHz and 2MHz, with an option for external frequency synchronization or ±25% spread spectrum frequency modulation.
DC2949A utilizes a USB-C port controller (CYPD3196) to interface between connected USB-C devices and the LT8253A power circuitry in order to comply with the latest USB Type-C and PD standards. This port controller device is powered directly from the INTVCC pin of the LT8253A. The port controller facilitates the power contract negotiation between the connected device and DC2949A and adjusts the voltage at the FB divider to set the output voltage accordingly. The LT8253A system monitors input voltage, output voltage and current, and measured temperature on board to help adjust output power capabilities based off measured operation parameters, as well as provide output overvoltage, undervoltage, and overcurrent protection.
The DC2949A is preloaded with firmware configured to support output power delivery up to 45W using the latest USB PD 3.0 protocol, and offers the following PDO/PPS output configuration options:
PDO: 5V AT 3A, 9V AT 3A, 15V AT 3A
PPS: 3.3V–5.9V AT 3A, 3.3–11V AT 3A, 3.3–16V AT 3A
DC2949A firmware is also configured to support legacy charge profiles including BC 1.2, QC 4.0 and 3.0, AFC, and Apple 2.4A charging. Firmware can be updated to support different PDO voltage and power levels. Contact factory apps for support.
The LT8253A data sheet gives a complete description of the part, operation, and applications information. The data sheet must be read in conjunction with the demo manual for DC2949A. The LT8253AJUFDM is assembled in a 28-lead plastic side-wettable QFN (UFDM) package with a thermally enhanced exposed ground pad. Proper board layout is essential for maximum thermal performance. See the data sheet section “PC Board Layout Checklist."