LM350K-ST.pdf

LM150/250

LM350

ADJUSTABLE VOLTAGE REGULATORS

THREE-TERMINAL 3 A

. GUARANTEED 3A OUTPUT CURRENT

. LINE REGULATION TYPICALLY 0.005% /V

. GUARANTEED THERMAL REGULATION

. CURRENT LIMIT CONSTANT WITH TEM-

PERATURE

. STANDARD 3-LEAD TRANSISTOR PACKAGE

TO3

K SUFFIX

(Steel Can)

ORDER CODE

PART

NUMBER

TEMPERATURE

RANGE

PACKAGE

LM150

LM250

LM350

-55 o C to + 150 o C

-25 o C to + 150 o C

0 o C to + 125 o C

EXAMPLE : LM150K

PIN CONNECTION

(bottom view)

Case is output

March 1993

1/7

. ADJUSTABLE OUTPUT DOWN TO 1.2V

. LOAD REGULATION TYPICALLY 0.1%

LM150-LM250-LM350

ABSOLUTE MAXIMUM RATING

Symbol

Parameter

Value

Unit

P tot

Power Dissipation

Internally Limited

V I - V O Input-Output Voltage DIfferential

T oper Operating Junction Temperature Range

LM150

LM250

LM350

-55 to 150

-25 to 150

0 to 125

o C

T stg

Storage Temperature Range

-65 to 150

o C

T lead Lead Temperature (Soldering, 10 seconds)

300

o C

THERMAL CHARACTERISTICS

Symbol

Parameter

Value

Unit

R th(j-c) Typical Junction-Case Thermal Resistance

1.5

o C/W

R th(j-a) Max Junction-Ambient Thermal Resistance

o C/W

SCHEMATIC DIAGRAM

2/7

LM150-LM250-LM350

ELECTRICAL CHARACTERISTICS

LM150: -55 o C

T j

150 o C, V I - V O = 5V, I O = 1.5A

T j

150 o C, V I - V O = 5V, I O = 1.5A

Although power dissipation is internally limited, these specifications apply to power dissipation up to

30W (unless otherwise specified).

T j

Symbol

Parameter

LM150-LM250

LM350

Unit

Min. Typ. Max. Min. Typ. Max.

K VI

Line Regulation - (note 1)

T amb = 25 o C, 3 V

0.005 0.01

0.005 0.03

%/V

(V I - V O )

35 V

K VO Load Regulation T amb = 25 o C, 10 mA

I O

3 A

V O

5V - (note 1)

0.1

0.3

0.1

0.5

V O

5V - (note 1)

Thermal Regulation (pulse = 20 ms)

0.002 0.01

0.002 0.02 %/W

I adj

Adjustment Pin Current

100

I adj Adjustment Pin Current Change

10 mA

0.2

I L

3 A, 3 V

(V I - V O )

35 V

v (ref) Reference Voltage

1.19

1.24

1.29

1.19

1.24

1.29

(V I - V O )

35 V, 10 mA

I O

3A, P

30W

K VI

Line Regulation - (note 1)

3 V

0.02

0.05

0.02

0.05

%/V

(V I - V O )

35 V

K VO Load Regulation 10 mA

I O

3 A

V O

5V - (note 1)

0.3

1.5

V O

5V - (note 1)

K VT

Temperature Stability (T min

T j

T max )

I O(min) Minimum Load Current (V I - V O

35 V)

3.5

I O(max) Current Limit (V I - V O

10 V)

V I - V O = 30 V

4.5

RMS Output Noise, % of V O

(T amb = 25 o C, 10 Hz

0.001

10 KHz)

R vf

Ripple Rejection Ratio

V O = 10 V, f = 120 Hz

C adi = 10

K VH Long Term Stability (T amb = 125 o C) 0.3 1 0.3 1 %

Note 1 : Regulation is measured at constant junction temperature. Changes in output voltage due to heating effects are taken

into account separately by thermal rejection.

3/7

LM250: -25 o C

150 o C, V I - V O = 5V, I O = 1.5A

LM350: 0 o C

LM150-LM250-LM350

TYPICAL APPLICATIONS

A current from the adjustment termi-

nal represents an error term, the LM350 was de-

signed to minimize I adj and make it very constant

with line and load changes. To do this, all quiescent

operating current is returned to the output establi-

shing a minimum load current requirement. If there

is insufficient load on the output, the output will rise.

+ 1.2V to + 25V ADJUSTABLE REGULATOR

LM350

F solid tantalum on the input is suit-

able input by passing for almost all applications.

The device is more sensitive to the absence of input

bypassing when adjustment or output capacitors

are used byt the above values will eliminate the

possibility of problems.

The adjustment terminal can be bypassed to

ground on the LM350 to improve ripple rejection.

This bypass capacitor prevents ripple form being

amplified as the output voltage is increased. With

a 10

F disc or 1

Needed if device is far from filter capacitors.

* Optional-improves transient response. Output capacitors in the

range of 1

F of aluminium or tantalum electrolytic are

commonly used to provide improved output impedance and rejec-

tion of transients.

F to 100

do not appreciably improve the ripple rejection at

frequencies above 120Hz. If the bypass capacitor

is used, it is sometimes necessary to include pro-

tection diodes to prevent the capacitor from dis-

charging through internal low current paths and

damaging the device.

In general, the best type of capacitors to use are

solid tantalum. Solid tantalum capacitors have low

impedance even at high frequencies. Depending

upon capacitor construction, it takes about 25

* * V O = 1.25V (1 + )

* * * R1 = 240

for LM150 and LM250

APPLICATION HINTS

In operation, the LM350 develops a nominal 1.25V

reference voltage, V (ref) , between the output and

adjustment terminal. The reference voltage is im-

pressed across program resistor R1 and, since the

voltage is constant, a constant current I 1 then flows

through the output set resistor R2, giving an output

voltage of

V O = V (ref) ( 1+ R 2

F in

F solid tantalum at

high frequencies. Ceramic capacitors are also

good at high frequencies, but some types have a

large decrease in capacitance at frequencies

around 0.5MHz. For this reason, 0.01

F disc may

R 1 ) + I adj R 2

F disc as a bypass.

Although the LM350 is stable with no output capa-

citors, like any feedback circuit, certain values of

external capacitance can cause excessive ringing.

This occurs with values between 500pF and

5000pF. A 1

Figure 1.

LM350

F aluminium

electrolytic) on the output swamps this effect and

insures stability.

F solid tantalum (or 25

LOAD REGULATION

The LM350 is capable of providing extremely good

load regulation but a few precautions are needed

to obtain maximum performance. The current set

resistor connected between the adjustment termi-

nal and the output terminal (usually 240

resistance between the regu-

lator and load will have a load regulation due to line

resistance of 0.05

x I L . If the set resistor is con-

nected near the load the effective line resistance

4/7

Since the 50

EXTERNAL CAPACITORS

An input bypass capacitor is recommended. A

0.1

F bypass capacitor 75dB ripple rejection is

obtainable at any output level. Increases over 20

aluminum electrolytic to equal 1

seem to work better than a 0.1

) should

be tied directly to the output of the regulator rather

than near the load. This eliminates line drops from

appearing effectively in series with the reference

and degrading regulation. For example, a 15V

regulator with 0.05

LM150-LM250-LM350

will be 0.05

(1 + R 2 /R 1 ) or in this case, 11.5 times

F capacitors have low enough internal series re-

sistance to deliver 20A spikes when shorted. Al-

though the surge is short, there is enough energy to

damage parts of the IC.

When an output capacitor is connected to a regula-

tor and the input is shorted, the output capacitor will

discharge into the output of the regulator. The dis-

charge current depends on the value of the capaci-

tor, the output voltage of the regulator, and the rate

of decrease of V I . In the LM350 this discharge path

is through a large junction that is able to sustain 25A

surge with no problem. This is not true of other types

of positive regulators. For output capacitors of

100

worse.

Figure 2 shows the effect of resistance between the

regulator and 140

set resistor.

With the TO-3 package, it is easy to minimize the re-

sistance from the case to the set resistor, by using

2 separate leads to the case. The ground of R2 can

be returned near the ground of the load to provide

remote ground sensing and improve load regula-

tion.

PROTECTION DIODES

When external capacitors are used with any IC regu-

lator it is sometimes necessary to add protection

diodes to prevent the capacitors from discharging

through low current points into the regulator. Most

F or less at output of 15V or less, there is no

need to use diodes.

The bypass capacitor on the adjustment terminal

can discharge through a low current junction. Dis-

charge occurs when either the input or output is

shorted. Internal to the LM350 is a 50

Figure 2 : Regulator with Line Resistance in Out-

put Lead.

resistor

which limits the peak discharge current. No protec-

tion is needed for output voltages of 25V or less and

LM350

F capacitance. Figure 3 shows an LM350 with

protection diodes included for use with outputs

greater than 25V and high values of output capacit-

ance.

Figure 3 : Regulator with Protection Diodes.

LM350

5/7

Plik z chomika:

Inne pliki z tego folderu:

Inne foldery tego chomika: