TPS65251RHAT

The TPS65251 features three high-efficiency synchronous buck converters with a wide input range. This converter is designed to simplify its application while enabling designers to optimize their usage for target applications. The converter operates in 5V, 9V, 12V, or 15V systems with integrated power transistors. An external resistor divider can be used to set the output voltage to any value between 0.8V and the input supply voltage. Each converter includes the following pins: an enable pin that can delay startup for sequencing purposes; a soft-start pin that allows adjustment of the soft-start time by selecting a soft-start capacitor; and a current limit (RLIMx) pin that enables designers to adjust the current limit and optimize inductor selection by choosing an external resistor. The current mode control feature of the converter simplifies RC compensation. The switching frequency can be set using an external resistor connected to the ROSC pin or synchronized to an external clock connected to the SYNC pin. The switching regulator is designed to operate within a frequency range of 300kHz to 2.2MHz. The 180° out-of-phase operation between Buck Converter 1 and Buck Converters 2 and 3 (with Buck Converters 2 and 3 operating in phase) minimizes input filter requirements. The TPS65251 includes monitoring circuitry for each converter output. Upon completion of power sequencing, the PGOOD pin is asserted and all PG signals are reported after a selectable power-on reset delay period. The PGOOD signal is active-high. The TPS65251 also features a light-load pulse skip mode (PSM), which can be enabled by connecting the LOW_P pin to V3V. PSM mode allows reducing the input power supplied to the system when the host processor is in standby (low-activity) mode. The TPS65251 is a power management IC with three step-down buck converters. Both high-side and low-side MOSFETs are integrated to provide fully synchronous conversion with higher efficiency. TPS65251 can support 4.5-V to 18-V input supply, high load current, 300-kHz to 2.2-MHz clocking. The buck converters have an optional PSM mode, which can improve power dissipation during light loads. Alternatively, the device implements a constant frequency mode by connecting the LOW_P pin to ground. The wide switching frequency of 300 kHz to 2.2 MHz allows for efficiency and size optimization. The switching frequency is adjustable by selecting a resistor to ground on the ROSC pin. The SYNC pin also provides a means to synchronize the power converter to an external signal. Input ripple is reduced by 180 degree out-of-phase operation between Buck 1 and Buck 2. Buck 3 operates in phase with Buck 2. All three buck converters have peak current mode control which simplifies external frequency compensation. A traditional type II compensation network can stabilize the system and achieve fast transient response. Moreover, an optional capacitor in parallel with the upper resistor of the feedback divider provides one more zero and makes the crossover frequency over 100 kHz.

Applications

• Set-Top Box
• Blu-Ray DVD
• DVR
• Digital Television (DTV)
• Automotive Audio/Video
• Security Camera

Key features

• Wide input supply voltage range (4.5V to 18V)
• 0.8V voltage reference with 1% accuracy
• Continuous load current: 3A (Buck Switch 1), 2A (Buck Switch 2 and 3)
• Maximum current: 3.5A (Buck Switch 1), 2.5A (Buck Switch 2 and 3)
• Adjustable switching frequency 300kHz to 2.2MHz (set by external resistor)
• Dedicated enable pin for each buck switch
• External sync pin for oscillator
• External enable/sequencing and soft-start pins
• Adjustable current limit set by external resistor
• Soft-start pin
• Current mode control with simple compensation network
• Power good indication
• Optional low-power operating mode for light-load conditions
• 40-pin 6mm×6mm RHA VQFN package