PS501 datasheet(8/42 Pages) MICROCHIP

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PS501

DS21818C-page 8

 2004 Microchip Technology Inc.

3.0

OPERATIONAL MODES

The PS501 operates on a continuous cycle. The

frequency of the cycles depends on the power mode

selected. There are four power modes: Run, Sample,

Sleep and Shelf-Sleep. Each mode has specific entry

and exit conditions as listed below.

3.1

Run Mode

Whether the PS501 is in Run mode or Sample mode

depends on the magnitude of the current. The Run and

Sample mode entry-exit threshold is calculated using

the EEPROM parameter, SampleLimit.

SampleLimit is a programmable EEPROM value and

CFCurr is an EEPROM value set by calibration.

Entry to Run mode occurs when the current is more

than +/- SampleLimit mA for two consecutive mea-

surements. Run mode may only be exited to Sample

mode, not to Sleep mode, when Sample mode is

enabled. Exit from Run mode to Sample mode occurs

when the converted measured current is less than the

+/- SampleLimit mA threshold for two consecutive

measurements.

Run mode is the highest power consuming mode.

During Run mode, all measurements and calculations

occur once per measurement period. Current, voltage

and temperature measurements are each typically

made sequentially during every measurement period.

3.2

Sample Mode

Entry to Sample mode occurs when the measured

current is less than +/- SampleLimit (EE parameter)

two consecutive measurements. Sample mode may be

exited to either Run mode or Sleep mode.

While in Sample mode, measurements of voltage, cur-

rent and temperature occur only once per NSample

counts of measurement periods, where NSample is a

programmable EEPROM value. Calculations of State-

Of-Charge, SMBus requests, etc. still continue at the

normal Run mode rate, but measurements only occur

once every measurement period x NSample. The

minimum value for NSample is two.

The purpose of Sample mode is to reduce power con-

sumption during periods of inactivity (low rate charge or

discharge). Since the analog-to-digital converter is not

active, except every NSample counts of measurement

periods, the overall power consumption is significantly

reduced.

EXAMPLE 3-1:

CONFIGURATION

3.3

Low-Voltage Sleep Mode

Entry to Sleep mode can only occur when the

measured pack voltage at the VC(1) input is below a

preset limit, set by the EEPROM value SleepVPack (in

mV). Sleep mode may be exited to Run mode, but only

when one of the wake-up conditions is satisfied.

While in Sleep mode, no measurements occur and no

calculations are made. The fuel gauge display is not

operational, no SMBus communications are recog-

nized and only a wake-up condition will permit an exit

from Sleep mode. Sleep mode is one of the lowest

power consuming modes and is used to conserve

battery energy following a complete discharge.

There are two levels of Low-Voltage Sleep mode that

can be used, each with a different wake-up criteria.

Default Low-Power mode will use 25

µA typical and will

wake-up when the voltage exceeds the WakeUp voltage

level. By setting bit 1 of the WakeUp register to ‘1’, the

Ultra Low-Power mode can be used. This will be entered

by low voltage, but wake-up occurs by pulling the

SMBus lines high. Ultra Low-Power mode uses less

than 1

µA.

3.4

Shelf-Sleep Mode

Shelf-Sleep mode is used to put the PS501 into Low-

Power mode, regardless of voltage level, for long term

storage of battery packs. It is entered by an SMBus

command. It is exited by the conditions selected in the

WakeUp register. These can be voltage, GPIO or

SMBus activity. If any of these four are selected for

wake-up, the Shelf-Sleep mode will be Low-Power

mode and will draw 25

µA typical. If none of these

options are selected and bit 3 of the WakeUp register

is set, the Shelf-Sleep mode will be Ultra Low-Power

mode, which will draw less than 1

µA and wake-up will

be by pulling SMBus high.

Measurement period is 500 ms

SampleLimit is set to 20

NSample is set to 16

Result:

Run/Sample mode entry-exit threshold = 20 mA

During Sample mode, measurements will occur

every:

16 measurement periods of 500 mS = every 8 seconds

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