SMM665B
Preliminary Information
APPLICATIONS INFORMATION (CONTINUED)
SMM665 Brownout Recovery/Handling
During a power ‘brown-out’ (Figure 9) the SMM665B
can default to a power-off state, thus requiring toggling
of the PWR_ON/OFF pin to enable the device to
perform a power-on sequence. For applications using
I2C control of the power-on/power-off function, the
same result may be effected by, upon recovery of
power, issuing a software (I2C) ‘Power-Off’ command
followed by a ‘Power-On’ command and ending with
a ‘Clear’ command. If the PWR_ON/OFF pin is in the
asserted state, the SMM665B will initiate a power-on
sequence once all input conditions are met. Otherwise
the PWR_ON/OFF pin may require toggling if, upon
recovery from the ‘brownout’, it is in the de-asserted
state.
-48V Supply
0V
Power Brown-Out
-48V
SMM665 Supplies
+12VIN
SMM665 Hold-Up Time
VDD_CAP
Figure 9 - Power Brown-Out with Resulting Loss of SMM665B Supply Voltages
Summit Microelectronics, Inc
2089 1.1 10/20/04
17
SUMMIT [ SUMMIT MICROELECTRONICS, INC. ]
