TIDUEM8B March   2019  – February 2021

 

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3.2.1.1 SVS and eFuse Functionality Testing

In addition to metrology accuracy testing, functionality testing is done on the TPS3840 SVS device and the TPS25921L eFuse device. For the TPS3840 testing, the board is powered by connecting an external power supply directly to DVCC (a jumper should not be placed on J2 to properly power DVCC directly) and the output voltage of the power supply is slowly varied from 3.3 V down to 1.9 V. The threshold voltage at which the MSP432 MCU is reset by the TPS3840 device, which is referred to as the negative voltage threshold, is logged. After the negative voltage threshold is reached, the power supply output voltage is slowly increased from 1.9 V back to 3.3 V. The voltage at which the reset is released, which is equal to the negative voltage threshold plus hysteresis voltage, is logged as well.

For testing the TPS25921L device, the MSP432 MCU is powered through the TPS70933 device by placing a jumper at J2. The TPS70933 is powered from the 5-V rail applied at header J4 by placing a jumper at J1. In addition to the jumpers at J1 and J2, a jumper is also placed at J6 to connect the TPS25921L output to header J12. An external power supply is connected to J4 (positive lead of power supply) and GND (negative lead of power supply). Also, a multimeter is placed at header J12 to measure the output voltage on the TPS25921L OUT pin. For the first test, the undervoltage lockout threshold is measured by slowly varying the external power supply output from 5 V to 4 V. Before the undervoltage threshold is reached, the voltage at the TPS25921L OUT pin should be equal to the voltage supplied by the external power supply. When the undervoltage threshold is reached, the OUT pin is disconnected from its IN pin, which causes the output voltage to read 0 V instead of the external power supply voltage. After the undervoltage voltage is reached, the power supply voltage is slowly increased back to 5 V. The power supply voltage at which the TPS25921L OUT pin is reconnected to its IN pin is, which is evident by the OUT pin voltage being equal to the external power supply voltage again instead of 0 V, is logged.

In addition to testing the undervoltage threshold, the overvoltage threshold is also tested. The overvoltage threshold test is performed by increasing the power supply voltage from 5 V to 6 V and logging at which voltage would the OUT pin of the TPS25921L device get disconnected from the IN pin. After determining the overvoltage threshold, the voltage is decreased back towards 5 V to determine at what voltage from the external power supply would the OUT pin of the TPS25921L device get reconnected to its IN pin.

For testing the current-limiting functionality of the TPS25921L, a similar setup is used as the undervoltage and overvoltage tests with the exception that header J12 is connected to a Chroma DC Electronic Load instead of just a multimeter. The thermal shutdown feature is specifically tested for current limiting by increasing the current consumption of the load connected to the OUT pin of the TPS25921L device and then measuring at what current would the load get disconnected from the voltage applied at the IN pin of the TPS25921L device. After thermal shutdown is reached, the load current was set to a lower value and the software was modified to provide a pulse on the TPS25921L ENUV pin to verify the OUT pin was reconnected to the external power supply.