Constant-Frequency, Current-Mode Step-Up DC/DC Controller
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Product Details

The ADP1621 is a fixed-frequency, pulse-width modulation (PWM), current-mode, step-up converter controller. It drives an external n-channel MOSFET to convert the input voltage to a higher output voltage. The ADP1621 can also be used to drive flyback, SEPIC, and forward converter topologies, either isolated or nonisolated.

The ADP1621 eliminates the use of a current-sense power resistor by measuring the voltage drop across the on resistance of the n-channel MOSFET. This technique, allowed up to a maximum voltage of 30 V at the switch node, maximizes efficiency and reduces cost. For switch-node voltages higher than 30 V or for more accurate current limiting, the CS pin can be connected to a current-sense resistor in the source of the MOSFET. The slope compensation is implemented by an external resistor, allowing a wide range of external components (inductors and MOSFETs), and can be chosen for various switching frequencies and input and output voltages.

The ADP1621 supply input voltage range is 2.9 V to 5.5 V, although higher input voltages are possible with the use of a small-signal NPN pass transistor or a single resistor. The voltage of the power input can be as low as 1 V for fuel cell applications. The switching frequency is set by an external resistor over a range of 100 kHz to 1.5 MHz and can be synchronized to an external clock by using the SDSN pin. The shutdown quiescent current is less than 10 μA. The ADP1621 has a thermal shutdown feature that shuts down the gate driver when the junction temperature reaches approximately 150°C. The internal soft start circuit limits inrush current at startup. The ADP1621 is available in the 10-lead MSOP lead-free package and is specified over the −40°C to +125°C junction temperature range.


  • APD bias
  • Portable electronic equipment
  • Isolated dc/dc converter
  • Step-up/step-down dc/dc converter
  • LED driver for laptop computer and navigation system
  • LCD backlighting

Product Lifecycle

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At least one model within this product family is in production and available for purchase. The product is appropriate for new designs but newer alternatives may exist.

Evaluation Kits

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Product Details

The input range for the demo board is 3.0 V to 3.6 V, and the output voltage is 5 V with a maximum load of 2 A. The design is done in a bootstrapped configuration as shown in Figure 13. The switching frequency fSW is set to 600 kHz with a 36 kΩ resistor. This design is done in all multilayer ceramic capacitors (MLCC), although other types of capacitors can be used, such as the aluminum polymer or aluminum electrolytic capacitors. The PCB is laid out in such a way that the user can easily modify the demo board for other input and output configurations.

Product Details

In order to get the correct unpopulated evaluation board with an appropriate Bill of Materials and Schematic, you need to use the button for "Request Evaluation Board" from within the design tool. Make sure the design tool is in a state that matches your desired power requirements.

This will create a template email that will request from us the proper blank evaluation board for that ADI part and your application's power parameters.

Note: Some parts have multiple blank boards for high/low current or for different topologies (Boost, SEPIC, SEPIC-Cuk), while other blank boards support multiple ADI parts. This is why it is important to run the design tool with your parameters before making your email request from the tool.

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Reference Designs

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CN0328 Circuit Diagram

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CN0342 Circuit Diagram

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ADI has always placed the highest emphasis on delivering products that meet the maximum levels of quality and reliability. We achieve this by incorporating quality and reliability checks in every scope of product and process design, and in the manufacturing process as well.  "Zero defects" for shipped products is always our goal.

ADP1621 Material Declaration
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Evaluation Boards Pricing displayed is based on 1-piece.
Pricing displayed is based on 1-piece. The USA list pricing shown is for budgetary use only, shown in United States dollars (FOB USA per unit), and is subject to change. International prices may vary due to local duties, taxes, fees and exchange rates.