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PDF LM4510 Data sheet ( Hoja de datos )
| Número de pieza | LM4510 | |
| Descripción | Synchronous Step-Up DC/DC Converter | |
| Fabricantes | National Semiconductor | |
| Logotipo |  |
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October 2007
LM4510
Synchronous Step-Up DC/DC Converter with True
Shutdown Isolation
General Description
The LM4510 is a current mode step-up DC/DC converter with
a 1.2A internal NMOS switch designed to deliver up to 120
mA at 16V from a Li-Ion battery.
The device's synchronous switching operation (no external
Schottky diode) at heavy-load, and non-synchronous switch-
www.DataSheeitn4gUo.cpoemration at light-load, maximizes power efficiency.
True shutdown function by synchronous FET and related cir-
cuitry ensures input and output isolation.
A programmable soft-start circuit allows the user to limit the
amount of inrush current during startup. The output voltage
can be adjusted by external resistors.
The LM4510 features advanced short-circuit protection to
maximize safety during output to ground short condition. Dur-
ing shutdown the feedback resistors and the load are discon-
nected from the input to prevent leakage current paths to
ground.
The LM4510 is available in a 10-pin thermally enhanced
Leadless Leadframe Package: LLP-10.
Features
■ 18V@80 mA from 3.2V input
■ 5V@280 mA from 3.2V input
■ No external Schottky diode required
■ 85% peak efficiency
■ Soft start
■ True shutdown isolation
■ Stable with small ceramic or tantalum output capacitors
■ Output short-circuit protection
■ Feedback fault protection
■ Input under-voltage lock out
■ Thermal shutdown
■ 0.002 µA shutdown current
■ Wide input voltage range: 2.7V to 5.5V
■ 1.0 MHz fixed frequency operation
■ Low-profile 10–pin LLP package (3mm x 3mm x 0.8mm)
Applications
■ Organic LED Panel Power Supply
■ Charging Holster
■ White LED Backlight
■ USB Power Supply
■ Class D Audio Amplifier
■ Camera Flash LED Driver
Typical Application Circuit
FIGURE 1. Typical Application Circuit
© 2007 National Semiconductor Corporation 300310
30031001
www.national.com
1 page  
Note 1: Absolute maximum ratings are limits beyond which damage to the device may occur. Operating Ratings are conditions for which the device is intended
to be functional, but device parameter specifications may not be guaranteed. For guaranteed specifications and test conditions, see the Electrical Characteristics.
Note 2: All voltages are with respect to the potential at the GND pin.
Note 3: This condition applies if VIN < VOUT. If VIN > VOUT, a voltage greater than VIN + 0.3V should not be applied to the VOUT or VSW pins. The absolute
maximum specification applies to DC voltage. An extended negative voltage limit of -1V applies for a pulse of up to 1 µs, and -2V for a pulse of up to 40 ns. An
extended positive voltage limit of 22V applies for a pulse of up to 20 ns.
Note 4: Internal thermal shutdown circuitry protects the device from permanent damage. Thermal shutdown engages at TJ=150°C (Typ.) and disengages at
TJ=140°C (Typ.).
Note 5: For detailed soldering information and specifications, please refer to National Semiconductor Application Note 1187: Leadless Leadframe Package (LLP) ,
available at www.national.com.
Note 6: In applications where high power dissipation and/or poor package thermal resistance is present, the maximum ambient temperature may have to be
derated. Maximum ambient temperature (TA-MAX) is dependent on the maximum operating junction temperature (TJ-MAX-OP = 125°C), 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 × PD-MAX)
Note 7: Junction-to-ambient thermal resistance (θJA) is taken by a numerical analysis conforming to JEDEC standards. In applications where high maximum
power dissipation exists (high VIN, high IOUT), special care must be paid to thermal dissipation issues when designing the board layout. For more information on
these topics, please refer to Application Note 1187: Leadless Leadframe Package (LLP).
Note 8: All limits guaranteed at room temperature (standard typeface) and at temperature extremes (bold typeface). All room temperature limits are production
tested, guaranteed through statistical analysis or guaranteed by design. All limits at temperature extremes are guaranteed via correlation using standard Statistical
www.DataQSuhaelietyt4CUon.ctroolm(SQC) methods. All limits are used to calculate Average Outgoing Quality Level (AOQL).
Note 9: Typical numbers are at 25°C and represent the most likely norm.
Note 10: Current flows out of the pin.
Note 11: Current flows into the pin.
Note 12: The Human body model is a 100 pF capacitor discharged through a 1.5 kΩ resistor into each pin (MIL-STD-883 3015.7). The machine model is a 200
pF capacitor discharged directly into each pin.
5 www.national.com
5 Page 
Synchronous boost converter is shown in Figure 3. At the start
of each cycle, the oscillator sets the driver logic and turns on
the NMOS power device and turns off the PMOS power de-
vice.
Cycle 1 Description
Refer to Figure 4. NMOS switch turn-on → Inductor current
increases and flows to GND.
PMOS switch turn-off → Isolate VOUT from SW → Output ca-
pacitor supplies load current.
www.DataSheet4U.com
30031015
FIGURE 4. Equivalent Circuit During Cycle 1
During operation, EAMP output voltage (VCOMP) increases for
larger loads and decreases for smaller loads. When the sum
of the ramp compensation and the sensed NMOS current
reaches a level determined by the EAMP output voltage, the
PWM COMP resets the logic, turning off the NMOS power
device and turning on the PMOS power device.
Cycle 2 Description
Refer to Figure 5. NMOS Switch turn-off → PMOS Switch turn-
on→ Inductor current decreases and flows through PMOS
→ Inductor current recharges output capacitor and supplies
load current.
30031016
FIGURE 5. Equivalent Circuit During Cycle 2
After the switching period the oscillator then sets the driver
logic again repeating the process.
ON/OFF CONTROL
The LM4510 shuts down when the EN pin is low. In this mode
the feedback resistors and the load are disconnected from the
input in order to avoid leakage current flow and to allow the
output voltage to drop to 0V.
The LM4510 turns on when EN is high. There is an internal
pull-down resistor on the EN pin so the device is in a normally
off state.
SHORT CIRCUIT PROTECTION
When VOUT goes down to VIN–0.7V (typ.), the device stops
switching due to the short-circuit protection circuitry and the
short-circuit output current is limited to IINIT_CHARGE.
FEEDBACK FAULT PROTECTION
The LM4510 features unique Feedback Fault Protection to
maximize safety when the feedback resistor is not properly
connected to a circuit or the feedback node is shorted directly
to ground.
Feedback fault triggers VOUT monitoring. During monitoring,
if VOUT reaches a protection level, the device shuts down.
When the feedback network is reconnected and VOUT is lower
than the OFF threshold level of Feedback Fault Protection,
VOUT monitoring stops. VOUT is then regulated by the control
loop.
INPUT UNDER-VOLTAGE LOCK-OUT
The LM4510 has dedicated circuitry to protect the IC and the
external components when the battery voltage is lower than
the preset threshold. This under-voltage lock-out with hys-
teresis prevents malfunctions during startup or abnormal
power off.
THERMAL SHUTDOWN
If the die temperature exceeds 150°C (typ.), the thermal pro-
tection circuitry shuts down the device. The switches remain
off until the die temperature is reduced to approximately
140°C (typ.).
Application Information
ADJUSTING OUTPUT VOLTAGE
The output voltage is set using the feedback pin and a resistor
voltage divider (RF1, RF2) connected to the output as shown
in the Typical Application Circuit.
The ratio of the feedback resistors sets the output voltage.
RF2 Selection
First of all choose a value for RF2 generally between 10 kΩ
and 25 kΩ.
RF1 Selection
Calculate RF1 using the following equation:
Table 1 gives suggested component values for several typical
output voltages.
11 www.national.com
11 Page | ||
| Páginas | Total 18 Páginas | |
| PDF Descargar | [ Datasheet LM4510.PDF ] | |
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