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25 page 
ZM7300G Series Digital Power Manager Data Sheet REV. 3.3 NOV 26, 2007 www.power-one.com Page 25 of 32 Figure 19: INT0 Configured as Group A Reprogramming Trigger In this configuration the Interrupt 0 (INT0_N) is configured as the group A reprogramming trigger. The DPM is installed on a mother board or a backplane. A daughter card with a group of POL converters is being inserted in the system during normal operation. At first, the long pins carrying power and the OK_A line signal make contact. Then the short pins carrying the SD and interrupt signals make contact. Once the interrupt senses low input voltage, it will command the DPM to program all POL converters in the group A. Upon completion of the programming, the DPM will turn-on the POL converters, if the Auto Turn-On is enabled. When the daughter card is being removed, the interrupt input is released as soon as the short pins break the contact. The DPM will immediately pull the OK_A line low turning off all POL converters in the group A according to the turn-off delay and falling slew rate settings. 10.6 Controls 10.6.1 ACFAIL_N and RES_N The ACFAIL_N and RES_N are active low digital inputs. When one of the inputs is pulled low, the DPM will pull all OK lines low turning off all the POL converters and the Auxiliary Devices in all groups. The POL converters will execute regular turn-off ramping their output voltages down according to the turn-off delay and falling slew rate settings. In addition, the DPM will clear all bits in the POL Programming Status Registers and save the contents of the Run Time Counter into the non-volatile memory. The AC_FAIL in or RES_N in bit in the IBS Monitoring Window will change to red. When the input is released, the DPM will first program all POL converters and then turn them on, if the Auto Turn-On is enabled. Otherwise, the user will need to send the turn-on command via the I 2C bus. The ACFAIL_N is typically connected to an AC-DC front end. Whenever the AC voltage disappears, the ACFAIL_N signal will be set low. If there is no battery backup, it usually means the DC output will disappear after 20ms. If the turn-off delays and falling slew rates of each POL converter are set to the values such that all POL converters will have fully turned off within the hold time of the AC-DC front end, then output voltage tracking during turn-off is guaranteed. The RES_N input has the same functionality as the ACFAIL_N input and can be connected to a simple turn on/off switch or to a sensor that shuts the entire system down when it is activated. |
