IL2576-xx

TECHNICAL DATA
3.0 A, 15 V, Step-Down
Switching Regulator
IL2576-xx
The IL2576 series of regulators are monolithic integrated
circuits ideally suited for easy and convenient design of a
step–down switching regulator (buck converter). All circuits of
this series are capable of driving a 3.0 A load with excellent
line and load regulation. These devices are available in fixed
output voltages of 3.3 V, 5.0 V, 12 V, 15 V, and an adjustable
output version.
These regulators were designed to minimize the number
of external components to simplify the power supply design.
Standard series of inductors optimized for use with the IL2576
are offered by several different inductor manufacturers. Since
the IL2576 converter is a switch–mode power supply, its
efficiency is significantly higher in comparison with popular
three–terminal linear regulators, especially with higher input
voltages. In many cases, the power dissipated is so low that
no heatsink is required or its size could be reduced
dramatically.
A standard series of inductors optimized for use with the
IL2576 are available from several different manufacturers.
This feature greatly simplifies the design of switch–mode
power supplies. The IL2576 features include a guaranteed
±4% tolerance on output voltage within specified input
voltages and output load conditions, and ±10% on the
oscillator frequency (±2% over 0°C to 125°C). External
shutdown is included, featuring 80 ㎂ (typical) standby current.
The output switch includes cycle–by–cycle current limiting, as
well as thermal shutdown for full protection under fault
conditions.
Features











3.3 V, 5.0 V, 12 V, 15 V, and Adjustable
Device
Output Versions
Adjustable Version Output Voltage Range,
IL2576xxD2T
1.23 to 37 V ±4%
Maximum Over Line and Load Conditions
IL2576xxKB
Guaranteed 3.0 A Output Current
Wide Input Voltage Range
Requires Only 4 External Components
52 kHz Fixed Frequency Internal Oscillator
TTL Shutdown Capability, Low Power Standby Mode
High Efficiency
Uses Readily Available Standard Inductors
Thermal Shutdown and Current Limit Protection
TO-220-5L
IL2576KB
TO-263-5L
IL2576D2T
Pin connections
1. Vin
2. Output
3. Ground
4. Feedback
5. ON/OFF
ORDERING INFORMATION
Operating
Temperature Range
TA = -40 to 125 C
for all packages
Package
Packing
TO-263
Tape & Reel
TO-220
Tube
Applications






Simple High–Efficiency Step–Down (Buck) Regulator
Efficient Pre–Regulator for Linear Regulators
On–Card Switching Regulators
Positive to Negative Converter (Buck–Boost)
Negative Step–Up Converters
Power Supply for Battery Chargers
2012, July, Rev. 04
IL2576-xx
Typical Application (Fixed Output Voltage Versions)
Figure 1.
Representative Block Diagram and Typical Application
This device contains 162 active transistors.
Figure 2.
ABSOLUTE MAXIMUM RATINGS
(Absolute Maximum Ratings indicate limits beyond which damage to the device may occur.)
Rating
Symbol
Value
Unit
Maximum Supply Voltage
Vin
45
V
ON/OFF Pin Input Voltage
–
V
–0.3 V  V  +Vin
Output Voltage to Ground (Steady–State)
–
–1.0
V
Power Dissipation
TO–220, 5–Lead
PD
Internally Limited
W
Thermal Resistance, Junction–to–Ambient
RθJA
65
°C/W
Thermal Resistance, Junction–to–Case
RθJC
5.0
°C/W
TO–263, 5–Lead (D2PAK)
PD
Internally Limited
W
Thermal Resistance, Junction–to–Ambient
RθJA
70
°C/W
Thermal Resistance, Junction–to–Case
RθJC
5.0
°C/W
Storage Temperature Range
Tstg
–65 to +150
°C
Minimum ESD Rating (Human Body Model:
–
2.0
kV
C = 100 pF, R = 1.5 kΩ)
Lead Temperature (Soldering, 10 seconds)
–
260
°C
Maximum Junction Temperature
TJ
150
°C
* Stresses beyond those listed under “absolute maximum ratings” may cause permanent damage to the device.
These are stress ratings only and functional operation of the device at these or any other conditions beyond those
indicated under “recommended operating conditions” is not implied.
Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
2012, July, Rev. 04
IL2576-xx
OPERATING RATINGS
(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.)
Rating
Operating Junction Temperature Range
Supply Voltage
Symbol
TJ
Vin
Value
–40 to +125
40
Unit
°C
V
SYSTEM PARAMETERS [Note 1]
ELECTRICAL CHARACTERISTICS
(Unless otherwise specified, Vin = 12 V for the 3.3 V, 5.0 V, and Adjustable version, V in = 25 V for the 12 V version, and V in = 30 V for
the 15 V version. ILoad = 500 mA, TJ = 25°C, for min/max values TJ is the operating junction temperature range that applies [Note 2],
unless otherwise noted.)
Characteristics
IL2576–3.3 ([Note 1] Test Circuit Figure 3)
Output Voltage
Output Voltage (6.0 V  Vin  40 V, 0.5 A  ILoad  3.0
A)
TJ = 25°C
TJ = –40 to +125°C
Efficiency (Vin = 12 V, ILoad = 3.0 A)
IL2576–5 [Note 1]
Output Voltage
Output Voltage (8.0 V  Vin  40 V, 0.5 A  ILoad
 3.0 A)
TJ = 25°C
TJ = –40 to +125°C
Efficiency (Vin = 12 V, ILoad = 3.0 A)
IL2576–12 [Note 1]
Output Voltage
Output Voltage (15.0 V  Vin  40 V, 0.5 A  ILoad  3.0
A)
TJ = 25°C
TJ = –40 to +125°C
Efficiency (Vin = 12 V, ILoad = 3.0 A)
IL2576–15 [Note 1]
Output Voltage
Output Voltage (18 V  Vin  40 V, 0.5 A  ILoad  3.0
A)
TJ = 25°C
TJ = –40 to +125°C
Efficiency (Vin = 12 V, ILoad = 3.0 A)
IL2576 ADJUSTABLE VERSION [Note 1]
Feedback Voltage (Vin = 12 V, ILoad = 0.5 A, Vout = 5.0 V, TJ
= 25°C)
Feedback Voltage (8.0 V  Vin  40 V, 0.5 A  ILoad
 3.0 A, Vout = 5.0 V)
TJ = 25°C
TJ = –40 to +125°C
Efficiency (Vin = 12 V, ILoad = 3.0 A, Vout = 5.0 V)
Symbol
Vout
Vout
Min
Max
Unit
3.234
3.366
3.168
3.135
3.432
3.465

65
-
%
Vout
Vout
4.9
5.1
V
V
4.8
4.75
5.2
5.25

67
-
%
Vout
Vout
11.76
12.24
V
V
11.52
11.4
12.48
12.6

78
-
%
Vout
Vout
14.7
15.3
V
V
14.4
14.25
15.6
15.75

78
-
%
Vout
1.217
1.243
V
Vout

V
V
V
1.193
1.18
67
1.267
1.28
-
%
1. External components such as the catch diode, inductor, input and output capacitors can affect switching regulator system
performance.
When the IL2576 is used as shown in the test circuit, system performance will be as shown in system parameters section .
2. Tested junction temperature range for the IL2576: Tlow = –40°C Thigh = +125°C
2012, July, Rev. 04
IL2576-xx
DEVICE PARAMETERS
ELECTRICAL CHARACTERISTICS
(Unless otherwise specified, Vin = 12 V for the 3.3 V, 5.0 V, and Adjustable version, Vin = 25 V
for the 12 V version, and Vin = 30 V for the 15 V version. ILoad = 500 mA, TJ = 25°C, for min/max values TJ is the
operating junction temperature range that applies [Note 2], unless otherwise noted.)
Characteristics
ALL OUTPUT VOLTAGE VERSIONS
Feedback Bias Current (Vout = 5.0 V [Adjustable Version
Only])
TJ = 25°C
TJ = –40 to +125°C
Oscillator Frequency [Note 3]
TJ = 25°C
TJ = –40 to +125°C
Saturation Voltage (Iout = 3.0 A [Note 4])
TJ = 25°C
TJ = –40 to +125°C
Max Duty Cycle (“on”) [Note 5]
Current Limit (Peak Current [Notes 3 and 4])
TJ = 25°C
TJ = –40 to +125°C
Output Leakage Current [Notes 6 and 7], TJ = 25°C
Output = 0 V
Output = –1.0 V
Quiescent Current [Note 6]
TJ = 25°C
TJ = –40 to +125°C
Standby Quiescent Current (ON/OFF Pin = 5.0 V (“off”))
TJ = 25°C
ON/OFF Pin Logic Input Level
Vout = 0 V
TJ = 25°C
TJ = –40 to +125°C
Vout = Nominal Output Voltage
TJ = 25°C
TJ = –40 to +125°C
ON/OFF Pin Input Current
ON/OFF Pin = 5.0 V (“off”), TJ = 25°C
ON/OFF Pin = 0 V (“on”), TJ = 25°C
Symbol
Min
Max
Ib
fosc
Vsat
DC
ICL
IL
IQ
Unit
nA
–
–
100
500
–
42
–
63
–
–
93
1.8
2.0
–
4.2
3.5
6.9
7.5
–
–
2.0
30
–
–
10
11
–
200
kHz
V
%
A
mA
mA
Istby
uA
V
VIH
VIL
2.2
2.4
–
–
–
–
1.0
0.8
–
–
30
10
uA
IIH
IIL
3. The oscillator frequency reduces to approximately 18 kHz in the event of an output short or an overload which causes the regulated
output voltage to drop approximately 40% from the nominal output voltage. This self protection feature lowers the average dissipation of
the IC by lowering the minimum duty cycle from 5% down to approximately 2%.
4. Output (Pin 2) sourcing current. No diode, inductor or capacitor connected to output pin.
5. Feedback (Pin 4) removed from output and connected to 0 V.
6. Feedback (Pin 4) removed from output and connected to +12 V for the Adjustable, 3.3 V, and 5.0 V versions, and +25 V for the 12 V
and 15 V versions, to force the output transistor “off”.
7. Vin = 40 V.
2012, July, Rev. 04
IL2576-xx
Fixed Output Voltage Versions
Figure 3.
Cin – 100 mF, 75 V, Aluminium Electrolytic
Cout – 1000 mF, 25 V, Aluminium Electrolytic
D1 – Schottky, MBR360
L1 – 100 mH, Pulse Eng. PE–92108
R1 – 2.0 k, 0.1%
R2 – 6.12 k, 0.1%
Adjustable Output Voltage Versions
Figure 4.

R 
Vout  Vref 1.0  2  ,
R1 

V

R2  R1  out  1.0 
V

 ref

Where Vref = 1.23 V, R1 between 1.0 k and 5.0 k
C1 = 10 nF
C2 = 1 nF
2012, July, Rev. 04
IL2576-xx
Application Information
INVERTING REGULATOR
Figure 5 shows a IL2576-12 in a buck-boost configuration to generate a negative 12V output from a positive input
voltage. This circuit bootstraps the regulator’s ground pin to the negative output voltage, then by grounding the feedback pin, the
regulator senses the inverted output voltage and regulates it to −12V.
For an input voltage of 12V or more, the maximum available output current in this configuration is approximately 700 mA.
At lighter loads, the minimum input voltage required drops to approximately 4.7V.
The switch currents in this buck-boost configuration are higher than in the standard buck-mode design, thus lowering the
available output current. Also, the start-up input current of the buck-boost converter is higher than the standard buck-mode
regulator, and this may overload an input power source with a current limit less than 5A. Using a delayed turn-on or an
undervoltage lockout circuit (described in the next section) would allow the input voltage to rise to a high enough level before the
switcher would be allowed to turn on.
Because of the structural differences between the buck and the buck-boost regulator topologies, the buck regulator
design procedure section can not be used to to select the inductor or the output capacitor. The recommended range of inductor
values for the buck-boost design is between 68 µH and 220 µH, and the output capacitor values must be larger than what is
normally required for buck designs. Low input voltages or high output currents require a large value output capacitor (in the
thousands of micro Farads).
The peak inductor current, which is the same as the peak switch current, can be calculated from the following formula:
Where fosc = 52 kHz. Under normal continuous inductor current operating conditions, the minimum V IN represents the
worst case. Select an inductor that is rated for the peak current anticipated.
FIGURE 5. Inverting Buck-Boost Develops −12V
Also, the maximum voltage appearing across the regulator is the absolute sum of the input and output voltage. For a
−12V output, the maximum input voltage for the IL2576 is +28V.
NEGATIVE BOOST REGULATOR
Another variation on the buck-boost topology is the negative boost configuration. The circuit in Figure 6 accepts an input
voltage ranging from −5V to −12V and provides a regulated −12V output. Input voltages greater than −12V will cause the output
to rise above −12V, but will not damage the regulator.
Typical Load Current
400 mA for VIN = −5.2V
750 mA for VIN = −7V
Note: Heat sink may be required.
FIGURE 6. Negative Boost
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IL2576-xx
Because of the boosting function of this type of regulator, the switch current is relatively high, especially at low input
voltages.
Output load current limitations are a result of the maximum current rating of the switch. Also, boost regulators can not
provide current limiting load protection in the event of a shorted load, so some other means (such as a fuse) may be necessary.
UNDERVOLTAGE LOCKOUT
In some applications it is desirable to keep the regulator off until the input voltage reaches a certain threshold. An
undervoltage lockout circuit which accomplishes this task is shown in Figure 7 while Figure 8 shows the same circuit applied to
a buck-boost configuration. These circuits keep the regulator off until the input voltage reaches a predetermined level.
VTH =VZ1 + 2VBE(Q1)
Note: Complete circuit not shown.
FIGURE 7. Undervoltage Lockout for Buck Circuit
Note: Complete circuit not shown (see Figure 10).
FIGURE 8. Undervoltage Lockout for Buck-Boost Circuit
DELAYED STARTUP
The ON /OFF pin can be used to provide a delayed startup feature as shown in Figure 9. With an input voltage of 20V and for
the part values shown, the circuit provides approximately 10 ms of delay time before the circuit begins switching.
Increasing the RC time constant can provide longer delay times. But excessively large RC time constants can cause problems
with input voltages that are high in 60 Hz or 120 Hz ripple, by coupling the ripple into the ON /OFF pin.
Note: Complete circuit not shown.
FIGURE 9. Delayed Startup
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IL2576-xx
ADJUSTABLE OUTPUT, LOW-RIPPLE POWER SUPPLY
A 3A power supply that features an adjustable output voltage is shown in Figure 10. An additional L-C filter that reduces the
output ripple by a factor of 10 or more is included in this circuit.
FIGURE 10. Adjustable 3A Power Supply with Low Output Ripple
Definition of Terms
BUCK REGULATOR
A switching regulator topology in which a higher voltage is converted to a lower voltage. Also known as a step-down switching
regulator.
BUCK-BOOST REGULATOR
A switching regulator topology in which a positive voltage is converted to a negative voltage without a transformer.
DUTY CYCLE (D)
Ratio of the output switch’s on-time to the oscillator period.
CATCH DIODE OR CURRENT STEERING DIODE
The diode which provides a return path for the load current when the IL2576 switch is OFF.
EFFICIENCY ()
The proportion of input power actually delivered to the load.
2012, July, Rev. 04
IL2576-xx
TO-220-5L
2012, July, Rev. 04
IL2576-xx
TO-263-5L
2012, July, Rev. 04