NSC LM2594HVN-5.0, LM2594HVN-12, LM2594HVMX-ADJ, LM2594HVMX-5.0, LM2594HVMX-3.3 Datasheet
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December 1999
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 of external components, these regulators are simple to use and feature internal frequency compensation², a fixed-frequency oscillator, and improved line and load regulation specifications.
The LM2594/LM2594HV series operates at a switching frequency 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
n3.3V, 5V, 12V, and adjustable output versions
nAdjustable version output voltage range, 1.2V to 37V (57V for the HV version)±4% max over line and load conditions
nAvailable in 8-pin surface mount and DIP-8 package
nGuaranteed 0.5A output current
nInput voltage range up to 60V
nRequires only 4 external components
n150 kHz fixed frequency internal oscillator
nTTL Shutdown capability
nLow power standby mode, IQ typically 85 µA
nHigh Efficiency
nUses readily available standard inductors
nThermal shutdown and current limit protection
Applications
nSimple high-efficiency step-down (buck) regulator
nEfficient pre-regulator for linear regulators
nOn-card switching regulators
nPositive to Negative convertor
Typical Application (Fixed Output Voltage Versions)
DS012439-1
SIMPLE SWITCHER and Switchers Made Simple™ are registered trademarks of National Semiconductor Corporation.
Voltage Down-Step 5A.0 kHz 150 Converter Power SWITCHER SIMPLE LM2594/LM2594HV
Regulator
© 1999 National Semiconductor Corporation |
DS012439 |
www.national.com |
LM2594/LM2594HV
Connection Diagrams and Order Information
8-Lead DIP (N)
8-Lead Surface Mount (M)
DS012439-2 |
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Top View |
DS012439-3 |
Order Number |
Top View |
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LM2594N-3.3, LM2594N-5.0, |
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Order Number LM2594M-3.3, |
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LM2594N-12 or LM2594N-ADJ |
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LM2594M-5.0, LM2594M-12 or |
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LM2594HVN-3.3, LM2594HVN-5.0, |
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LM2594M-ADJ |
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LM2594HVN-12 or LM2594HVN-ADJ |
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LM2594HVM-3.3, LM2594HVM-5.0, |
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See NS Package Number N08E |
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LM2594HVM-12 or LM2594HVM-ADJ |
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See NS Package Number M08A |
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*No internal connection, but should be soldered to pc board for best heat transfer. |
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³Patent Number 5,382,918. |
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www.national.com |
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 |
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LM2594 |
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45V |
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LM2594HV |
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60V |
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−0.3 |
≤ V ≤ +25V |
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ON |
/OFF Pin Input Voltage |
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Feedback Pin Voltage |
−0.3 |
≤ V ≤+25V |
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Output Voltage to Ground |
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(Steady State) |
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−1V |
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Power Dissipation |
Internally limited |
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Storage Temperature Range |
−65ÊC to +150ÊC |
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ESD Susceptibility |
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Human Body Model (Note 2) |
2 kV |
Lead Temperature |
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M8 Package |
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Vapor Phase (60 sec.) |
+215ÊC |
Infrared (15 sec.) |
+220ÊC |
N Package (Soldering, 10 sec.) |
+260ÊC |
Maximum Junction Temperature |
+150ÊC |
Operating Conditions
Temperature Range |
−40ÊC ≤ TJ +125ÊC |
Supply Voltage |
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LM2594 |
4.5V to 40V |
LM2594HV |
4.5V to 60V |
LM2594/LM2594HV-3.3 Electrical Characteristics
Specifications with standard type face are for TJ = 25ÊC, and those with boldface type apply over full Operating Temperature Range.VINmax= 40V for the LM2594 and 60V for the LM2594HV.
Symbol |
Parameter |
Conditions |
LM2594/LM2594HV-3.3 |
Units |
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Typ |
Limit |
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(Note 3) |
(Note 4) |
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SYSTEM PARAMETERS (Note 5) Test Circuit Figure 1 |
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VOUT |
Output Voltage |
4.75V ≤ VIN ≤ VINmax, 0.1A ≤ ILOAD ≤ 0.5A |
3.3 |
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V |
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3.168/3.135 |
V(min) |
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3.432/3.465 |
V(max) |
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η |
Efficiency |
VIN = 12V, ILOAD = 0.5A |
80 |
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LM2594/LM2594HV-5.0 Electrical Characteristics
Specifications with standard type face are for TJ = 25ÊC, and those with boldface type apply over full Operating Temperature Range
Symbol |
Parameter |
Conditions |
LM2594/LM2594HV-5.0 |
Units |
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(Limits) |
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Typ |
Limit |
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(Note 3) |
(Note 4) |
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SYSTEM PARAMETERS (Note 5) Test Circuit Figure 1 |
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VOUT |
Output Voltage |
7V ≤ VIN ≤ VINmax, 0.1A ≤ ILOAD ≤ 0.5A |
5.0 |
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V |
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4.800/4.750 |
V(min) |
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5.200/5.250 |
V(max) |
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η |
Efficiency |
VIN = 12V, ILOAD = 0.5A |
82 |
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LM2594/LM2594HV-12 Electrical Characteristics
Specifications with standard type face are for TJ = 25ÊC, and those with boldface type apply over full Operating Temperature Range
Symbol |
Parameter |
Conditions |
LM2594/LM2594HV-12 |
Units |
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(Limits) |
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Typ |
Limit |
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(Note 3) |
(Note 4) |
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SYSTEM PARAMETERS (Note 5) Test Circuit Figure 1 |
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VOUT |
Output Voltage |
15V ≤ VIN ≤ VINmax, 0.1A ≤ ILOAD ≤ 0.5A |
12.0 |
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V |
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11.52/11.40 |
V(min) |
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12.48/12.60 |
V(max) |
η |
Efficiency |
VIN = 25V, ILOAD = 0.5A |
88 |
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% |
LM2594/LM2594HV
3 |
www.national.com |
LM2594/LM2594HV
LM2594/LM2594HV-ADJ
Electrical Characteristics
Specifications with standard type face are for TJ = 25ÊC, and those with boldface type apply over full Operating Temperature Range
Symbol |
Parameter |
Conditions |
LM2594/LM2594HV-ADJ |
Units |
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(Limits) |
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Typ |
Limit |
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(Note 3) |
(Note 4) |
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SYSTEM PARAMETERS (Note 5) Test Circuit Figure 1 |
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VFB |
Feedback Voltage |
4.5V ≤ VIN ≤ VINmax, 0.1A ≤ ILOAD ≤ 0.5A |
1.230 |
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V |
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VOUT programmed for 3V. Circuit of Figure 1 |
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1.193/1.180 |
V(min) |
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1.267/1.280 |
V(max) |
η |
Efficiency |
VIN = 12V, ILOAD = 0.5A |
80 |
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All Output Voltage Versions Electrical Characteristics
Specifications with standard type face are for TJ = 25ÊC, and those with boldface type apply over full Operating Temperature Range . Unless otherwise specified, VIN = 12V for the 3.3V, 5V, and Adjustable version and VIN = 24V for the 12V version. ILOAD = 100 mA
Symbol |
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Parameter |
Conditions |
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LM2594/LM2594HV-XX |
Units |
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(Limits) |
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Typ |
Limit |
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(Note 3) |
(Note 4) |
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DEVICE PARAMETERS |
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Ib |
Feedback Bias Current |
Adjustable Version Only, VFB = 1.3V |
10 |
50/100 |
nA |
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fO |
Oscillator Frequency |
(Note 6) |
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150 |
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kHz |
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127/110 |
kHz(min) |
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173/173 |
kHz(max) |
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VSAT |
Saturation Voltage |
IOUT = 0.5A (Note 7) (Note 8) |
0.9 |
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V |
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1.1/1.2 |
V(max) |
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DC |
Max Duty Cycle (ON) |
(Note 8) |
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100 |
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% |
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Min Duty Cycle (OFF) |
(Note 9) |
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0 |
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ICL |
Current Limit |
Peak Current, (Note 7) (Note 8) |
0.8 |
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A |
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0.65/0.58 |
A(min) |
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1.3/1.4 |
A(max) |
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IL |
Output Leakage Current |
(Note 7) (Note 9) (Note 10) |
Output = 0V |
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50 |
µA(max) |
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Output = −1V |
2 |
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mA |
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15 |
mA(max) |
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IQ |
Quiescent Current |
(Note 9) |
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5 |
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mA |
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10 |
mA(max) |
ISTBY |
Standby Quiescent |
ON/OFF pin = 5V (OFF) |
(Note 10) |
85 |
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µA |
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Current |
LM2594 |
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200/250 |
µA(max) |
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LM2594HV |
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140 |
250/300 |
µA(max) |
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θJA |
Thermal Resistance |
N Package, Junction to Ambient (Note 11) |
95 |
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ÊC/W |
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M Package, Junction to Ambient (Note 11) |
150 |
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ON/OFF CONTROL Test Circuit Figure 1 |
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ON |
/OFF Pin Logic Input |
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1.3 |
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V |
VIH |
Threshold Voltage |
Low (Regulator ON) |
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0.6 |
V(max) |
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VIL |
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High (Regulator OFF) |
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2.0 |
V(min) |
IH |
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VLOGIC = 2.5V (Regulator OFF) |
5 |
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µA |
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ON |
/OFF Pin |
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Input Current |
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15 |
µA(max) |
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IL |
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VLOGIC = 0.5V (Regulator ON) |
0.02 |
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µA |
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5 |
µA(max) |
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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.
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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 25ÊC 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% 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 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 overload.
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: VIN = 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 |
Line Regulation |
Efficiency |
Output Voltage |
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DS012439-5 |
DS012439-6 |
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DS012439-4 |
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Switch Saturation |
Switch Current Limit |
Dropout Voltage |
Voltage |
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DS012439-8 |
DS012439-9 |
DS012439-7
LM2594/LM2594HV
5 |
www.national.com |
LM2594/LM2594HV
Typical Performance Characteristics (Continued)
Quiescent Current |
Standby |
Minimum Operating |
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Quiescent Current |
Supply Voltage |
DS012439-10
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DS012439-11 |
DS012439-12 |
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ON /OFF Threshold |
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ON /OFF Pin |
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Switching Frequency |
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Voltage |
Current (Sinking) |
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DS012439-15
DS012439-13 |
DS012439-14 |
Feedback Pin
Bias Current
DS012439-16
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6 |
Typical Performance Characteristics
Continuous Mode Switching Waveforms |
Discontinuous Mode Switching Waveforms |
VIN = 20V, VOUT = 5V, ILOAD = 400 mA |
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L = 100 µH, C OUT = 120 µF, C OUT ESR = 140 mΩ |
VIN = 20V, VOUT = 5V, ILOAD = 200 mA |
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L = 33 µH, C OUT = 220 µF, C OUT ESR = 60 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.
Load Transient Response for Continuous Mode
VIN = 20V, VOUT = 5V, ILOAD = 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.
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 Discontinuous Mode
VIN = 20V, VOUT = 5V, ILOAD = 100 mA to 200 mA L = 33 µH, C OUT = 220 µF, C OUT ESR = 60 mΩ
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
7 |
www.national.com |
LM2594/LM2594HV
Typical Circuit and Layout Guidelines
Fixed Output Voltage Versions
DS012439-22
CIN Ð 68 µF, 35V, Aluminum Electrolytic Nichicon ªPL Seriesº
COUT Ð 120 µF, 25V Aluminum Electrolytic, Nichicon ªPL Seriesº
D1 Ð 1A, 40V Schottky Rectifier, 1N5819
L1 Ð 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 Ð 68 µF, 35V, Aluminum Electrolytic Nichicon ªPL Seriesº
COUT Ð 120 µF, 25V Aluminum Electrolytic, Nichicon ªPL Seriesº
D1 Ð 1A, 40V Schottky Rectifier, 1N5819
L1 Ð 100 µH, L20
R1 Ð 1 k Ω, 1%
CFF Ð See Application Information Section
FIGURE 1. Typical Circuits and Layout Guides
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 COUT 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.)
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8 |
LM2594/LM2594HV Series Buck Regulator Design Procedure (Fixed
Output)
PROCEDURE (Fixed Output Voltage Version) |
EXAMPLE (Fixed Output Voltage Version) |
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Given: |
Given: |
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VOUT = Regulated Output Voltage (3.3V, 5V or 12V) |
VOUT = 5V |
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VIN(max) = Maximum DC Input Voltage |
VIN(max) = 12V |
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ILOAD(max) = Maximum Load Current |
ILOAD(max) = 0.4A |
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1. Inductor Selection (L1) |
1. Inductor Selection (L1) |
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A. Select the correct inductor value selection guide from Fig- |
A. Use the inductor selection guide for the 5V version shown |
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ures 4, 5 or Figure 6. (Output voltages of 3.3V, 5V, or 12V re- |
in Figure 5. |
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spectively.) For all other voltages, see the design procedure |
B. From the inductor value selection guide shown in Figure 5, |
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for the adjustable version. |
the inductance region intersected by the 12V horizontal line |
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B. From the inductor value selection guide, identify the induc- |
and the 0.4A vertical line is 100 µH, and the inductor code is |
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tance region intersected by the Maximum Input Voltage line |
L20. |
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and the Maximum Load Current line. Each region is identified |
C. The inductance value required is 100 µH. From the table |
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by an inductance value and an inductor code (LXX). |
in Figure 8, go to the L20 line and choose an inductor part |
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C. Select an appropriate inductor from the four manufactur- |
number from any of the four manufacturers shown. (In most |
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er's part numbers listed in Figure 8. |
instance, both through hole and surface mount inductors are |
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available.) |
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2. Output Capacitor Selection (COUT) |
2. Output Capacitor Selection (COUT) |
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A. In the majority of applications, low ESR (Equivalent Series |
A. See section on output capacitors in application infor- |
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Resistance) electrolytic capacitors between 82 µF and |
mation section. |
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220 µF and low ESR solid tantalum capacitors between 15 |
B. From the quick design component selection table shown |
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µF and 100 µF provide the best results. This capacitor should |
in Figure 2, locate the 5V output voltage section. In the load |
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be located close to the IC using short capacitor leads and |
current column, choose the load current line that is closest to |
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short copper traces. Do not use capacitors larger than |
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the current needed in your application, for this example, use |
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220 µF. |
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the 0.5A line. In the maximum input voltage column, select |
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For additional information, see section on output capaci- |
the line that covers the input voltage needed in your applica- |
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tors in application information section. |
tion, in this example, use the 15V line. Continuing on this line |
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B. To simplify the capacitor selection procedure, refer to the |
are recommended inductors and capacitors that will provide |
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quick design component selection table shown in Figure 2. |
the best overall performance. |
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This table contains different input voltages, output voltages, |
The capacitor list contains both through hole electrolytic and |
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and load currents, and lists various inductors and output ca- |
surface mount tantalum capacitors from four different capaci- |
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pacitors that will provide the best design solutions. |
tor manufacturers. It is recommended that both the manufac- |
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C. The capacitor voltage rating for electrolytic capacitors |
turers and the manufacturer's series that are listed in the |
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should be at least 1.5 times greater than the output voltage, |
table be used. |
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and often much higher voltage ratings are needed to satisfy |
In this example aluminum electrolytic capacitors from several |
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the low ESR requirements for low output ripple voltage. |
different manufacturers are available with the range of ESR |
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D. For computer aided design software, see Switchers Made |
numbers needed. |
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Simple version 4.1 or later. |
120 µF |
25V |
Panasonic HFQ Series |
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120 µF |
25V |
Nichicon PL Series |
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C. For a 5V output, a capacitor voltage rating at least 7.5V or |
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more is needed. But, in this example, even a low ESR, |
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switching grade, 120 µF 10V aluminum electrolytic capacitor |
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would exhibit approximately 400 mΩ of ESR (see the curve |
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in Figure 14 for the ESR vs voltage rating). This amount of |
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ESR would result in relatively high output ripple voltage. To |
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reduce the ripple to 1% of the output voltage, or less, a ca- |
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pacitor with a higher voltage rating (lower ESR) should be se- |
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lected. A 16V or 25V capacitor will reduce the ripple voltage |
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by approximately half. |
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LM2594/LM2594HV
9 |
www.national.com |
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