TPS62421DRCT

TPS62421DRCT application field and working principle

The TPS62421DRCT, a 4.5- V to 36-V, 1-A synchronous step-down converter, belongs to the PMIC – Voltage Regulators – DC DC Switching Regulators, category. This device features a fast transient response with a minimal amount of external components. It offers high efficiency, low output noise and high accuracy with wide input/output voltage range.

Applications
The TPS62421DRCT is suitable for multiple high power-supply applications such as notebook adapters, line cards, communication and sensor nodes, display controller and backlight applications. This device is suitable for medium-to-high current applications over a wide input range (4.5 to 36 V).

Features
• 4.5-V to 36-V Input Voltage Range
• Adjustable Output Voltage Down to 0.6 V
• Output Current up to 1A
• Programmable Switching Frequency up to 2.2 MHz
• Internal Synchronous N-Channel MOSFET
• Output Discharge during Shutdown
• Thermal Shutdown Protection
• Cycle-by-Cycle Current Limit
• Low Profile 0.75-mm 5-pin SON Package

Working Principle

The TPS62421DRCT is a regulator with an integrated DC-DC controller that provides a step-down converter with a high efficiency, high performance and low noise output. It offers an adjustable output voltage of 0.6 V to 5 V and an output current of up to 1 A.

The TPS62421DRCT regulates the output voltage by starting a switching cycle in response to certain inputs. When the EN (enable) and SYNC (synchronization) inputs are low, the switch turns off and the DRAIN signal goes to V_IN, producing a high-impedance state. When EN is high, the oscillator will be enabled and a complete cycle will start.

The cycle starts with the input signal going low, indicating the start of a switching cycle. The frequency of the oscillator is determined by a combination of the resistors and capacitor values connected to the SYNC and COM pins. The switching cycle will start at the beginning of the SYNC pin rising edge and a continuous pulse train of oscillations is generated.

When a switching cycle starts, the oscillator signal goes low, producing a high-impedance state. This stops the flow of current from the input voltage source to the output, thus regulating the output voltage. At the end of the cycle, when the oscillator signal goes high, the DRAIN signal is driven low and the switch is turned on. This circulates current from the input to the output terminals.

The DRAIN voltage is compared to the internal reference voltage and the comparative result will be used to adjust the PWM cycle of the switching period. This continuous process is known as the regulation loop. With this regulation loop, the required output voltage is obtained.

To maintain constant output voltage, the device uses an internal reference voltage of 0.6 V. The output voltage set point is set by an external resistor divider network connected between the feedback pin and GND. The voltage divider network adjusts the voltage presented to the internal regulator. Once the output voltage reaches the set point, the internal comparator drives the DRAIN signal low and the oscillator signal is stopped.

The TPS62421DRCT also features cycle-to-cycle current limit, an output discharge circuit and thermal shutdown protection. The cycle-by-cycle current limit prevents the device from supplying current beyond its rated limit. The output discharge circuit enables the output voltage to be discharged to GND during shutdown. The thermal shutdown circuit disables the device in case of over-temperature conditions.

The TPS62421DRCT is a high performance and efficient step-down switching converter. It offers a wide input voltage range, adjustable output voltage, programmable switching frequency, current limit and thermal shutdown protection. Design engineers can use it in notebook adapter, communications, sensors, display controller and backlight applications.