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We have a customer with a lines down issue using the DM37x microprocessor and several power chips from TI. Can you please forward the information below to the appropriate team? We would like to understand the behavior describe below from the TPS79928 since it doesn’t specify a specific ramp time for the supply voltage.
They are using the TPS63000 Buck Converter to provide 3.3 volts into the TPS79928 LDO.
They are seeing an unexplained pulse out (VIO_2V8) of the TPS79928 LDO when the enable signal (seen below as LCD_PANEL_PWR) is low the whole time from power-on-reset.
Currently this issues seem related to the ramp time for the TPS7992 but we don’t see anything in the specification for power into the TPS79928.
Figure 1 below shows the unexplained pulse and figure 2 shows the pulse go when changing the ramp time into the TPS79928.
TPS79928 (IN) - VIO_3V3
TPS79928 (EN) - LCD_PANEL_PWR
TPS79928 (OUT) - VIO_2V8
Figure 1: Pulse on output seen with Enable (LCD_PANEL_PWR) Low.
Figure 2: Modified Ramp Time into the TPS79928
