And8350.rev0

Prepared by: Alan Ball
ON Semiconductor
http://onsemi.com
APPLICATION NOTE
Introduction
the high side or an n-channel FET can be added in the low Semiconductor’s eFuses offer low cost, low impedance solutions for bus protection and offer much N-channel FETs are more cost effective and are normally faster protection than many fuse solutions. They are an preferred if it is acceptable to break the ground line. If the effective replacement for a polyfuse and TVS clamping load has other connections to circuits that may be energized under a reverse polarity input condition, the ground should One area in which they differ in performance is reverse polarity protection. While a TVS device and polyfuse will If it is required to break the high side, a p-channel FET protect against reverse voltages, the nature of an integrated should be used. The two circuit configurations are shown in semiconductor device does not inherently allow for this type The reverse protection circuit includes a zener protection This simple circuit allows the device to protect against diode to protect against excessive gate to source voltage that reverse voltage situations by simply blocking the reverse could damage the FET. For FETs with 12 V or lower gates, voltage. This is equivalent of the action of a poly fuse only this is recommended. For FETs with 20 V gates, the zener with less leakage. In comparison to a mechanical fuse, this and resistor can be eliminated and the gate tied directly to the is a far superior solution since the mechanical fuse will not other rail as long as the maximum system transient spec is reset and this circuit will automatically reset when the A table of suggested FETs is included. The voltage and Circuit Description
DS(on) are only suggestions. The system voltage specifications should be taken into account to determine the In order to protect against reverse voltages an external maximum FET voltage and the losses due to the R switch is required. There are two basic topologies that can the FET. Please see the ON Semiconductor website accomplish this function. A p-channel FET can be added in (www.onsemi.com) for more options for FET choices.
Figure 1. High-side Protection Circuit.
Semiconductor Components Industries, LLC, 2008 November, 2008 − Rev. 0
AND8350/D
Figure 2. Low-side Protection Circuit.
Table 1. SUGGESTED FETS FOR REVERSE PROTECTION CIRCUITS
Recommended
N-Channel FETs
Recommended
P-Channel FETs
ON Semiconductor and are registered trademarks of Semiconductor Components Industries, LLC (SCILLC). SCILLC reserves the right to make changes without further notice
to any products herein. SCILLC makes no warranty, representation or guarantee regarding the suitability of its products for any particular purpose, nor does SCILLC assume any liability arising out of the application or use of any product or circuit, and specifically disclaims any and all liability, including without limitation special, consequential or incidental damages.
“Typical” parameters which may be provided in SCILLC data sheets and/or specifications can and do vary in different applications and actual performance may vary over time. All operating parameters, including “Typicals” must be validated for each customer application by customer’s technical experts. SCILLC does not convey any license under its patent rights nor the rights of others. SCILLC products are not designed, intended, or authorized for use as components in systems intended for surgical implant into the body, or other applications intended to support or sustain life, or for any other application in which the failure of the SCILLC product could create a situation where personal injury or death may occur. Should Buyer purchase or use SCILLC products for any such unintended or unauthorized application, Buyer shall indemnify and hold SCILLC and its officers, employees, subsidiaries, affiliates, and distributors harmless against all claims, costs, damages, and expenses, and reasonable attorney fees arising out of, directly or indirectly, any claim of personal injury or death associated with such unintended or unauthorized use, even if such claim alleges that SCILLC was negligent regarding the design or manufacture of the part. SCILLC is an Equal Opportunity/Affirmative Action Employer. This literature is subject to all applicable copyright laws and is not for resale in any manner.
PUBLICATION ORDERING INFORMATION
LITERATURE FULFILLMENT:
N. American Technical Support: 800−282−9855 Toll Free
ON Semiconductor Website: www.onsemi.com
Literature Distribution Center for ON Semiconductor P.O. Box 5163, Denver, Colorado 80217 USA Europe, Middle East and Africa Technical Support:
Order Literature: http://www.onsemi.com/orderlit
Phone: 303−675−2175 or 800−344−3860 Toll Free USA/Canada
Fax: 303−675−2176 or 800−344−3867 Toll Free USA/Canada
Japan Customer Focus Center
For additional information, please contact your local Email: [email protected]
http://onsemi.com
AND8350/D

Source: http://www.ansenmei.com.cn/pub/Collateral/AND8350-D.PDF