Rainbow Electronics DS2778 - Manual (Page 25)

DS2775/DS2776/DS2777/DS2778
2-Cell, Stand-Alone, Li+ Fuel-Gauge IC with
Protector and Optional SHA-1 Authentication
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Status Register Format
The Status register contains bits that report the device status. All bits are set internally. The CHGTF, AEF, SEF, and
LEARNF bits are read-only. The UVF and PORF bits can be cleared by writing a 0 to the bit locations.
Status Register (01h)
Bit 7: Charge-Termination Flag (CHGTF). CHGTF is set to indicate that the average of the voltages on V IN1 and
V IN2 and the Average Current register values have persisted above the VCHG and below the IMIN thresholds suffi-
ciently long enough to detect a fully charged condition. CHGTF is cleared when RARC is less than 90%. CHGTF is
read-only.
Bit 6: Active-Empty Flag (AEF). AEF is set to indicate that the battery is at or below the active-empty point. AEF is
set when the average of the voltages on V
IN1
and V
IN2
is less than the VAE threshold. AEF is cleared when RARC is
greater than 5%. AEF is read-only.
Bit 5: Standby-Empty Flag (SEF). SEF is set to indicate RSRC is less than 10%. SEF is cleared when RSRC is
greater than 15%. SEF is read-only.
Bit 4: Learn Flag (LEARNF). LEARNF indicates that the current-charge cycle can be used to learn the battery
capacity. LEARNF is set when the active-empty point is detected. This occurs when the average of the voltages on
V
IN1 and V IN2 drops below the VAE threshold and the two previous current register values were negative and
greater in magnitude than the IAE threshold. See the Active-Empty Point Detect section for additional information.
LEARNF is cleared when any of the following occur:
1) Learn cycle completes (CHGTF set).
2) Current register value becomes negative indicating discharge current flow.
3) ACR = 0.
4) ACR value is written or recalled from EEPROM.
5) Sleep mode is entered.
LEARNF is read-only.
Bit 3 and 0: Reserved.
Bit 2: Undervoltage Flag (UVF). UVF is set to indicate that the average of the voltages on V IN1 and V IN2 is less than
V UV and must be written to 0 to allow subsequent undervoltage events to be reported. UVF is not cleared internally.
Writing UVF to 0 is effective only when the average of the voltages on V IN1 and V IN2 is greater than or equal to V UV ,
otherwise, UVF remains set due to the persistent undervoltage condition. UVF is set on power-up.
Bit 1: Power-On Reset Flag (PORF). PORF is set to indicate initial power-up. PORF is not cleared internally. The
user must write this flag value to a 0 to use it to indicate subsequent power-up events. If PORF indicates a power-on
reset, the ACR could be misaligned with the actual battery state of charge. The system can request a charge to full
to synchronize the ACR with the battery charge state. PORF is read/write to 0.
BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0
CHGTF AEF SEF LEARNF X UVF PORF X