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 de-
vices 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 of external components, 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 compo-
nents than what would be needed with lower frequency
switching regulators. Because of its high efficiency, the cop-
per traces on the printed circuit board are normally the only
heat sinking needed.
A standard series of inductors (both through hole and sur-
face mount types) are available from several different manu-
facturers optimized for use with the LM2594/LM2594HV se-
ries.
This
feature
greatly
simplifies
the
design
of
switch-mode power supplies.
Other features include a guaranteed
4% tolerance on out-
put voltage under all conditions of input voltage and output
load conditions, and
15% on the oscillator frequency. Ex-
ternal shutdown is included, featuring typically 85 A
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 A
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
TM
are registered trademarks of National Semiconductor Corporation.
DS012439-1
December 1999
LM2594/LM2594HV
SIMPLE
SWITCHER
Power
Converter
150
kHz
0.5A
Step-Down
V
oltage
Regulator
1999 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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2
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
-65C to +150C
ESD Susceptibility
Human Body Model (Note 2)
2 kV
Lead Temperature
M8 Package
Vapor Phase (60 sec.)
+215C
Infrared (15 sec.)
+220C
N Package (Soldering, 10 sec.)
+260C
Maximum Junction Temperature
+150C
Operating Conditions
Temperature Range
-40C
T
J
+125C
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 T
J
= 25C, and those with boldface type apply over full Operating Tempera-
ture 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
V
IN
V
INmax
, 0.1A
I
LOAD
0.5A
3.3
V
3.168/3.135
V(min)
3.432/3.465
V(max)
Efficiency
V
IN
= 12V, I
LOAD
= 0.5A
80
%
LM2594/LM2594HV-5.0
Electrical Characteristics
Specifications with standard type face are for T
J
= 25C, and those with boldface type apply over full Operating Tempera-
ture 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
V
IN
V
INmax
, 0.1A
I
LOAD
0.5A
5.0
V
4.800/4.750
V(min)
5.200/5.250
V(max)
Efficiency
V
IN
= 12V, I
LOAD
= 0.5A
82
%
LM2594/LM2594HV-12
Electrical Characteristics
Specifications with standard type face are for T
J
= 25C, and those with boldface type apply over full Operating Tempera-
ture 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
V
IN
V
INmax
, 0.1A
I
LOAD
0.5A
12.0
V
11.52/11.40
V(min)
12.48/12.60
V(max)
Efficiency
V
IN
= 25V, I
LOAD
= 0.5A
88
%
LM2594/LM2594HV
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3
LM2594/LM2594HV-ADJ
Electrical Characteristics
Specifications with standard type face are for T
J
= 25C, and those with boldface type apply over full Operating Tempera-
ture 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
V
IN
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)
Efficiency
V
IN
= 12V, I
LOAD
= 0.5A
80
%
All Output Voltage Versions
Electrical Characteristics
Specifications with standard type face are for T
J
= 25C, and those with boldface type apply over full Operating Tempera-
ture Range . Unless otherwise specified, V
IN
= 12V for the 3.3V, 5V, and Adjustable version and V
IN
= 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
A(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
A
Current
LM2594
200/250
A(max)
LM2594HV
140
250/300
A(max)
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
A
Input Current
15
A(max)
I
L
V
LOGIC
= 0.5V (Regulator ON)
0.02
A
5
A(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 in-
tended 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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4
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 25C 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 sys-
tem 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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