71M6531D_10 Datasheet, PDF (56/120 Pages) Teridian Semiconductor Corporation – Energy Meter IC

Data Sheet 71M6531D/F-71M6532D/F
FDS 6531/6532 005
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 71M6531 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.
MISSION
RESET
V3P3SYS
rises
IE_PLLRISE
V3P3SYS
falls
IE_PLLFALL
V3P3SYS
rises
V1 > VBIAS
V1 <= VBIAS
LCD_ONLY
BROWNOUT
IE_PB
PB
timer
IE_WAKE
V3P3SYS
rises
RESET &
VBAT_OK
SLEEP or
VBAT_OK
LCD
VBAT_OK
timer
PB
RESET &
VBAT_OK
VBAT_OK
SLEEP
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.
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