TPS73601DBVR datasheet(13/26 Pages) TI

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(Fixed Voltage Version)

dV dt

OUT

80kW ø RLOAD

(4)

POWER DISSIPATION

(Adjustable Voltage Version)

dV dt

OUT

80kW ø (R1 ) R2) ø RLOAD

(5)

REVERSE CURRENT

+ (VIN * VOUT)

OUT

(6)

THERMAL PROTECTION

PACKAGE MOUNTING

TPS736xx

www.ti.com .................................................................................................................................................. SBVS038R – SEPTEMBER 2003 – REVISED MAY 2008

The TPS736xx does not have active pull-down when

Any tendency to activate the thermal protection circuit

the output is over-voltage. This allows applications

indicates

excessive

power

dissipation

that

connect

higher

voltage

sources,

such

inadequate heat sink. For reliable operation, junction

alternate power supplies, to the output. This also

temperature should be limited to +125

°C maximum.

results in an output overshoot of several percent if

To estimate the margin of safety in a complete design

load current quickly drops to zero when a capacitor is

(including

heat

sink),

increase

the

ambient

connected to the output. The duration of overshoot

temperature until the thermal protection is triggered;

can be reduced by adding a load resistor. The

use worst-case loads and signal conditions. For good

overshoot decays at a rate determined by output

reliability, thermal protection should trigger at least

capacitor

COUT

and

the

internal/external

load

+35

°C above the maximum expected ambient

resistance. The rate of decay is given by:

condition

your

application.

This

produces

worst-case junction temperature of +125

°C at the

highest

expected

ambient

temperature

and

worst-case load.

The internal protection circuitry of the TPS736xx has

been designed to protect against overload conditions.

It was not intended to replace proper heat sinking.

Continuously running the TPS736xx into thermal

shutdown degrades device reliability.

The ability to remove heat from the die is different for

each

package

type,

presenting

different

considerations in the PCB layout. The PCB area

The NMOS pass element of the TPS736xx provides

around the device that is free of other components

inherent protection against current flow from the

moves the heat from the device to the ambient air.

output of the regulator to the input when the gate of

Performance data for JEDEC low- and high-K boards

the pass device is pulled low. To ensure that all

are shown in the Power Dissipation Ratings table.

charge is removed from the gate of the pass element,

Using heavier copper will increase the effectiveness

the EN pin must be driven low before the input

in removing heat from the device. The addition of

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

plated through-holes to heat-dissipating layers will

element may be left on due to stored charge on the

also improve the heat-sink effectiveness.

gate.

Power dissipation depends on input voltage and load

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

conditions. Power dissipation (PD) is equal to the

needed on any pin for reverse current blocking. Note

product of the output current times the voltage drop

that reverse current is specified as the current flowing

across the output pass element (VIN to VOUT):

out of the IN pin due to voltage applied on the OUT

pin. There will be additional current flowing into the

OUT pin due to the 80k

Ω internal resistor divider to

ground (see Figure 1 and Figure 2).

Power dissipation can be minimized by using the

For the TPS73601, reverse current may flow when

lowest possible input voltage necessary to assure the

VFB is more than 1.0V above VIN.

required output voltage.

Thermal protection disables the output when the

Solder

pad

footprint

recommendations

for

the

junction temperature rises to approximately +160

°C,

TPS736xx are presented in Application Bulletin

allowing the device to cool. When the junction

Solder Pad Recommendations for Surface-Mount

temperature cools to approximately +140

°C, the

Devices

(SBFA015),

available

from

the

Texas

output circuitry is again enabled. Depending on power

Instruments web site at www.ti.com.

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.

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TPS73601DBVR Datasheet(PDF) 13 Page - Texas Instruments

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