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Four-Pin Fan Header Functional Test Emulator

IP.com Disclosure Number: IPCOM000032220D
Publication Date: 2004-Oct-26
Document File: 2 page(s) / 34K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method that uses a low pass filter and voltage controlled oscillator to emulate a cooling fan for functional test purposes. Benefits include a solution that is more durable and costs less than a fan assembly.

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Four-Pin Fan Header Functional Test Emulator

Disclosed is a method that uses a low pass filter and voltage controlled oscillator to emulate a cooling fan for functional test purposes. Benefits include a solution that is more durable and costs less than a fan assembly.

Background

Upcoming products will have a new four-pin fan header, instead of the three-pin fan header that is currently used. The fourth signal corresponds to the fan speed control; using the current emulator card, there is no way to test this fourth signal. Currently, the only way to test the new solution would be to use a four-pin cooling fan to test the integrity of the header.

General Description

The disclosed method’s emulator circuit consists of a low pass filter section (R11 and C3) that converts the PWM signal to a DC voltage (see Figure 1). This DC voltage drives an integrator with a mid-voltage reference (U1B). The output of the integrator drives a comparator with a variable threshold. The output of the comparator feeds back to the input of the comparator and the integrator. The output of the comparator controls the input threshold level of the comparator through R1, R2, R3, and R9.  The comparator threshold varies between .25Vcc1 and .75Vcc1.  The output of the comparator also controls the input level to the integrator. The reference voltage for the integrator is half the input from the low pass filter.

When the comparator output is low, the input to the integrator (U1B pin 6) is equal to the vol...