Summit Microelectronics - Applications Note 35

This application note was jointly authored by Volterra Semiconductor and Summit Microelectronics.

Tech Support: Applications Note 35
Lossless Tracking Procedure and Results Summary
Reference Design: Volterra VT223 Regulator and SMT4214 TRAKKER™

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Lossless Tracking Procedure and Results Summary
Reference Design: Volterra VT223 Regulator and SMT4214 TRAKKER

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Figure 5. SMT4214 to VT223 Active Interface

To permit the SMT4214 to control the output voltage of the VT223, an active device is employed as a 'bridge' between the SMT4214's VGATE output and the VT223's VREF input. A suitable choice is a depletion-mode, JFET transistor.

The JFET's drain to source resistance is low when its gate to source voltage is zero volts and increases to a virtual open circuit when the pinch-off voltage (V_GS(off)) is reached. Figure 4 displays the electrical connections made to the VT223 using a P-channel JFET. The gate terminal is driven by the SMT4214's VGATE output.

Connecting the SMT4214 to the VT223, as shown in Figure 6, results in the Track-Up and Track-Down waveforms displayed in Figures 7 and 8, respectively. Note the linearity of the waveforms provided by the SMT4214's closed loop control of the slew-rate and maximum voltage differential allowed between channels.

Figure 6. SMT4214/VT223 Interface Schematic (Simplified) for Tracking 2 Voltages with Reset Control.

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SUMMIT Microelectronics, Inc. reserves the right to make changes to the products contained in this publication in order to improve design, performance or reliability. SUMMIT Microelectronics, Inc. assumes no responsibility for the use of any circuits described herein, conveys no license under any patent or other right, and makes no representation that the circuits are free of patent infringement. Charts and schedules contained herein reflect representative operating parameters, and may vary depending upon a user's specific application. While the information in this publication has been carefully checked, SUMMIT Microelectronics, Inc. shall not be liable for any damages arising as a result of any error or omission.

SUMMIT Microelectronics, Inc. does not recommend the use of any of its products in life support or aviation applications where the failure or malfunction of the product can reasonably be expected to cause any failure of either system or to significantly affect their safety or effectiveness. Products are not authorized for use in such applications unless SUMMIT Microelectronics, Inc. receives written assurances, to its satisfaction, that: (a) the risk of injury or damage has been minimized; (b) the user assumes all such risks; and (c) potential liability of SUMMIT Microelectronics, Inc. is adequately protected under the circumstances.

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