Load

Transient

Line

Transient

VIN

VOUT

NOM

~90%

~85%

VERROR

Power-Down

~2.25V

~1.55V

~1.25V

~1.25V

~2.50V

~2.50V

Power-Up

Load

Transient

Line

Transient

VIN

VOUT

NOM

~90%

~85%

VERROR

Power-Up

~2.25V

~1.55V

~1.25V

~2.50V

Power-Down

1.80V

LP38511

www.ti.com

SNOSAU6E – NOVEMBER 2007 – REVISED APRIL 2013

The timing diagram in Figure 23 shows the relationship between the ERROR flag and the output voltage.

Figure 23. ERROR Flag Operation, see Typical Application Circuit

Figure 24. ERROR Flag Operation, biased from VIN

POWER DISSIPATION/HEATSINKING

A heatsink may be required depending on the maximum power dissipation (PD(MAX)), maximum ambient

temperature (TA(MAX)) of the application, and the thermal resistance (θJA) of the package. Under all possible

conditions, the junction temperature (TJ) must be within the range specified in the Operating Ratings. The total

power dissipation of the device is given by:

PD = ( (VIN−VOUT) x IOUT) + (VIN x IGND)

where

•

IGND is the operating ground current of the device (specified under ELECTRICAL CHARACTERISTICS).

(1)

The maximum allowable junction temperature rise (

ΔTJ) depends on the maximum expected ambient

temperature (TA(MAX)) of the application, and the maximum allowable junction temperature (TJ(MAX)):

ΔTJ = TJ(MAX)− TA(MAX)

(2)

The maximum allowable value for junction to ambient Thermal Resistance,

θJA, can be calculated using the

formula:

θJA = ΔTJ / PD(MAX)

(3)

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