SM6780AS View Datasheet(PDF) - Nippon Precision Circuits
Part Name
Description
Manufacturer
SM6780AS Datasheet PDF : 11 Pages
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SM6780AS
−∆V Invalid Time
Generally, the battery voltage becomes unstable just
after quick charging starts, so the −∆V battery volt-
age detection is disabled for 5 minutes to avoid error
in battery voltage detection. However, the ∆T/∆t
−∆V Detection (BATT)
After Ni-Cd and Ni-MH batteries are fully charged
in quick charge mode, the battery voltage begins to
drop after reaching a peak value. The SM6780AS
monitors the delta voltage (−∆V) to help determine
when the battery is fully charged. When the voltage
has fallen a minimum of 8mV (typ), the battery is
fully charged and quick charge mode terminates.
Note that −∆V detection is disabled for 5 minutes
when quick charge mode is first started to avoid error
in battery voltage detection, as described in the pre-
vious section.
∆T/∆t Detection (TEMP)
When Ni-Cd and Ni-MH batteries are close to full
charge in quick charge mode, the temperature of the
battery begins to greatly increase. The SM6780AS
monitors the temperature change rate (∆V/∆t) to help
determine when the battery is fully charged. When
the temperature voltage on TEMP decreases by a
temperature detection function continues to operate.
After the −∆V detection is enabled, both detection
functions operate.
Vpeak
8mV
Quick charge time
− ∆V detect
Figure 7. Battery voltage change
minimum of 25mV (typ) within a 60-second interval,
the battery is considered to be fully charged and
quick charge mode terminates.
Note that the TEMP voltage decreases with increas-
ing temperature due to the negative temperature
coefficient of the thermistor.
Cell voltage
Cell temperature
Quick charge time
Figure 8. Battery temperature change
Cell voltage
25mV
∆t
∆T
60s
VTEMP
Quick charge time
∆T/∆t detect
Figure 9. VTEMP change
NIPPON PRECISION CIRCUITS—7
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