PS401-I/SS Microchip Technology, PS401-I/SS Datasheet - Page 14

• 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
DS40238B-page 14
5.0
A SBS configuration normally allows the Smart Battery
to broadcast the ChargingVoltage and Charging-
Current values to the Smart Battery Charger (SMBus
address 12 HEX) to ‘control’ when to start charge, stop
charge, and when to signal a valid ‘fully charged’
condition. AlarmWarnings are also sent from the Smart
Battery (SMBus address 16 HEX) to the Smart Battery
Charger.
Alternately, the SMBus Host or a “Level 3” Smart
Battery Charger may simply read the SBData values
for ChargingVoltage and ChargingCurrent from the
Smart Battery directly. The Host or “Level 3” Smart
Battery Charger is also required to read the SBData
value of BatteryStatus to obtain the appropriate alarm
and status bit flags. When used in this configuration,
the ChargingCurrent and ChargingVoltage broadcasts
can be disabled from the Smart Battery by setting the
CHARGER_MODE (bit 14) in the BatteryMode
register. The PS401 IC’s support all of these functions.
(Please refer to the SBS Smart Battery Charger
Specification, for a definition of “Level 3” Smart Battery
Charger.)
The ChargingCurrent and ChargingVoltage registers
contain the maximum charging parameters desired by
the particular chemistry, configuration and environmen-
tal conditions. The environmental conditions include
the measured temperature and the measured cell or
pack voltages.
For Li-based systems, ChargingVoltage is the product
of the EOCVolt and Cells values from the EEPROM:
The ChargingCurrent value is set to a maximum using
the ChrgCurr value from the EEPROM. For lithium
systems, both ChargingCurrent and ChargingVoltage
values are maximums. When the current reaches
ChrgCurr it will be held constant at this value. Then
when the voltage reaches ChrgVolt, the current must
be reduced so that the voltage will be constant and not
exceed the maximum. This is accomplished by setting
ChargingCurrent to ChrgCurrOff. For safety reasons,
this current change also occurs when the temperature
limits are exceeded. When temperature or voltage
limits are exceeded, the value of ChargingCurrent
changes to ChrgCurrOff value from the EEPROM.
When a valid End-Of-Charge (EOC) condition is
detected and a fully charged state is reached, the
ChargingCurrent value is set equal to the ChrgCurrOff
value.
ChargingVoltage = EOCVolt x Cells
CHARGE CONTROL
When ChargingCurrent is set to the ChrgCurrOff
value, no broadcasts of either ChargingCurrent or
ChargingVoltage will occur unless a charge current
greater than NullCurr is detected by the A/D
measurements. Temperature limits are set using the
ChrgMaxTemp, DischrgMaxTemp and ChrgMinTemp
values from OTP EPROM. These values represent the
temperate limits within which ChargingCurrent will be
set to ChrgCurr. Temperatures outside these limits will
cause ChargingCurrent to be set to ChrgCurrOff.
If ChargingCurrent is set to ChrgCurrOff and the
measured
DischrgMaxTemp and less than ChrgMaxTemp and a
charge current is measured which is significantly larger
than the ChrgCurrOff value, then ChargingCurrent will
be set to ChrgCurr unless a fully charged condition
has already been reached.
If the CHARGER_MODE bit in BatteryMode is cleared
(enabling
ChargingVoltage) then these broadcasts will occur
every
Broadcasts only occur when ChargingCurrent is set to
the ChrgCurr value and/or when the A/D converter
measures a charge current greater than NullCurr.
The Smart Battery Data and Smart Battery Charger
Specifications require that ChargingCurrent and
ChargingVoltage broadcasts occur no faster than once
per 5 seconds and no slower than once per 60 seconds
when charging is occurring or desired. This requires
that the NChrgBroadcast value must be set between
10 and 120. The SMBus Specification also requires
that no broadcasts occur during the first 10 seconds
after SMBus initialization. This, therefore, requires the
NSilent value be set to 20 or higher.
Configuration Example:
Results:
ChargingCurrent and ChargingVoltage broadcasts:
Broadcast delay after SMBus initialization:
Measurement cycle is 500 msec
NChrgBroadcast
NSilent
ChrgCurr
ChrgCurrOff
ChrgMaxTemp
DischrgMaxTemp = 550 decimal
ChrgMinTemp
100 cycles of 500 msec = every 50 seconds
24 cycles of 500 msec = 12 seconds
ChargingCurrent if Temperature > 45°C: 10 mA
ChargingCurrent if Temperature < 0°C: 10 mA
ChargingCurrent if Temperature < 35°C and
> 0°C: 2500 mA
NChrgBroadcast
broadcasts
temperature
 2003 Microchip Technology Inc.
= 100 decimal
= 24 decimal
= 2500 decimal
= 10 decimal
= 650 decimal
= 200 decimal
of
measurement
ChargingCurrent
is
greater
cycles.
than
and