QUAD SUPPLY MANAGER (SMT4004): FIGURE 3

Note: See the SMT4004 Data Sheet, AN20, AN22 and the SMT4004EV User's Guide for basic design information.

Nuisance Tripping Avoidance Tips

Some applications using the SMT4004 benefit from the addition of minor external filtering. Additional immunity to transient overcurrent events is obtained by adding an R-C filter between the current sense resistor and the CBx input pin. A 1mS time constant delay results from the addition of R18 and C51.

DC-DC converters exhibiting poor transient output voltage response or excessive output ripple voltage may disturb the tracking waveforms. The addition of a small-value capacitor to each VGATE output (C50) of 1-10nF lowers the effective output impedance of these pins making them less vulnerable to step voltage changesoccurring on the drain and source terminals of the MOSFET (Q1).

The capacitor values shown for the VGG_CAP, VDD_CAP and 1.25VREF pins are proven to be ideal for most applications. Be certain to locate these components physically close to the SMT4004 and connect them directly to the device's ground pins.

Systems exhibiting a pre-existing 'early voltage' on the card-side may not track properly if this voltage is excessive (>0.5V). Use a suitable MOSFET (Q10) to discharge this voltage prior to the tracking interval. This function is covered in more detail in the SMT4004 data sheet.

Figure 3: Quad Tracker/Manager Filtering and 'Early Voltage' Circuits

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.

Version 2.0 - This document supersedes all previous versions.

return to top

home

technical support

Copyright © 2002 SUMMIT MICROELECTRONICS, Inc.
I²C is a trademark of Philips Corporation.