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LOW-POWER DISSIPATION, MATRIX ADDRESSING SCHEME FOR A THIN FILM MAGNETIC HEAD IMAGE BAR

IP.com Disclosure Number: IPCOM000025523D
Original Publication Date: 1985-Dec-31
Included in the Prior Art Database: 2004-Apr-04
Document File: 6 page(s) / 312K

Publishing Venue

Xerox Disclosure Journal

Abstract

The lifetime and reliability of electronic devices generally suffer if heat resulting frorn power dissipation is excessive. All electronic marking devices are subject to the usual heat-related failure mechanisms, such as, impurity diffusion and thermal stress, and for those in contact with heat sensitive materials (e.g., toner and magnetic particles), the marking process itself may be made inoperative by too much heat. While one approach is to take measures to remove the heat, a better approach is to reduce the power dissipated by effectively reducing the duty cycle of current passing through high resistance matrix addressing leads. This better approach is discussed below in terms of a specific low power dissipation matrix addressing scheme for a two-current-turn-per-head, thin film magnetic head (TFMH) image bar, but the same principles may be used in other multiplexing operations.

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XEROX DISCLOSURE JOURNAL

LOW -POWER DISSIPATION, MATRIX ADDRESSING SCHEME FOR A THIN FILM MAGNETIC HEAD IMAGE BAR Gary A. Kneezel

Proposed Classification US. CI. 346/74.5
Int. CI. Gllb 9/00

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Volume 10 Number 6 November/December 1985 34 1

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LOW-POWER DISSIPATION, MATRIX ADDRESSING SCHEME FOR A THIN FILM MAGNETIC HEAD IMAGE BAR (Cont'd)

The lifetime and reliability of electronic devices generally suffer if heat resulting frorn power dissipation is excessive. All electronic marking devices are subject to the usual heat-related failure mechanisms, such as, impurity diffusion and thermal stress, and for those in contact with heat sensitive materials (e.g., toner and magnetic particles), the marking process itself may be made inoperative by too much heat. While one approach is to take measures to remove the heat, a better approach is to reduce the power dissipated by effectively reducing the duty cycle of current passing through high resistance matrix addressing leads. This better approach is discussed below in terms of a specific low power dissipation matrix addressing scheme for a two-current-turn-per-head, thin film magnetic head (TFMH) image bar, but the same principles may be used in other multiplexing operations.

The TFMH image bar is an electronic printing device used to record latent images on a magnetic tape which are subsequently developed with magnetic toner and transferred to a permanent copy sheet such as plain paper. Presently, it is not considered practical to make a page-width line of thin film magnetic heads at a density of 300 per inch or higher on a single substrate. Instead, smaller modules are batch fabricated and butted together to form the desired full-width array. A matrix-addressable module for a 512 head, two-independent-current- turn-per- head module has arbitrarily been chosen as the configuration to be used when discussing this better approach of low power dissipation.

It was realized early that writing all elements or heads in a parallel fashion would be unwieldy, while writing all elements in serial fashion would yield a process speed that is too low using presently practical switching speeds. Switching must be particularly fast for the TFMH image bar, because each head needs to be pulsed on the order of 10 times to form each pixel. However, by writing 32 heads at once, the process speed goal of 20 inches per second for a 4096 head bar with a 3 mil downtrack resolution could be achieved with reasonable 8 MHz switching speed.

From a simplicity of addressing electronics point of view, addressing schemes, which rely on current through two independent current turns through each head, are advantageous. Figure 1 is a diagram of the 512 head two-turn-per-head array module 10. Passing through each head 12 (shown in dashed line) are two conductor lines 11, 13 which are independent of each other. As shown in Figure 1, geo...