TPS65258RHAR

TPS65258 is a power management IC featuring three buck converters. With integrated high-side and low-side MOSFETs, it delivers highly efficient fully synchronous conversion. These converters are designed to simplify applications while allowing designers to optimize their use for the target application. The converters operate in 5-, 9-, 12-, or 15-V systems. Output voltage can be set externally using a resistor divider to any value between 0.8 V and the input voltage minus the resistive voltage drop across the converter path. Each converter has a dedicated enable pin that allows delayed startup for sequencing purposes; a soft-start pin allows adjustment of the soft-start time by selecting an appropriate soft-start capacitor; and a current limit (RLIM) pin enables designers to adjust the current limit and optimize inductor selection by choosing an external resistor. All converters operate in "hiccup mode": once any converter detects an overcurrent condition lasting more than 10 ms, it shuts down for 10 ms and then retries the startup sequence. If the overload has been removed, the converter ramps up and resumes normal operation. Otherwise, the converter treats the condition as another overload event and shuts down again; this hiccup process repeats until the fault is cleared. If the overload duration is less than 10 ms, only the affected converter shuts down and restarts — this does not trigger a global hiccup mode. The switching frequency of the converters is set by an external resistor connected to the ROSC pin. The switching regulators are designed to operate at frequencies from 300 kHz to 1.2 MHz. The converters operate 180° out of phase with each other to minimize input filter requirements. All converters feature peak current mode control to simplify external frequency compensation. The device incorporates a built-in slope compensation ramp to prevent subharmonic oscillation in peak current mode control. A conventional Type II compensation network stabilizes the system and achieves fast transient response. Additionally, an optional capacitor placed in parallel with the upper resistor of the feedback divider provides a 10× increase in crossover frequency, enabling crossover frequencies above 100 kHz. All converters feature an automatic low-power PFM mode, which improves efficiency during light-load and standby operation while maintaining very low output ripple — the allowable value is less than 2% at low output voltages. The device includes a transient overvoltage protection circuit to minimize voltage overshoot. Through a circuit that compares the FB pin voltage against the OVP threshold voltage (109% of the internal voltage reference), OVP minimizes output overshoot. If the FB pin voltage exceeds the OVP threshold, the high-side MOSFET is disabled to prevent current from flowing to the output and to minimize output overshoot. When the FB voltage drops below the lower OVP threshold (107% of the internal reference voltage), the high-side MOSFET is enabled at the next clock cycle. The TPS65258 features a monitoring circuit that monitors each buck output; once sequencing is complete, the PGOOD pin is asserted. The PGOOD pin has an open-drain output. When any buck converter's output is pulled below 85% of its rated output voltage, the PGOOD pin is driven low. When all converter outputs exceed 90% of their rated output voltages, the PGOOD pin is driven high. The default reset time is 100 ms. PGOOD polarity is active high. The two USB switches provide up to 1-A current for downstream USB devices. When the output load exceeds the current limit threshold or a short circuit occurs, the PMU limits the output current to a safe level by switching to constant current mode and pulling the overload logic output low. When sustained high overload or short circuit conditions in the switch increase power dissipation and cause the junction temperature to rise, an overtemperature warning protection circuit shuts down the USB switch while allowing the buck converters to continue operating. If the junction temperature exceeds 160°C, the device performs an internal thermal shutdown to protect itself. When the junction temperature exceeds the thermal cutoff threshold, thermal shutdown forces the device to stop operating. Once the temperature drops below 140°C, the device restarts the power-on sequence. The thermal shutdown hysteresis protection temperature is 20°C.

Key features

• Wide input supply voltage range: 4.5 V – 16 V
• 0.8-V, ±1% accuracy reference
• Continuous load current: 3 A (Buck Converter 1), 2 A (Buck Converters 2 and 3)
• Peak current: 3.5 A (Buck Converter 1), 2.5 A (Buck Converters 2 and 3)
• Synchronous operation, external resistor-programmable 300-kHz – 2.2-MHz switching frequency
• External enable pin with built-in current source for simple sequencing
• External soft-start pin
• External resistor-programmable adjustable cycle-by-cycle current limit
• Current mode control with simple compensation network
• Automatic low pulse skip mode (PSM) allowing output current ripple less than 2%
• Forced PWM mode
• Pre-biased output support
• Power-good monitor and reset generator
• Two 1-A USB power switches with overload and overtemperature protection
• Small, high thermal efficiency 40-pin 6-mm × 6-mm RHA (QFN) package
• –40°C to 125°C junction temperature range