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 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
n
n
n
Simple high-efficiency step-down (buck) regulator
Efficient pre-regulator for linear regulators
On-card switching regulators
Positive to Negative convertor
Typical Application
(Fixed Output Voltage Versions)
DS012439-1
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2014 NOV
LM2594
Connection Diagrams and Order Information
8-Lead DIP (N)
8-Lead Surface Mount (M)
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
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.
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2014 NOV
LM2594
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
LM2594HV
ON /OFF Pin Input Voltage
Feedback Pin Voltage
Output Voltage to Ground
(Steady State)
Power Dissipation
Storage Temperature Range
ESD Susceptibility
45V
60V
−0.3
≤
V
≤
+25V
−0.3
≤
V
≤+25V
−1V
Internally limited
−65˚C to +150˚C
Human Body Model (Note 2)
Lead Temperature
M8 Package
Vapor Phase (60 sec.)
Infrared (15 sec.)
N Package (Soldering, 10 sec.)
Maximum Junction Temperature
2 kV
+215˚C
+220˚C
+260˚C
+150˚C
Operating Conditions
Temperature Range
Supply Voltage
LM2594
LM2594HV
−40˚C
≤
T
J
+125˚C
4.5V to 40V
4.5V to 60V
LM2594/LM2594HV-3.3
Electrical Characteristics
Specifications with standard type face are for T
J
= 25˚C, 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
Typ
(Note 3)
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
3.168/3.135
3.432/3.465
η
Efficiency
V
IN
= 12V, I
LOAD
= 0.5A
80
V
V(min)
V(max)
%
Limit
(Note 4)
Units
(Limits)
LM2594/LM2594HV-5.0
Electrical Characteristics
Specifications with standard type face are for T
J
= 25˚C, and those with
boldface type
apply over
full Operating Tempera-
ture Range
Symbol
Parameter
Conditions
LM2594/LM2594HV-5.0
Typ
(Note 3)
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
4.800/4.750
5.200/5.250
η
Efficiency
V
IN
= 12V, I
LOAD
= 0.5A
82
V
V(min)
V(max)
%
Limit
(Note 4)
Units
(Limits)
LM2594/LM2594HV-12
Electrical Characteristics
Specifications with standard type face are for T
J
= 25˚C, and those with
boldface type
apply over
full Operating Tempera-
ture Range
Symbol
Parameter
Conditions
LM2594/LM2594HV-12
Typ
(Note 3)
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
11.52/11.40
12.48/12.60
η
Efficiency
V
IN
= 25V, I
LOAD
= 0.5A
88
V
V(min)
V(max)
%
Limit
(Note 4)
Units
(Limits)
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2014 NOV
LM2594
LM2594/LM2594HV-ADJ
Electrical Characteristics
Specifications with standard type face are for T
J
= 25˚C, and those with
boldface type
apply over
full Operating Tempera-
ture Range
Symbol
Parameter
Conditions
LM2594/LM2594HV-ADJ
Typ
(Note 3)
SYSTEM PARAMETERS
(Note 5) Test Circuit
Figure 1
V
FB
Feedback Voltage
4.5V
≤
V
IN
≤
V
INmax
, 0.1A
≤
I
LOAD
≤
0.5A
V
OUT
programmed for 3V. Circuit of
Figure 1
η
Efficiency
V
IN
= 12V, I
LOAD
= 0.5A
80
1.230
1.193/1.180
1.267/1.280
V
V(min)
V(max)
%
Limit
(Note 4)
Units
(Limits)
All Output Voltage Versions
Electrical Characteristics
Specifications with standard type face are for T
J
= 25˚C, 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
Typ
(Note 3)
DEVICE PARAMETERS
I
b
f
O
Feedback Bias Current
Oscillator Frequency
Adjustable Version Only, VFB = 1.3V
(Note 6)
10
150
127/110
173/173
V
SAT
DC
I
CL
Saturation Voltage
Max Duty Cycle (ON)
Min Duty Cycle (OFF)
Current Limit
I
OUT
= 0.5A (Note 7) (Note 8)
(Note 8)
(Note 9)
Peak Current, (Note 7) (Note 8)
0.9
1.1/1.2
100
0
0.8
0.65/0.58
1.3/1.4
I
L
Output Leakage Current
(Note 7) (Note 9) (Note 10)
Output = 0V
2
15
I
Q
I
STBY
Quiescent Current
Standby Quiescent
Current
θ
JA
Thermal Resistance
(Note 9)
ON/OFF pin = 5V (OFF)
LM2594
LM2594HV
N Package, Junction to Ambient (Note 11)
M Package, Junction to Ambient (Note 11)
ON/OFF CONTROL
Test Circuit
Figure 1
ON /OFF Pin Logic Input
V
IH
V
IL
I
H
I
L
ON /OFF Pin
Input Current
V
LOGIC
= 0.5V (Regulator ON)
0.02
5
Threshold Voltage
Low (Regulator ON)
High (Regulator OFF)
V
LOGIC
= 2.5V (Regulator OFF)
5
15
1.3
0.6
2.0
V
V(max)
V(min)
µA
µA(max)
µA
µA(max)
140
95
150
(Note 10)
5
10
85
200/250
250/300
50
Output = −1V
A
A(min)
A(max)
µA(max)
mA
mA(max)
mA
mA(max)
µA
µA(max)
µA(max)
˚C/W
50/100
nA
kHz
kHz(min)
kHz(max)
V
V(max)
%
Limit
(Note 4)
Units
(Limits)
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.
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2014 NOV
LM2594
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 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
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