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

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 adjustable.

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 regulators. 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, current 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 voltages and output load conditions, is guaranteed for the power supply system.

Features

nRequires few external components

nFamily of standard inductors and transformers

nNPN output switches 3.0A, can stand off 65V

nWide input voltage range: 4V to 40V

nCurrent-mode operation for improved transient response, line regulation, and current limit

n100 kHz switching frequency

nInternal soft-start function reduces in-rush current during start-up

nOutput transistor protected by current limit, under voltage lockout, and thermal shutdown

nSystem Output Voltage Tolerance of ±4% max over line and load conditions

Typical Applications

nFlyback regulator

nMultiple-output regulator

nSimple boost regulator

nForward converter

Flyback Regulator

			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,
			LM2585SX-ADJ

SIMPLE SWITCHER and Switchers Made Simple™ are registered trademarks of National Semiconductor Corporation.

Regulator Flyback 3A SWITCHER SIMPLE LM2585

© 1999 National Semiconductor Corporation

DS012515

www.national.com

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		≤ VIN ≤ 45V
Switch Voltage	−0.4V		≤ VSW ≤ 65V
Switch Current (Note 2)	Internally Limited
Compensation Pin Voltage	−0.4V	≤ VCOMP ≤ 2.4V
Feedback Pin Voltage	−0.4V	≤ VFB ≤ 2 VOUT
Storage Temperature Range		−65ÊC to +150ÊC
Lead Temperature
(Soldering, 10 sec.)			260ÊC

Maximum Junction Temperature
(Note 3)	150ÊC
Power Dissipation (Note 3)	Internally Limited
Minimum ESD Rating
(C = 100 pF, R = 1.5 kΩ)	2 kV

Operating Ratings

Supply Voltage	4V ≤ VIN ≤ 40V
Output Switch Voltage	0V ≤ VSW ≤ 60V
Output Switch Current	ISW ≤ 3.0A
Junction Temperature Range	−40ÊC ≤ TJ ≤ +125ÊC

Electrical Characteristics LM2585-3.3

Specifications with standard type face are for TJ = 25ÊC, and those in bold type face apply over full Operating Temperature Range. Unless otherwise specified, VIN = 5V.

Symbol	Parameters	Conditions	Typical	Min	Max	Units
SYSTEM PARAMETERS Test Circuit of Figure 2 (Note 4)
VOUT	Output Voltage	VIN = 4V to 12V	3.3	3.17/3.14	3.43/3.46	V
		ILOAD = 0.3A to 1.2A
VOUT/	Line Regulation	VIN = 4V to 12V	20		50/100	mV
VIN		ILOAD = 0.3A
VOUT/	Load Regulation	VIN = 12V	20		50/100	mV
ILOAD		ILOAD = 0.3A to 1.2A
η	Efficiency	VIN = 5V, ILOAD = 0.3A	76			%
UNIQUE DEVICE PARAMETERS (Note 5)
VREF	Output Reference	Measured at Feedback Pin	3.3	3.242/3.234	3.358/3.366	V
	Voltage	VCOMP = 1.0V
VREF	Reference Voltage	VIN = 4V to 40V	2.0			mV
	Line Regulation
GM	Error Amp	ICOMP = −30 µA to +30 µA	1.193	0.678	2.259	mmho
	Transconductance	VCOMP = 1.0V
AVOL	Error Amp	VCOMP = 0.5V to 1.6V	260	151/75		V/V
	Voltage Gain	RCOMP = 1.0 MΩ (Note 6)

LM2585-5.0

Symbol	Parameters	Conditions	Typical	Min	Max	Units
SYSTEM PARAMETERS Test Circuit of Figure 2 (Note 4)
VOUT	Output Voltage	VIN = 4V to 12V	5.0	4.80/4.75	5.20/5.25	V
		ILOAD = 0.3A to 1.1A
VOUT/	Line Regulation	VIN = 4V to 12V	20		50/100	mV
VIN		ILOAD = 0.3A
VOUT/	Load Regulation	VIN = 12V	20		50/100	mV
ILOAD		ILOAD = 0.3A to 1.1A
η	Efficiency	VIN = 12V, ILOAD = 0.6A	80			%
UNIQUE DEVICE PARAMETERS (Note 5)
VREF	Output Reference	Measured at Feedback Pin	5.0	4.913/4.900	5.088/5.100	V
	Voltage	VCOMP = 1.0V
VREF	Reference Voltage	VIN = 4V to 40V	3.3			mV
	Line Regulation

www.national.com

2

LM2585-5.0 (Continued)

Symbol	Parameters	Conditions	Typical	Min	Max	Units
UNIQUE DEVICE PARAMETERS (Note 5)
GM	Error Amp	ICOMP = −30 µA to +30 µA	0.750	0.447	1.491	mmho
	Transconductance	VCOMP = 1.0V
AVOL	Error Amp	VCOMP = 0.5V to 1.6V	165	99/49		V/V
	Voltage Gain	RCOMP = 1.0 MΩ (Note 6)

LM2585-12

Symbol	Parameters	Conditions	Typical	Min	Max	Units
SYSTEM PARAMETERS Test Circuit of Figure 3 (Note 4)
VOUT	Output Voltage	VIN = 4V to 10V	12.0	11.52/11.40	12.48/12.60	V
		ILOAD = 0.2A to 0.8A
VOUT/	Line Regulation	VIN = 4V to 10V	20		100/200	mV
VIN		ILOAD = 0.2A
VOUT/	Load Regulation	VIN = 10V	20		100/200	mV
ILOAD		ILOAD = 0.2A to 0.8A
η	Efficiency	VIN = 10V, ILOAD = 0.6A	93			%
UNIQUE DEVICE PARAMETERS (Note 5)
VREF	Output Reference	Measured at Feedback Pin	12.0	11.79/11.76	12.21/12.24	V
	Voltage	VCOMP = 1.0V
VREF	Reference Voltage	VIN = 4V to 40V	7.8			mV
	Line Regulation
GM	Error Amp	ICOMP = −30 µA to +30 µA	0.328	0.186	0.621	mmho
	Transconductance	VCOMP = 1.0V
AVOL	Error Amp	VCOMP = 0.5V to 1.6V	70	41/21		V/V
	Voltage Gain	RCOMP = 1.0 MΩ (Note 6)

LM2585-ADJ

Symbol	Parameters	Conditions	Typical	Min	Max	Units
SYSTEM PARAMETERS Test Circuit of Figure 3 (Note 4)
VOUT	Output Voltage	VIN = 4V to 10V	12.0	11.52/11.40	12.48/12.60	V
		ILOAD = 0.2A to 0.8A
VOUT/	Line Regulation	VIN = 4V to 10V	20		100/200	mV
VIN		ILOAD = 0.2A
VOUT/	Load Regulation	VIN = 10V	20		100/200	mV
ILOAD		ILOAD = 0.2A to 0.8A
η	Efficiency	VIN = 10V, ILOAD = 0.6A	93			%
UNIQUE DEVICE PARAMETERS (Note 5)
VREF	Output Reference	Measured at Feedback Pin	1.230	1.208/1.205	1.252/1.255	V
	Voltage	VCOMP = 1.0V
VREF	Reference Voltage	VIN = 4V to 40V	1.5			mV
	Line Regulation
GM	Error Amp	ICOMP = −30 µA to +30 µA	3.200	1.800	6.000	mmho
	Transconductance	VCOMP = 1.0V
AVOL	Error Amp	VCOMP = 0.5V to 1.6V	670	400/200		V/V
	Voltage Gain	RCOMP = 1.0 MΩ (Note 6)
IB	Error Amp	VCOMP = 1.0V	125		425/600	nA
	Input Bias Current

3	www.national.com

Electrical Characteristics (All Versions)

Symbol	Parameters	Conditions	Typical	Min	Max	Units
COMMON DEVICE PARAMETERS for all versions (Note 5)
IS	Input Supply	(Switch Off)	11		15.5/16.5	mA
	Current	(Note 8)
		ISWITCH = 1.8A	50		100/115	mA
VUV	Input Supply	RLOAD = 100Ω	3.30	3.05	3.75	V
	Undervoltage
	Lockout
fO	Oscillator Frequency	Measured at Switch Pin
		RLOAD = 100Ω	100	85/75	115/125	kHz
		VCOMP = 1.0V
fSC	Short-Circuit	Measured at Switch Pin
	Frequency	RLOAD = 100Ω	25			kHz
		VFEEDBACK = 1.15V
VEAO	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)
IEAO	Error Amp	(Note 9)
	Output Current		165	110/70	260/320	µA
	(Source or Sink)
ISS	Soft Start Current	VFEEDBACK = 0.92V	11.0	8.0/7.0	17.0/19.0	µA
		VCOMP = 1.0V
D	Maximum Duty	RLOAD = 100Ω	98	93/90		%
	Cycle	(Note 7)
IL	Switch Leakage	Switch Off	15		300/600	µA
	Current	VSWITCH = 60V
VSUS	Switch Sustaining	dV/dT = 1.5V/ns		65		V
	Voltage
VSAT	Switch Saturation	ISWITCH = 3.0A	0.45		0.65/0.9	V
	Voltage
ICL	NPN Switch		4.0	3.0	7.0	A
	Current Limit
θJA	Thermal Resistance	T Package, Junction to	65
		Ambient (Note 10)
θJA		T Package, Junction to	45
		Ambient (Note 11)
θJC		T Package, Junction to	2
		Case
θJA
		S Package, Junction to	56			ÊC/W
		Ambient (Note 12)
θJA		S Package, Junction to	35
		Ambient (Note 13)
θJA		S Package, Junction to	26
		Ambient (Note 14)
θJC		S Package, Junction to	2
		Case

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).

www.national.com

4

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 (qJA), 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 qJA + TA(MAX) ³ TJ- (MAX). For a safe thermal design, check that the maximum power dissipated by the device is less than: PD £ [TJ(MAX) − T A(MAX))]/qJA. When calculating the maximum allowable power dissipation, derate the maximum junction temperature Ð 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 Quality Control (SQC) methods.

Note 6: A 1.0 MW 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	Reference Voltage	Reference Voltage
vs Temperature	vs Temperature	vs Supply Voltage

DS012515-2 DS012515-3 DS012515-4

Supply Current	Current Limit	Feedback Pin Bias
vs Switch Current	vs Temperature	Current vs Temperature

DS012515-5	DS012515-6	DS012515-7

5	www.national.com

Typical Performance Characteristics (Continued)

Switch Saturation	Switch Transconductance	Oscillator Frequency
Voltage vs Temperature	vs Temperature	vs Temperature

DS012515-8	DS012515-9	DS012515-10

Error Amp Transconductance	Error Amp Voltage	Short Circuit Frequency
vs Temperature	Gain vs Temperature	vs Temperature

DS012515-11	DS012515-12	DS012515-13

Connection Diagrams

Bent, Staggered Leads	Bent, Staggered Leads
5-Lead TO-220 (T)	5-Lead TO-220 (T)
Top View	Side View
	DS012515-15
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)	5-Lead TO-263 (S)
Top View	Side View
	DS012515-17

DS012515-16

Order Number LM2585S-3.3, LM2585S-5.0,

LM2585S-12 or LM2585S-ADJ

See NS Package Number TS5B

www.national.com

6

Block Diagram

DS012515-18

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

FIGURE 1.

7	www.national.com

Test Circuits

DS012515-19

CIN1 Ð 100 µF, 25V Aluminum Electrolytic

CIN2 Ð 0.1 µF Ceramic

T Ð 22 µH, 1:1 Schott #67141450

D Ð 1N5820

COUT Ð 680 µF, 16V Aluminum Electrolytic

CC Ð 0.47 µF Ceramic

RC Ð 2k

FIGURE 2. LM2585-3.3 and LM2585-5.0

DS012515-20

CIN1 Ð 100 µF, 25V Aluminum Electrolytic

CIN2 Ð 0.1 µF Ceramic

L Ð 15 µH, Renco #RL-5472-5

D Ð 1N5820

COUT Ð 680 µF, 16V Aluminum Electrolytic

CC Ð 0.47 µF Ceramic

RC Ð 2k

For 12V Devices: R1 = Short (0Ω) and R2 = Open

For ADJ Devices: R1 = 48.75k, ±0.1% and R2 = 5.62k, ±1%

FIGURE 3. LM2585-12 and LM2585-ADJ

www.national.com

8