LM2597/LM2597HV
SIMPLE SWITCHER
Power Converter 150 kHz 0.5A
Step-Down Voltage Regulator, with Features
General Description
The LM2597/LM2597HV 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
an 8-lead DIP and an 8-lead surface mount package.
This series of switching regulators is similar to the LM2594
series, with additional supervisory and performance features
added.
Requiring a minimum number of external components, these
regulators are simple to use and include internal frequency
compensation
, improved line and load specifications,
fixed-frequency oscillator, Shutdown /Soft-start, error flag
delay and error flag output.
The LM2597/LM2597HV 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 LM2597/LM2597HV 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
current limit for the output switch and an over temperature
shutdown for complete protection under fault conditions.
The LM2597HV is for use in applications requiring and 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 HV version)
4% max over line and load
conditions
n
Guaranteed 0.5A output current
n
Available in 8-pin surface mount and DIP-8 package
n
Input voltage range up to 60V
n
150 kHz fixed frequency internal oscillator
n
Shutdown /Soft-start
n
Out of regulation error flag
n
Error output delay
n
Bias Supply Pin (V
BS
) for internal circuitry improves
efficiency at high input voltages
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 converter
Typical Application
(Fixed Output Voltage Versions)
SIMPLE SWITCHER
and
Switchers Made Simple
are registered trademarks of National Semiconductor Corporation.
DS012440-1
Patent Number 5,382,918.
December 2000
LM2597/LM2597HV
SIMPLE
SWITCHER
Power
Converter
150
kHz
0.5A
Step-Down
V
oltage
Regulator
,
with
Features
2001 National Semiconductor Corporation
DS012440
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.
Maximum Supply Voltage (V
IN
)
LM2597
45V
LM2597HV
60V
SD /SS Pin Input Voltage (Note 2)
6V
Delay Pin Voltage (Note 2)
1.5V
Flag Pin Voltage
-0.3
V
45V
Bias Supply Voltage (V
BS
)
-0.3
V
30V
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 3)
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
LM2597
4.5V to 40V
LM2597HV
4.5V to 60V
LM2597/LM2597HV-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 LM2597 and 60V for the LM2597HV
Symbol
Parameter
Conditions
LM2597/LM2597HV-3.3
Units
(Limits)
Typ
Limit
(Note 4)
(Note 5)
SYSTEM PARAMETERS (Note 6) Test Circuit
Figure 12
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
%
LM2597/LM2597HV-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.V
INmax
=40V for the LM2597 and 60V for the LM2597HV
Symbol
Parameter
Conditions
LM2597/LM2597HV-5.0
Units
(Limits)
Typ
Limit
(Note 4)
(Note 5)
SYSTEM PARAMETERS (Note 6) Test Circuit
Figure 12
V
OUT
Output Voltage
7V
V
IN
V
INmax
, 0.1A
I
LOAD
0.5A
5
V
4.800/4.750
V(min)
5.200/5.250
V(max)
Efficiency
V
IN
= 12V, I
LOAD
= 0.5A
82
%
LM2597/LM2597HV
www.national.com
2
LM2597/LM2597HV-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.V
INmax
=40V for the LM2597 and 60V for the LM2597HV
Symbol
Parameter
Conditions
LM2597/LM2597HV-12
Units
(Limits)
Typ
Limit
(Note 4)
(Note 5)
SYSTEM PARAMETERS (Note 6) Test Circuit
Figure 12
V
OUT
Output Voltage
15V
V
IN
V
INmax
, 0.1A
I
LOAD
0.5A
12
V
11.52/11.40
V(min)
12.48/12.60
V(max)
Efficiency
V
IN
= 25V, I
LOAD
= 0.5A
88
%
LM2597/LM2597HV-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.V
INmax
=40V for the LM2597 and 60V for the LM2597HV
Symbol
Parameter
Conditions
LM2597/LM2597HV-ADJ
Units
(Limits)
Typ
Limit
(Note 4)
(Note 5)
SYSTEM PARAMETERS (Note 6) Test Circuit
Figure 12
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 12.
1.193/1.180
V(min)
1.267/1.280
V(max)
Efficiency
V
IN
= 12V, V
OUT
= 3V, 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
LM2597/LM2597HV-XX
Units
(Limits)
Typ
Limit
(Note 4)
(Note 5)
DEVICE PARAMETERS
I
b
Feedback Bias Current
Adjustable Version Only, V
FB
= 1.235V
10
50/100
nA
f
O
Oscillator Frequency
(Note 7)
150
kHz
127/110
kHz(min)
173/173
kHz(max)
V
SAT
Saturation Voltage
I
OUT
= 0.5A (Notes 8 and 9)
0.9
V
1.1/1.2
V(max)
DC
Max Duty Cycle (ON)
(Note 9)
100
%
Min Duty Cycle (OFF)
(Note 10)
0
I
CL
Current Limit
Peak Current, (Notes 8 and 9)
0.8
A
0.65/0.58
A(min)
1.3/1.4
A(max)
I
L
Output Leakage Current
(Notes 8, 10 and 11)
Output = 0V
50
A(max)
Output = -1V
2
mA
15
mA(max)
I
Q
Operating Quiescent
SD /SS Pin Open, V
BS
Pin Open(Note 10)
5
mA
LM2597/LM2597HV
www.national.com
3
All Output Voltage Versions
Electrical Characteristics
(Continued)
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
LM2597/LM2597HV-XX
Units
(Limits)
Typ
Limit
(Note 4)
(Note 5)
DEVICE PARAMETERS
Current
10
mA(max)
I
STBY
Standby Quiescent
SD /SS pin = 0V
(Note 10)LM2597
85
A
Current
200/250
A(max)
LM2597HV
140
250/300
A(max)
JA
Thermal Resistance
N Package, Junction to Ambient (Note 12)
95
C/W
M Package, Junction to Ambient (Note 12)
150
SHUTDOWN/SOFT-START CONTROL Test Circuit of
Figure 12
V
SD
Shutdown Threshold
1.3
V
Voltage
Low, (Shutdown Mode)
0.6
V(max)
High, (Soft-start Mode)
2
V(min)
V
SS
Soft-start Voltage
V
OUT
= 20% of Nominal Output Voltage
2
V
V
OUT
= 100% of Nominal Output Voltage
3
I
SD
Shutdown Current
V
SHUTDOWN
= 0.5V
5
A
10
A(max)
I
SS
Soft-start Current
V
Soft-start
= 2.5V
1.6
A
5
A(max)
FLAG/DELAY CONTROL Test Circuit of
Figure 12
Regulator Dropout
Low (Flag ON)
96
%
Detector
92
%(min)
Threshold Voltage
98
%(max)
VF
SAT
Flag Output Saturation
I
SINK
= 3 mA
0.3
V
Voltage
V
DELAY
= 0.5V
0.7/1.0
V(max)
IF
L
Flag Output Leakage
Current
V
FLAG
= 40V
0.3
A
Delay Pin Threshold
1.25
V
Voltage
Low (Flag ON)
1.21
V(min)
High (Flag OFF) and V
OUT
Regulated
1.29
V(max)
Delay Pin Source
V
DELAY
= 0.5V
3
A
Current
6
A(max)
Delay Pin Saturation
Low (Flag ON)
55
mV
350/400
mV(max)
BIAS SUPPLY
I
BS
Bias Supply Pin Current
V
BS
= 2V
(Note 10)
120
A
400
A(max)
V
BS
= 4.4V (Note 10)
4
mA
10
mA(max)
I
Q
Operating Quiescent
Current
V
BS
= 4.4V , V
in
pin current(Note 10)
1
2
mA
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 1 mA.
Note 3: The human body model is a 100 pF capacitor discharged through a 1.5k resistor into each pin.
Note 4: Typical numbers are at 25C and represent the most likely norm.
LM2597/LM2597HV
www.national.com
4
All Output Voltage Versions
Electrical Characteristics
(Continued)
Note 5: All limits guaranteed at room temperature (standard type face) and at temperature extremes (bold type face). All room temperature limits are 100%
production 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 6: External components such as the catch diode, inductor, input and output capacitors can affect switching regulator system performance. When the
LM2597/LM2597HV is used as shown in the
Figure 12
test circuit, system performance will be as shown in system parameters section of Electrical Characteristics.
Note 7: The switching frequency is reduced when the second stage current limit is activated. The amount of reduction is determined by the severity of current
overload.
Note 8: No diode, inductor or capacitor connected to output pin.
Note 9: Feedback pin removed from output and connected to 0V to force the output transistor switch ON.
Note 10: 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 11: V
IN
= 40V for the LM2597 and 60V for the LM2597HV.
Note 12: 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
TM
software.
Typical Performance Characteristics
Normalized
Output Voltage
DS012440-2
Line Regulation
DS012440-3
Efficiency
DS012440-4
Switch Saturation
Voltage
DS012440-5
Switch Current Limit
DS012440-6
Dropout Voltage
DS012440-7
LM2597/LM2597HV
www.national.com
5
PDF 
ZIP