71m6521be Maxim Integrated Products, Inc., 71m6521be Datasheet - Page 50

• Manufacturer Part Number: 71m6521be
• Description: Energy Meter Ic
• Manufacturer: Maxim Integrated Products, Inc.

BROWNOUT Mode
In BROWNOUT mode, most non-metering digital functions, as shown in Table 59, are active, including ICE, UART, EEPROM,
and LCD. In BROWNOUT mode, a low bias current regulator will provide 2.5 Volts to V2P5 and the nonvolatile V2P5 net. The
regulator has an output called BAT_OK to indicate that it has sufficient overhead. When BAT_OK = 0, the part will enter
SLEEP mode.
The V3P3D output pin is active in BROWNOUT mode, and low-current external components, such as EEPROMs can be
supplied with the current from this pin while the chip is in BROWNOUT mode.
From BROWNOUT mode, the processor can voluntarily enter LCD or SLEEP modes. When system power is restored, the part
will automatically transition from any of the battery modes to mission mode, once the PLL has settled.
The MPU will run at crystal clock rate in BROWNOUT mode. The value of MPU_DIV will be remembered (not changed) as the
part enters and exits BROWNOUT.
While PLL_OK = 0, the I/O RAM bits ADC_E and CE_E are held in zero state disabling both ADC and CE. When PLL_OK falls,
the CE program counter is cleared immediately and all FIR processing halts. Figure 19 shows the functional blocks active in
BROWNOUT mode.
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V3P3SYS
rises
LCD
LCD_ONLY
PB
VBAT_OK
© 2005-2008 TERIDIAN Semiconductor Corporation
IE_PB -> 1
Figure 18: Operation Modes State Diagram
timer
IE_PLLRISE
-> 1
BROWNOUT
V3P3SYS
VBAT_OK
MISSION
RESET &
rises
IE_WAKE ->
1
PB
IE_PLLFALL
-> 1
V3P3SYS
falls
timer
SLEEP
VBAT_OK
SLEEP or
RESET &
VBAT_OK
RESET
V3P3SYS
rises
Energy Meter IC
V1 <= VBIAS
V1 > VBIAS
VBAT_OK
71M6521BE
DATA SHEET
JANUARY 2008
V1.0