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PDF LM5009 Data sheet ( Hoja de datos )
| Número de pieza | LM5009 | |
| Descripción | 100V Step-Down Switching Regulator | |
| Fabricantes | National Semiconductor | |
| Logotipo |  |
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February 2006
LM5009
150 mA, 100V Step-Down Switching Regulator
General Description
The LM5009 Step Down Switching Regulator features all of
the functions needed to implement a low cost, efficient, Buck
bias regulator. This device is capable of driving a 150 mA
load current from a 9.5V to 95V input source. The switching
frequency can exceed 600 kHz, depending on the input and
output voltages. The output voltage may be set from 2.5V to
85V. This high voltage regulator contains an N-Channel buck
www.DataSheet4U.csowmitch and internal startup regulator. The device is easy to
implement and is provided in the MSOP-8 and the thermally
enhanced LLP-8 packages. The LM5009 is a well suited
alternative to a high voltage monolithic or discrete linear
solution where the power loss becomes unacceptable. The
regulator’s operation is based on a hysteretic control
scheme using an ON time inversely proportional to VIN. This
feature allows the operating frequency to remain relatively
constant over load and input voltage variations. The hyster-
etic control requires no loop compensation, resulting in an
ultra-fast transient response. An intelligent current limit is
implemented with forced OFF time, which is inversely pro-
portional to Vout. This scheme ensures short circuit protec-
tion while providing minimum foldback. Other features in-
clude: Thermal Shutdown, Vcc under-voltage lockout, Gate
drive under-voltage lockout, and Maximum Duty Cycle lim-
iter.
Features
n Integrated N-Channel MOSFET
n Guaranteed 150 mA output current capability
n Ultra-Fast Transient Response
n No loop compensation required
n Vin feed forward provides constant operating frequency
n Switching frequency can exceed 600 kHz
n Highly efficient operation
n 2% accurate 2.5V feedback from -40˚C to 125˚C
n Internal startup regulator
n Intelligent current limit protection
n External shutdown control
n Thermal shutdown
n MSOP-8 and thermally enhanced LLP packages
Typical Applications
n Heat sink eliminator for classic linear regulator
applications
n 12V, 24V, 36V, and 48V rectified AC systems
n 42V Automotive
n Non-isolated AC mains charge coupled supplies
n LED Current Source
Package
n MSOP - 8
n LLP - 8 (4mm x 4mm) (Available Soon)
Typical Application Circuit
Basic Stepdown Regulator
© 2006 National Semiconductor Corporation DS201658
20165828
www.national.com
1 page  
Electrical Characteristics (Continued)
Limits in standard type are for TJ = 25˚C only, and limits in boldface type apply over the junction temperature (TJ) range of
-40˚C to +125˚C. Minimum and Maximum limits are guaranteed through test, design, or statistical correlation. Typical values
represent the most likely parametric norm at TJ = 25˚C, and are provided for reference purposes only. Unless otherwise stated,
the following conditions apply: VIN = 48V, RON = 200kΩ. See (Note 3)
Symbol
Parameter
Conditions
Min Typ
Max
Units
Minimum Off Time
Minimum Off Timer
FB = 0V
300 ns
Regulation and OV Comparators
FB Reference Threshold
Internal reference
2.445
2.5
2.550
V
Trip point for switch ON
FB Over-Voltage Threshold
Trip point for switch OFF
2.875
V
FB Bias Current
1 nA
Thermal Shutdown
www.DataSThesedt4U.com Thermal Shutdown Temp.
Thermal Shutdown Hysteresis
165 ˚C
25 ˚C
Thermal Resistance
θJA Junction to Ambient
MUA Package
SDC Package
200 ˚C/W
˚C/W
Note 1: Absolute Maximum Ratings are limits beyond which damage to the device may occur. Operating Ratings are conditions under which operation of the device
is intended to be functional. For guaranteed specifications and test conditions, see the Electrical Characteristics.
Note 2: For detailed information on soldering plastic MSOP and LLP packages, refer to the Packaging Data Book available from National Semiconductor
Corporation.
Note 3: All limits are guaranteed. All electrical characteristics having room temperature limits are tested during production with TA = TJ = 25˚C. All hot and cold limits
are guaranteed by correlating the electrical characteristics to process and temperature variations and applying statistical process control.
Note 4: The VCC output is intended as a self bias for the internal gate drive power and control circuits. Device thermal limitations limit external loading.
Note 5: The human body model is a 100pF capacitor discharged through a 1.5kΩ resistor into each pin. All pins are rated for 2 kV, except VIN and VCC which are
rated for 1 kV.
Note 6: For devices procured in the LLP-8 package the Rds(on) limits are guaranteed by design characterization data only.
5 www.national.com
5 Page 
Applications Information (Continued)
supplies the surge current to charge the buck switch gate at
turn-on. A low ESR also ensures a quick recharge during
each off-time. At minimum VIN, when the on-time is at maxi-
mum, it is possible during start-up that C4 will not fully
recharge during each 300 ns off-time. The circuit will not be
able to complete the start-up, and achieve output regulation.
This can occur when the frequency is intended to be low
(e.g., RON = 500K). In this case C4 should be increased so
it can maintain sufficient voltage across the buck switch
driver during each on-time.
C5: This capacitor helps avoid supply voltage transients and
ringing due to long lead inductance at VIN. A low ESR, 0.1µF
ceramic chip capacitor is recommended, located close to the
LM5009.
FINAL CIRCUIT
www.DataSheet4U.com
The final circuit is shown in Figure 5. The circuit was tested,
and the resulting performance is shown in Figure 6 through
Figure 9. For these graphs, the load current was varied from
50mA to 200mA.
PC BOARD LAYOUT
The LM5009 regulation and over-voltage comparators are
very fast, and as such will respond to short duration noise
pulses. Layout considerations are therefore critical for opti-
mum performance. The components at pins 1, 2, 3, 5, and 6
should be as physically close as possible to the IC, thereby
minimizing noise pickup in the PC tracks. The current loop
formed by D1, L1, and C2 should be as small as possible.
The ground connection from C2 to C1 should be as short
and direct as possible.
If the internal dissipation of the LM5009 produces excessive
junction temperatures during normal operation, good use of
the pc board’s ground plane can help considerably to dissi-
pate heat. The exposed pad on the bottom of the LLP-8
package can be soldered to a ground plane on the PC board,
and that plane should extend out from beneath the IC to help
dissipate the heat. Additionally, the use of wide PC board
traces, where possible, can also help conduct heat away
from the IC. Judicious positioning of the PC board within the
end product, along with use of any available air flow (forced
or natural convection) can help reduce the junction
temperatures.
FIGURE 5. LM5009 Example Circuit
20165822
11 www.national.com
11 Page | ||
| Páginas | Total 14 Páginas | |
| PDF Descargar | [ Datasheet LM5009.PDF ] | |
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