PS401-I/SS Microchip Technology, PS401-I/SS Datasheet - Page 25

• 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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TABLE 8-2:
 2003 Microchip Technology Inc.
CurrError
Cycles
InitialCap
LowCurrError
mWhVolt
NChangeState
Parameter
Name
CAPACITY CALCULATIONS
Loc.
OTP
OTP
OTP
OTP
EE
EE
# Bytes
1
2
2
1
2
1
Lower
Limit
0
0
0
0
0
0
Upper
65535
65535
65535
Limit
255
255
255
Typical
32402
Value
2048
0
0
0
8
Current measurement error. This is the error
due to the accuracy of the A/D converter to
measure and integrate the current,
255 = 100%.
SBData register for CycleCount. Cycles is
updated to keep track of the total usage of
the battery. Cycles is increased whenever
an amount of charge has been delivered to,
or removed from the battery, equivalent to
the full capacity. For a 4000 mAh battery,
Cycles is increased every time 4000 mAh
goes through the battery terminals in any
direction.
The Initial Capacity of the battery. When the
PS401 is first powered up and initialized,
before a learning cycle takes place to learn
the full capacity, the full capacity will take the
value programmed into InitialCap to
compute relative state-of-charge
percentage.
Current offset for error calculation. Since the
error of the A/D converter is proportional to
the level of current it is measuring, the error
term can be too low when the current is very
low. For this reason, the LowCurrError will
compensate the ERR term for low currents.
LowCurrError milli-Amps are added to the
current when factoring in the error.
Thus, the error is: ERROR = (current +
LowCurrError) * CurrError.
AtRate and other time-based calculations
can be more accurate using a different
formula for mWh. All calculations, except
remaining capacity, will use mWhVolt for
conversion. This approximates a straight
line for the entire battery curve. mWhVolt is
typically the full pack voltage plus the empty
pack voltage, V_full + V_empty.
State change delay filter. Delays the change
between "charge increasing" state and
"charge decreasing" state based on current
direction. To avoid problems with current
spikes in opposite directions, a delay filter is
built-in to control when to change from
charging status to discharging status. The
current must change directions and stay in
the new direction for CST_DELAY * period
before the status is changed and capacity is
increased or decreased as a result of the
new current direction.
Operational Description
DS40238B-page 25
PS401