DRV101_15 Datasheet, PDF (12/27 Pages) Texas Instruments – PWM SOLENOID/VALVE DRIVER

THERMAL RESISTANCE
vs ALUMINUM PLATE AREA
18
Vertically Mounted
in Free Air
16
Aluminum Plate Area
Flat, Rectangular
Aluminum Plate
14
0.030in Al
12
0.050in Al
10
Aluminum
Plate Thickness
8
0.062in Al
0
1
2
3
4
5
6
7
8
Aluminum Plate Area (inches²)
Optional mica or film insulator
for electrical isolation. Adds
DRV101
approximately 1°C/W.
TO-220 Package
FIGURE 10. TO-220 Thermal Resistance vs Aluminum Plate Area.
THERMAL RESISTANCE vs
CIRCUIT BOARD COPPER AREA
50
DRV101
DDPAK
40
Surface-Mount Package
1oz. copper
30
Circuit Board Copper Area
20
10
0
0
1
2
3
4
5
Copper Area (inches²)
FIGURE 11. DDPAK Thermal Resistance vs Circuit Board Copper Area.
DRV101
DDPAK
Surface-Mount Package
Figure 10). For lowest overall thermal resistance, it is best to
isolate the entire heat sink/DRV101 structure from the
mounting surface rather than to use an insulator between the
semiconductor and heat sink.
For best thermal performance, the tab of the DDPAK sur-
face-mount version should be soldered directly to a circuit
board copper area. Increasing the copper area improves heat
dissipation. Figure 11 shows typical thermal resistance from
junction-to-ambient as a function of the copper area.
POWER DISSIPATION
Power dissipation depends on power supply, signal, and load
conditions. Power dissipation is equal to the product of
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.
Application Bulletin AB-039 explains how to calculate or
measure power dissipation with unusual signals and loads.
THERMAL PROTECTION
Power dissipated in the DRV101 will cause the junction
temperature to rise. The DRV101 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
device to cool. When the junction temperature cools to
approximately +150°C, the output circuitry is again enabled.
Depending on load and signal conditions, the thermal protec-
tion circuit may cycle on and off. This limits the dissipation
of the amplifier 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
40°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 DRV101 was de-
signed to protect against overload conditions. It was not
intended to replace proper heat sinking. Continuously run-
ning the DRV101 into thermal shutdown will degrade reli-
ability.
12
DRV101
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