PC Motherboard Testing Application Note

General

It is often desirable to verify the proper operation of PC motherboards before final computer assembly. Also it is sometimes beneficial to subject computer boards to environmental stresses while testing. Test schemes of today often range from very simple to those of high complexity. While there are many different test schemes being applied today, it is understood that no test scheme is right for all situations. The purpose of this application note is to acquaint you with how Thermotron's Product Test System (PTS) may be applied in the testing of motherboards. The Product Test System is ideal for functional testing in design validation, stress screening, production validation and accelerated life test schemes. Figure 1 illustrates one Product Test System configuration for PC Motherboard testing.

Motherboard Test Strategies

Figure 1

Voltage Margining, or controlling operating voltages to high and low specifications is often performed in conjunction with temperature and/or humidity control. In addition, it is quite common to perform other types of tests as the motherboard supply voltage is adjusted.

Power supply output can be controlled by the PTS Power Supply Module (PSM-02) while the Environmental Chamber operation is controlled by PTS software. The PSM-02 Function Module can control two resistive programmable power supplies. To voltage margin a typical motherboard operating on four voltages, four power supplies and two PSM-02 Function Modules would be required. The number of boards that may be voltage margined at a given time is directly dependent on the output capability of the test system's power supplies.

Verification of on-board operating voltages can be provided by the use of an Analog Input Module (AIM-32). The AIM-32 can monitor 32 single ended or 16 differential analog signals. As a result, a large number of motherboards can be monitored efficiently and continuously.

Current Draw Monitoring of each motherboard can provide an excellent method of monitoring the proper operation of the board. Voltage outputs produced by inductive current sensors or shunt resistors can be monitored by an Analog Input Module. Voltage levels from either type of current sensor are compared to user defined high and low limits of the AIM-32 Module. If a limit is exceeded, the failure is displayed and logged. In addition, the AIM-32 module provides a method of controlling the removal of product power once an error is detected.

Serial Communication to a computer motherboard provides an excellent opportunity for initiating diagnostic routines, downloading test programs and monitoring the product for diagnostic error codes. The PTS Serial Communication Module (SCM-05) provides five individual serial I/O channels for product testing. The SCM-05 can transmit user programmed data strings to products employing a RS-232, RS-422 or RS-485 serial interface. In addition, the SCM-05 can verify the response from the product. If an failure is detected, it will be displayed and stored in a log file. Like all PTS function modules, the SCM-05 can also provide the capability of removing product power if a failure is detected.

PTS Profiles

Once the PTS equipment is configured, the PTS software must be configured. To configure the PTS software, profiles are defined for the function modules that are used. In this case, AIM-32, PSM-02, SCM-05 and temperature/humidity profiles need to be defined. No code generation is required, only test values need to be defined.

Possible PC Motherboard Tester Physical Configuration

Figure 2

A 19 inch console is typically used for PTS equipment mounting. AC power is normally distributed with an outlet strip and excess heat is dissipated with a blower located at the top of the console. Casters on the bottom of the console will contribute to convenience. Figure 3 illustrates a possible PTS configuration.

Load boards are typically located toward the top of the console and the PTS base unit is located toward the bottom, near the power supply. The PTS PC is typically located at a height that allows for easy operator access.

Connections between the PTS console and the products can be accomplished via cables that connect to the back of the PTS cabinet. These cables can connect directly to the air bag controllers, or to replaceable adapters. Note that is often desirable to locate PTS and product connections inside the console (as opposed to the front of the console). This increases the cabling protection, limits cable lengths and reduces the chance of tampering.

Conclusions

This application note demonstrates the possibility of creating a capable, cost effective and flexible method of testing computer motherboards. with the Thermotron Industries Product Test System. This testing can be done in either production or laboratory environments. Look to Thermotron for assistance in solving your testing requirements.