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Hardware improvements as part of RI's robustness program for the RI8589B1 Bulk Power and RI8589C1 Bulk Power TIMs increase field reliability by and accuracy for the FetPulser instrument. Over current events can be caused by failed DUTs or while debugging new measurement techniques. The polyfuse allows the TIM to be "reset" after an over current event occurs instead of damaging the components and requiring repair service. High Voltage measurement accuracy was improved by selecting components with ultra low Vcr.

Symptom: FetPulser instrument's high voltage capabilities begin failing after an over current event.

Resolution: Choose any of the four (4) methods below to reset an open polyfuse: a) cycle the Enable state, b) power off the TIM, c) unlatch the TIM, or d) perform a Startup. All steps assume that the Cassini software is launched from a recent Short Cut. Contact [email protected] if diagnostics continue to fail after performing any of the steps below.

A) To Unlatch the TIM To Reset an Open Polyfuse:
    1. Unlatch the TIM from testhead
    2. Choose System > Check to remove the TIM from the configuration,
    3. Latch the TIM back to the testhead.
    4. Choose System > Check to add the TIM to the configuration.
B) To Power Off TIM To Reset an Open Polyfuse:
    1. Open the Equipment Pool window by choosing System > Equip > Nodes
    2. Highlight the FetPulser TIM in the node list, choose Power Off from the right mouse button menu
    3. Then choose System > Check from the main Cassini window. (See Figure 1)

C) To Cycle Enable State To Reset an Open Polyfuse:
    1. Open configuration by choosing System > Tester
    2. Choose Tester > Control to open the Control panel
    3. Choose the FetPulser instrument, High Voltage control function
    4. Choose Hv # Enable button and change from on to off and then back to on. (See Figure 2)

D) To Unlatch the TIM To Reset an Open Polyfuse:
    1. Choose System > Equip > Startup and confirm OK to perform a full startup. This powers off every TIM and restarts each one and will take the longest time of any of the options.

HV Module Issues:

As of Feb 2021, any FET Pulser TIM (model B or C) will include dual polyfuse protection circuitry onto all HV modules. The polyfuses protect the input and output of the Murata high voltage SMPS power module from over current events. When the HV modules encounter a high current event on either the input or output or both, the polyfuses will open, preventing the over current from damaging the power module.

The polyfuses are ONLY installed on the HV modules. It should also be noted that we have observed failed Murata high voltage SMPS power modules that will fail in such a way as to disable the TIMs primary power supply and cause the TIM to power cycle. The polyfuses will also protect the primary supply from this state as well.

Accuracy Issues:

While investigating HV # accuracy issues, it was found that in the voltage sense and setting circuitry, a high value 1M ohm resistor was suffering from extremely poor voltage coefficient of resistance performance.

This effect is normally not seen until voltages become greater than 45-60V. Basically what is happening is that the value of resistance will become smaller as the voltage becomes greater. It is a separate phenomena and unrelated to temperature coefficient and self heating. RI has purchased and is installing/upgrading HV modules with these new ultra low Vcr components (<20ppm per volt) Vcr is typically not specified on thick and thin film SMD resistors and is typically 300 to 2,000ppm per volt.. This has improved voltage set and accuracy of the 8589C revision units by an order of magnitude over the original units. The RevC TIM uses a newer HV2 pcb assembly. The accuracy of 8589B1 HV has also improved but the architecture of HV2 from 95 to180V is not an order of magnitude like the 8589C due to circuitry topology.

Figure 1: Equipment Pool > FetPulser > Power Off

Figure 2: FetPulser > High Voltage control > Hv # Enable Control Panel

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