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Data Sheet 71M6531D/F-71M6532D/F

FDS 6531/6532 005

Rev 2

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.

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.

V3P3SYS

rises

V3P3SYS

falls

MISSION

BROWNOUT

LCD

SLEEP or

V1 > VBIAS

V1 <= VBIAS

LCD_ONLY

RESET &

VBAT_OK

RESET

IE_PLLRISE

IE_PLLFALL

IE_PB

IE_WAKE

timer

RESET &

V3P3SYS

rises

V3P3SYS

rises

VBAT_OK

SLEEP

71M6532D/F Datasheet(PDF) 56 Page - Maxim Integrated Products

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