D2576HV
3A Step-Down HV Voltage Regulator
General Description
The D2576HV series of regulators are monolithic integrated circuit
that provides all the active functions for a step-down (buck) switching
regulator, capable of driving 3A load with excellent line and load
TO220T-5L
regulation. The D2576HV available in fixed output voltages of 3.3V, 5V,
12Vand an adjustable output version.
TO263-5L
Requiring a minimum number of external components, these
regulators are simple to use and include internal frequency compensation and a fixed-frequency oscillator.
The D2576HV series offers a high-efficiency replacement for popular three-terminal linear regulators. It
substantially reduces the size of the heat sink, and in some cases no heat sink is required. A standard series of
inductors optimized for use with the D2576HV are available from several different manufacturers. This feature
greatly simplifies the design of switch-mode power supplies.
Other features include a guaranteed ±4% tolerance on output voltage within specified input voltages and
output load conditions, and ±10% on the oscillator frequency. External shutdown is included, featuring 50 µA
(typical) standby current. The output switch includes cycle-by-cycle current limiting, as well as thermal shutdown
for full protection under fault conditions.
The D2576HV is available in TO220T-5L and TO263-5L package.
Features
3.3V, 5V, 12V and adjustable output versions
Wide input voltage range, 40V up to 60V for HV version
High efficiency
Specified 3A output current
52 kHz fixed frequency internal oscillator
TTL shutdown capability, low power standby mode
Uses readily available standard inductors
Thermal shutdown and current limit protection
Adjustable version output voltage range, 1.23V to 57V ±4% max over line and load conditions
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D2576HV
Applications
Simple high-efficiency step-down (Buck) regulator
Efficient pre-regulator for linear regulators
On-card switching regulators
Positive to negative converter (Buck-Boost)
Functional Block Diagram
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D2576HV
Pin Configuration
TO220T-5L
TO263-5L
Pin Description
Pin Number
Pin Name
1
VIN
2
OUTPUT
3
GND
4
FEEDBACK
5
ON / OFF
Function Description
This is the positive input supply for the IC switching regulator.
A suitable input bypass capacitor must be present at this pin to minimize
voltage transients and to supply the switching currents needed by the
regulator.
Internal switch, the voltage at this pin switches between (+VIN VSAT) and
approximately -0.5V. To minimize coupling to sensitive circuitry, the PC
board copper area connected to this pin should be kept to a minimum.
Circuit Ground
Senses the regulated output voltage to complete the feedback loop.
Allows the switching regulator circuit to be shut down using logic level
signals
Absolute Maximum Ratings
Parameter Name
Symbol
Value
Unit
VIN
63
V
ON / OFF
-0.3V≤V≤+VIN
V
Output Voltage to Ground(steady state)
VOUT
-1
V
Power Dissipation
PDMAX
Internally Limited
Storage Temperature Range
Tstg
-65~+150
℃
Maximum Junction Temperature
TJA
150
℃
ESD Susceptibility (Human Body Model)
ESD
2
kV
Lead Temperature (Soldering, 10 Seconds)
TL
260
℃
Maximum Supply Voltage
ON / OFF Pin Input Voltage
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D2576HV
Recommended Operating Conditions
Parameter Name
Symbol
Value
Unit
Supply Voltage
VIN
6~60
V
Operating temperature range
Topr
-40~+125
℃
Electrical Characteristics
(Unless otherwise specified: TJ = 25°C)
Parameter Name
Symbol
Test Conditions
Ib
Adjustable version only,
VOUT=5V
Min
Typ
Max
Units
50
100
nA
52
58
kHz
1.4
1.8
V
Device Parameters
Feedback Bias Current
Oscillator Frequency
VSAT Saturation Voltage
Max. Duty Cycle(ON)
Current Limit
fo
VSAT
DC
ICL
Output Leakage Current
IL
Quiescent Current
IQ
Standby Quiescent Current
ISTBY
(Note 1)
47
IOUT=3A
(Note 1)
93
98
4.2
5.8
6.9
A
2
mA
7.5
30
mA
5
10
mA
50
200
µA
Output=0V
Output=-1V
ON / OFF pin=5V(OFF)
%
ON / OFF Control
ON / OFF Pin Logic
Input Level
ON / OFF Pin Input Current
VIH
VOUT=0V
VIL
IIH
VOUT=nominal output
voltage
ON / OFF pin=5V(OFF)
IIL
ON / OFF pin=0V(ON)
2.0
V
0.8
V
12
30
µA
0
10
µA
Note 1: The oscillator frequency reduces to approximately 11 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
power dissipation of the IC by lowering the minimum duty cycle from 5% down to approximately 2%.
Output pin sourcing current. No diode, inductor or capacitor connected to output.
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D2576HV
Parameter Name
Symbol
Test Conditions
Min
Typ
Max
Units
VIN=12V, IO=500mA
6V≤VIN≤60V
0.5A≤ILOAD≤3A
VIN=12V, ILOAD=3A
3.234
3.3
3.366
V
3.168
3.3
3.450
V
VIN=12V, IO=500mA
8V≤VIN≤60V
0.5A≤ILOAD≤3A
VIN=12V, ILOAD=3A
4.90
5.00
5.10
V
4.800
5.0
5.225
V
D2576HV-3.3V
Output Voltage
VOUT
η
Efficiency
75
%
D2576HV-5.0V
Output Voltage
VOUT
η
Efficiency
77
%
D2576HV-12V
Output Voltage
VOUT
η
Efficiency
Parameter Name
Symbol
VIN=25V, IO=500mA
15V≤VIN≤60V
0.5A≤ILOAD≤3A
VIN=25V, ILOAD=3A
11.76
12.00
12.24
V
11.52
12.00
12.54
V
Test Conditions
Min
Typ
Max
Units
1.217
1.230
1.243
V
1.193
1.230
1.273
V
88
%
D2576HV-ADJ
Output Voltage
VOUT
Efficiency
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η
VIN=12V,IO=500mA,
VOUT=5V
8V≤VIN≤60V, VOUT=5V
0.5A≤ILOAD≤3A
VIN=12V,ILOAD=3A,
VOUT=5V
CHMC
77
%
Dec 2019 Rev. 2.0
Page 5 of 18
D2576HV
Test Circuit
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D2576HV
Typical Application
Application Information
Input Capacitor (CIN)
To maintain stability, the regulator input pin must be bypassed with at least a 100 µF electrolytic capacitor. The
capacitor’s leads must be kept short, and located near the regulator. If the operating temperature range includes
temperatures below -25°C, the input capacitor value may need to be larger. With most electrolytic capacitors, the
capacitance value decreases and the ESR increases with lower temperatures and age. Paralleling a ceramic or solid
tantalum capacitor will increase the regulator stability at cold temperatures. For maximum capacitor operating
lifetime, the capacitor’s RMS ripple current rating should be greater than
t
1.2 ON I LOAD
T
Where
and
tON VOUT
for a buck regulator
T
VIN
tON
| VOUT |
for a buck-boost regulator.
T
| VOUT | VIN
Inductor Selection
All switching regulators have two basic modes of operation: continuous and discontinuous. The difference
between the two types relates to the inductor current, whether it is flowing continuously, or if it drops to zero for
a period of time in the normal switching cycle. Each mode has distinctively different operating characteristics,
which can affect the regulator performance and requirements. The D2576HV can be used for both continuous and
discontinuous modes of operation. When using inductor values shown in the inductor selection guide, the
peak-to-peak inductor ripple current will be approximately 20% to 30% of the maximum DC current. With
relatively heavy load currents, the circuit operates in the continuous mode (inductor current always flowing),
but under light load conditions, the circuit will be forced to the discontinuous mode (inductor current falls to zero
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D2576HV
for a period of time). This discontinuous mode of operation is perfectly acceptable. For light loads(less than
approximately 300mA) it may be desirable to operate the regulator in the discontinuous mode, primarily because
of the lower inductor values required for the discontinuous mode. The selection guide chooses inductor values
suitable for continuous mode operation, but if the inductor value chosen is prohibitively high, the designer should
investigate the possibility of discontinuous operation.
Inductors are available in different styles such as pot core, toriod, E-frame, bobbin core, etc., as well as
different core materials, such as ferrites and powdered iron. The least expensive, the bobbin core type, consists of
wire wrapped on a ferrite rod core. This type of construction makes for an inexpensive inductor, but since the
magnetic flux is not completely contained within the core, it generates more electromagnetic interference (EMI).
This EMI can cause problems in sensitive circuits, or can give incorrect scope readings because of induced
voltages in the scope probe. The inductors listed in the selection chart include ferrite pot core construction for AIE,
powdered iron toroid for Pulse Engineering, and ferrite bobbin core for Renco.
An inductor should not be operated beyond its maximum rated current because it may saturate. When an
inductor begins to saturate, the inductance decreases rapidly and the inductor begins to look mainly resistive (the
DC resistance of the winding) This will cause the switch current to rise very rapidly. Different inductor types have
different saturation characteristics, and this should be kept in mind when selecting an inductor.
The inductor manufacturer’s data sheets include current and energy limits to avoid inductor saturation.
Inductor Ripple Current
When the switcher is operating in the continuous mode, the inductor current waveform ranges from a
triangular to a sawtooth type of waveform (depending on the input voltage).For a given input voltage and output
voltage, the peak-to-peak amplitude of this inductor current waveform remains constant. As the load current rises
or falls, the entire sawtooth current waveform also rises or falls. The average DC value of this waveform is equal
to the DC load current (in the buck regulator configuration). If the load current drops to a low enough level, the
bottom of the sawtooth current waveform will reach zero, and the switcher will change to a discontinuous mode of
operation. This is a perfectly acceptable mode of operation. Any buck switching regulator (no matter how large
the inductor value is) will be forced to run discontinuous if the load current is light enough.
Catch Diode
Buck regulators require a diode to provide a return path for the inductor current when the switch is off. This
diode should be located close to the D2576HV using short leads and short printed circuit traces. Because of their
fast switching speed and low forward voltage drop, Schottky diodes provide the best efficiency, especially in low
output voltage switching regulators (less than 5V). Fast-Recovery, High-Efficiency, or Ultra-Fast Recovery
diodes are also suitable, but some types with an abrupt turn-off characteristic may cause instability and EMI
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D2576HV
problems. A fast-recovery diode with soft recovery characteristics is a better choice. Standard 60 Hz diodes
(e.g., 1N4001 or1N5400, etc.) are also not suitable.
Output Capacitor
An output capacitor is required to filter the output voltage and is needed for loop stability. The capacitor
should be located near the D2576HV using short pc board traces. Standard aluminum electrolytics are usually
adequate, but low ESR types are recommended for low output ripple voltage and good stability. The ESR of a
capacitor depends on many factors, some which are: the value, the voltage rating, physical size and the type of
construction. In general, low value or low voltage (less than 12V) electrolytic capacitors usually have higher ESR
numbers.
The amount of output ripple voltage is primarily a function of the ESR (Equivalent Series Resistance) of the
output capacitor and the amplitude of the inductor ripple current (ΔIIND). See the section on inductor ripple current
in Application Hints. The lower capacitor values (220 µF–1000 µF) will allow typically 50 mV to 150 mV of
output ripple voltage, while larger-value capacitors will reduce the ripple to approximately20 mV to 50mV.Output
Ripple Voltage = (ΔIIND) (ESR of COUT). To further reduce the output ripple voltage, several standard electrolytic
capacitors may be paralleled, or a higher-grade capacitor may be used. Such capacitors are often called
“high-frequency” “low-inductance” or “low-ESR” These will reduce the output ripple to 10 mV or 20 mV.
However, when operating in the continuous mode, reducing the ESR below 0.03Ω can cause instability in the
regulator. Tantalum capacitors can have a very low ESR, and should be carefully evaluated if it is the only output
capacitor. Because of their good low temperature characteristics, a tantalum can be used in parallel with aluminum
electrolytics, with the tantalum making up 10% or 20% of the total capacitance. The capacitor’s ripple current
rating at 52 kHz should be at least 50% higher than the peak-to-peak inductor ripple current.
Output Voltage Ripple and Transients
The output voltage of a switching power supply will contain a sawtooth ripple voltage at the switcher
frequency, typically about 1% of the output voltage, and may also contain short voltage spikes at the peaks of the
sawtooth waveform. The output ripple voltage is due mainly to the inductor sawtooth ripple current multiplied by
the ESR of the output capacitor. The voltage spikes are present because of the fast switching action of the output
switch, and the parasitic inductance of the output filter capacitor. To minimize these voltage spikes, special low
inductance capacitors can be used, and their lead lengths must be kept short. Wiring inductance, stray capacitance,
as well as the scope probe used to evaluate these transients, all contribute to the amplitude of these spikes. An
additional small LC filter (20 µH & 100 µF) can be added to the output to further reduce the amount of output
ripple and transients. A 10 × reduction in output ripple voltage and transients is possible with this filter.
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D2576HV
Feedback Connection
The D2576HV (fixed voltage versions) feedback pin must be wired to the output voltage point of the
switching power supply. When using the adjustable version, physically locate both output voltage programming
resistors near the D2576HV to avoid picking up unwanted noise. Avoid using resistors greater than 100kΩ
because of the increased chance of noise pickup.
ON / OFF Input
For normal operation, the ON / OFF pin should be grounded or driven with a low-level TTL voltage (typically
below 1.6V). To put the regulator into standby mode, drive this pin with a high-level TTL or CMOS signal. The
ON / OFF pin can be safely pulled up to +VIN without a resistor in series with it. The ON / OFF pin should not
be left open.
Inductor Value Selection Guides ( For Continuous Mode Operation)
D2576HV-3.3
D2576HV-5.0
D2576HV-12
D2576HV-ADJ
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D2576HV
Inductor Selection Guide
Diode Selection Guide
Grounding
To maintain output voltage stability, the power ground connections must be low-impedance. For the 5-lead
TO-220T and TO-263 style package, both the tab and pin 3 are ground and either connection may be used, as they
are both part of the same copper lead frame.
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D2576HV
Heat Sink/Thermal Considerations
In many cases, only a small heat sink is required to keep the D2576HV junction temperature within the
allowed operating range. For each application, to determine whether or not a heat sink will be required, the
following must be identified:
1.
Maximum ambient temperature (in the application).
2.
Maximum regulator power dissipation (in application).
3.
Maximum allowed junction temperature (125°C for the D2576HV). For a safe, conservative design, a
temperature approximately 15°C cooler than the maximum temperatures should be selected.
4.
D2576HV package thermal resistances θJA and θJC.
Total power dissipated by the D2576HV can be estimated as follows:
PD = (VIN)(IQ) + (VO/VIN)(ILOAD)(VSAT)
where
• IQ (quiescent current) and VSAT can be found in Typical Performance Characteristics shown previously,
• VIN is the applied minimum input voltage, VO is the regulated output voltage,
• and ILOAD is the load current.
(3)
The dynamic losses during turn-on and turn-off are negligible if a Schottky type catch diode is used.
When no heat sink is used, the junction temperature rise can be determined by the following:
ΔTJ = (PD) (θJA)
(4)
To arrive at the actual operating junction temperature, add the junction temperature rise to the maximum ambient
temperature.
TJ = ΔTJ + TA
(5)
If the actual operating junction temperature is greater than the selected safe operating junction temperature
determined in step 3, then a heat sink is required.
When using a heat sink, the junction temperature rise can be determined by the following:
ΔTJ = (PD) (θJC + θinterface + θHeat sink)
(6)
The operating junction temperature will be:
TJ = TA + ΔTJ
(7)
If the actual operating junction temperature is greater than the selected safe operating junction temperature,
then a larger heat sink is required (one that has a lower thermal resistance). Included on the Switcher Made Simple
design software is a more precise (non-linear) thermal model that can be used to determine junction temperature
with different input-output parameters or different component values. It can also calculate the heat sink thermal
resistance required to maintain the regulators junction temperature below the maximum operating temperature.
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D2576HV
Characteristic Curves
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D2576HV
Characteristic Curves (Continued)
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D2576HV
Characteristic Curves (Continued)
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D2576HV
Outline Dimensions
TO220T-5L:
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D2576HV
TO263-5L:
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D2576HV
Statements
Silicore Technology reserves the right to make changes without further notice to any products or
specifications herein. Before customers place an order, customers need to confirm whether datasheet
obtained is the latest version, and to verify the integrity of the relevant information.
Failure or malfunction of any semiconductor products may occur under particular conditions, customers
shall have obligation to comply with safety standards when customers use Silicore Technology products to
do their system design and machine manufacturing, and take corresponding safety measures in order to
avoid potential risk of failure that may cause personal injury or property damage.
The product upgrades without end, Silicore Technology will wholeheartedly provide customers integrated
circuits that have better performance and better quality.
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