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MC34709 Power Up Control

Question asked by jhelder on Nov 7, 2012



When can the registers of the MC34709 be modified prior to power-on from COLD START or WARM START and will these written values remain during the internal start-up sequence?  Or, are the Voltages and MODE (Off, PWM, APS, etc.) values set at each sequence step and so pre-programming the necessary values are impossible


I need a different voltage/power-on scheme (lower than the default, but within the range of the PMIC control) and the ability to not power-on various rails at boot.  This is for a non-i.MX5 system that has a custom supervisory control unit that can program the PMIC via SPI prior to toggling the PWRON1/PWRON2 pins, or immediately afterwards within the 8ms delay (such as might need to be the case for the MODE registers to keep the supply off as indicated by note 73 in Table 109).


In the datasheet, many of the switching registers (numbers 24-27) have NONE listed as their reset cause and * as their default value.  Unfortunately it is unclear what this means given the PUMS[4:1] tables in Section 7.1.