TPS73201DBVR datasheet(13/23 Pages) TI

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dV dt

OUT

80kW ø (R1 ) R2) ø RLOAD

(5)

REVERSE CURRENT

POWER DISSIPATION

THERMAL PROTECTION

+ (VIN * VOUT)

OUT

(6)

Package Mounting

TPS732xx

SBVS037I – AUGUST 2003 – REVISED MAY 2006

(Adjustable voltage version)

35°C

above

the

maximum

expected

ambient

condition of your application. This produces a

worst-case junction temperature of 125°C at the

highest

expected

ambient

temperature

and

worst-case load.

The internal protection circuitry of the TPS732xx has

The NMOS pass element of the TPS732xx provides

been

designed

protect

against

overload

inherent protection against current flow from the

conditions. It was not intended to replace proper

output of the regulator to the input when the gate of

heatsinking. Continuously running the TPS732xx into

the pass device is pulled low. To ensure that all

thermal shutdown will degrade device reliability.

charge is removed from the gate of the pass

element, the enable pin must be driven low before

the input voltage is removed. If this is not done, the

The ability to remove heat from the die is different for

pass element may be left on due to stored charge on

each

package

type,

presenting

different

the gate.

considerations in the PCB layout. The PCB area

After the enable pin is driven low, no bias voltage is

around the device that is free of other components

needed on any pin for reverse current blocking. Note

moves the heat from the device to the ambient air.

that reverse current is specified as the current

Performance data for JEDEC low- and high-K boards

flowing out of the IN pin due to voltage applied on

are shown in the Power Dissipation Ratings table.

the OUT pin. There will be additional current flowing

Using heavier copper will increase the effectiveness

into the OUT pin due to the 80k

Ω internal resistor

in removing heat from the device. The addition of

divider to ground (see Figure 1 and Figure 2).

plated through-holes to heat-dissipating layers will

also improve the heat-sink effectiveness.

For the TPS73201, reverse current may flow when

VFB is more than 1.0V above VIN.

Power dissipation depends on input voltage and load

conditions. Power dissipation is equal to the product

of the output current times the voltage drop across

the output pass element (VIN to VOUT):

Thermal protection disables the output when the

junction temperature rises to approximately 160°C,

allowing the device to cool. When the junction

Power dissipation can be minimized by using the

temperature cools to approximately 140°C, the

lowest possible input voltage necessary to assure

output circuitry is again enabled. Depending on

the required output voltage.

power dissipation, thermal resistance, and ambient

temperature, the thermal protection circuit may cycle

on and off. This limits the dissipation of the regulator,

protecting it from damage due to overheating.

Solder

pad

footprint

recommendations

for

the

TPS732xx are presented in Application Bulletin

Any tendency to activate the thermal protection

Solder Pad Recommendations for Surface-Mount

circuit indicates excessive power dissipation or an

Devices

(AB-132),

available

from

the

Texas

inadequate heatsink. For reliable operation, junction

Instruments web site at www.ti.com.

temperature should be limited to 125°C maximum.

To estimate the margin of safety in a complete

design (including heatsink), increase the ambient

temperature until the thermal protection is triggered;

use worst-case loads and signal conditions. For good

reliability, thermal protection should trigger at least

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