MP2670 – CHARGE SYSTEM PROTECTION CIRCUIT

MP2670 Rev. 0.91

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10

5/13/2010

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Battery Over-voltage Protection (BOVP)

The battery voltage OVP threshold is internally

set to 4.4V. The threshold has 75mV 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

input will reset the counter and restart the

MP2670.

The resistor between the VB pin and the battery,

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 being used.

Thermal Protection

The MP2670 monitors its own die temperature

to prevent thermal failures. When the internal

temperature reaches 150°C, the internal N-

channel power MOSFET is turned off. The IC

does not resume operation until the internal

temperature drops below 110°C.

External Enable Function

can be used to enable or disable the IC. When

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

or driving it to below 0.4V enables the IC.

Warning Indication Output

indicates a LOW signal when any of the three

protection events happens. To pull the FLT pin

voltage low when fault, a recommended 10kΩ

to 200kΩ resistor should be used as the pull up

resistor.