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PDF LM2585 Data sheet ( Hoja de datos )
| Número de pieza | LM2585 | |
| Descripción | SIMPLE SWITCHER 3A Flyback Regulator | |
| Fabricantes | National Semiconductor | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de LM2585 (archivo pdf) en la parte inferior de esta página. Total 25 Páginas | ||
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March 1998
LM2585
SIMPLE SWITCHER® 3A Flyback Regulator
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, and adjust-
able.
Requiring a minimum number of external components, these
regulators are cost effective, and simple to use. Included in
the datasheet are typical circuits of boost and flyback regula-
tors. Also listed are 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 reduce in-rush current during start up, cur-
rent mode control for improved rejection of input voltage and
output load transients and cycle-by-cycle current limiting. An
output voltage tolerance of ±4%, within specified input volt-
ages and output load conditions, is guaranteed for the power
supply system.
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 ±4% max over line
and load conditions
Typical Applications
n Flyback regulator
n Multiple-output regulator
n Simple boost regulator
n Forward converter
Flyback Regulator
Ordering Information
DS012515-1
Package Type
5-Lead TO-220 Bent, Staggered Leads
5-Lead TO-263
5-Lead TO-263 Tape and Reel
NSC Package
Drawing
T05D
TS5B
TS5B
Order Number
LM2585T-3.3, LM2585T-5.0, LM2585T-12, LM2585T-ADJ
LM2585S-3.3, LM2585S-5.0, LM2585S-12, LM2585S-ADJ
LM2585SX-3.3, LM2585SX-5.0, LM2585SX-12,
LM2585SX-ADJ
SIMPLE SWITCHER and Switchers Made Simple™ are registered trademarks of National Semiconductor Corporation.
© 1999 National Semiconductor Corporation DS012515
www.national.com
1 page  
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 (PD). A thermal shutdown will occur if the temperature exceeds the maximum junction temperature of the device: PD x θJA + TA(MAX) ≥ TJ-
(MAX). For a safe thermal design, check that the maximum power dissipated by the device is less than: PD ≤ [TJ(MAX) − TA(MAX))]/θJA. When calculating the maximum
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 Figure 2 and Figure 3 , system performance will be as specified by the system parameters.
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 measuring AVOL.
Note 7: To measure 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: VFB = 1.05V; 3.3V: VFB = 2.81V; 5.0V: VFB = 4.25V; 12V: VFB = 10.20V.
Note 8: To measure 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: VFB = 1.41V; 3.3V: VFB = 3.80V; 5.0V: VFB = 5.75V; 12V: VFB = 13.80V.
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 1⁄2 inch leads in a socket, or on a PC
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 1⁄2 inch leads soldered to a PC board
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 lead TO-263 mounted horizontally against a PC board area of 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 Switchers Made
Simple software.
Typical Performance Characteristics
Supply Current
vs Temperature
Reference Voltage
vs Temperature
∆Reference Voltage
vs Supply Voltage
Supply Current
vs Switch Current
DS012515-2
Current Limit
vs Temperature
DS012515-3
DS012515-4
Feedback Pin Bias
Current vs Temperature
DS012515-5
DS012515-6
5
DS012515-7
www.national.com
5 Page 
Typical Flyback Regulator Applications (Continued)
FIGURE 8. Single-Output Flyback Regulator
DS012515-25
FIGURE 9. Single-Output Flyback Regulator
DS012515-26
11 www.national.com
11 Page | ||
| Páginas | Total 25 Páginas | |
| PDF Descargar | [ Datasheet LM2585.PDF ] | |
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