Datasheet

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REG50

TS+

TS–

IO_CTRL[TSn]

ALERT[OTn]

PINBOUNDARY

ToADCMux

–

DelayFilter

COMPARATOR

CONFIG_OT[] Selector

CONFIG_OTT[]

11 1

CONFIG_OT[]?0

VSS

–

PROTECTOR

REFERENCE

5VLDO

(User)

ToCOV-CUVCircuits

BAT

bq76PL536A

www.ti.com

SLUSAD3A –JUNE 2011–REVISED AUGUST 2012

Cell Undervoltage Fault Detection (CUV)

Cell undervoltage detection operates in a similar manner to the COV protection. When the voltage across a cell

falls below the programmed CUV threshold (CONFIG_CUV[]) for a period of time greater than CUVT

(CONFIG_CUVT[]), the CUV_FAULT[] flag for that cell is set. The bits in CUV_FAULT[] are then ORed into the

FAULT[CUV] flag, which is then ORed into the DEVICE_STATUS[FAULT] flag, which causes the FAULT_S (_H)

pin also to be asserted. The CUV flag is latched unless CUVT is programmed to 0, in which case the flag follows

the fault condition. Care should be taken when using this setting to avoid chatter of the fault status. To reset the

FAULT flag, first remove the source of the fault (i.e., the overvoltage condition) and then write a 1 to

FAULT[CUV], followed by a 0 to FAULT[CUV].

Overtemperature Detection

When the temperature input TS1 or TS2 exceeds the programmed OT1 or OT2 threshold (CONFIG_OT[]) for a

period of time greater than OTT (CONFIG_OTT[]) the ALERT_STATUS[OT1, OT2] flag is set. The ALERT[] flags

are then ORed into the DEVICE_STATUS[ALERT] flag, and the ALERT_S (_H) pin is also asserted. The OT flag

is latched unless OTT is programmed to 0, in which case the flag follows the fault condition. Care should be

taken when using this setting to avoid chatter of the fault status. To reset the FAULT flag, first remove the source

of the alert (i.e., the overtemperature condition) and then write a 1 to ALERT[OTn], followed by a 0 to

FAULT[OTn].

Figure 8. Simplified Overtemperature Detection Schematic

As shown in the drawing above, the OT thresholds are detectable in 11 steps representing approximately 5°C

divisions when a thermistor and gain/offset setting resistors are chosen using the formula in the External

Temperature Sensor Support (TS1+, TS1– and TS2+, TS2–) section. A DISABLED setting is also available. This

results in an adjustment range from approximately 40°C to 90°C, but the range center can be moved by

modifying the R

value. The steps are spaced in a non-linear fashion to correspond to typical thermistor

response curves. Typical accuracy of a few degrees C or better can be achieved (with no additional calibration

requirements) by careful selection of the thermistor and resistors.

Each input sensor can be adjusted independently via separate registers CONFIG_OT1[] and CONFIG_OT2[].

The two temperature setpoints share a common filter delay set in the CONFIG_OTT[] register. A setting of 0 in

the CONFIG_OTT[] register causes the fault sensing to be both instantaneous and not latched. All other settings

provide a latched ALERT state.

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