71M6543HT-IGTSLASHF datasheet(41/75 Pages) MAXIM

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Figure 8. Waveforms Comparing Voltage, Current, Energy per Interval, and Accumulated Energy

When system power is restored, the 71M654xT

automatically transitions from any of the battery modes

(BRN, LCD, SLP) back to MSN mode, switches back

to using system power (VV3P3SYS, VV3P3A), issues an

interrupt and updates VSTAT[1:0]. The MPU software

should restore MSN mode operation by issuing a soft

reset to restore system settings to values appropriate for

MSN mode.

Transitions from both LCD and SLP mode to BRN mode

can be initiated by the following events:

1) Wake-up timer timeout.

2) Pushbutton (PB) is activated.

3) A rising edge on SEGDIO4, SEGDIO52, or SEGDIO55.

4) Activity on the RX or OPT_RX pins.

Brownout Mode

In BRN mode, most nonmetering digital functions are

active including ICE, UART, EEPROM, LCD and RTC. In

BRN mode, the PLL continues to function at the same fre-

quencyasMSNmode.ItisuptotheMPUtoreducethe

PLLfrequencyortheMPUfrequencyinordertominimize

power consumption.

From BRN mode, the MPU can choose to enter LCD or

SLP modes. When system power is restored while the

71M654xT is in BRN mode, the part automatically transi-

tions to MSN mode.

LCD Only Mode

LCD mode may be commanded by the MPU at any time

by setting the LCD_ONLY control bit. However, it is rec-

ommended that the LCD_ONLY control bit be set by the

MPU only after the 71M654xT has entered BRN mode.

For example, if the 71M654xT is in MSN mode when

LCD_ONLY is set, the duration of LCD mode is very brief

and the 71M654xT immediately wakes.

In LCD mode, VV3P3D is disabled, thus removing all

current leakage from the VBAT pin. Before asserting

LCD_ONLY mode, it is recommended that the MPU

minimizePLLcurrentbyreducingtheoutputfrequencyof

the PLL to 6.2MHz (i.e., write PLL_FAST = 0).

-500

-400

-300

-200

-100

100

200

300

400

500

TIME (ms)

VOLTAGE (V)

CURRENT (A)

ENERGY PER INTERVAL (Ws)

ACCUMULATED ENERGY (Ws)

71M6543HT-IGT/F Datasheet(PDF) 41 Page - Maxim Integrated Products

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