DRV102 datasheet(13/23 Pages) TI

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DRV102

SBVS009A

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low as possible for increased reliability. Junction tempera-

ture can be determined according to the equation:

TJ = TA + PDθJA

(1)

where,

JA = θJC + θCH + θHA

(2)

TJ = Junction Temperature (°C)

TA = Ambient Temperature (°C)

PD = Power Dissipated (W)

JC = Junction-to-Case Thermal Resistance (°C/W)

CH = Case-to-Heat Sink Thermal Resistance (°C/W)

HA = Heat Sink-to-Ambient Thermal Resistance (°C/W)

JA = Junction-to-Air Thermal Resistance (°C/W)

Figure 13 shows maximum power dissipation versus ambi-

ent temperature with and without the use of a heat sink.

Using a heat sink significantly increases the maximum

power dissipation at a given ambient temperature as shown.

FIGURE 12. DDPAK Thermal Resistance versus Circuit Board Copper Area.

THERMAL RESISTANCE vs

CIRCUIT BOARD COPPER AREA

012345

Copper Area (inches2)

DRV102

DDPAK

Surface-Mount Package

1oz. copper

Circuit Board Copper Area

DRV102

DDPAK

Surface-Mount Package

output current times the voltage across the conducting out-

put transistor times the duty cycle. Power dissipation can be

minimized by using the lowest possible duty cycle necessary

to assure the required hold force.

THERMAL PROTECTION

Power dissipated in the DRV102 will cause the junction

temperature to rise. The DRV102 has thermal shutdown

circuitry that protects the device from damage. The thermal

protection circuitry disables the output when the junction

temperature reaches approximately +165

°C, allowing the de-

vice to cool. When the junction temperature cools to approxi-

mately +150

°C, the output circuitry is again enabled. Depend-

ing on load and signal conditions, the thermal protection

circuit may cycle on and off. This limits the dissipation of the

driver but may have an undesirable effect on the load.

Any tendency to activate the thermal protection circuit

indicates excessive power dissipation or an inadequate heat

sink. For reliable operation, junction temperature should be

limited to +125

°C, maximum. To estimate the margin of

safety in a complete design (including heat sink), increase

the ambient temperature until the thermal protection is

triggered. Use worst-case load and signal conditions. For

good reliability, thermal protection should trigger more than

°C above the maximum expected ambient condition of

your application. This produces a junction temperature of

125

°C at the maximum expected ambient condition.

The internal protection circuitry of the DRV102 was designed

to protect against overload conditions. It was not intended to

replace proper heat sinking. Continuously running the

DRV102 into thermal shutdown will degrade reliability.

HEAT SINKING

Most applications will not require a heat sink to assure that

the maximum operating junction temperature (125

°C) is not

exceeded. However, junction temperature should be kept as

FIGURE 13. Maximum Power Dissipation versus Ambient

Temperature.

255075

100

125

Ambient Temperature (

°C)

MAXIMUM POWER DISSIPATION

vs AMBIENT TEMPERATURE

TO-220 with Thermalloy

6030B Heat Sink

JA = 16.5°C/W

D = (TJ (max) – TA) /

J (max) = 125°C

With infinite heat sink

(

JA = 3°C/W),

max P

D = 33W

at T

A = 25°C

DDPAK

JA = 26°C/W (3 in

2 1 oz.

copper mounting pad)

DDPAK or TO-220

JA = 65°C/W (no heat sink)

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