76105DK8 Просмотр технического описания (PDF) - Fairchild Semiconductor

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76105DK8

5A, 30V, 0.050 Ohm, Dual N-Channel, Logic Level UltraFET Power MOSFET

Fairchild Semiconductor 

HUF76105DK8

Test Circuits and Waveforms (Continued)

VDS

RL

VGS

Ig(REF)

DUT

+

VDD

-

FIGURE 19. GATE CHARGE TEST CIRCUIT

VDD

VDS

Qg(TOT)

VGS

VGS = 1V

0

Qg(5)

Qg(TH)

VGS = 5V

VGS = 10

Ig(REF)

0

FIGURE 20. GATE CHARGE WAVEFORMS

VDS

RL

VGS

RGS

DUT

+

VDD

-

VGS

FIGURE 21. SWITCHING TIME TEST CIRCUIT

Thermal Resistance vs. Mounting Pad

Area

The maximum rated junction temperature, TJM, and the

thermal resistance of the heat dissipating path determines

the maximum allowable device power dissipation, PDM, in an

application. Therefore the application’s ambient temperature,

TA (oC), and thermal resistance RθJA (oC/W) must be

reviewed to ensure that TJM is never exceeded. Equation 1

mathematically represents the relationship and serves as

the basis for establishing the rating of the part.

PDM = (---T----J--Z-M---θ---J-–---A-T----A-----)

(EQ. 1)

In using surface mount devices such as the SOP-8 package,

the environment in which it is applied will have a significant

influence on the part’s current and maximum power

dissipation ratings. Precise determination of PDM is complex

and influenced by many factors:

1. Mounting pad area onto which the device is attached and

whether there is copper on one side or both sides of the

board

VDS

tON

td(ON)

tr

90%

tOFF

td(OFF)

tf

90%

10%

0

10%

VGS

10%

0

50%

PULSE WIDTH

90%

50%

FIGURE 22. SWITCHING TIME WAVEFORMS

2. The number of copper layers and the thickness of the board

3. The use of external heat sinks

4. The use of thermal vias

5. Air flow and board orientation

6. For non-steady state applications, the pulse width, the

duty cycle and the transient thermal response of the part,

the board and the environment they are in

Fairchild provides thermal information to assist the designer’s

preliminary application evaluation. Figure 23 defines the RθJA

for the device as a function of the top copper (component side)

area. This is for a horizontally positioned FR-4 board with 1oz

copper after 1000 seconds of steady state power with no air

flow. This graph provides the necessary information for

calculation of the steady state junction temperature or power

dissipation. Pulse applications can be evaluated using the

Fairchild device Spice thermal model or manually utilizing the

normalized maximum transient thermal impedance curve.

Displayed on the curve are RθJA values listed in the Electrical

Specifications table. The points were chosen to depict the

compromise between the copper board area, the thermal

resistance and ultimately the power dissipation, PDM.

©2003 Fairchild Semiconductor Corporation

HUF76105DK8 Rev. B1

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