UCD90120 Datasheet, PDF (25/40 Pages) Texas Instruments – UCD90120 12-Channel Sequencer and System Health Monitor

UCD90120
www.ti.com.......................................................................................................................................................................................... SLVS966 – SEPTEMBER 2009
Table 4. WDT Initial Wait
Time (continued)
WDT INITIAL WAIT TIME
800 ms
1.6 sec
3.2 sec
6.4 sec
12.8 sec
25.6 sec
51.2 sec
102 sec
205 sec
410 sec
819 sec
1638 sec
The watchdog timeout is programmable from 0 to 2.55s with a 10ms step size. If the WDT times out, the
UCD90120 can assert a GPIO pin configured as WDO that is separate from a GPIO defined as System Reset
pin or it can generate a System Reset pulse. After a timeout, the WDT is restarted by toggling the WDI pin or by
writing to SYSTEM_WATCHDOG_RESET over I²C.
<t_WDI
<t_WDI
<t_WDI
t_WDI
WDI
<t_WDI
WDO
Figure 17. Timing of GPIOs Configured for Watch-Dog Timer Operation
DATA AND ERROR LOGGING TO FLASH MEMORY
The UCD90120 can log faults and the number of device resets to flash memory. Peak voltage, current and
temperature measurements are also stored for each rail. To reduce stress on the flash memory, a 30-second
timer is started if a measured value exceeds the previously logged value. Only the highest value from the
30-second interval is written from RAM to flash.
Multiple faults can be stored in flash memory and can be accessed over PMBus to help debug power supply
bugs or failures. Each logged fault includes:
• Rail number
• Fault type
• Fault time since previous device reset
• Last measured rail voltage
The total number of device resets is also stored to flash memory. The value can be reset using PMBus.
With the Brownout function enabled, the run-time clock value, peak monitor values and faults are only logged to
flash when a power-down is detected. The device run-time clock value is stored across resets or power cycles
unless the Brownout function is disabled, in which case the run-time clock is returned to zero after each reset.
It is also possible to update and calibrate the UCD90120 internal run time clock via a PMBus host. For example,
a host processor with a Real Time Clock could periodically update the UCD90120 run time clock to a value that
corresponds to the actual date and time. The host must translate the UCD90120 timer value back into the
appropriate units based on the usage scenario chosen. Please see the REAL_TIME_CLOCK command in the
UCD9012x PMBus Command Reference for more details.
Copyright © 2009, Texas Instruments Incorporated
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