TPS65250RHAR

The TPS65250RHAR is a highly integrated triple-channel synchronous step-down DC/DC converter from Texas Instruments. Designed for applications requiring multiple regulated low-voltage rails from a higher-voltage input, this device combines three independent buck converters into a single 40-pin VQFN package, significantly reducing component count, PCB area, and system cost compared to discrete solutions.

Operating from a wide 4.5 V to 18 V input range, the TPS65250 can be powered from 5V, 12V, or multi-cell battery supplies. Buck1 provides up to 3 A of output current, while Buck2 and Buck3 each deliver up to 2 A. Each converter has an adjustable output voltage range of 0.765 V to 7 V, set via an external resistor divider from the 0.765 V internal reference.

All three converters operate at a fixed 1.5 MHz switching frequency using peak current-mode control, providing excellent line and load transient response. The converters operate with 180° phase shift between channels (Buck2 and Buck3 are 180° out of phase with Buck1), which reduces input ripple current and the required input capacitance, lowering both cost and EMI.

Each channel has dedicated enable and power-good pins, allowing independent control and monitoring. Integrated soft-start circuitry, with adjustable timing via external capacitors, ensures controlled inrush current during startup. The device includes comprehensive protection features: cycle-by-cycle current limit, hiccup-mode short circuit protection, output overvoltage protection, undervoltage lockout, and thermal shutdown.

Additionally, the TPS65250 includes two low-side gate driver outputs (LDO1 and LDO2 pins) capable of driving external N-channel MOSFETs for load switch or inrush control applications.

The TPS65250 contains three independent synchronous buck converters with the following operating principles:

1. Control Architecture: Each converter uses fixed-frequency peak current-mode control. The inner current loop regulates peak inductor current by comparing the current sense signal to the error amplifier output. The outer voltage loop regulates the output voltage through the error amplifier, which compares the feedback voltage to the internal 0.765 V bandgap reference.

2. Synchronous Rectification: Each converter integrates both a high-side (control) and low-side (synchronous) N-channel MOSFET. The low-side FET conducts during the off-time of the high-side FET, providing a low-loss current path that significantly improves efficiency compared to diode rectification, especially at low output voltages.

3. Out-of-Phase Operation: Buck2 and Buck3 operate 180° out of phase with Buck1. This interleaving reduces the peak input current drawn from the supply, reducing input ripple and allowing the use of smaller input capacitors. It also reduces conducted and radiated EMI.

4. Soft-Start: Each channel has an internal soft-start circuit that ramps the reference voltage during startup. An external capacitor on the SS pin can be used to extend the soft-start time, reducing inrush current when driving large capacitive loads.

5. Current Limit and Protection: Cycle-by-cycle peak current limit protects the power MOSFETs and inductor from overcurrent conditions. If the output is shorted, the device enters hiccup mode, periodically retrying to limit power dissipation. Output overvoltage protection clamps the output if it exceeds regulation limits.

6. Low-Side Drivers: Two integrated low-side drivers (LSD1 and LSD2) can drive external N-channel MOSFETs for use as load switches or inrush current limiters. These are controlled via the EN_LSD pins.

Note: Full pin details and recommended layout are available in the datasheet. The exposed thermal pad should be connected to the ground plane with multiple vias for optimal thermal performance.

• Industrial Control Systems: Powering multiple voltage rails in PLC modules, motor drives, and factory automation equipment where 12V or 24V input is stepped down to 5V, 3.3V, and 1.8V.
• Telecommunications and Networking: Multi-rail power supplies for routers, switches, and telecom modules, providing core, I/O, and memory voltages from a 12V system bus.
• FPGA and DSP Power: Power supply solutions for FPGA, DSP, and ASIC designs requiring multiple tightly-regulated voltage rails with sequencing and power-good signaling.
• Set-Top Boxes and Gateways: Consumer electronics and residential gateway devices needing multiple efficient DC-DC converters from a 12V adapter supply.
• Server and Storage Systems: Point-of-load (POL) converters in server motherboards and storage arrays, providing secondary regulation from a 12V intermediate bus.
• Test and Measurement Equipment: Benchtop and portable instruments requiring multiple high-efficiency power rails with good regulation and transient response.
• Automotive Infotainment: Infotainment and ADAS systems (with appropriate front-end protection) where the 12V battery supply must generate several low-voltage rails for processors, memories, and peripherals.