NSC LM2825N-ADJ, LM2825N-5.0, LM2825N-3.3, LM2825HN-ADJ Datasheet

LM2825
Integrated Power Supply 1A DC-DC Converter

LM2825 Integrated Power Supply 1A DC-DC Converter

May 1997

General Description

The LM2825 is a complete 1A DC-DC Buck converter pack­aged in a 24-lead molded Dual-In-Line integrated circuit
package.

Contained within the package are all the active and passive
components for ahighefficiency step-down (buck) switching
regulator. Available in fixed output voltages of 3.3V, 5V and
12V, as well as two adjustable versions, these devices can
provide up to 1A of load current with fully guaranteed electri­cal specifications.

Self-contained, this converter is also fully protected from out­put fault conditions, such as excessive load current, short
circuits, or excessive temperatures.

Highlights

n No external components required (fixed output voltage

versions)

n Integrated circuit reliability
n MTBF over 20 million hours
n Radiated EMI meets Class B stipulated by CISPR 22
n High power density, 35 W/in
n 24-pin DIP package profile (1.25 x 0.54 x 0.26 inches)

3

DS012661-27

Features

n Minimum design time required
n 3.3V, 5V and 12V fixed output versions
n Two adjustable versions allow 1.23V to 15V outputs
n Wide input voltage range, up to 40V
n Low-power standby mode, I
n High efficiency, typically 80

±

n

4%output voltage tolerance

n Excellent line and load regulation
n TTL shutdown capability/programmable Soft-start
n Thermal shutdown and current limit protection
n −40˚C to +85˚C ambient temperature range

typically 65 µA

Q

%

Applications

n Simple high-efficiency step-down (buck) regulator
n On-card switching regulators
n Efficient pre-regulator for linear regulators
n Distributed power systems
n DC/DC module replacement

Connection Diagram

Standard Application

(Fixed output voltage versions)

“NC (Do not use)” pins: See

DS012661-1

Radiated EMI

Radiated emission of electromagnetic fields is measured at
10m distance. The emission levels are within the Class B
limits stipulated by CISPR 22.

30. . . .230 MHz 30 dB µV/m

230. . . .1000 MHz 37 dB µV/m

1. . . .10 GHz 46 dB µV/m

© 1997 National Semiconductor Corporation DS012661 www.national.com

Ordering Information

Order Number LM2825N-3.3, LM2825N-5.0, LM2825N-12,
LM2825N-ADJ or LM2825HN-ADJ

See NS Package Number NA24F

Figure 11

Top View

.

DS012661-2

Absolute Maximum Ratings (Note 1)

If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/

ESD Susceptibility

Human Body Model (Note 3) 2 kV

Lead Temperature (Soldering 10 sec.) 260˚C

Distributors for availability and specifications.

Maximum Input Supply (V

) +45V

IN

SD/SS Pin Input Voltage (Note 2) 6V
Output Pin Voltage

(3.3V, 5.0V and ADJ) −1V ≤ V ≤ 9V

(12V and H-ADJ) −1V ≤ V ≤ 16V
ADJ Pin Voltage (ADJ, H-ADJ only) −0.3V ≤ V ≤ 25V
Power Dissipation Internally Limited

Operating Ratings

Ambient Temperature Range −40˚C ≤ TA≤ +85˚C
Junction Temperature Range −40˚C ≤ T
Input Supply Voltage (3.3V version) 4.75V to 40V
Input Supply Voltage (5V version) 7V to 40V
Input Supply Voltage (12V version) 15V to 40V
Input Supply Voltage (-ADJ, H-ADJ) 4.5V to 40V

≤ +125˚C

J

Storage Temperature Range −40˚C to +125˚C

LM2825-3.3 Electrical Characteristics (Note 4)

LOAD

IN
IN
IN

=

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

A

Typical Limit

(Note 6) (Note 7)

≤ 1A 3.3 V

LOAD

3.168/3.135 V(min)

3.432/3.465 V(max)

≤ 40V 1.5 mV

IN

=

100 mA

≤ 1A 8 mV

LOAD

=

12V
=
=

12V, I

12V, I

=

1A 40 mV p-p

LOAD

=

0.5A 75

LOAD

(Limits)

%

Specifications with standard type face are for T

Figure 2

ture Range. Test Circuit

.

Symbol Parameter Conditions LM2825-3.3 Units

V

Output Voltage 4.75V ≤ VIN≤ 40V, 0.1A ≤ I

OUT

Line Regulation 4.75V ≤ V

I

Load Regulation 0.1A ≤ I

V

Output Ripple Voltage V

η Efficiency V

LM2825-5.0 Electrical Characteristics (Note 4)

Specifications with standard type face are for T

Figure 2

ture Range. Test Circuit

.

Symbol Parameter Conditions LM2825-5.0 Units

V

Output Voltage 7V ≤ VIN≤ 40V, 0.1A ≤ I

OUT

Line Regulation 7V ≤ V

I

Load Regulation 0.1A ≤ I

V

Output Ripple Voltage V

η Efficiency V

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=

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

A

Typical Limit

(Note 6) (Note 7)

≤ 1A 5.0 V

LOAD

4.800/4.750 V(min)

5.200/5.250 V(max)

≤ 40V 2.7 mV

IN

=

100 mA

LOAD

IN
IN
IN

≤ 1A 8 mV

LOAD

=

12V
=
=

12V, I

12V, I

=

1A 40 mV p-p

LOAD

=

0.5A 80

LOAD

(Limits)

%

LM2825-12 Electrical Characteristics (Note 4)

Specifications with standard type face are for T

Figure 2

ture Range. Test Circuit

.

Symbol Parameter Conditions LM2825-12 Units

V

OUT

Output Voltage 15V ≤ VIN≤ 40V, 0.1A ≤ I

Line Regulation 15V ≤ V

I

LOAD

Load Regulation 0.1A ≤ I

V

Output Ripple Voltage V

η Efficiency V

IN
IN
IN

=

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

A

Typical Limit

(Note 6) (Note 7)

≤ 0.75A 12.0 V

LOAD

11.52/11.40 V(min)

12.48/12.60 V(max)

≤ 40V 8.5 mV

IN

=

100 mA

≤ 0.75A 12 mV

LOAD

=

24V
=
=

24V, I

24V, I

=

1A 100 mV p-p

LOAD

=

0.5A 87

LOAD

(Limits)

%

LM2825-ADJ Electrical Characteristics (Note 5)

Specifications with standard type face are for T

Figure 3

ture Range. Test Circuit

.

Symbol Parameter Conditions LM2825-ADJ Units

V

ADJ

Adjust Pin Voltage 4.5V ≤ VIN≤ 40V, 0.1A ≤ I

1.23V ≤ V

η Efficiency V

IN

V

OUT

=

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

A

≤ 1A 1.230 V

LOAD

=

0.5A 74

=

≤ 8V 1.193/1.180 V(min)

OUT

12V, I

LOAD

Programmed for 3V. See Circuit of

Figure 3

Typical Limit

(Note 6) (Note 7)

1.267/1.280 V(max)

(Limits)

%

LM2825H-ADJ Electrical Characteristics (Note 5)

Specifications with standard type face are for T

Figure 3

Range. Test Circuit

.

Symbol Parameter Conditions LM2825H-ADJ Units

V

Adjust Pin Voltage 9V ≤ VIN≤ 40V, 0.1A ≤ I

ADJ

7V ≤ V

η Efficiency V

=

IN

V

OUT

See Circuit of

=

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

A

Typical Limit

(Note 6) (Note 7)

≤ 0.55A 1.230 V

≤ 15V 1.193/1.180 V(min)

OUT

LOAD

1.267/1.280 V(max)

24V, I

=

0.5A 87

LOAD

Programmed for 12V.

Figure 3

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(Limits)

%

All Output Voltage Versions Electrical Characteristics

Specifications with standard type face are for T

=

less otherwise specified, V

12V for 3.3V, 5.0V and ADJ versions, V

IN

Symbol Parameter Conditions LM2825-XX Units

I

CL

I

Q

DC Output Current
Limit

Operating Quiescent
Current

R

L

SD/SS Pin=3.1V 5 mA

(Note 8) 10 mA(max)

I

STBY

Standby Quiescent
Current

SD/SS Pin=0V 65 µA

(Note 8) 200 µA(max)

I

ADJ

f

O

θ

JA

Adjust Pin Bias Current Adjustable Versions Only, V

Oscillator Frequency (Note 9) 150 kHz

Thermal Resistance Junction to Ambient (Note 10) 30 ˚C/W
SHUTDOWN/SOFT-START CONTROL Test Circuit
V

SD

Shutdown Threshold

Voltage

Low (Shutdown Mode) 0.6 V(max)
High (Soft-start Mode) 2.0 V(min)

V

SS

I

SD

Soft-start Voltage V

Shutdown Current V

OUT

V

OUT
SHUTDOWN

(Note 8) 10 µA(max)

I

SS

Soft-start Current V

SOFT-START

(Note 8) 5 µA(max)

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.

Note 2: Voltage internally clamped. If clamp voltage is exceeded, limit current to a maximum of 5 mA.
Note 3: The human body model is a 100 pF capacitor discharged through a 1.5k resistor into each pin.
Note 4: When the LM2825 is used as shown in
Note 5: When the LM2825 is used as shown in
Note 6: Typical numbers are at 25˚C and represent the most likely norm.
Note 7: All limits guaranteed at room temperature (standard type face) and at temperature extremes (bold type face) when output current is limited to the value given

in the temperature derating curves. Seethe application section for curves. All limits at temperature extremes are guaranteed using standard Statistical Quality Control
(SQC) methods. All limits are used to calculate Average Outgoing Quality Level (AOQL).

Note 8: I
Note 9: The switching frequency is reduced when the second stage current limit is activated. The amount of reduction is determined by the severity of current over-

load.
Note 10: Junction to ambient thermal resistance (no external heat sink) for the DIP-24 package with the leads soldered to a printed circuit board with (1 oz.) copper

area of approximately 2 in

LOAD

=

0A.

2

.

Figure 2
Figure 3

=

25˚C, and those with boldface type apply over full Operating Range. Un-

A

=

24V for 12V and H-ADJ versions, I

IN

LOAD

=

Typical Limit

(Note 6) (Note 7)

=

0Ω 1.4 A

1.2 A(min)

2.4 A(max)

=

1.3V 6 nA

FB

50/100 nA(max)

Figure 2

1.3 V

=

20%of Nominal Output Voltage 2 V

=

100%of Nominal Output Voltage 3

=

0.5V

=

2.5V 1.6 µA

test circuit, system performance will be as shown in Electrical Characteristics.
test circuit, system performance will be as shown in Electrical Characteristics.

5µA

100 mA.

(Limits)

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