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LM117/LM317A/LM317-N Three-Terminal Adjustable Regulator
Check for Samples: LM117,LM317A,LM317-N
Normally, no capacitors are needed unless the device
1FEATURES is situated more than 6 inches from the input filter
2• Specified 1% Output Voltage Tolerance capacitors in which case an input bypass is needed.
(LM317A) An optional output capacitor can be added to improve
• Specified max. 0.01%/V Line Regulation transient response. The adjustment terminal can be
bypassed to achieve very high ripple rejection ratios
(LM317A) which are difficult to achieve with standard 3-terminal
• Specified max. 0.3% Load Regulation (LM117) regulators.
• Specified 1.5A Output Current Besides replacing fixed regulators, the LM117 is
• Adjustable Output Down to 1.2V useful in a wide variety of other applications. Since
• Current Limit Constant with Temperature the regulator is “floating” and sees only the input-to-
output differential voltage, supplies of several
• P+Product Enhancement tested hundred volts can be regulated as long as the
• 80 dB Ripple Rejection maximum input to output differential is not exceeded,
• Output is Short-Circuit Protected i.e., avoid short-circuiting the output.
Also, it makes an especially simple adjustable
DESCRIPTION switching regulator, a programmable output regulator,
The LM117 series of adjustable 3-terminal positive or by connecting a fixed resistor between the
voltage regulators is capable of supplying in excess adjustment pin and output, the LM117 can be used
of 1.5A over a 1.2V to 37V output range. They are as a precision current regulator. Supplies with
exceptionally easy to use and require only two electronic shutdown can be achieved by clamping the
external resistors to set the output voltage. Further, adjustment terminal to ground which programs the
both line and load regulation are better than standard output to 1.2V where most loads draw little current.
fixed regulators. Also, the LM117 is packaged in
standard transistor packages which are easily For applications requiring greater output current, see
mounted and handled. LM150 series (3A) and LM138 series (5A) data
sheets. For the negative complement, see LM137
In addition to higher performance than fixed series data sheet.
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
remains fully functional even if the adjustment
terminal is disconnected.
1Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of
Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
2All trademarks are the property of their respective owners.
PRODUCTION DATA information is current as of publication date. Copyright © 2004–2013, Texas Instruments Incorporated
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
LM117, LM317A, LM317-N
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Typical Applications
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.
Figure 1. 1.2V–25V Adjustable Regulator
LM117/LM317A/LM317-N Package Options
Part Number Package Drawing Package Type Output Current
LM117K STEEL NDS TO-3
LM317K
LM317AT NDE 1.5A
LM317T TO-220
LM317T/LF01 NDG
LM317S KTT TO-263
LM317AEMP DCY SOT-223 1.0A
LM317EMP
LM117H
LM317AH NDT TO
LM317H 0.5A
LM317AMDT NDP TO-252
LM317MDT
NOTE
For part numbers that can be ordered, please see the Package Option Addendum at the
end of the datasheet.
SOT-223 vs. TO-252 Packages
Figure 2. Scale 1:1
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Connection Diagrams
CASE IS OUTPUT
CASE IS OUTPUT Figure 3. TO-3 (NDS) Figure 4. TO (NDT)
Metal Can Package Metal Can Package
Bottom View Bottom View
Package Drawing NDS Package Drawing NDT
Figure 5. TO-263 (KTT) Figure 6. TO-220 (NDE)
Surface-Mount Package Plastic Package
Top View Front View
Package Drawing KTT Package Drawing NDE
Figure 7. 4-Lead SOT-223 (DCY) Figure 8. TO-252 (NDP)
Top View Surface-Mount Package Front View Surface Mount Package
Package Number DCY Package Drawing NDP
These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam
during storage or handling to prevent electrostatic damage to the MOS gates.
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ABSOLUTE MAXIMUM RATINGS (1)(2)
Power Dissipation Internally Limited
Input-Output Voltage Differential +40V, −0.3V
Storage Temperature −65°C to +150°C
Lead Temperature Metal Package (Soldering, 10 seconds) 300°C
Plastic Package (Soldering, 4 seconds) 260°C
ESD Tolerance (3) 3 kV
(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 ensure specific performance limits. For ensured specifications and test
conditions, see the Electrical Characteristics. The ensured specifications apply only for the test conditions listed.
(2) If Military/Aerospace specified devices are required, please contact the Texas Instruments Sales Office/Distributors for availability and
specifications.
(3) Human body model, 100 pF discharged through a 1.5 kΩresistor.
OPERATING TEMPERATURE RANGE
LM117 −55°C ≤TJ≤+150°C
LM317A −40°C ≤TJ≤+125°C
LM317-N 0°C ≤TJ≤+125°C
Preconditioning
Thermal Limit Burn-In All Devices 100%
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LM117 ELECTRICAL CHARACTERISTICS(1)
Specifications with standard type face are for TJ= 25°C, and those with boldface type apply over full Operating
Temperature Range. Unless otherwise specified, VIN −VOUT = 5V, and IOUT = 10 mA. LM117 (2)
Parameter Conditions Min Typ Max Units
3V ≤(VIN −VOUT)≤40V,
Reference Voltage 1.20 1.25 1.30 V
10 mA ≤IOUT ≤IMAX(1)
0.01 0.02
Line Regulation 3V ≤(VIN −VOUT)≤40V (3) %/V
0.02 0.05
0.1 0.3
Load Regulation 10 mA ≤IOUT ≤IMAX(1) (3) %
0.3 1
Thermal Regulation 20 ms Pulse 0.03 0.07 %/W
Adjustment Pin Current 50 100 μA
10 mA ≤IOUT ≤IMAX(1)
Adjustment Pin Current Change 0.2 5 μA
3V ≤(VIN −VOUT)≤40V
Temperature Stability TMIN ≤TJ≤TMAX 1%
Minimum Load Current (VIN −VOUT) = 40V 3.5 5 mA
NDS Package 1.5 2.2 3.4
(VIN −VOUT)≤15V A
NDT Package 0.5 0.8 1.8
Current Limit NDS Package 0.3 0.4
(VIN −VOUT) = 40V A
NDT Package 0.15 0.20
RMS Output Noise, % of VOUT 10 Hz ≤f≤10 kHz 0.003 %
VOUT = 10V, f = 120 Hz, CADJ = 0 μF65 dB
Ripple Rejection Ratio VOUT = 10V, f = 120 Hz, CADJ = 10 μF66 80 dB
Long-Term Stability TJ= 125°C, 1000 hrs 0.3 1 %
NDS (TO-3) Package 2
Thermal Resistance, θJC °C/W
Junction-to-Case NDT (TO) Package 21
Thermal Resistance, θJA NDS (TO-3) Package 39
Junction-to-Ambient °C/W
NDT (TO) Package 186
(No Heat Sink)
(1) IMAX = 1.5A for the NDS (TO-3), NDE (TO-220), and KTT (TO-263) packages. IMAX = 1.0A for the DCY (SOT-223) package. IMAX = 0.5A
for the NDT (TO) and NDP (TO-252) packages. Device power dissipation (PD) is limited by ambient temperature (TA), device maximum
junction temperature (TJ), and package thermal resistance (θJA). The maximum allowable power dissipation at any temperature is :
PD(MAX) = ((TJ(MAX) - TA)/θJA). All Min. and Max. limits are ensured to TI's Average Outgoing Quality Level (AOQL).
(2) Specifications and availability for military and space grades of LM117/883 can be found in the LM117QML datasheet (SNVS356).
Specifications and availability for military and space grades of LM117/JAN can be found in the LM117JAN datasheet (SNVS365).
(3) 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.
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LM317A and LM317-N ELECTRICAL CHARACTERISTICS(1)
Specifications with standard type face are for TJ= 25°C, and those with boldface type apply over full Operating
Temperature Range. Unless otherwise specified, VIN −VOUT = 5V, and IOUT = 10 mA.
LM317A LM317-N
Parameter Conditions Unit
Min Typ Max Min Typ Max s
1.238 1.250 1.262 - 1.25 - V
Reference Voltage 3V ≤(VIN −VOUT)≤40V, 1.225 1.250 1.270 1.20 1.25 1.30 V
10 mA ≤IOUT ≤IMAX(1)
0.005 0.01 0.01 0.04
Line Regulation 3V ≤(VIN −VOUT)≤40V (2) %/V
0.01 0.02 0.02 0.07
0.1 0.5 0.1 0.5
Load Regulation 10 mA ≤IOUT ≤IMAX(1) (2) %
0.3 1 0.3 1.5
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 10 mA ≤IOUT ≤IMAX(1) 0.2 5 0.2 5 μA
Change 3V ≤(VIN −VOUT)≤40V
Temperature Stability TMIN ≤TJ≤TMAX 1 1 %
Minimum Load Current (VIN −VOUT) = 40V 3.5 10 3.5 10 mA
NDS, KTT Packages - - - 1.5 2.2 3.4
(VIN −VOUT)≤15V DCY, NDE Packages 1.5 2.2 3.4 1.5 2.2 3.4 A
NDT, MDT Packages 0.5 0.8 1.8 0.5 0.8 1.8
Current Limit NDS, KTT Packages - - 0.15 0.40
(VIN −VOUT) = 40V DCY, NDE Packages 0.112 0.30 0.112 0.30 A
NDT, MDT Packages 0.075 0.20 0.075 0.20
RMS Output Noise, % of 10 Hz ≤f≤10 kHz 0.003 0.003 %
VOUT VOUT = 10V, f = 120 Hz, CADJ = 0 μF65 65 dB
Ripple Rejection Ratio VOUT = 10V, f = 120 Hz, CADJ = 10 μF66 80 66 80 dB
Long-Term Stability TJ= 125°C, 1000 hrs 0.3 1 0.3 1 %
NDS (TO-3) Package - 2
NDE (TO-220) Package 4 4
KTT (TO-263) Package - 4
Thermal Resistance, θJC °C/W
Junction-to-Case DCY (SOT-223) Package 23.5 23.5
NDT (TO) Package 21 21
NDP (TO-252) Package 12 12
- 39
NDS (TO-3) Package 50 50
NDE (TO-220) Package
Thermal Resistance, θJA KTT (TO-263) Package (3) - 50
Junction-to-Ambient °C/W
DCY (SOT-223) Package (3) 140 140
(No Heat Sink) NDT (TO) Package 186 186
NDP (TO-252) Package (3) 103 103
(1) IMAX = 1.5A for the NDS (TO-3), NDE (TO-220), and KTT (TO-263) packages. IMAX = 1.0A for the DCY (SOT-223) package. IMAX = 0.5A
for the NDT (TO) and NDP (TO-252) packages. Device power dissipation (PD) is limited by ambient temperature (TA), device maximum
junction temperature (TJ), and package thermal resistance (θJA). The maximum allowable power dissipation at any temperature is :
PD(MAX) = ((TJ(MAX) - TA)/θJA). All Min. and Max. limits are ensured to TI's Average Outgoing Quality Level (AOQL).
(2) 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.
(3) When surface mount packages are used (TO-263, SOT-223, TO-252), the junction to ambient thermal resistance can be reduced by
increasing the PC board copper area that is thermally connected to the package. See the APPLICATION HINTS section for heatsink
techniques.
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TYPICAL PERFORMANCE CHARACTERISTICS
Output Capacitor = 0 μF unless otherwise noted
Load Regulation Current Limit
Figure 9. Figure 10.
Adjustment Current Dropout Voltage
Figure 11. Figure 12.
VOUT vs VIN, VOUT = VREF VOUT vs VIN, VOUT = 5V
Figure 13. Figure 14.
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TYPICAL PERFORMANCE CHARACTERISTICS (continued)
Output Capacitor = 0 μF unless otherwise noted
Temperature Stability Minimum Operating Current
Figure 15. Figure 16.
Ripple Rejection Ripple Rejection
Figure 17. Figure 18.
Ripple Rejection Output Impedance
Figure 19. Figure 20.
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TYPICAL PERFORMANCE CHARACTERISTICS (continued)
Output Capacitor = 0 μF unless otherwise noted
Line Transient Response Load Transient Response
Figure 21. Figure 22.
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APPLICATION HINTS
In operation, the LM117 develops a nominal 1.25V reference voltage, VREF, between the output and adjustment
terminal. The reference voltage is impressed across program resistor R1 and, since the voltage is constant, a
constant current I1then flows through the output set resistor R2, giving an output voltage of
(1)
Since the 100 μA current from the adjustment terminal represents an error term, the LM117 was designed to
minimize IADJ and make it very constant with line and load changes. 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. A 0.1 μF disc or 1μF 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 1μF 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 0.5 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 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 0.05Ωresistance between the regulator and load will have a load regulation due to
line resistance of 0.05Ω× IL. If the set 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 23 shows the effect of resistance between the regulator and 240Ωset resistor.
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Figure 23. 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 IC regulator it is 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 VIN. In the LM117, this discharge path is through a large junction that
is able to sustain 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 the output, is shorted. Internal to the LM117 is a 50Ωresistor which limits the peak
discharge current. No protection is needed for output voltages of 25V or less and 10 μF capacitance. Figure 24
shows an LM117 with 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 24. Regulator with Protection Diodes
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Heatsink Requirements
The LM317-N regulators have internal thermal shutdown to protect the device from over-heating. Under all
operating conditions, the junction temperature of the LM317-N should not exceed the rated maximum junction
temperature (TJ) of 150°C for the LM117, or 125°C for the LM317A and LM317-N. A heatsink may be required
depending on the maximum device power dissipation and the maximum ambient temperature of the application.
To determine if a heatsink is needed, the power dissipated by the regulator, PD, must be calculated:
PD= ((VIN −VOUT) × IL) + (VIN × IG) (2)
Figure 25 shows the voltage and currents which are present in the circuit.
The next parameter which must be calculated is the maximum allowable temperature rise, TR(MAX):
TR(MAX) = TJ(MAX) −TA(MAX) (3)
where TJ(MAX) is the maximum allowable junction temperature (150°C for the LM117, or 125°C for the
LM317A/LM317-N), and TA(MAX) is the maximum ambient temperature which will be encountered in the
application.
Using the calculated values for TR(MAX) and PD, the maximum allowable value for the junction-to-ambient thermal
resistance (θJA) can be calculated:
θJA = (TR(MAX) / PD) (4)
Figure 25. Power Dissipation Diagram
If the calculated maximum allowable thermal resistance is higher than the actual package rating, then no
additional work is needed. If the calculated maximum allowable thermal resistance is lower than the actual
package rating either the power dissipation (PD) needs to be reduced, the maximum ambient temperature TA(MAX)
needs to be reduced, the thermal resistance (θJA) must be lowered by adding a heatsink, or some combination of
these.
If a heatsink is needed, the value can be calculated from the formula:
θHA ≤(θJA - (θCH +θJC)) (5)
where (θCH is the thermal resistance of the contact area between the device case and the heatsink surface, and
θJC is thermal resistance from the junction of the die to surface of the package case.
When a value for θ(H−A) is found using the equation shown, a heatsink must be selected that has a value that is
less than, or equal to, this number.
The θ(H−A) rating is specified numerically by the heatsink manufacturer in the catalog, or shown in a curve that
plots temperature rise vs power dissipation for the heatsink.
Heatsinking Surface Mount Packages
The TO-263 (KTT), SOT-223 (DCY) and TO-252 (NDP) 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.
Heatsinking the SOT-223 (DCY) Package
Figure 26 and Figure 27 show the information for the SOT-223 package. Figure 27 assumes a θ(J−A) of 74°C/W
for 1 ounce copper and 51°C/W for 2 ounce copper and a maximum junction temperature of 125°C. Please see
AN-1028 (literature number SNVA036) for thermal enhancement techniques to be used with SOT-223 and TO-
252 packages.
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Figure 26. θ(J−A) vs Copper (2 ounce) Area for the SOT-223 Package
Figure 27. Maximum Power Dissipation vs TAMB for the SOT-223 Package
Heatsinking the TO-263 (KTT) Package
Figure 28 shows for the TO-263 the measured values of θ(J−A) for different copper area sizes using a typical PCB
with 1 ounce copper and no solder mask over the copper area used for heatsinking.
As shown in Figure 28, increasing the copper area beyond 1 square inch produces very little improvement. It
should also be observed that the minimum value of θ(J−A) for the TO-263 package mounted to a PCB is 32°C/W.
Figure 28. θ(J−A) vs Copper (1 ounce) Area for the TO-263 Package
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As a design aid, Figure 29 shows the maximum allowable power dissipation compared to ambient temperature
for the TO-263 device (assuming θ(J−A) is 35°C/W and the maximum junction temperature is 125°C).
Figure 29. Maximum Power Dissipation vs TAMB for the TO-263 Package
Heatsinking the TO-252 (NDP) Package
If the maximum allowable value for θJA is found to be ≥103°C/W (Typical Rated Value) for the TO-252 package,
no heatsink is needed since the package alone will dissipate enough heat to satisfy these requirements. If the
calculated value for θJA falls below these limits, a heatsink is required.
As a design aid, Table 1 shows the value of the θJA of NDP the package for different heatsink area. The copper
patterns that we used to measure these θJAs are shown in Figure 34.Figure 30 reflects the same test results as
what are in Table 1.
Figure 31 shows the maximum allowable power dissipation vs. ambient temperature for the TO-252 device.
Figure 32 shows the maximum allowable power dissipation vs. copper area (in2) for the TO-252 device. Please
see AN-1028 (literature number SNVA036) for thermal enhancement techniques to be used with SOT-223 and
TO-252 packages.
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Table 1. θJA Different Heatsink Area
Layout Copper Area Thermal Resistance
Top Side (in2)(1) Bottom Side (in2) (θJA°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
6 1.0 0 47
7 0.066 0.2 84
8 0.066 0.4 70
9 0.066 0.6 63
10 0.066 0.8 57
11 0.066 1.0 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
(1) Tab of device attached to topside of copper.
Figure 30. θJA vs 2oz Copper Area for TO-252
Figure 31. Maximum Allowable Power Dissipation vs. Ambient Temperature for TO-252
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Figure 32. Maximum Allowable Power Dissipation vs. 2oz Copper Area for TO-252
Figure 33. Top View of the Thermal Test Pattern in Actual Scale
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Typical Applications
NOTE: Min. output ≊1.2V
Figure 35. 5V Logic Regulator with Electronic Shutdown
Figure 36. Slow Turn-On 15V Regulator
†Solid tantalum
*Discharges C1 if output is shorted to ground
Figure 37. Adjustable Regulator with Improved Ripple Rejection
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Figure 38. High Stability 10V Regulator
‡Optional—improves ripple rejection
†Solid tantalum
*Minimum load current = 30 mA
Figure 39. High Current Adjustable Regulator
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Full output current not available at high input-output voltages
Figure 40. 0 to 30V Regulator
Figure 41. Power Follower
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