2762A25 Просмотр технического описания (PDF) - Maxim Integrated

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2762A25

High-Precision Li+ Battery Monitor With Alerts

Maxim Integrated 

DS2762 High-Precision Li+ Battery Monitor With Alerts

register, and enters sleep mode. The DS2762 provides a current-limited (IRC) recovery charge path from PLS to

VDD to gently charge severely depleted cells. The recovery path is enabled when 0 £ VDD < 3V (typ). Once VDD

reaches 3V (typ), the DS2762 returns to normal operation, awaiting connection of a charger to turn on the charge

FET and pull out of sleep mode.

Overcurrent, Charge Direction. The voltage difference between the IS1 pin and the IS2 pin (VIS = VIS1 - VIS2) is the

filtered voltage drop across the current-sense resistor. If VIS exceeds overcurrent threshold VOC for a period longer

than overcurrent delay tOCD, the DS2762 shuts off both external FETs and sets the COC flag in the protection

register. The charge current path is not re-established until the voltage on the PLS pin drops below VDD - VTP. The

DS2762 provides a test current of value ITST from PLS to VSS to pull PLS down to detect the removal of the

offending charge current source.

Overcurrent, Discharge Direction. If VIS is less than -VOC for a period longer than tOCD, the DS2762 shuts off the

external discharge FET and sets the DOC flag in the protection register. The discharge current path is not re-

established until the voltage on PLS rises above VDD - VTP. The DS2762 provides a test current of value ITST from

VDD to PLS to pull PLS up to detect the removal of the offending low-impedance load.

Short Circuit. If the voltage on the SNS pin with respect to VSS exceeds short-circuit threshold VSC for a period

longer than short-circuit delay tSCD, the DS2762 shuts off the external discharge FET and sets the DOC flag in the

protection register. The discharge current path is not re-established until the voltage on PLS rises above VDD - VTP.

The DS2762 provides a test current of value ITST from VDD to PLS to pull PLS up to detect the removal of the short

circuit.

Figure 3. Li+ Protection Circuitry Example Waveforms

VCELL

CHARGE

VIS

DISCHARGE

CC

tOVD

(NOTE 1)

tOVD

DC

tSCD

tOCD

SLEEP

MODE

tOCD

VOV

VCE

VUV

VOC

0

-VOC

-VSC

VPLS

VSS

tUVD

VDD

VSS

ACTIVE

INACTIVE

NOTE 1: TO ALLOW THE DEVICE TO REACT QUICKLY TO SHORT CIRCUITS, DETECTION OCCURS ON THE SNS PIN RATHER THAN ON THE

FILTERED IS1 AND IS2 PINS. THE ACTUAL SHORT-CIRCUIT DETECT CONDITION IS VSNS > VSC.

Summary. All of the protection conditions described above are ORed together to affect the CC and DC outputs.

DC = (Undervoltage) or (Overcurrent, Either Direction) or (Short Circuit) or (Protection Register Bit DE = 0)

or (Sleep Mode)

CC = (Overvoltage) or (Undervoltage) or (Overcurrent, Charge Direction) or (Protection Register bit CE = 0)

or (Sleep Mode)

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