NCV8665 データシートの表示（PDF） - ON Semiconductor

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NCV8665

Linear Regulator - Low Dropout, Very Low Iq, Reset, Delay Reset 150 mA

ON Semiconductor 

NCV8665

VI

VQ

VD

Reset

Delay Time

VRO

Reset

Reaction

Time

t

< Reset Reaction Time

VQ,rt

t

dVD

dt

+

Reset

Charge

CD

Current

Upper Timing Threshold VDU

Lower Timing Threshold VDL

t

t

Power−on−Reset

Thermal

Shutdown

Voltage Dip

at Input

Undervoltage

Secondary

Spike

Figure 11. Reset Timing

Overload

at Output

Calculating Power Dissipation

in a Single Output Linear Regulator

The maximum power dissipation for a single output

regulator (Figure 12) is:

PD(max) + [VI(max) * VQ(min)] IQ(max)

(1)

) VI(max)Iq

where

VI(max)

voltage,

is the maximum input

VQ(min)

voltage,

is the minimum output

IQ(max)

is the maximum output

current for the application,

Iq is the quiescent current the regulator consumes

at IQ(max).

Once the value of PD(max) is known, the maximum

permissible value of RqJA can be calculated:

RqJA

+

150°

C*

PD

TA

(2)

The value of RqJA can then be compared with those in the

package section of the data sheet. Those packages with

RqJA’s less than the calculated value in Equation NO TAG

will keep the die temperature below 150°C.

In some cases, none of the packages will be sufficient to

dissipate the heat generated by the IC, and an external

heatsink will be required.

II

IQ

VI

SMART

VQ

REGULATOR®

} Control

Features

Iq

Figure 12. Single Output Regulator with Key

Performance Parameters Labeled

Heatsinks

A heatsink effectively increases the surface area of the

package to improve the flow of heat away from the IC and

into the surrounding air.

Each material in the heat flow path between the IC and the

outside environment will have a thermal resistance. Like

series electrical resistances, these resistances are summed to

determine the value of RqJA:

RqJA + RqJC ) RqCS ) RqSA

(3)

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