DS2764 Просмотр технического описания (PDF) - Maxim Integrated

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DS2764

High-Precision Li+ Battery Monitor with 2-Wire Interface

Maxim Integrated 

DS2764 High-Precision Li+ Battery Monitor With 2-Wire Interface

POWER MODES

The DS2764 has two power modes: active and sleep. While in active mode, the DS2764 continually measures

current, voltage, and temperature to provide data to the host system and to support current accumulation and Li+

safety monitoring. In sleep mode, the DS2764 ceases these activities. The DS2764 enters sleep mode when any of

the following conditions occurs:

§ The PMOD bit in the Status Register has been set to 1 and both SCL and SDA are low for longer

than 2.1s (pack disconnection).

§ The voltage on VIN drops below undervoltage threshold VUV for tUVD (cell depletion).

The DS2764 returns to active mode when any of the following occurs:

§ The PMOD bit has been set to 1 and either the SDA or SCL line is pulled high (pack connection).

§ The PS pin is pulled low (power switch).

§ The voltage on PLS becomes greater than the voltage on VDD (charger connection).

The DS2764 defaults to active mode when power is first applied.

Li+ PROTECTION CIRCUITRY

During active mode, the DS2764 constantly monitors cell voltage and current to protect the battery from overcharge

(overvoltage), overdischarge (undervoltage), and excessive charge and discharge currents (overcurrent, short

circuit). Conditions and DS2764 responses are described in the following sections and summarized in Table 1 and

Figure 4.

Table 1. Li+ Protection Conditions and DS2764 Responses

CONDITION

Overvoltage

Undervoltage

Overcurrent, Charge

THRESHOLD

VIN > VOV

VIN < VUV

VIS > VOC(2)

ACTIVATION

DELAY

tOVD

tUVD

tOCD

RESPONSE

CC high

CC, DC high,

Sleep Mode

CC, DC high

RELEASE THRESHOLD

VIN < VCE, or

VIS ≤ -2mV

VPLS > VDD (1)

(charger connected)

VPLS < VDD - VTP (3)

Overcurrent, Discharge

VIS < -VOC(2)

tOCD

DC high

VPLS > VDD - VTP (4)

Short Circuit

VSNS > VSC

tSCD

DC high

VPLS > VDD - VTP (4)

VIS = VIS1 - VIS2. Logic high = VPLS for CC and VDD for DC. All voltages are with respect to VSS. ISNS references current delivered from pin SNS.

Note 1:

Note 2:

Note 3:

Note 4:

If VDD < 2.2V, release is delayed until the recovery charge current passed from PLS to VDD charges the battery and allows VDD to

exceed 2.2V.

For the internal sense resistor configuration, the overcurrent thresholds are expressed in terms of current: ISNS > IOC for charge

direction and ISNS < -IOC for discharge direction.

With test current ITST flowing from PLS to VSS (pulldown on PLS).

With test current ITST flowing from VDD to PLS (pullup on PLS).

Overvoltage. If the cell voltage on VIN exceeds the overvoltage threshold, VOV, for a period longer than overvoltage

delay, tOVD, the DS2764 shuts off the external charge FET and sets the OV flag in the protection register. When the

cell voltage falls below charge enable threshold VCE, the DS2764 turns the charge FET back on (unless another

protection condition prevents it). Discharging remains enabled during overvoltage, and the DS2764 re-enables the

charge FET before VIN < VCE if a discharge current of -80mA (VIS ≤ -2mV) or less is detected.

Undervoltage. If the voltage of the cell drops below undervoltage threshold, VUV, for a period longer than

undervoltage delay, tUVD, the DS2764 shuts off the charge and discharge FETs, sets the UV flag in the protection

register, and enters sleep mode. The DS2764 provides a recovery charge path from PLS to VDD to power the

DS2764 by the charger when the cell is severely depleted. Once the DS2764 regains power it will enter active

mode of operation and allow full charging of the cell. The recovery charge path is disabled when the cell voltage is

above 3.0V to prevent cell overcharge through the PLS pin.

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