PS401-I/SS Microchip Technology, PS401-I/SS Datasheet - Page 8

• Manufacturer Part Number: PS401-I/SS
• Description: IC FUEL GAUGE BATTERY MGR 28SSOP
• Manufacturer: Microchip Technology

Specifications of PS401-I/SS

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PS401
3.0
The PS401 operates on a continuous cycle, as
illustrated in Figure 3-1. The frequency of the cycles
depends on the Power mode selected. There are three
Power modes: Run, Sample and SLEEP. Each mode
has specific entry and exit conditions as listed below.
3.1
Whether the PS401 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 following EEPROM data values and formula:
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 +/- X mA for two consecutive measurements. Run
mode may only be exited to Sample mode, not to
SLEEP mode. Exit from Run mode to Sample mode
occurs when the converted measured current is less
than the +/- X 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 made
sequentially during every measurement period. Only
one
measurement period. For Li-based applications, each
cell input is measured in turn. For example, in 4-cell
Li-based configurations, four measurement periods are
required to read all cell input voltages.
3.2
Entry to Sample mode occurs when the converted
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,
current 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.
DS40238B-page 8
+/- X mA = SampleLimit x CFCurr / 16384
cell
OPERATIONAL MODES
Run Mode
Sample Mode
voltage
measurement
occurs
per
The purpose of Sample mode is to reduce power
consumption 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.
Configuration Example:
Result:
3.3
Entry to SLEEP mode can only occur when the
measured pack voltage at 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.
If the voltage measured at the VC(1) input is below the
SleepVPack threshold, but the measured current is
above the Sample mode threshold (which maintains
Run mode), then SLEEP mode will NOT be entered.
SLEEP mode can only be entered from Sample mode.
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.
When in the SLEEP mode (entry due to low voltage and
Sample mode), there are four methods for waking up.
They are voltage level, current level, SMBus activity
and I/O pin activity. The EEPROM value, WakeUp,
defines which wake-up functions are enabled, and
also the voltage wake-up level. Table 3-1 indicates
the appropriate setting. Note that the setting is
independent of the number of cells or their
configuration.
Measurement period is 500 ms
CFCurr current calibration factor is 12500
SampleLimit is set to 27
NSample is set to 16
Run/Sample mode entry-exit threshold:
27 x 12500 / 16384 = +/- 20.6 mA
During Sample mode, measurements will occur
every:
16 measurement periods of 500 mS = every 8 seconds
SLEEP Mode
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