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부품번호 LM2750LD-5.0 기능
기능 Low Noise/ 5.0V Regulated Switched Capacitor Voltage Converter
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LM2750LD-5.0 데이터시트, 핀배열, 회로
February 2003
LM2750
Low Noise, 5.0V Regulated Switched Capacitor Voltage
Converter
General Description
The LM2750 is a switched-capacitor doubler that produces a
low-noise, well regulated, 5.0V output. It can supply up to
120mA of output current over a 2.9V to 5.6V input range, as
well as up to 40mA of output current when the input voltage
is as low as 2.7V. The LM2750 has been placed in National’s
10-pin LLP, a package with excellent thermal properties that
keeps the part from overheating under almost all rated op-
erating conditions
A perfect fit for space-constrained, battery-powered applica-
tions, the LM2750 requires only 3 external components: one
input capacitor, one output capacitor, and one flying capaci-
tor. Small, inexpensive ceramic capacitors are recom-
mended for use. These capacitors, in conjunction with the
1.7MHz fixed switching frequency of the LM2750, yield low
output voltage ripple, beneficial for systems requiring a low-
noise 5V supply. Pre-regulation minimizes input current
ripple, reducing input noise to negligible levels.
A tightly controlled soft-start feature limits inrush currents
during part activation. Shutdown completely disconnects the
load from the input. Output current limiting and thermal
shutdown circuitry protect both the LM2750 and connected
devices in the event of output shorts or excessive current
loads.
Features
n Inductorless solution: Application requires only 3 small
ceramic capacitors
n Low Noise, 5.0V ± 4% Regulated Output
n 85% Peak Efficiency
70% Average Efficiency over Li-Ion Input Range
(2.9V-to-4.2V)
n Output Current up to 120mA with 2.9V VIN 5.6V
Output Current up to 40mA with 2.7V VIN 2.9V
n Wide Input Voltage Range: 2.7V to 5.6V
n Fixed 1.7MHz switching frequency for a low-noise,
low-ripple output signal
n Pre-regulation minimizes input current ripple, keeping
the battery line (VIN) virtually noise-free
n Tiny LLP package with outstanding power dissipation:
Usually no derating required.
n Shutdown Supply Current less than 2µA
Applications
n White and Colored LED-based Display Lighting
n Cellular Phone SIM cards
n Audio Amplifier Power Supplies
n General Purpose Li-Ion-to-5V Conversion
Typical Application Circuit
© 2003 National Semiconductor Corporation DS200351
20035101
www.national.com




LM2750LD-5.0 pdf, 반도체, 판매, 대치품
Electrical Characteristics (Notes 2, 7) (Continued)
Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the component may occur. Operating Ratings are conditions under which operation of
the device is guaranteed. Operating Ratings do not imply guaranteed performance limits. For guaranteed performance limits and associated test conditions, see the
Electrical Characteristics tables.
Note 2: All voltages are with respect to the potential at the GND pin.
Note 3: Thermal shutdown circuitry protects the device from permanent damage.
Note 4: The Human body model is a 100 pF capacitor discharged through a 1.5 kresistor into each pin. The machine model is a 200pF capacitor discharged
directly into each pin.
Note 5: Maximum ambient temperature (TA-MAX) is dependent on the maximum operating junction temperature (TJ-MAX-OP = 125oC), the maximum power
dissipation of the device in the application (PD-MAX), and the junction-to ambient thermal resistance of the part/package in the application (θJA), as given by the
following equation: TA-MAX = TJ-MAX-OP - (θJA x PD-MAX). Maximum power dissipation of the LM2750 in a given application can be approximated using the following
equation: PD-MAX = (VIN-MAX x IIN-MAX) - (VOUT x IOUT-MAX) = [VIN-MAX x ((2 x IOUT-MAX) + 5mA)] - (VOUT x IOUT-MAX). In this equation, VIN-MAX, IIN-MAX, and
IOUT-MAX are the maximum voltage/current of the specific application, and not necessarily the maximum rating of the LM2750.
The maximum ambient temperature rating of 85oC is determined under the following application conditions: θJA = 55oC/W, PD-MAX = 727mW (achieved when
VIN-MAX = 5.5V and IOUT-MAX = 115mA, for example). Maximum ambient temperature must be derated by 1.1oC for every increase in internal power dissipation of
20mW above 727mW (again assuming that θJA = 55oC/W in the application). For more information on these topics, please refer to Application Note 1187: Leadless
Leadframe Package (LLP) and the Power Efficiency and Power Dissipation section of this datasheet.
Note 6: Junction-to-ambient thermal resistance (θJA) is taken from a thermal modeling result, performed under the conditions and guidelines set forth in the JEDEC
standard JESD51-7. The test board is a 4 layer FR-4 board measuring 102mm x 76mm x 1.6mm with a 2 x 1 array of thermal vias. The ground plane on the board
is 50mm x 50mm. Thickness of copper layers are 36mm/18 mm /18 mm /36 mm (1.5oz/1oz/1oz/1.5oz). Ambient temperature in simulation is 22˚C, still air. Power
dissipation is 1W.
The value of θJA of the LM2750 in LLP-10 could fall in a range as wide as 50oC/W to 150oC/W (if not wider), depending on PCB material, layout, and environmental
conditions. In applications where high maximum power dissipation exists (high VIN, high IOUT), special care must be paid to thermal dissipation issues. For more
information on these topics, please refer to Application Note 1187: Leadless Leadframe Package (LLP) and the Power Efficiency and Power Dissipation
section of this datasheet. and the following sections of this datasheet:
Note 7: All room temperature limits are 100% tested or guaranteed through statistical analysis. All limits at temperature extremes are guaranteed by correlation
using standard Statistical Quality Control methods (SQC). All limits are used to calculate Average Outgoing Quality Level (AOQL). Typical numbers are not
guaranteed, but do represent the most likely norm.
Note 8: CFLY, CIN, and COUT : Low-ESR Surface-Mount Ceramic Capacitors (MLCCs) used in setting electrical characteristics
Note 9: Turn-on time is measured from when SD signal is pulled high until the output voltage crosses 90% of its final value.
Note 10: Efficiency is measured versus VIN, with VIN being swept in small increments from 3.0V to 4.2V. The average is calculated from these measurements
results. Weighting to account for battery voltage discharge characteristics (VBAT vs. Time) is not done in computing the average.
Note 11: SD Input Current (IIH ) is due to a 200k(typ.) pull-down resistor connected internally between the SD pin and GND.
Note 12: Limit is the minimum required output capacitance to ensure proper operation. This electrical specification is guaranteed by design.
Block Diagram
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20035103
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LM2750LD-5.0 전자부품, 판매, 대치품
Operation Description
OVERVIEW
The LM2750 is a regulated switched capacitor doubler that,
by combining the principles of a switched-capacitor voltage
doubler and a linear regulator, generates a regulated 5V
output from an extended Li-Ion input voltage range. A two-
phase non-overlapping clock generated internally controls
the operation of the doubler. During the charge phase (φ1),
the flying capacitor (CFLY) is connected between the input
and ground through internal pass-transistor switches and is
charged to the input voltage. In the pump phase that follows
(φ2), the flying capacitor is connected between the input and
output through similar switches. Stacked atop the input, the
charge of the flying capacitor boosts the output voltage and
supplies the load current.
A traditional switched capacitor doubler operating in this
manner will use switches with very low on-resistance, ideally
0, to generate an output voltage that is 2x the input voltage.
The LM2750 regulates the output voltage by controlling the
resistance of the two input-connected pass-transistor
switches in the doubler.
PRE-REGULATION
The very low input current ripple of the LM2750, resulting
from internal pre-regulation, adds very little noise to the input
line. The core of the LM2750 is very similar to that of a basic
switched capacitor doubler: it is composed of four switches
and a flying capacitor (external). Regulation is achieved by
modulating the on-resistance of the two switches connected
to the input pin (one switch in each phase). The regulation is
done before the voltage doubling, giving rise to the term
"pre-regulation". It is pre-regulation that eliminates most of
the input current ripple that is a typical and undesirable
characteristic of a many switched capacitor converters.
INPUT, OUTPUT, AND GROUND CONNECTIONS
Making good input, output, and ground connections is es-
sential to achieve optimal LM2750 performance. The two
input pads, pads 8 and 9, must be connected externally. It is
strongly recommended that the input capacitor (CIN) be
placed as close as possible to the LM2750, so that the traces
from the input pads are as short and straight as possible. To
minimize the effect of input noise on LM2750 performance, it
is best to bring two traces out from the LM2750 all the way to
the input capacitor pad, so that they are connected at the
capacitor pad. Connecting the two input traces between the
input capacitor and the LM2750 input pads could make the
LM2750 more susceptible to noise-related performance deg-
radation. It is also recommended that the input capacitor be
on the same side of the PCB as the LM2750, and that traces
remain on this side of the board as well (vias to traces on
other PCB layers are not recommended between the input
capacitor and LM2750 input pads).
The two output pads, pads 1 and 2, must also be connected
externally. It is recommended that the output capacitor
(COUT) be placed as close to the LM2750 output pads as
possible. It is best if routing of output pad traces follow
guidelines similar to those presented for the input pads and
capacitor. The flying capacitor (CFLY) should also be placed
as close to the LM2750 as possible to minimize PCB trace
length between the capacitor and the IC. Due to the pad-
layout of the part, it is likely that the trace from one of the
flying capacitor pads (C+ or C-) will need to be routed to an
internal or opposite-side layer using vias. This is acceptable,
and it is much more advantageous to route a flying capacitor
trace in this fashion than it is to place input traces on other
layers.
The following pads of the LM2750 are ground connections
and must be connected externally: pads 3, 5, 6 and the
die-attach pad (DAP). Large, low impedance copper fills and
via connections to an internal ground plane are the preferred
way of connecting together the ground pads of the LM2750,
the input capacitor, and the output capacitor, as well as
connecting this circuit ground to the system ground of the
PCB.
SHUTDOWN
When the voltage on the active-low-logic shutdown pin is
low, the LM2750 will be in shutdown mode. In shutdown, the
LM2750 draws virtually no supply current. There is a 200k
pull-down resistor tied between the SD pin and GND that
pulls the SD pin voltage low if the pin is not driven by a
voltage source. When pulling the part out of shutdown, the
voltage source connected to the SD pin must be able to drive
the current required by the 200kresistor. For voltage man-
agement purposes required upon startup, internal switches
connect the output of the LM2750 to an internal pull-down
resistor (1ktyp) when the part is shutdown. Driving the
output of the LM2750 by another supply when the LM2750 is
shutdown is not recommended, as the pull-down resistor
was not sized to sink continuous current.
SOFT START
The LM2750 employs soft start circuitry to prevent excessive
input inrush currents during startup. The output voltage is
programmed to rise from 0V to the nominal output voltage
(5.0V) in 500µs (typ.). Soft-start is engaged when a part, with
input voltage established, is taken out of shutdown mode by
pulling the SD pin voltage high. Soft-start will also engage
when voltage is established simultaneously to the input and
SD pins.
OUTPUT CURRENT CAPABILITY
The LM2750 is guaranteed to provide 120mA of output
current when the input voltage is within 2.9V-to-5.6V. Using
the LM2750 to drive loads in excess of 120mA is possible.
IMPORTANT NOTE: Understanding relevant application is-
sues is recommended and a thorough analysis of the appli-
cation circuit should be performed when using the part out-
side operating ratings and/or specifications to ensure
satisfactory circuit performance in the application. Special
care should be paid to power dissipation and thermal effects.
These parameters can have a dramatic impact on high-
current applications, especially when the input voltage is
high. (see "Power Efficiency and Power Dissipation" section,
to come).
The schematic of Figure 1 is a simplified model of the
LM2750 that is useful for evaluating output current capability.
The model shows a linear pre-regulation block (Reg), a
voltage doubler (2x), and an output resistance (ROUT). Out-
put resistance models the output voltage droop that is inher-
ent to switched capacitor converters. The output resistance
of the LM2750 is 5(typ.), and is approximately equal to
twice the resistance of the four LM2750 switches. When the
output voltage is in regulation, the regulator in the model
controls the voltage V’ to keep the output voltage equal to
5.0V ± 4%. With increased output current, the voltage drop
across ROUT increases. To prevent droop in output voltage,
the voltage drop across the regulator is reduced, V’ in-
creases, and VOUT remains at 5V. When the output current
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부품번호상세설명 및 기능제조사
LM2750LD-5.0

Low Noise/ 5.0V Regulated Switched Capacitor Voltage Converter

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