PS401-I/SS Microchip Technology, PS401-I/SS Datasheet - Page 7

• 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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FIGURE 2-2:
CFVPack is the "Correction Factor for Pack Voltage"
which compensates for any variance in the actual A/D
response versus an ideal A/D response over varying
voltage inputs.
The COVPack and CFVPack are calibration constants
that are stored in EEPROM.
Figure 2-3 shows the relationship of the COVPack and
CFVPack values.
FIGURE 2-3:
 2003 Microchip Technology Inc.
COVPack
A/D Output
V
V
PACK
PACK
POS (+)
NEG (-)
PACK RESISTANCE
VALUE COMPENSATIONS
+
COVPack AND CFVPack
VALUE RELATIONSHIP
+
+
+
-
-
-
-
Current
Sense
R2
High Side
Safety Circuit
Ideal A/D
Response
CFVPack
VC(3)
VC(4)
VC(1)
VC(2)
V
SSA
Actual A/D
Response
Voltage Input
In-circuit calibration of the voltage is done at the time of
manufacture to obtain absolute accuracy in addition to
high resolution. Accuracy of ±40 mV at zero current
and ±80 mV during charge or discharge is possible.
Individual cell voltage measurements can be accurate
to within ±40 mV.
The individual cell voltage inputs are also calibrated the
same way the pack voltage is. There is one offset value
COVCell for all individual cells and up to four different
correction factors CFVCell1 through CFVCell4, one for
each cell input.
2.4
The A/D receives input from the internal temperature
sensor to measure the temperature. Optionally, an
external thermistor can be connected to the V
which is also monitored by the A/D converter. An output
reference voltage for use with an external thermistor is
provided on the V
Resolution mode for the temperature measurements.
A standard 10 kOhms at 25°C Negative-Temperature-
Coefficient (NTC) device of the 103ETB type is
suggested for the optional external thermistor. One leg
of the NTC should be connected to the V
the other to both the V
tor to analog ground (V
lower leg of a voltage divider circuit. To maintain high
accuracy in temperature measurements, a 1% resistor
should be used.
A lookup table is used to convert the voltage measure-
ment seen at the V
external thermistor should be placed as close as
possible to the battery cells and should be isolated from
any other sources of heat that may affect its operation.
An algorithm feature is activated to disable temperature
readings for 30 seconds, following an LED switch
activation (SWITCH pin is shorted to V
false temperature readings due to LED heating.
Calibration of the temperature measurements involves
a correction factor and an offset exactly like the current
and voltage measurements. The internal temperature
measurement makes use of correction factor CFTempI
and offset COTempI, while the V
the optional external thermistor make use of correction
factor CFTempE and offset COTempE.
Temperature Measurements
NTC
REFT
NTC
pin to a temperature value. The
pin. The A/D uses an 11-bit
SSA
pin and a 3.65 kOhms resis-
). The resistor forms the
NTC
and V
PS401
DS40238B-page 7
DDD
REFT
REFT
) to prevent
NTC
pin and
pins for
pin