GND

IN

EN1

EN2

OC1

OC2

OUT1

OUT2

TPS2062

V+

TPS2061, TPS2062, TPS2063

TPS2065, TPS2066, TPS2067

www.ti.com

SLVS490I – DECEMBER 2003 – REVISED OCTOBER 2009

Figure 26. Typical Circuit for the OC Pin

POWER DISSIPATION AND JUNCTION TEMPERATURE

The low on-resistance on the N-channel MOSFET allows the small surface-mount packages to pass large

currents. The thermal resistances of these packages are high compared to those of power packages; it is good

N-channel MOSFET relative to the input voltage and operating temperature. As an initial estimate, use the

dissipation per switch can be calculated by:

•

2

Multiply this number by the number of switches being used. This step renders the total power dissipation from

the N-channel MOSFETs.

Dissipation Ratings Table. Thermal resistance is a strong function of the printed circuit board construction , and

the copper trace area connecting the integrated circuit.

Finally, calculate the junction temperature:

•

Where:

•

•

•

Compare the calculated junction temperature with the initial estimate. If they do not agree within a few degrees,

repeat the calculation, using the calculated value as the new estimate. Two or three iterations are generally

sufficient to get a reasonable answer.

THERMAL PROTECTION

Thermal protection prevents damage to the IC when heavy-overload or short-circuit faults are present for

extended periods of time. The TPS206x implements a thermal sensing to monitor the operating junction

temperature of the power distribution switch. In an overcurrent or short-circuit condition, the junction temperature

rises due to excessive power dissipation. Once the die temperature rises above a minimum of 135°C due to

overcurrent conditions, the internal thermal sense circuitry turns the power switch off, thus preventing the power

switch from damage. Hysteresis is built into the thermal sense circuit, and after the device has cooled

approximately 10°C, the switch turns back on. The switch continues to cycle in this manner until the load fault or

input power is removed. The OCx open-drain output is asserted (active low) when an overtemperature shutdown

or overcurrent occurs.

Copyright © 2003–2009, Texas Instruments Incorporated

Submit Documentation Feedback

17

Product Folder Link(s): TPS2061 TPS2062 TPS2063 TPS2065 TPS2066 TPS2067