Power distribution system design using LT3694 DC DC converter

The LT3694 is a monolithic, current mode DC-DC converter that can be designed as a simple step-down converter, supporting a maximum output current of 2.6 A. This switching step-down converter is capable of generating up to 2.6 A at its output and features independent track/soft-start circuits for each regulator, simplifying power supply sequencing and interfacing with microcontrollers and DSPs. The switching frequency can be set with a single resistor, ranging from 250 kHz to 2.5 MHz. The high switching frequency allows for the use of small inductors and ceramic capacitors, resulting in compact triple output solutions. Protection circuitry monitors the current in the power switch and external Schottky catch diode, safeguarding the LT3694 against short-circuit conditions. Frequency foldback and thermal shutdown offer additional protection. As illustrated in the circuit diagram, this switching DC-DC converter circuit provides three independent output voltages of 1.8 V, 2.5 V, and 3.3 V, with a maximum output current of approximately 2.6 A. The input voltage range required by this circuit spans from 6 V to 36 V. The BIAS pin enables the internal circuitry to draw its current from a voltage supply lower than VIN, thereby reducing power dissipation and enhancing efficiency. If the voltage on the BIAS pin drops below 2.7 V, the quiescent current will flow from VIN. The LDO regulator employs an external NPN pass transistor to establish a linear regulator, with the loop internally compensated to ensure stability with a minimum load capacitance of 2.2 µF. The LDO also incorporates a foldback current limiter to protect the external transistor under overload conditions. This DC-DC power converter circuit is suitable for various electronic projects, including cable modems, power distributions, automotive, and industrial applications.

The LT3694 monolithic DC-DC converter is designed for high efficiency and versatility in power management applications. Its ability to provide three independent output voltages makes it particularly useful in systems requiring multiple voltage levels. The configuration allows for a seamless integration into compact designs, thanks to the high switching frequency, which minimizes the size of passive components.

Key components of this circuit include the power switch, Schottky diode, and the external NPN pass transistor for the LDO regulator. The power switch operates efficiently under varying load conditions, while the Schottky diode ensures quick response times for current rectification. The external NPN transistor allows for higher output currents than might otherwise be possible with an integrated solution alone.

The protection features are critical for maintaining the integrity of the circuit during operation. The current sensing mechanism ensures that any excessive current draw is detected promptly, triggering protective measures to prevent damage. The frequency foldback feature reduces the switching frequency under overload conditions, further protecting the circuit from thermal stress.

In applications such as automotive power distribution, the LT3694’s wide input voltage range accommodates fluctuations in supply voltage, making it reliable for use in harsh environments. Its efficiency and compact design make it suitable for use in battery-powered devices, where power conservation is paramount.

Overall, the LT3694 DC-DC converter represents an effective solution for designers seeking a reliable, efficient, and compact power supply for a variety of electronic applications.Using the LT3694 monolithic, current mode DC DC converter can be designed a very simple step down converter that will can support a maximum output current of 2. 6A. LT3694 switching step-down converter (capable of generating up to 2. 6A at its output) has independent track/soft-start circuits (for each regulators ) simplifying power supply sequenci

ng and interfacing with micro-controllers and DSPs. The switching frequency is set with a single resistor with a range of 250kHz to 2. 5MHz. The high switching frequency permits the use of small inductors and ceramic capacitors leading to very small triple output solutions. Protection circuitry senses the current in the power switch and external Schottky catch diode to protect the LT3694 against short-circuit conditions.

Frequency foldback and thermal shutdown provide additional protection. As you can see in the circuit diagram this switching DC DC converter circuit will provide three independent output voltages of 1. 8V, 2. 5V and 3. 3 volt. The maximum output current that can be provided by this circuit is around 2. 6A. The input voltage range required by this circuit can be from 6 volt up to 36 volt. The BIAS pin allows the internal circuitry to draw its current from a voltage supply lower than VIN, reducing power dissipation and increasing efficiency.

If the voltage on the BIAS pin falls below 2. 7V, then its quiescent current will flow from VIN. The LDO regulator uses an external NPN pass transistor to form a linear regulator. The loop is internally compensated to be stable with a minimum load capacitance of 2. 2 F. The LDO also has a foldback current limiter available to protect the external transistor under overload conditions. This DC DC power converter circuit can be used in various electronic projects like :cable modems, power distributions, automotive and industrial applications.

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