NSC LM2594HV5.0MWC, LM2594HV5.0MDC, LM2594HV3.3MWC, LM2594HV-12MWC, LM2594HV-12MDC Datasheet
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LM2594/LM2594HV
SIMPLE SWITCHER
®
Power Converter 150 kHz 0.5A
Step-Down Voltage Regulator
General Description
The LM2594/LM2594HV series of regulators are monolithic
integrated circuits that provide all the active functions for a
step-down (buck) switching regulator, capable of driving a
0.5A load with excellent line and load regulation. These devices are available in fixed output voltages of 3.3V, 5V, 12V,
and an adjustable output version, and are packaged in a
8-lead DIP and a 8-lead surface mount package.
Requiring a minimum number ofexternalcomponents,these
regulators are simple to use and feature internal frequency
compensation
†
, a fixed-frequency oscillator, and improved
line and load regulation specifications.
The LM2594/LM2594HV series operates at a switching fre-
quency of 150 kHz thus allowing smaller sized filter components than what would be needed with lower frequency
switching regulators. Because of its high efficiency, the copper traces on the printed circuit board are normally the only
heat sinking needed.
A standard series of inductors (both through hole and surface mount types) are available from several different manufacturers optimized for use with the LM2594/LM2594HV series. This feature greatly simplifies the design of
switch-mode power supplies.
Other features include a guaranteed
±
4% tolerance on output voltage under all conditions of input voltage and output
load conditions, and
±
15% on the oscillator frequency. External shutdown is included, featuring typically 85 µA
standby current. Self protection features include a two stage
frequency reducing current limit for the output switch and an
over temperature shutdown for complete protection under
fault conditions.
The LM2594HV is for applications requiring an input voltage
up to 60V.
Features
n 3.3V, 5V, 12V, and adjustable output versions
n Adjustable version output voltage range, 1.2V to 37V
(57V for the HV version)
±
4% max over line and load
conditions
n Available in 8-pin surface mount and DIP-8 package
n Guaranteed 0.5A output current
n Input voltage range up to 60V
n Requires only 4 external components
n 150 kHz fixed frequency internal oscillator
n TTL Shutdown capability
n Low power standby mode, I
Q
typically 85 µA
n High Efficiency
n Uses readily available standard inductors
n Thermal shutdown and current limit protection
Applications
n Simple high-efficiency step-down (buck) regulator
n Efficient pre-regulator for linear regulators
n On-card switching regulators
n Positive to Negative convertor
Typical Application (Fixed Output Voltage Versions)
SIMPLE SWITCHER and
Switchers Made Simple
™
are registered trademarks of National Semiconductor Corporation.
DS012439-1
December 1999
LM2594/LM2594HV SIMPLE SWITCHER Power Converter 150 kHz 0.5A Step-Down Voltage
Regulator
© 2000 National Semiconductor Corporation DS012439 www.national.com
Connection Diagrams and Order Information
8-Lead DIP (N)
DS012439-2
Top View
Order Number
LM2594N-3.3, LM2594N-5.0,
LM2594N-12 or LM2594N-ADJ
LM2594HVN-3.3, LM2594HVN-5.0,
LM2594HVN-12 or LM2594HVN-ADJ
See NS Package Number N08E
8-Lead Surface Mount (M)
DS012439-3
Top View
Order Number LM2594M-3.3,
LM2594M-5.0, LM2594M-12 or
LM2594M-ADJ
LM2594HVM-3.3, LM2594HVM-5.0,
LM2594HVM-12 or LM2594HVM-ADJ
See NS Package Number M08A
*No internal connection, but should be soldered to pc board for best heat transfer.
‡
Patent Number 5,382,918.
LM2594/LM2594HV
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Absolute Maximum Ratings (Note 1)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
Maximum Supply Voltage
LM2594 45V
LM2594HV 60V
ON /OFF Pin Input Voltage
−0.3 ≤ V ≤ +25V
Feedback Pin Voltage −0.3 ≤ V ≤+25V
Output Voltage to Ground
(Steady State) −1V
Power Dissipation Internally limited
Storage Temperature Range −65˚C to +150˚C
ESD Susceptibility
Human Body Model (Note 2) 2 kV
Lead Temperature
M8 Package
Vapor Phase (60 sec.) +215˚C
Infrared (15 sec.) +220˚C
N Package (Soldering, 10 sec.) +260˚C
Maximum Junction Temperature +150˚C
Operating Conditions
Temperature Range −40˚C ≤ TJ+125˚C
Supply Voltage
LM2594 4.5V to 40V
LM2594HV 4.5V to 60V
LM2594/LM2594HV-3.3
Electrical Characteristics
Specifications with standard type face are for TJ= 25˚C, and those with boldface type apply over full Operating Temperature Range.V
INmax
= 40V for the LM2594 and 60V for the LM2594HV.
Symbol Parameter Conditions LM2594/LM2594HV-3.3 Units
(Limits)
Typ Limit
(Note 3) (Note 4)
SYSTEM PARAMETERS (Note 5) Test Circuit
Figure 1
V
OUT
Output Voltage 4.75V ≤ VIN≤ V
INmax
, 0.1A ≤ I
LOAD
≤ 0.5A 3.3 V
3.168/3.135 V(min)
3.432/3.465 V(max)
η Efficiency V
IN
= 12V, I
LOAD
= 0.5A 80 %
LM2594/LM2594HV-5.0
Electrical Characteristics
Specifications with standard type face are for TJ= 25˚C, and those with boldface type apply over full Operating Temperature Range
Symbol Parameter Conditions LM2594/LM2594HV-5.0 Units
(Limits)
Typ Limit
(Note 3) (Note 4)
SYSTEM PARAMETERS (Note 5) Test Circuit
Figure 1
V
OUT
Output Voltage 7V ≤ VIN≤ V
INmax
, 0.1A ≤ I
LOAD
≤ 0.5A 5.0 V
4.800/4.750 V(min)
5.200/5.250 V(max)
η Efficiency V
IN
= 12V, I
LOAD
= 0.5A 82 %
LM2594/LM2594HV-12
Electrical Characteristics
Specifications with standard type face are for TJ= 25˚C, and those with boldface type apply over full Operating Temperature Range
Symbol Parameter Conditions LM2594/LM2594HV-12 Units
(Limits)
Typ Limit
(Note 3) (Note 4)
SYSTEM PARAMETERS (Note 5) Test Circuit
Figure 1
V
OUT
Output Voltage 15V ≤ VIN≤ V
INmax
, 0.1A ≤ I
LOAD
≤ 0.5A 12.0 V
11.52/11.40 V(min)
12.48/12.60 V(max)
η Efficiency V
IN
= 25V, I
LOAD
= 0.5A 88 %
LM2594/LM2594HV
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LM2594/LM2594HV-ADJ
Electrical Characteristics
Specifications with standard type face are for TJ= 25˚C, and those with boldface type apply over full Operating Temperature Range
Symbol Parameter Conditions LM2594/LM2594HV-ADJ Units
(Limits)
Typ Limit
(Note 3) (Note 4)
SYSTEM PARAMETERS (Note 5) Test Circuit
Figure 1
V
FB
Feedback Voltage 4.5V ≤ VIN≤ V
INmax
, 0.1A ≤ I
LOAD
≤ 0.5A 1.230 V
V
OUT
programmed for 3V. Circuit of
Figure 1
1.193/1.180 V(min)
1.267/1.280 V(max)
η Efficiency V
IN
= 12V, I
LOAD
= 0.5A 80 %
All Output Voltage Versions
Electrical Characteristics
Specifications with standard type face are for TJ= 25˚C, and those with boldface type apply over full Operating Temperature Range . Unless otherwise specified, V
IN
= 12V for the 3.3V, 5V, and Adjustable version and VIN= 24V for the 12V ver-
sion. I
LOAD
= 100 mA
Symbol Parameter Conditions LM2594/LM2594HV-XX Units
(Limits)
Typ Limit
(Note 3) (Note 4)
DEVICE PARAMETERS
I
b
Feedback Bias Current Adjustable Version Only, VFB = 1.3V 10 50/100 nA
f
O
Oscillator Frequency (Note 6) 150 kHz
127/110 kHz(min)
173/173 kHz(max)
V
SAT
Saturation Voltage I
OUT
= 0.5A (Note 7) (Note 8) 0.9 V
1.1/1.2 V(max)
DC Max Duty Cycle (ON) (Note 8) 100 %
Min Duty Cycle (OFF) (Note 9) 0
I
CL
Current Limit Peak Current, (Note 7) (Note 8) 0.8 A
0.65/0.58 A(min)
1.3/1.4 A(max)
I
L
Output Leakage Current (Note 7) (Note 9) (Note 10) Output = 0V 50 µA(max)
Output = −1V 2 mA
15 mA(max)
I
Q
Quiescent Current (Note 9) 5 mA
10 mA(max)
I
STBY
Standby Quiescent ON/OFF pin = 5V (OFF) (Note 10) 85 µA
Current LM2594 200/250 µA(max)
LM2594HV 140 250/300 µA(max)
θ
JA
Thermal Resistance N Package, Junction to Ambient (Note 11) 95 ˚C/W
M Package, Junction to Ambient (Note 11) 150
ON/OFF CONTROL Test Circuit
Figure 1
ON /OFF Pin Logic Input 1.3 V
V
IH
Threshold Voltage Low (Regulator ON) 0.6 V(max)
V
IL
High (Regulator OFF) 2.0 V(min)
I
H
ON /OFF Pin V
LOGIC
= 2.5V (Regulator OFF) 5 µA
Input Current 15 µA(max)
I
L
V
LOGIC
= 0.5V (Regulator ON) 0.02 µA
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.
LM2594/LM2594HV
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All Output Voltage Versions
Electrical Characteristics
(Continued)
Note 2: The human body model is a 100 pF capacitor discharged through a 1.5k resistor into each pin.
Note 3: Typical numbers are at 25˚C and represent the most likely norm.
Note 4: All limits guaranteed at room temperature (standard type face) and at temperature extremes (bold type face). All room temperature limits are 100% produc-
tion tested. All limits at temperature extremes are guaranteed via correlation using standard Statistical Quality Control (SQC) methods. All limits are used to calculate
Average Outgoing Quality Level (AOQL).
Note 5: External components such as the catch diode, inductor, input and output capacitors, and voltage programming resistors can affect switching regulator system performance. When the LM2594/LM2594HV is used as shown in the
Figure 1
test circuit, system performance will be as shown in system parameters section
of Electrical Characteristics.
Note 6: 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 7: No diode, inductor or capacitor connected to output pin.
Note 8: Feedback pin removed from output and connected to 0V to force the output transistor switch ON.
Note 9: Feedback pin removed from output and connected to 12V for the 3.3V, 5V,and the ADJ. version, and 15V for the 12V version, to force the output transistor
switch OFF.
Note 10: V
IN
= 40V for the LM2594 and 60V for the LM2594HV.
Note 11: Junction to ambient thermal resistance with approximately 1 square inch of printed circuit board copper surrounding the leads. Additional copper area will
lower thermal resistance further. See application hints in this data sheet and the thermal model in Switchers Made Simple
®
software.
Typical Performance Characteristics
Normalized
Output Voltage
DS012439-4
Line Regulation
DS012439-5
Efficiency
DS012439-6
Switch Saturation
Voltage
DS012439-7
Switch Current Limit
DS012439-8
Dropout Voltage
DS012439-9
LM2594/LM2594HV
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Typical Performance Characteristics (Continued)
Quiescent Current
DS012439-10
Standby
Quiescent Current
DS012439-11
Minimum Operating
Supply Voltage
DS012439-12
ON /OFF Threshold
Voltage
DS012439-13
ON /OFF Pin
Current (Sinking)
DS012439-14
Switching Frequency
DS012439-15
Feedback Pin
Bias Current
DS012439-16
LM2594/LM2594HV
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Typical Performance Characteristics
Continuous Mode Switching Waveforms
V
IN
= 20V, V
OUT
=5V,I
LOAD
= 400 mA
L = 100 µH, C
OUT
= 120 µF, C
OUT
ESR = 140 mΩ
DS012439-17
A: Output Pin Voltage, 10V/div.
B: Inductor Current 0.2A/div.
C: Output Ripple Voltage, 20 mV/div.
Horizontal Time Base: 2 µs/div.
Discontinuous Mode Switching Waveforms
V
IN
= 20V, V
OUT
=5V,I
LOAD
= 200 mA
L = 33 µH, C
OUT
= 220 µF, C
OUT
ESR=60mΩ
DS012439-18
A: Output Pin Voltage, 10V/div.
B: Inductor Current 0.2A/div.
C: Output Ripple Voltage, 20 mV/div.
Horizontal Time Base: 2 µs/div.
Load Transient Response for Continuous Mode
V
IN
= 20V, V
OUT
=5V,I
LOAD
= 200 mA to 500 mA
L = 100 µH, C
OUT
= 120 µF, C
OUT
ESR = 140 mΩ
DS012439-19
A: Output Voltage, 50 mV/div. (AC)
B: 200 mA to 500 mA Load Pulse
Horizontal Time Base: 50 µs/div.
Load Transient Response for Discontinuous Mode
V
IN
= 20V, V
OUT
=5V,I
LOAD
= 100 mA to 200 mA
L = 33 µH, C
OUT
= 220 µF, C
OUT
ESR=60mΩ
DS012439-20
A: Output Voltage, 50 mV/div. (AC)
B: 100 mA to 200 mA Load Pulse
Horizontal Time Base: 200 µs/div.
LM2594/LM2594HV
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Typical Circuit and Layout Guidelines
As in any switching regulator, layout is very important. Rapidly switching currents associated with wiring inductance can
generate voltage transients which can cause problems. For
minimal inductance and ground loops, the wires indicated by
heavy lines should be wide printed circuit traces and
should be kept as short as possible. For best results, ex-
ternal components should be located as close to the
switcher lC as possible using ground plane construction or
single point grounding.
If open core inductors are used, special care must be
taken as to the location and positioning of this type of inductor.Allowing the inductor flux to intersect sensitive feedback,
lC groundpath and C
OUT
wiring can cause problems.
When using the adjustable version, special care must be
taken as to the location of the feedback resistors and the associated wiring. Physically locate both resistors near the IC,
and route the wiring away from the inductor, especially an
open core type of inductor. (See application section for more
information.)
Fixed Output Voltage Versions
DS012439-22
CIN— 68 µF, 35V, Aluminum Electrolytic Nichicon “PL Series”
C
OUT
— 120 µF, 25V Aluminum Electrolytic, Nichicon “PL Series”
D1 — 1A, 40V Schottky Rectifier, 1N5819
L1 — 100 µH, L20
Select components with higher voltage ratings for designs using the LM2594HV with an input voltage between 40V and 60V.
Adjustable Output Voltage Versions
DS012439-23
CIN— 68 µF, 35V, Aluminum Electrolytic Nichicon “PL Series”
C
OUT
— 120 µF, 25V Aluminum Electrolytic, Nichicon “PL Series”
D1 — 1A, 40V Schottky Rectifier, 1N5819
L1 — 100 µH, L20
R
1
—1kΩ,1%
C
FF
— See Application Information Section
FIGURE 1. Typical Circuits and Layout Guides
LM2594/LM2594HV
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LM2594/LM2594HV Series Buck Regulator Design Procedure (Fixed
Output)
PROCEDURE (Fixed Output Voltage Version) EXAMPLE (Fixed Output Voltage Version)
Given:
V
OUT
= Regulated Output Voltage (3.3V, 5V or 12V)
V
IN
(max) = Maximum DC Input Voltage
I
LOAD
(max) = Maximum Load Current
Given:
V
OUT
=5V
V
IN
(max) = 12V
I
LOAD
(max) = 0.4A
1. Inductor Selection (L1)
A. Select the correct inductor value selection guide from
Fig-
ures 4, 5
or
Figure 6
. (Output voltages of 3.3V, 5V, or 12V respectively.) For all other voltages, see the design procedure
for the adjustable version.
B. From the inductor value selection guide, identify the inductance region intersected by the Maximum Input Voltage line
and the Maximum Load Current line. Each region is identified
by an inductance value and an inductor code (LXX).
C. Select an appropriate inductor from the four manufacturer’s part numbers listed in
Figure 8
.
1. Inductor Selection (L1)
A. Use the inductor selection guide for the 5V version shown
in
Figure 5
.
B. From the inductor value selection guide shown in
Figure 5
,
the inductance region intersected by the 12V horizontal line
and the 0.4A vertical line is 100 µH, and the inductor code is
L20.
C. The inductance value required is 100 µH. From the table
in
Figure 8
, go to the L20 line and choose an inductor part
number from any of the four manufacturers shown. (In most
instance, both through hole and surface mount inductors are
available.)
2. Output Capacitor Selection (C
OUT
)
A. In the majority of applications, low ESR (Equivalent Series
Resistance) electrolytic capacitors between 82 µF and
220 µF and low ESR solid tantalum capacitors between 15
µF and 100 µF provide the best results. This capacitor should
be located close to the IC using short capacitor leads and
short copper traces. Do not use capacitors larger than
220 µF.
For additional information, see section on output capacitors in application information section.
B. To simplify the capacitor selection procedure, refer to the
quick design component selection table shown in
Figure 2
.
This table contains different input voltages, output voltages,
and load currents, and lists various inductors and output capacitors that will provide the best design solutions.
C. The capacitor voltage rating for electrolytic capacitors
should be at least 1.5 times greater than the output voltage,
and often much higher voltage ratings are needed to satisfy
the low ESR requirements for low output ripple voltage.
D. For computer aided design software, see
Switchers Made
Simple
version 4.1 or later.
2. Output Capacitor Selection (C
OUT
)
A. See section on output capacitors in application information section.
B. From the quick design component selection table shown
in
Figure 2
, locate the 5V output voltage section. In the load
current column, choose the load current line that is closest to
the current needed in your application, for this example, use
the 0.5A line. In the maximum input voltage column, select
the line that covers the input voltage needed in your application, in this example, use the 15V line. Continuing on this line
are recommended inductors and capacitors that will provide
the best overall performance.
The capacitor list contains both through hole electrolytic and
surface mount tantalum capacitors from four different capacitor manufacturers. It is recommended that both the manufacturers and the manufacturer’s series that are listed in the
table be used.
In this example aluminum electrolytic capacitors from several
different manufacturers are available with the range of ESR
numbers needed.
120 µF 25V Panasonic HFQ Series
120 µF 25V Nichicon PL Series
C. For a 5V output, a capacitor voltage rating at least 7.5V or
more is needed. But, in this example, even a low ESR,
switching grade, 120 µF 10V aluminum electrolytic capacitor
would exhibit approximately 400 mΩ of ESR (see the curve
in
Figure 14
for the ESR vs voltage rating). This amount of
ESR would result in relatively high output ripple voltage. To
reduce the ripple to 1% of the output voltage, or less, a capacitor with a higher voltage rating (lower ESR) should be selected. A 16V or 25V capacitor will reduce the ripple voltage
by approximately half.
LM2594/LM2594HV
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