71M6533 Datasheet, PDF (57/132 Pages) Teridian Semiconductor Corporation – Energy Meter IC

FDS_6533_6534_004
71M6533/G/H and 71M6534/H Data Sheet
2.3 Battery Modes
Shortly after system power (V3P3SYS) is applied, the part will be in MISSION mode. MISSION mode
means that the part is operating with system power and that the internal PLL is stable. This mode is the
normal operation mode where the part is capable of measuring energy.
When system power is not available (i.e. when V1<VBIAS), the 71M6533 and 71M6534 will be in one of
three battery modes: BROWNOUT, LCD, or SLEEP mode. Figure 21 shows a state diagram of the various
operation modes, with the possible transitions between modes. For information on the timing of mode
transitions refer to Figure 22 through Figure 24.
Figure 21: Operation Modes State Diagram
When V1 falls below VBIAS or the part wakes up under battery power, the part will automatically enter
BROWNOUT mode (see Section 2.5 Wake Up Behavior). From BROWNOUT mode, the part may enter
either LCD mode or SLEEP mode, as controlled by the MPU via the I/O RAM bits LCD_ONLY and SLEEP.
The transition from MISSION mode to BROWNOUT mode is signaled by the IE_PLLFALL interrupt flag
(SFR 0xE8[7]). The transition in the other direction is signaled by the IE_PLLRISE interrupt flag (SFR
0xE8[6]), when the PLL becomes stable.
Meters that do not require functionality in the battery modes, e.g. meters that only use the SLEEP
mode to maintain the RTC, still need to contain code that brings the chip from BROWNOUT
mode to SLEEP mode. Otherwise, the chip remains in BROWNOUT mode once the system
power is missing and consumes more current than intended.
Similarly, meters equipped with batteries need to contain code that transitions the chip to SLEEP
mode as soon as the battery is attached in production. Otherwise, remaining in BROWNOUT
mode would unnecessarily drain the battery.
Rev 2
57