ON SEMICONDUCTOR CORP — Director's Dealing 2010

Mar 5, 2010

SEC Form 4 — Statement of Changes in Beneficial Ownership

Issuer: ON SEMICONDUCTOR CORP (ONNN)
CIK: 0001097864
Period of Report: 2010-03-03

Reporting Person: Mahoney Robert Charles (Exec VP Sales & Marketing)

Non-Derivative Transactions

Date	Security	Code	Shares	Price	A/D	Holdings After	Ownership
2010-03-03	Common	F	4204	$8.2	Disposed	73738	Direct
2010-03-04	Common	M	22500	$5.93	Acquired	96238	Direct
2010-03-04	Common	S	22500	$8.0835	Disposed	73738	Direct
2010-03-04	Common	S	25000	$8.0835	Disposed	48738	Direct

Derivative Transactions

Date	Security	Exercise Price	Code	Shares	A/D	Expiration	Underlying	Ownership
2010-03-04	Stock Option (right to buy)	$5.93	M	22500	Disposed	2018-03-03	Common (22500)	Direct

Footnotes

F1: This disposition transaction represents shares withheld by the Issuer pursuant to the Reporting Person's March 3, 2008 award of restricted stock units. On March 3, 2010, certain of these units vested. These shares were withheld to satisfy the Reporting Person's withholding obligations for various taxes and similar items. The Issuer will pay these taxes on behalf of the Reporting Person.

F2: This disposition transaction was executed in multiple trades at prices ranging from $8.08 to $8.0926. The price reported above reflects the weighted average sale price. The Reporting Person hereby undertakes to provide, upon request, to the SEC staff, the Issuer, or a security holder of the Issuer, full information regarding the number of shares and prices at which the transaction was effected.