71M6543GH MAXIM [Maxim Integrated Products], 71M6543GH Datasheet - Page 76

• Manufacturer Part Number: 71M6543GH
• Description: Selectable Gain of 1 or 8 for One Current Energy Meter ICs Metrology Compensation
• Manufacturer: MAXIM [Maxim Integrated Products]

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An internal comparator monitors the voltage at the V3P3SYS pin (note that V3P3SYS and V3P3A are
typically connected together at the PCB level). When the V3P3SYS dc voltage drops below 2.8 VDC, the
comparator resets an internal power status bit called V3OK . As soon as system power is removed and
V3OK = 0, the 71M6543 is forced to BRN mode. The MPU continues to execute code when the system
transitions from MSN to BRN mode or from BRN to MSN mode. A soft reset should be executed when
returning from BRN to MSN mode in order to re-initialize the I/O RAM. Depending on the MPU code, the
MPU can choose to stay in BRN mode, or transition to LCD or to SLP mode (via the I/O RAM bits
LCD_ONLY, I/O RAM 0x28B2[6] and SLEEP, I/O RAM 0x28B2[7]). BRN mode is similar to MSN mode except
that resources powered by system power, such as the ADC and the CE, are not available (see
and that the supply current is drawn from the VBAT pin. In BRN mode, the PLL continues to function at
the same frequency as in MSN mode. The MPU can configure BRN mode as it desires. For instance, it
may choose to minimize battery power by reducing the PLL or MPU clock speed (see
(BRN, LCD, SLP) back to MSN mode.
Figure 25
71M6543F/H and 71M6543G/GH Data Sheet
When system power is not available, the 71M6543 is in one of three battery modes:
for the recommended settings to realize minimum power consumption in BRN mode).
When system power is restored, the 71M6543 automatically transitions from any of the battery modes
When the part wakes-up under battery power, the part automatically enters BRN mode (see
Behavior). From BRN mode, the part may enter either LCD mode or SLP mode, as controlled by the MPU.
76
BRN mode (brownout mode)
LCD mode (LCD-only mode)
SLP mode (sleep mode).
shows a state diagram of the various operating modes, with the possible transitions between modes.
V3P3SYS
rises
© 2008–2011 Teridian Semiconductor Corporation
LCD
LCD_ONLY
Figure 25: Operation Modes State Diagram
insufficient
VBAT
VSTAT=00X
Wake
event
V3P3SYS
insufficient
RESET &
rises
VBAT
Wake Flags
MSN
BRN
VSTAT=001
V3P3SYS
Wake
event
falls
RESET &
SLP
sufficient
VBAT
insufficient
SLEEP or
VBAT
RESET
V3P3SYS
rises
System Power
Battery Power
insufficient
VBAT
3.2.1 BRN
3.4 Wake-Up
Table
Mode,
62),
v1.2