4

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©

1999 IMP, Inc.

IMP3

Application Information

The IMP37 voltage regulator ICs offer self-protection features

which include short-circuit current protection and automatic thermal

shutdown (for junction temperature above 165°C).

Circuit Stability

Like all regulators, an output filter capacitor is required for circuit sta-

bility. Besides smoothing the output, the output capacitor

“completes” the regulator’s frequency compensation. The ESR of the

output capacitor should be less than 0.5

Ω. Low ESR capacitors are

preferred.

Table 1 shows recommended minimum capacitance values for both

aluminum and tantalum capacitors. Larger values of output capaci-

tance do not cause stability problems.

Table 1. Recommended Output Bypass Capacitors

An input bypass capacitor is recommended. A 10

µF or larger tanta-

lum capacitor is suitable for most applications.

5

.

0

<

R

S

E

(

r

o

t

i

c

a

p

a

C

s

s

a

p

y

B

t

u

p

t

u

O

Ω)

0

1

µ

0

0

1

,

m

u

l

a

t

n

a

T

F

µ

m

u

n

i

m

u

l

A

F

Figure 1. Fixed 3.3V Regulator

Thermal Management

The maximum operating junction temperature for the IMP37 devices

is 150°C. The junction temperature can be calculated when the

power dissipation and ambient temperature are known with this

The thermal resistance from juntion-to-ambient (

the three thermal resistances:

Where

Table 2. Thermal Resistance of Packages

The IMP37 series devices have thermal limiting circuitry to protect

the device from over current. For continuous operation, the maxi-

mum junction temperature rating must not be exceeded.

e

p

y

T

e

g

a

k

c

a

P

e

c

n

a

t

s

i

s

e

R

l

a

m

r

e

h

T

,

b

a

T

o

t

n

o

i

t

c

n

u

J

Θ

T

J

3

2

2

-

T

O

S

5

1 °

W

/

C

3

6

2

-

O

T

0

1 °

W

/

C

IMP37

OUT

*

**

IN

3.3V

37_02.eps

GND

* Min. 15

µF Tantalum or 100µF Aluminum.

Capacitor May Be Increased Without Limit.

** 10

µF Tantalum or 100µF Aluminum

+

+