NSC LM2585S-3.3, LM2585S-12, LM2585T-ADJ, LM2585T-3.3, LM2585T-12 Datasheet

LM2585
SIMPLE SWITCHER

®

3A Flyback Regulator

LM2585 SIMPLE SWITCHER 3A Flyback Regulator

March 1998

General Description

The LM2585 series of regulators are monolithic integrated
circuits specifically designed for flyback, step-up (boost), and
forward converter applications. The device is available in 4
different output voltage versions: 3.3V, 5.0V,12V,andadjust­able.

Requiring a minimum number of external components,these
regulators are cost effective, and simple to use. Included in
the datasheet are typical circuits of boostandflybackregula­tors.Alsolistedare selector guides for diodes and capacitors
and a family of standard inductors and flyback transformers
designed to work with these switching regulators.

The power switch is a 3.0A NPN device that can stand-off
65V. Protecting the power switch are current and thermal
limiting circuits, and an undervoltage lockout circuit. This IC
contains a 100 kHz fixed-frequency internal oscillator that
permits the use of small magnetics. Other features include
soft start mode to reducein-rush current during start up, cur­rent mode control forimproved rejection of input voltage and
output load transients and cycle-by-cycle current limiting.An
output voltage tolerance of
ages and output load conditions, is guaranteedforthepower
supply system.

±

4%, within specified input volt-

Flyback Regulator

Features

n Requires few external components
n Family of standard inductors and transformers
n NPN output switches 3.0A, can stand off 65V
n Wide input voltage range: 4V to 40V
n Current-mode operation for improved transient

response, line regulation, and current limit

n 100 kHz switching frequency
n Internal soft-start function reduces in-rush current during

start-up

n Output transistor protected by current limit, under

voltage lockout, and thermal shutdown

n System Output Voltage Tolerance of

and load conditions

±

4%max over line

Typical Applications

n Flyback regulator
n Multiple-output regulator
n Simple boost regulator
n Forward converter

DS012515-1

Ordering Information

Package Type NSC Package Order Number

Drawing

5-Lead TO-220 Bent, Staggered Leads T05D LM2585T-3.3, LM2585T-5.0, LM2585T-12, LM2585T-ADJ
5-Lead TO-263 TS5B LM2585S-3.3, LM2585S-5.0, LM2585S-12, LM2585S-ADJ
5-Lead TO-263 Tape and Reel TS5B LM2585SX-3.3, LM2585SX-5.0, LM2585SX-12,

SIMPLE SWITCHER and

© 1999 National Semiconductor Corporation DS012515 www.national.com

Switchers Made Simple

™

are registered trademarks of National SemiconductorCorporation.

LM2585SX-ADJ

Absolute Maximum Ratings (Note 1)

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

Input Voltage −0.4V ≤ V
Switch Voltage −0.4V ≤ V
Switch Current (Note 2) Internally Limited
Compensation Pin Voltage −0.4V ≤ V
Feedback Pin Voltage −0.4V ≤ V
Storage Temperature Range −65˚C to +150˚C
Lead Temperature

(Soldering, 10 sec.) 260˚C

COMP

FB

IN

SW

≤ 2.4V

≤ 2V

≤ 45V
≤ 65V

OUT

Maximum Junction Temperature

(Note 3) 150˚C
Power Dissipation (Note 3) Internally Limited
Minimum ESD Rating

(C=100 pF, R=1.5 kΩ)2kV

Operating Ratings

Supply Voltage 4V ≤ VIN≤ 40V
Output Switch Voltage 0V ≤ V
Output Switch Current I
Junction Temperature Range −40˚C ≤ T

≤ 60V

SW

≤ 3.0A

SW

≤ +125˚C

J

Electrical Characteristics
LM2585-3.3

Specifications with standard type face are for T
Range. Unless otherwise specified, V

IN

Symbol Parameters Conditions Typical Min Max Units

SYSTEM PARAMETERS Test Circuit of

V

OUT

∆V

OUT

∆V

IN

∆V

OUT

∆I

LOAD

η Efficiency V

Output Voltage V

/ Line Regulation V

/ Load Regulation V

I

LOAD

I

LOAD

I

LOAD

IN

IN

IN

IN

UNIQUE DEVICE PARAMETERS (Note 5)
V

∆V

REF

REF

Output Reference Measured at Feedback Pin 3.3 3.242/3.234 3.358/3.366 V
Voltage V
Reference Voltage V

COMP
IN

Line Regulation

G

M

A

VOL

Error Amp I
Transconductance V
Error Amp V
Voltage Gain R

COMP

COMP
COMP
COMP

=

25˚C, and those in bold type face apply over full Operating Temperature

J

=

5V.

Figure 2

(Note 4)

=

4V to 12V 3.3 3.17/3.14 3.43/3.46 V
=

0.3A to 1.2A

=

4V to 12V 20 50/100 mV
=

0.3A

=

12V 20 50/100 mV
=

0.3A to 1.2A

=

5V, I

=

4V to 40V 2.0 mV

=

=

0.3A 76

LOAD

=

1.0V

−30 µA to +30 µA 1.193 0.678 2.259 mmho

=

1.0V

=

0.5V to 1.6V 260 151/75 V/V

=

1.0 MΩ (Note 6)

%

LM2585-5.0

Symbol Parameters Conditions Typical Min Max Units

SYSTEM PARAMETERS Test Circuit of

V

∆V
∆V
∆V
∆I

OUT

OUT
IN
OUT

LOAD

Output Voltage V

/ Line Regulation V

/ Load Regulation V

η Efficiency V
UNIQUE DEVICE PARAMETERS (Note 5)
V

REF

Output Reference Measured at Feedback Pin 5.0 4.913/4.900 5.088/5.100 V
Voltage V

∆V

REF

Reference Voltage V
Line Regulation

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Figure 2

(Note 4)

=

4V to 12V 5.0 4.80/4.75 5.20/5.25 V

IN

=

I

0.3A to 1.1A

LOAD

=

4V to 12V 20 50/100 mV

IN

=

I

0.3A

LOAD

=

12V 20 50/100 mV

IN

=

I

0.3A to 1.1A

LOAD

=

12V, I

IN

=

COMP

=

4V to 40V 3.3 mV

IN

1.0V

=

0.6A 80

LOAD

%

LM2585-5.0 (Continued)

Symbol Parameters Conditions Typical Min Max Units

UNIQUE DEVICE PARAMETERS (Note 5)

G

M

Error Amp I
Transconductance V

A

VOL

Error Amp V
Voltage Gain R

=

−30 µA to +30 µA 0.750 0.447 1.491 mmho

COMP

=

1.0V

COMP

=

0.5V to 1.6V 165 99/49 V/V

COMP

=

1.0 MΩ (Note 6)

COMP

LM2585-12

Symbol Parameters Conditions Typical Min Max Units

SYSTEM PARAMETERS Test Circuit of

V

∆V
∆V
∆V
∆I

OUT

OUT
IN
OUT

LOAD

Output Voltage V

/ Line Regulation V

/ Load Regulation V

η Efficiency V
UNIQUE DEVICE PARAMETERS (Note 5)
V

REF

Output Reference Measured at Feedback Pin 12.0 11.79/11.76 12.21/12.24 V
Voltage V

∆V

REF

Reference Voltage V
Line Regulation

G

M

Error Amp I
Transconductance V

A

VOL

Error Amp V
Voltage Gain R

Figure 3

(Note 4)

=

4V to 10V 12.0 11.52/11.40 12.48/12.60 V

IN

=

I

0.2A to 0.8A

LOAD

=

4V to 10V 20 100/200 mV

IN

=

I

0.2A

LOAD

=

10V 20 100/200 mV

IN

=

I

0.2A to 0.8A

LOAD

=

10V, I

IN

=

COMP

=

4V to 40V 7.8 mV

IN

=

COMP

=

COMP

=

COMP

=

COMP

=

0.6A 93

LOAD

1.0V

−30 µA to +30 µA 0.328 0.186 0.621 mmho

1.0V

0.5V to 1.6V 70 41/21 V/V

1.0 MΩ (Note 6)

%

LM2585-ADJ

Symbol Parameters Conditions Typical Min Max Units

SYSTEM PARAMETERS Test Circuit of

V

∆V
∆V
∆V
∆I

OUT

OUT
IN
OUT

LOAD

Output Voltage V

/ Line Regulation V

/ Load Regulation V

η Efficiency V
UNIQUE DEVICE PARAMETERS (Note 5)
V

REF

Output Reference Measured at Feedback Pin 1.230 1.208/1.205 1.252/1.255 V
Voltage V

∆V

REF

Reference Voltage V
Line Regulation

G

M

Error Amp I
Transconductance V

A

VOL

Error Amp V
Voltage Gain R

I

B

Error Amp V
Input Bias Current

Figure 3

(Note 4)

=

4V to 10V 12.0 11.52/11.40 12.48/12.60 V

IN

=

I

0.2A to 0.8A

LOAD

=

4V to 10V 20 100/200 mV

IN

=

I

0.2A

LOAD

=

10V 20 100/200 mV

IN

=

I

0.2A to 0.8A

LOAD

=

10V, I

IN

=

COMP

=

4V to 40V 1.5 mV

IN

=

COMP

=

COMP

=

COMP

=

COMP

=

COMP

=

0.6A 93

LOAD

1.0V

−30 µA to +30 µA 3.200 1.800 6.000 mmho

1.0V

0.5V to 1.6V 670 400/200 V/V

1.0 MΩ (Note 6)

1.0V 125 425/600 nA

%

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Electrical Characteristics (All Versions)

Symbol Parameters Conditions Typical Min Max Units

COMMON DEVICE PARAMETERS for all versions (Note 5)

I

S

V

UV

f

O

f

SC

V

EAO

I

EAO

I

SS

D Maximum Duty R

I

L

V

SUS

V

SAT

I

CL

θ

JA

θ

JA

θ

JC

θ

JA

θ

JA

θ

JA

θ

JC

Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating ratings indicate conditions the device is intended to
be functional, but device parameter specifications may not be guaranteed under these conditions. For guaranteed specifications and test conditions, see the Electrical
Characteristics.

Note 2: Note that switch current and output current are not identical in a step-up regulator. Output current cannot be internally limited when the LM2585 is used as
a step-up regulator. To prevent damage to the switch, the output current must be externally limited to 3A. However, output current is internally limited when the
LM2585 is used as a flyback regulator (see the Application Hints section for more information).

Input Supply (Switch Off) 11 15.5/16.5 mA
Current (Note 8)

=

Input Supply R

I

SWITCH

1.8A 50 100/115 mA

=

100Ω 3.30 3.05 3.75 V

LOAD

Undervoltage
Lockout

Oscillator Frequency Measured at Switch Pin

=

R

100Ω 100 85/75 115/125 kHz

LOAD

=

V

1.0V

COMP

Short-Circuit Measured at Switch Pin
Frequency R

=

100Ω 25 kHz

LOAD

V

FEEDBACK

=

1.15V
Error Amplifier Upper Limit 2.8 2.6/2.4 V
Output Swing (Note 7)

Lower Limit 0.25 0.40/0.55 V

(Note 8)
Error Amp (Note 9)
Output Current 165 110/70 260/320 µA
(Source or Sink)
Soft Start Current V

FEEDBACK

V

COMP

LOAD

=

0.92V 11.0 8.0/7.0 17.0/19.0 µA

=

1.0V

=

100Ω 98 93/90

%
Cycle (Note 7)
Switch Leakage Switch Off 15 300/600 µA
Current V

SWITCH

=

60V
Switch Sustaining dV/dT=1.5V/ns 65 V
Voltage
Switch Saturation I

SWITCH

=

3.0A 0.45 0.65/0.9 V
Voltage
NPN Switch 4.0 3.0 7.0 A
Current Limit
Thermal Resistance T Package, Junction to

65

Ambient (Note 10)
T Package, Junction to

45

Ambient (Note 11)
T Package, Junction to

2

Case
S Package, Junction to

Ambient (Note 12)
S Package, Junction to

56

˚C/W

35

Ambient (Note 13)
S Package, Junction to

26

Ambient (Note 14)
S Package, Junction to

2

Case

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Electrical Characteristics (All Versions) (Continued)

Note 3: The junction temperature of the device (TJ) is a function of the ambient temperature (TA), the junction-to-ambient thermal resistance (θJA), and the power

dissipation of the device (P

. For a safe thermal design, check that the maximum power dissipated by the device is less than: PD≤ [T

(MAX)

allowable power dissipation, derate the maximum junction temperature — this ensures a margin of safety in the thermal design.
Note 4: External components such as the diode, inductor, input and output capacitors can affect switching regulator performance. When the LM2585 is used as

shown in Figures
Note 5: All room temperature limits are 100%production tested, and all limits at temperature extremes are guaranteed via correlation using standard Statistical Qual-

ity Control (SQC) methods.

Note 6: A 1.0 MΩ resistor is connected to the compensation pin (which is the error amplifier output) to ensure accuracy in measuringA
Note 7: Tomeasure this parameter, the feedback voltage is set to a low value, depending on the output version of the device, to force the error amplifier output high.

=

Adj: V

1.05V; 3.3V: V

FB

Note 8: Tomeasure this parameter, the feedback voltage is set to a high value, depending on the output version of the device, to force the error amplifier output low.

=

Adj: V

1.41V; 3.3V: V

FB

Note 9: To measure the worst-case error amplifier output current, the LM2585 is tested with the feedback voltage set to its low value (specified in (Note 7) and at
its high value (specified in (Note 8) .

Note 10: Junction to ambient thermal resistance (no external heat sink) for the 5 lead TO-220 package mounted vertically,with
board with minimum copper area.

Note 11: Junction to ambient thermal resistance (no external heat sink) for the 5 lead TO-220 package mounted vertically,with
containing approximately 4 square inches of (1oz.) copper area surrounding the leads.

Note 12: Junction to ambient thermal resistance for the 5 lead TO-263 mounted horizontally against a PC board area of 0.136 square inches (the same size as the
TO-263 package) of 1 oz. (0.0014 in. thick) copper.

Note 13: Junction to ambient thermal resistance for the 5 leadTO-263 mounted horizontally against a PC board areaof 0.4896 square inches (3.6 times the area
of the TO-263 package) of 1 oz. (0.0014 in. thick) copper.

Note 14: Junction to ambient thermal resistance for the 5 lead TO-263 mounted horizontally against a PC board copper area of 1.0064 square inches (7.4 times the
area of the TO-263 package) of 1 oz. (0.0014 in. thick) copper.Additional copper area will reduce thermal resistance further. See the thermal model in

software.

Simple

). A thermal shutdown will occur if the temperature exceedsthe maximum junction temperature of the device: PDx θJA+T

Figure 2

D

and

Figure 3

=

2.81V; 5.0V: V

FB

=

3.80V; 5.0V: V

FB

, system performance will be as specified by the system parameters.

=

FB

=

FB

4.25V; 12V: V

5.75V; 12V: V

=

10.20V.

FB

=

13.80V.

FB

J(MAX)−TA(MAX)

)]/θJA. When calculating the maximum

1

1

⁄2inch leads soldered to a PC board

≥ T

A(MAX)

.

VOL

⁄2inch leads in a socket, or on a PC

Switchers Made

Typical Performance Characteristics

-

J

Supply Current
vs Temperature

Supply Current
vs Switch Current

DS012515-2

DS012515-5

Reference Voltage
vs Temperature

Current Limit
vs Temperature

DS012515-3

DS012515-6

∆Reference Voltage
vs Supply Voltage

DS012515-4

Feedback Pin Bias
Current vs Temperature

DS012515-7

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Typical Performance Characteristics (Continued)

Switch Saturation
Voltage vs Temperature

DS012515-8

Error Amp Transconductance
vs Temperature

DS012515-11

Connection Diagrams

Switch Transconductance
vs Temperature

Error Amp Voltage
Gain vs Temperature

DS012515-9

DS012515-12

Oscillator Frequency
vs Temperature

DS012515-10

Short Circuit Frequency
vs Temperature

DS012515-13

Bent, Staggered Leads

5-Lead TO-220 (T)

Top View

DS012515-14

Order Number LM2585T-3.3, LM2585T-5.0,

LM2585T-12 or LM2585T-ADJ

See NS Package Number T05D

5-Lead TO-263 (S)

Top View

DS012515-16

Order Number LM2585S-3.3, LM2585S-5.0,

LM2585S-12 or LM2585S-ADJ

See NS Package Number TS5B

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Bent, Staggered Leads

5-Lead TO-220 (T)

Side View

DS012515-15

5-Lead TO-263 (S)

Side View

DS012515-17

Block Diagram

For Fixed Versions

3.3V, R1=3.4k, R2=2k
5V, R1=6.15k, R2=2k
12V, R1=8.73k, R2=1k
For Adj. Version
R1=Short (0Ω), R2=Open

DS012515-18

FIGURE 1.

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Test Circuits

C

— 100 µF, 25V Aluminum Electrolytic

IN1

— 0.1 µF Ceramic

C

IN2

T— 22 µH, 1:1 Schott
D— 1N5820

— 680 µF, 16V Aluminum Electrolytic

C

OUT

— 0.47 µF Ceramic

C

C

—2k

R

C

C

— 100 µF, 25V Aluminum Electrolytic

IN1

— 0.1 µF Ceramic

C

IN2

L— 15 µH, Renco
D— 1N5820

— 680 µF, 16V Aluminum Electrolytic

C

OUT

— 0.47 µF Ceramic

C

C

—2k

R

C

For 12V Devices: R
For ADJ Devices: R

#

67141450

#

RL-5472-5

=

Short (0Ω) and R

1

=

48.75k,

1

=

Open

2

±

0.1%and R2=5.62k,±1

DS012515-19

FIGURE 2. LM2585-3.3 and LM2585-5.0

DS012515-20

%

FIGURE 3. LM2585-12 and LM2585-ADJ

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