71M6541DSLASHFSLASHG datasheet(57/166 Pages) MAXIM

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71M6541D/F/G and 71M6542F/G Data Sheet

Rev 5

Name

Location

Rst

Dir

Description

TEMP_BAT

28A0[4]

–

R/W

Causes VBAT to be measured whenever a

temperature measurement is performed.

TEMP_START

28B4[6]

–

R/W

TEMP_PER[2:0] must be zero in order for TEMP_START

to function. If TEMP_PER[2:0] = 0, then setting

TEMP_START starts a temperature measurement.

Ignored in SLP and LCD modes. Hardware clears

TEMP_START when the temperature measurement is

complete. The MPU must wait for TEMP_START to

clear before reading STEMP[10:0] and before setting

TEMP_START again.

TEMP_PWR

28A0[6]

–

R/W

Selects the power source for the temperature sensor:

1 = V3P3D, 0 = VBAT_RTC. This bit is ignored in

SLP and LCD modes, where the temperature sensor is

always powered by VBAT_RTC.

TEMP_BSEL

28A0[7]

–

R/W

Selects which battery is monitored by the

temperature sensor: 1 = VBAT, 0 = VBAT_RTC

TEMP_TEST[1:0]

2500[1:0]

–

R/W

Test bits for the temperature monitor VCO.

TEMP_TEST must be 00 in regular operation. Any

other value causes the VCO to run continuously with

the control voltage described below.

TEMP_TEST

Function

Normal operation

Reserved for factory test

STEMP[10:3]

STEMP[2:0]

2881[7:0]

2882[7:5]

The result of the temperature measurement.

To correctly form STEMP[10:0], the MPU must read

0x2881[7:0], shift it left by three bit positions (padding

LSBs with zeros), then read 0x2882[7:5], shift it right

by 5-bits (padding the 5 MSBs with zeros), and then

logically OR the two quantities together.

BSENSE[7:0]

2885[7:0]

–

The result of the battery measurement.

BCURR

2704[3]

R/W

Connects a 100 µA load to the battery selected by

TEMP_BSEL.

Refer to the 71M6xxx Data Sheet for information on reading the temperature sensor in the 71M6x01

devices.

2.5.6

71M654x Battery Monitor

The 71M654x temperature measurement circuit can also monitor the batteries at the VBAT and

VBAT_RTC pins. The battery to be tested (i.e., VBAT or VBAT_RTC pin) is selected by TEMP_BSEL (I/O

RAM 0x28A0[7]).

When TEMP_BAT (I/O RAM 0x28A0[4]) is set, a battery measurement is performed as part of each

temperature measurement. The value of the battery reading is stored in register BSENSE[7:0] (I/O RAM

0x2885). The following equation is used to calculate the voltage measured on the VBAT pin (or VBAT_RTC

pin) from the BSENSE[7:0] and STEMP[10:0] values. The result of the equation below is in volts.

STEMP

BSENSE

RTC

orVBAT

VBAT

000276

]

[

0246

)

142

]

[

(

293

)

(

⋅

−

In MSN mode, a 100 µA de-passivation load can be applied to the selected battery (i.e., selected by the

TEMP_BSEL bit) by setting the BCURR (I/O RAM 0x2704[3]) bit. Battery impedance can be measured by

taking a battery measurement with and without BCURR. Regardless of the BCURR bit setting, the battery

load is never applied in BRN, LCD, and SLP modes.

71M6541D/F/G Datasheet(PDF) 57 Page - Maxim Integrated Products

71M6541D/F/G Datasheet(HTML) 57 Page - Maxim Integrated Products

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