DIA7965

Version 1.0, Dec 2023

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© 2023 DIOO MICROCIRCUITS CO., LTD.

9

9.4. Output current limit

The DIA7965 internal current limit helps to protect the regulator during fault conditions. Output current is

internally limited within the IC to a typical 700 mA. During the current limit, the output sources a fixed amount of

current that is largely independent of the output voltage. In such a case, the output voltage is not regulated, and

VOUT = ICL × RLOAD. The PMOS pass transistor dissipates (VIN – VOUT) × ICL until the thermal shutdown is triggered

and the device turns off. As the device cools down, it is turned on by the internal thermal shutdown circuit. If the

fault condition continues, the device cycles between the current limit and thermal shutdown.

9.5. Short circuits protection

The DIA7965 has integrated internally the function of short circuit protection for the device. When the output is

shorted, the short circuit protection will limit the output current to a typical 200 mA, which is called short circuit

limit (ISC). When a short circuit occurs, the PMOS pass transistor dissipates (VIN – VOUT) × ISC until the thermal

shutdown is triggered and the device turns off. As the device cools down, it is turned on by the internal thermal

shutdown circuit.

9.6. Thermal shutdown

When the chip temperature exceeds the thermal shutdown point (TSD = 160°C typical), the device goes to the

disabled state and the output voltage is not delivered until the die temperature decreases to 135°C. The thermal

shutdown feature protects from a catastrophic device failure at accidental overheating. Using this protection in

place of proper heat sinking is not recommended.

9.7. Dropout voltage

The DIA7965 uses a PMOS pass transistor to achieve low dropout. When (VIN – VOUT) is less than the dropout

voltage (VDO), the PMOS pass device is in the linear region of operation and the input-to-output resistance is the

RDS(on) of the PMOS pass element. VDO scales approximately with output current because the PMOS device

behaves as a resistor in dropout.

9.8. Power dissipation and heat sinking

The maximum power dissipation supported by the device is dependent upon board design and layout. Mounting

pad configuration on the PCB, the board material, and the ambient temperature affect the rate of junction

temperature rise for the part. The maximum power dissipation the DIA7965 device can handle is given by:

θJA

A

J(MAX)

D(MAX)

R

]

T

-

[T

P



(1)

The power dissipated by the DIA7965 device for given application conditions can be calculated from the

following equations:

(

)

OUT

IN

OUT

GND

IN

D

V

V

I

+

I

×

V

P

-

≈

(2)