MP2671 datasheet(9/11 Pages) MPS

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MP2671 – CHARGE SYSTEM PROTECTION CIRCUIT

MP2671 Rev. 0.9

www.MonolithicPower.com

2/23/2009

MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.

Battery Over-voltage Protection (BOVP)

The battery voltage OVP threshold is internally

set to 4.34V. The threshold has 30mV built-in

hysteresis. The comparator CP3, as shown in

Figure 1, monitors the VB pin and issues an

over-voltage signal to turn off the internal power

FET when the battery voltage exceeds the

battery OVP threshold. The comparator CP3

has a built-in 180µs blanking time to prevent

any transient voltage from triggering the OVP. If

the OVP situation still exists after the blanking

time, the power FET is turned off. There is an

internal 4-bit binary counter monitoring the

occurrences of the battery over-voltage event. If

the battery over-voltage occurs 16 times, the

power FET is turned off permanently. Recycling

the input power or toggling the enable ( EN )

input will reset the counter and restart the

MP2671.

The resistor between the VB pin and the

battery,

RVB, as shown in the Typical

Applications circuit, is an important component.

This resistor provides a current limit in case the

VB pin is shorted to the input voltage under a

failure mode. The VB pin leakage current under

normal operation is negligible to allow a

resistance of 200kΩ to 1MΩ be used.

Thermal Protection

The MP2671 monitors its own die temperature

to prevent thermal failures. When the internal

temperature reaches 140°C, the internal N-

channel power MOSFET is turned off. The IC

does not resume operation until the internal

temperature drops below 90°C.

External Enable Function

The MP2671 offers an enable (EN ) input which

can be used to enable or disable the IC. When

the EN pin is pulled to logic HIGH, the

protection IC is shut down. The internal control

circuit as well as the power FET is turned off.

Both 4-bit binary counters for the battery OVP

and the OCP are reset to zero when the IC is

re-enabled. The EN pin has an internal 200kΩ

pull-down resistor. Leaving the EN pin floating

or driving it to below 0.4V enables the IC.

Warning Indication Output

The WRN pin is an open-drain output that

indicates a LOW signal when any of the three

protection events happens. To pull the WRN

pin voltage low when fault, a 1k Ω resistor

should used as the pull up resistor.

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