NSC LM317AH Datasheet

LM117/LM317A/LM317 3-Terminal Adjustable Regulator

General Description

The LM117 series of adjustable 3-terminal positive voltage regulators is capable of supplying in excess of 1.5A over a

1.2V to 37V output range. They are exceptionally easy to use and require only two external resistors to set the output voltage. Further, bothlineand load regulation are better than standard fixed regulators. Also, the LM117 is packaged in standard transistor packages which are easily mounted and handled.

In addition to higher performance than fixed regulators, the LM117 series offers full overload protection available only in IC’s. Included on the chip are current limit, thermal overload protection and safe area protection. All overload protection circuitry remainsfully functional even if the adjustment terminal is disconnected.

Normally,no capacitorsare needed unless the device is situated more than 6 inches from the input filter capacitors in which case an input bypass is needed. An optional output capacitor can be added to improve transient response. The adjustment terminal can be bypassed to achieve very high ripple rejection ratios which are difficult to achieve with standard 3-terminal regulators.

Besides replacing fixed regulators, the LM117 is useful in a wide variety of other applications. Since the regulator is “floating” and sees only the input-to-output differential volt-

age, supplies of several hundred volts can be regulated as long as the maximum input to output differential is not exceeded, i.e., avoid short-circuiting the output.

Also, it makes an especially simple adjustable switching regulator,a programmable output regulator,or by connecting a fixed resistor between the adjustment pin and output, the LM117 can be used as a precision current regulator. Supplies with electronic shutdown can be achieved by clamping the adjustment terminal to ground which programs the output to 1.2V where most loads draw little current.

For applications requiring greater output current, see LM150 series (3A) and LM138 series (5A) data sheets. For the negative complement, see LM137 series data sheet.

Features

n Guaranteed 1%output voltage tolerance (LM317A) n Guaranteed max. 0.01%/V line regulation (LM317A) n Guaranteed max. 0.3%load regulation (LM117) n Guaranteed 1.5A output current n Adjustable output down to 1.2V n Current limit constant with temperature n P n 80 dB ripple rejection n Output is short-circuit protected

Product Enhancement tested

LM117/LM317A/LM317 3-Terminal Adjustable Regulator

August 1999

Typical Applications LM117 Series Packages

1.2V–25V Adjustable Regulator

Full output current not available at high input-output voltages

Needed if device is more than 6 inches from filter capacitors.

†

Optional— improves transient response. Output capacitors in the range of 1 µF to 1000 µF of aluminum or tantalum electrolytic are commonly used to provide improved output impedance and rejection of transients.

DS009063-1

Part Number Design

Suffix Package Load

Current

K TO-3 1.5A

H TO-39 0.5A

T TO-220 1.5A

E LCC 0.5A

S TO-263 1.5A

EMP SOT-223 1A

MDT TO-252 0.5A

SOT-223 vs D-Pak (TO-252) Packages

DS009063-54

Scale 1:1

Absolute Maximum Ratings (Note 1)

If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications.

Power Dissipation Internally Limited Input-Output Voltage Differential +40V, −0.3V Storage Temperature −65˚C to +150˚C Lead Temperature

Operating Temperature Range

LM117 −55˚C ≤ TJ≤ +150˚C LM317A −40˚C ≤ T LM317 0˚C ≤ T

≤ +125˚C

Preconditioning

Thermal Limit Burn-In All Devices 100 Metal Package (Soldering, 10 seconds) 300˚C Plastic Package (Soldering, 4 seconds) 260˚C

ESD Tolerance (Note 5) 3 kV

Electrical Characteristics (Note 3)

Specifications with standard type face are for T

ture Range. Unless otherwise specified, V

Parameter Conditions LM117 (Note 2) Units

Reference Voltage V

3V ≤ (V 10 mA ≤ I

Line Regulation 3V ≤ (VIN−V

Load Regulation 10 mA ≤ I

Thermal Regulation 20 ms Pulse 0.03 0.07 Adjustment Pin Current 50 100 µA Adjustment Pin Current Change 10 mA ≤ I

3V ≤ (V Temperature Stability T Minimum Load Current (V Current Limit (V

RMS Output Noise,%of V

OUT

10 Hz ≤ f ≤ 10 kHz 0.003 Ripple Rejection Ratio V

C Long-Term Stability T Thermal Resistance, K Package 2.3 3 ˚C/W Junction-to-Case H Package 12 15 ˚C/W

E Package ˚C/W Thermal Resistance, Junction- K Package 35 ˚C/W to-Ambient (No Heat Sink) H Package 140 ˚C/W

E Package ˚C/W

25˚C, and those with boldface type apply over full Operating Tempera-

IN−VOUT

5V, and I

OUT

10 mA.

Min Typ Max

IN−VOUT

) ≤ 40V, 1.20 1.25 1.30 V

≤ I

OUT

,P≤P

MAX

) ≤ 40V (Note 4) 0.01 0.02

OUT

MAX

0.02 0.05

≤ I

OUT

(Note 4) 0.1 0.3

MAX

0.3 1

≤ TJ≤ T

MIN

IN−VOUT IN−VOUT

≤ I

OUT

MAX

IN−VOUT

) ≤ 40V

MAX

)=40V 3.5 5 mA ) ≤ 15V

0.2 5 µA

K Package 1.5 2.2 3.4 A H Packages 0.5 0.8 1.8 A

IN−VOUT

)=40V

K Package 0.3 0.4 A

H Package 0.15 0.2 A

10V, f=120 Hz, 65 dB

OUT

0µF

ADJ

10V, f=120 Hz, 66 80 dB

OUT

10 µF

ADJ

125˚C, 1000 hrs 0.3 1

/V % %

www.national.com 2

Electrical Characteristics (Note 3)

Specifications with standard type face are for T

ture Range. Unless otherwise specified, V

Parameter Conditions LM317A LM317 Units

Reference Voltage 1.238 1.250 1.262 V

3V ≤ (V 10 mA ≤ I

Line Regulation 3V ≤ (VIN−V

Load Regulation 10 mA ≤ I

Thermal Regulation 20 ms Pulse 0.04 0.07 0.04 0.07%/W Adjustment Pin Current 50 100 50 100 µA Adjustment Pin Current

Change Temperature Stability T

Minimum Load Current (V Current Limit (V

10 mA ≤ I 3V ≤ (V

≤ TJ≤ T

MIN

IN−VOUT IN−VOUT

K, T, S Packages 1.5 2.2 3.4 1.5 2.2 3.4 A H Package

MP Package

IN−VOUT

K, T, S Packages 0.15 0.4 0.15 0.4 A H Package

MP Package RMS Output Noise,%of V Ripple Rejection Ratio V

Long-Term Stability T Thermal Resistance,

Junction-to-Case

10 Hz ≤ f ≤ 10 kHz 0.003 0.003

OUT

ADJ

OUT

ADJ

125˚C, 1000 hrs 0.3 1 0.3 1

K Package MDT Package

H Package 12 15 12 15 ˚C/W T Package

MP Package

Thermal Resistance, Junction-to-Ambient (No Heat Sink)

K Package MDT Package(Note 6)

H Package 140 140 ˚C/W T Package 50 50 ˚C/W S Package (Note 6) 50 50 ˚C/W

Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the device is intended to be functional, but do not guarantee specific performance limits. For guaranteed specifications and test conditions, see the Electrical Characteristics. The guaranteed specifications apply only for the test conditions listed.

Note 2: Refer to RETS117H drawing for the LM117H, or the RETS117K for the LM117K military specifications. Note 3: Although power dissipation is internally limited, these specifications are applicable for maximum power dissipations of 2W for the TO-39 and SOT-223and

20W for the TO-3, TO-220, and TO-263. I All limits (i.e., the numbers in the Min. and Max. columns) are guaranteed to National’s AOQL (Average Outgoing Quality Level).

Note 4: Regulation is measured at a constant junction temperature, using pulse testing with a low duty cycle. Changes in output voltage due to heating effects are covered under the specifications for thermal regulation.

Note 5: Human body model, 100 pF discharged through a 1.5 kΩ resistor. Note 6: If the TO-263 or TO-252 packages are used, the thermal resistance can be reduced by increasing the PC board copper area thermally connected to the

package. If the SOT-223 package is used, the thermal resistance can be reduced by increasing the PC board copper area (see applications hints for heatsinking).

is 1.5A for the TO-3, TO-220, and TO-263 packages, 0.5A for the TO-39 package and 1A for the SOT-223 Package.

MAX

25˚C, and those with boldface type apply over full Operating Tempera-

IN−VOUT

5V, and I

OUT

10 mA.

Min Typ Max Min Typ Max

IN−VOUT

) ≤ 40V, 1.225 1.250 1.270 1.20 1.25 1.30 V

≤ I

OUT

,P≤P

MAX

) ≤ 40V (Note 4) 0.005 0.01 0.01 0.04%/V

OUT

MAX

0.01 0.02 0.02 0.07%/V

≤ I

OUT

(Note 4) 0.1 0.5 0.1 0.5

MAX

0.3 1 0.3 1.5

OUT

IN−VOUT

MAX

≤ I

MAX

) ≤ 40V

0.2 5 0.2 5 µA

)=40V 3.5 10 3.5 10 mA ) ≤ 15V

0.5

0.8

1.8

0.5

0.8

1.5

2.2

3.4

1.5

2.2

1.8

3.4AA

)=40V

0.075

10V, f=120 Hz, 65 65 dB

0µF

10V, f=120 Hz, 66 80 66 80 dB

10 µF

0.55

0.2

0.4

0.075

0.15

0.2

0.4

2.353 ˚C/W

23.5

35 35

% %

A A

˚C/W

˚C/W ˚C/W

www.national.com3

Typical Performance Characteristics

Output Capacitor=0 µF unless otherwise noted

Load Regulation

Dropout Voltage

Ripple Rejection

DS009063-37

DS009063-40

Current Limit

Temperature Stability

Ripple Rejection

DS009063-38

DS009063-41

Adjustment Current

DS009063-39

Minimum Operating Current

DS009063-42

Ripple Rejection

DS009063-43

Output Impedance

DS009063-46

Line Transient Response

www.national.com 4

DS009063-44

DS009063-47

DS009063-45

Load Transient Response

DS009063-48

Application Hints

In operation,the LM117develops a nominal1.25V reference voltage, V The reference voltage is impressed across program resistor R1 and, since the voltage is constant, a constant current I then flows through the output set resistor R2, giving an output voltage of

Since the 100 µAcurrent from the adjustment terminal represents an error term, the LM117 was designed to minimize I

ADJ

To do this, all quiescent operating current is returned to the output establishing a minimum load current requirement. If there is insufficient load on the output, the output will rise.

External Capacitors

An input bypass capacitor is recommended. A0.1 µF disc or 1 µF solid tantalum on the input is suitable input bypassing for almost all applications. The device is more sensitive to the absence of input bypassing when adjustment or output capacitors are used but the above values will eliminate the possibility of problems.

The adjustment terminal can be bypassed to ground on the LM117 to improve ripple rejection. This bypass capacitor prevents ripple from being amplified as the output voltage is increased. With a 10 µF bypass capacitor 80 dB ripple rejection is obtainable at any output level. Increases over 10 µF do not appreciably improve the ripple rejection at frequencies above 120 Hz. If the bypass capacitor is used, it is sometimes necessary to include protection diodes to prevent the capacitor from discharging through internal low current paths and damaging the device.

In general, the best type of capacitors to use is solid tantalum. Solid tantalum capacitors have low impedance even at high frequencies. Depending upon capacitor construction, it takes about 25 µF in aluminum electrolytic to equal 1 µF solid tantalum at high frequencies. Ceramic capacitors are also good at high frequencies; but some types have a large decrease incapacitance at frequenciesaround 0.5 MHz. For this reason, 0.01 µF disc may seem to work better than a 0.1 µF disc as a bypass.

Although the LM117 is stable with no output capacitors, like any feedback circuit, certain values of external capacitance can cause excessive ringing. This occurs with values between 500 pF and 5000 pF.A 1 µF solid tantalum (or 25 µF

, between the output and adjustment terminal.

REF

DS009063-5

FIGURE 1.

and make it very constant with line and load changes.

aluminum electrolytic) on the output swamps this effect and insures stability.Any increase of the load capacitance larger than 10 µF will merely improve the loop stability and output impedance.

Load Regulation

The LM117 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 terminal and the output terminal (usually 240Ω) should be tied directly to the output (case) 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

0.05Ω resistance between the regulator and load will have a load regulation due to line resistance of 0.05Ω xI resistor is connected near the load the effective line resistance will be 0.05Ω (1 + R2/R1) or in this case, 11.5 times worse.

Figure 2

shows the effect of resistance between the regula-

tor and 240Ω set resistor.

FIGURE 2. Regulator with Line Resistance in Output

Lead

With the TO-3 package, it is easy to minimize the resistance from the case to the set resistor,by using two separate leads to the case. However, with the TO-39 package, care should be taken to minimize the wire length of the output lead. The ground of R2 can be returned near the ground of the load to provide remote ground sensing and improve load regulation.

Protection Diodes

When external capacitors are used with

any

sometimes necessary to add protection diodes to prevent the capacitors from discharging through low current points into the regulator. Most 10 µF capacitors have low enough internal series resistance to deliver 20A spikes when shorted. Although the surge is short, there is enough energy to damage parts of the IC.

When an output capacitor is connected to a regulator and the input is shorted, the output capacitor will discharge into the output of the regulator. The discharge current depends on the value of the capacitor, the output voltage of the regulator, and the rate of decrease of V charge path is through a large junction that is able to sustain

. In the LM117, this dis-

15A surge with no problem. This is not true of other types of positive regulators. For output capacitors of 25 µF or less, there is no need to use diodes.

The bypass capacitor on the adjustment terminal can discharge through a low current junction. Discharge occurs when

either

the input or output is shorted. Internal to the LM117is a 50Ω resistor which limits the peak discharge current. No protection is needed for output voltages of 25V or

. If the set

DS009063-6

IC regulator it is

www.national.com5

Application Hints (Continued)

less and 10 µF capacitance. protection diodes included for use with outputs greater than 25V and high values of output capacitance.

D1 protects against C1 D2 protects against C2

FIGURE 3. Regulator with Protection Diodes

When a value for θ

a heatsinkmust be selectedthat has a value that is less than

(H−A)

or equal to this number.

is specified numerically by the heatsink manufacturer

(H−A)

in the catalog, or shown ina curve that plots temperature rise vs power dissipation for the heatsink.

HEATSINKING TO-263, SOT-223 AND TO-252 PACKAGE PARTS

The TO-263 (“S”), SOT-223 (“MP”) and TO-252 (”DT”) packages use a copper plane on the PCB and the PCB itself as a heatsink. To optimize the heat sinking ability of the plane and PCB, solder the tab of the package to the plane.

Figure 4

shows for the TO-263the measured values of θ for different copper area sizes using a typical PCB with 1 ounce copper

and no solder maskover the copper area used

for heatsinking.

Figure 3

shows an LM117 with

DS009063-7

is found using the equation shown,

(J−A)

As a design aid,

Figure 5

shows the maximum allowable power dissipation compared to ambient temperature for the TO-263 device (assuming θ mum junction temperature is 125˚C).

FIGURE 5. Maximum Power Dissipation vs T

the TO-263 Package

Figure 6

and

Figure 7

package.

Figure 7

show the information for the SOT-223

assumes a θ

copper and 51˚C/W for 2 ounce copper and a maximum

is 35˚C/W and the maxi-

(J−A)

DS009063-56

of 74˚C/W for 1 ounce

(J−A)

AMB

for

junction temperature of 125˚C.

DS009063-57

FIGURE 6. θ

vs Copper (2 ounce) Area for the

(J−A)

SOT-223 Package

DS009063-55

FIGURE 4. θ

vs Copper (1 ounce) Area for the

(J−A)

TO-263 Package

As shown in the figure, increasing the copper area beyond 1 square inch produces very little improvement. It should also be observed that the minimum value of θ package mounted to a PCB is 32˚C/W.

www.national.com 6

for the TO-263

(J−A)

DS009063-58

FIGURE 7. Maximum Power Dissipation vs T

the SOT-223 Package

AMB

for

Application Hints (Continued)

The LM317 regulators have internal thermal shutdown to protect the device from over-heating. Under all possible operating conditions, the junction temperature of the LM317 must be within the range of 0˚C to 125˚C. Aheatsink may be required depending on the maximum power dissipation and maximum ambient temperature of the application. To determine if a heatsink is needed, the power dissipated by the regulator, P

Figure 8

the circuit.

, must be calculated:

L+IG

IN−VOUT)IL+VINIG

shows the voltage andcurrents whichare present in

DS009063-60

FIGURE 8. Power Dissipation Diagram

The next parameter which must be calculated is the maximum allowable temperature rise, T

(max)=TJ(max) − TA(max)

(max) is the maximum allowable junction tempera-

where T

ture (125˚C), and T perature which will be encountered in the application.

(max) is the maximum ambient tem-

Using the calculated values for T mum allowable value for the junction-to-ambient thermal resistance (θ

) can be calculated:

(max)/P

(max):

(max) and PD, the maxi-

If the maximum allowable value for θJAis found to be ≥92˚C/W (Typical Rated Value) for TO-252 package, no heatsink is needed since the package alone will dissipate enough heat to satisfy these requirements. If the calculated value for θ

As a design aid,

falls below these limits, a heatsink is required.

Table 1

shows the value of the θJAof TO-252 for different heatsink area. The copper patterns that we used to measure these θ Application Notes Section. sults as what are in the

Figure 10

shows the maximum allowable power dissipation vs. ambient temperature for the TO-252 device. shows the maximum allowable power dissipation vs. copper

area (in

) for the TO-252 device. Please see AN1028 for

s are shown at the end of the

Figure 9

reflects the same test re-

Table 1

Figure 11

power enhancement techniques to be used with SOT-223 and TO-252 packages.

TABLE 1. θ

Different Heatsink Area

Layout Copper Area Thermal Resistance

Top Side (in

)* Bottom Side (in2)(θ

˚C/W) TO-252

1 0.0123 0 103 2 0.066 0 87 3 0.3 0 60 4 0.53 0 54 5 0.76 0 52 61 0 47 7 0 0.2 84 8 0 0.4 70

9 0 0.6 63 10 0 0.8 57 11 0 1 57 12 0.066 0.066 89 13 0.175 0.175 72 14 0.284 0.284 61 15 0.392 0.392 55 16 0.5 0.5 53

Note:*Tab of device attached to topside of copper.

www.national.com7

Application Hints (Continued)

FIGURE 9. θJAvs 2oz Copper Area for TO-252

FIGURE 10. Maximum Allowable Power Dissipation vs. Ambient Temperature for TO-252

DS009063-61

DS009063-63

FIGURE 11. Maximum Allowable Power Dissipation vs. 2oz Copper Area for TO-252

www.national.com 8

DS009063-62

+ 18 hidden pages