National Semiconductor LM3501 Technical data

查询LM3501TL-16供应商

LM3501
Synchronous Step-up DC/DC Converter for White LED
Applications

Synchronous Step-up DC/DC Converter for White LED Applications

May 2005

General Description

The LM3501 is a fixed-frequency step-up DC/DC converter
that is ideal for driving white LEDs for display backlighting
and other lighting functions. With fully intergrated synchro­nous switching (no external schottky diode required) and a
low feedback voltage (515 mV), power efficiency of the
LM3501 circuit has been optimized for lighting applications
in wireless phones and other portable products (single cell
Li-Ion or 3-cell NiMH battery supplies). The LM3501 oper­ates with a fixed 1 MHz switching frequency. When used with
ceramic input and output capacitors, the LM3501 provides a
small, low-noise, low-cost solution.

Two LM3501 options are available with different output volt­age capabilities. The LM3501-21 has a maximum output
voltage of 21V and is typically suited for driving 4 or 5 white
LEDs in series. The LM3501-16 has a maximum output
voltage of 16V and is typically suited for driving 3 or 4 white
LEDs in series (maximum number of series LEDs dependent
on LED forward voltage). If the primary white LED network
should be disconnected, the LM3501 uses internal protec­tion circuitry on the output to prevent a destructive overvolt­age event.

A single external resistor is used to set the maximum LED
current in LED-drive applications. The LED current can eas­ily be adjusted by varying the analog control voltage on the
control pin or by using a pulse width modulated (PWM)
signal on the shutdown pin. In shutdown, the LM3501 com­pletely disconnects the input from output, creating total iso­lation and preventing any leakage currents from trickling into
the LEDs.

Features

n Synchronous rectification, high efficiency and no

external schottky diode required

n Uses small surface mount components
n Can drive 2-5 white LEDs in series (may function with

more low V

n 2.7V to 7V input range
n True shutdown isolation, no LED leakage current
n DC voltage LED current control
n Input undervoltage lockout
n Internal output over-voltage protection (OVP) circuitry,

with no external zener diode required LM3501-16: 15.5V
OVP; LM3501-21: 20.5V OVP.

n Requires only a small 16V (LM3501-16) or 25V

(LM3501-21) ceramic capacitor at the input and output

n Thermal Shutdown
n 0.1µA shutdown current
n Small 8-bump thin micro SMD package

LEDs)

F

Applications

n LCD Bias Supplies
n White LED Back-Lighting
n Handheld Devices
n Digital Cameras
n Portable Applications

Typical Application Circuit

20065301

FIGURE 1. Typical 3 LED Application

© 2005 National Semiconductor Corporation DS200653 www.national.com

Connection Diagram

LM3501

Top View

8-bump micro SMD

20065302

Ordering Information

Order Number Package Type NSC Package Drawing Top Mark Supplied As

LM3501TL-16 micro SMD TL08SSA 19 250 Units, Tape and Reel

LM3501TLX-16 micro SMD TL08SSA 19 3000 Units, Tape and Reel

LM3501TL-21 micro SMD TL08SSA 30 250 Units, Tape and Reel

LM3501TLX-21 micro SMD TL08SSA 30 3000 Units, Tape and Reel

Pin Description/Functions

Pin Name Function

A1 AGND Analog ground.

B1 V

C1 V

C2 V

IN

OUT

SW

C3 GND Power Ground.

B3 FB Output voltage feedback connection.

A3 CNTRL Analog LED current control.

A2 SHDN

AGND (pin A1): Analog ground pin. The analog ground pin
should tie directly to the GND pin.

V

(pin B1):Analog and Power supply pin. Bypass this pin

IN

with a capacitor, as close to the device as possible, con­nected between the V

(pin C1):Source connection of internal PMOS power

V

OUT

and GND pins.

IN

device. Connect the output capacitor between the V
GND pins as close as possible to the device.

(pin C2):Drain connection of internal NMOS and PMOS

V

SW

switch devices. Keep the inductor connection close to this
pin to minimize EMI radiation.

GND (pin C3):Power ground pin. Tie directly to ground
plane.

Analog and Power supply input.

PMOS source connection for synchronous rectification.

Switch pin. Drain connections of both NMOS and PMOS power devices.

Shutdown control pin.

FB (pin B3):Output voltage feedback connection. Set the
primary White LED network current with a resistor from the
FB pin to GND. Keep the current setting resistor close to the
device and connected between the FB and GND pins.

CNTRL (pin A3): Analog control of LED current. A voltage
above 125 mV will begin to regulate the LED current. De-

OUT

and

creasing the voltage below 75 mV will turn off the LEDs.
SHDN (pin A2):Shutdown control pin. Disable the device

with a voltage less than 0.3V and enable the device with a
voltage greater than 1.1V. The white LED current can be
controlled using a PWM signal at this pin. There is an
internal pull down on the SHDN pin, the device is in a
normally off state.

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LM3501

Absolute Maximum Ratings (Note 1)

If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.

V

IN

V

(LM3501-16)(Note 2) −0.3V to 16V

OUT

V

(LM3501-21)(Note 2) −0.3V to 21V

OUT

V

(Note 2) −0.3V to V

SW

FB Voltage −0.3V to 7.5V

SHDN Voltage

−0.3V to 7.5V

+0.3V

OUT

−0.3V to VIN+0.3V

ESD Ratings (Note 3)

Human Body Model 2kV

Machine Model 200V

Operating Conditions

Junction Temperature
(Note 4) −40˚C to +125˚C

Supply Voltage 2.7V to 7V

CNTRL Max. 2.7V

CNTRL −0.3V to 7.5V

Maximum Junction Temperature 150˚C

Lead Temperature
(Soldering 10 sec.) 300˚C

Thermal Properties

Junction to Ambient Thermal
Resistance (θ

) (Note 5)

JA

Vapor Phase
(60 sec.) 215˚C

Infrared
(15 sec.) 220˚C

Electrical Characteristics

Specifications in standard type face are for TA= 25˚C and those in boldface type apply over the Operating Temperature
Range of T

LM3501-21.

Symbol Parameter Conditions

I

Q

V

FB

∆V

FB

I

CL

I

B

V

IN

R

DSON

D

Limit

F

SW

= −10˚C to +85˚C. Unless otherwise specified VIN= 2.7V and specifications apply to both LM3501-16 and

A

Quiescent Current, Device Not

FB>0.54V

Switching

Quiescent Current, Device

FB=0V

Switching

Shutdown SHDN = 0V

Feedback Voltage CNTRL = 2.7V,

= 2.7V to 7V

V

IN

CNTRL = 1V,

= 2.7V to 7V

V

IN

Feedback Voltage Line

VIN= 2.7V to 7V

Regulation

Switch Current Limit
(LM3501-16)

VIN= 2.7V,
Duty Cycle = 80%

= 3.0V,

V

IN

Duty Cycle = 70%

Switch Current Limit
(LM3501-21)

VIN= 2.7V,
Duty Cycle = 70%

= 3.0V,

V

IN

Duty Cycle = 63%

Min

(Note 6)

0.485 0.515 0.545

0.14 0.19 0.24

275 400 480

255 400 530

420 640 770

450 670 800

Typ

(Note 7)

Max

(Note 6)

0.95 1.2

2 2.5

0.1 2 µA

0.1 0.5 %/V

FB Pin Bias Current FB = 0.5V (Note 8) 45 200 nA

Input Voltage Range 2.7 7.0 V

NMOS Switch R

PMOS Switch R

Duty Cycle Limit
(LM3501-16)

Duty Cycle Limit
(LM3501-21)

DSON

DSON

VIN= 2.7V, ISW= 300 mA 0.43

V

= 6V, ISW= 300 mA 1.3 2.3

OUT

FB=0V

FB=0V

80 87

85 94

Switching Frequency 0.85 1.0 1.15 MHz

75˚C/W

Units

mA

V

mA

Ω

%

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Electrical Characteristics (Continued)

Specifications in standard type face are for TA= 25˚C and those in boldface type apply over the Operating Temperature

LM3501

Range of T

LM3501-21.

Symbol Parameter Conditions

I

SD

I

CNTRL

I

L

UVP Input Undervoltage Lockout ON Threshold 2.4 2.5 2.6

OVP Output Overvoltage Protection

I

Vout

I

VL

CNTRL
Threshold

SHDN
Threshold

Specifications in standard type face are for TJ= 25˚C and those in boldface type apply over the full Operating Temperature

Range (T

LM3501-21.

Symbol Parameter Conditions

I

Q

V

FB

∆V

FB

I

CL

I

B

V

IN

= −10˚C to +85˚C. Unless otherwise specified VIN= 2.7V and specifications apply to both LM3501-16 and

A

Min

(Note 6)

Typ

(Note 7)

Max

(Note 6)

SHDN Pin Current (Note 9) SHDN = 5.5V 1.8 4

1 2.5

CNTRL Pin Current (Note 9) V

Switch Leakage Current
(LM3501-16)

Switch Leakage Current
(LM3501-21)

SHDN = GND

= 2.7V 10 20

CNTRL

V

=1V 4 15

CNTRL

VSW= 15V

VSW= 20V

0.1

0.01 0.5

0.01 2.0

OFF Threshold 2.3 2.4 2.5

ON Threshold 15 15.5 16

(LM3501-16)

Output Overvoltage Protection
(LM3501-21)

V

Bias Current

OUT

(LM3501-16)

V

Bias Current

OUT

(LM3501-21)

PMOS Switch Leakage Current
(LM3501-16)

PMOS Switch Leakage Current
(LM3501-21)

OFF Threshold 14 14.6 15

ON Threshold 20 20.5 21

OFF Threshold 19 19.5 20

V

= 15V, SHDN = 1.5V

OUT

V

= 20V, SHDN = 1.5V

OUT

V

= 15V, VSW=0V

OUT

= 20V, VSW=0V

V

OUT

260 400

300 460

0.01 3

0.01 3

LED power off 75

LED power on 125

SHDN low

SHDN High

= −40˚C to +125˚C). Unless otherwise specified VIN=2.7V and specifications apply to both LM3501-16 and

J

1.1 0.65

Min

(Note 6)

Quiescent Current, Device Not

FB>0.54V

Switching

Quiescent Current, Device

FB=0V

Switching

Shutdown SHDN = 0V

0.65 0.3

Typ

(Note 7)

Max

(Note 6)

0.95 1.2

2 2.5

0.1 2 µA

Feedback Voltage CNTRL = 2.7V, VIN= 2.7V to 7V 0.485 0.515 0.545

Feedback Voltage Line
Regulation

Switch Current Limit
(LM3501-16)

Switch Current Limit
(LM3501-21)

CNTRL = 1V, V

VIN= 2.7V to 7V

VIN= 3.0V,
Duty Cycle = 70%

VIN= 3.0V,
Duty Cycle = 63%

= 2.7V to 7V 0.14 0.19 0.24

IN

0.1 0.5 %/V

400

670

FB Pin Bias Current FB = 0.5V (Note 8) 45 200 nA

Input Voltage Range 2.7 7.0 V

Units

µASHDN = 2.7V

µA

µA

V

V

V

µA

µA

mV

V

Units

mA

V

mA

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Electrical Characteristics (Continued)

Specifications in standard type face are for TJ= 25˚C and those in boldface type apply over the full Operating Temperature
Range (T

LM3501-21.

Symbol Parameter Conditions

R

DSON

D

Limit

F

SW

I

SD

I

CNTRL

I

L

UVP Input Undervoltage Lockout ON Threshold 2.4 2.5 2.6

OVP Output Overvoltage Protection

I

Vout

I

VL

CNTRL
Threshold

SHDN
Threshold

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: This condition applies if V

Note 3: The human body model is a 100 pF capacitor discharged through a 1.5 kΩ resistor into each pin. The machine model is a 200 pF capacitor discharged

directly into each pin.

Note 4: The maximum allowable power dissipation is a function of the maximum operating junction temperature, T
resistance, θ
ambient temperature is calculated using: P

Note 5: Junction-to-ambient thermal resistance (θ
board conforming to JEDEC standards. In applications where high maximum power dissipation exists, special care must be paid to thermal dissipation issues when
designing the board layout.

Note 6: 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
Quality Control (SQC) methods. All limits are used to calculate Average Outgoing Quality Level (AOQL).

Note 7: Typical numbers are at 25˚C and represent the most likely norm.

Note 8: Feedback current flows out of the pin.

Note 9: Current flows into the pin.

= −40˚C to +125˚C). Unless otherwise specified VIN=2.7V and specifications apply to both LM3501-16 and

J

NMOS Switch R

PMOS Switch R

Duty Cycle Limit
(LM3501-16)

Duty Cycle Limit
(LM3501-21)

DSON

DSON

Min

(Note 6)

VIN= 2.7V, ISW= 300 mA 0.43

V

= 6V, ISW= 300 mA 1.3 2.3

OUT

FB=0V

FB=0V

Typ

(Note 7)

87

94

Max

(Note 6)

Switching Frequency 0.8 1.0 1.2 MHz

SHDN Pin Current (Note 9) SHDN = 5.5V 1.8 4

1 2.5

CNTRL Pin Current (Note 9) V

Switch Leakage Current

SHDN = GND

= 2.7V 10 20

CNTRL

V

=1V 4 15

CNTRL

VSW= 15V 0.01 0.5

0.1

(LM3501-16)

Switch Leakage Current

VSW= 20V 0.01 2.0

(LM3501-21)

OFF Threshold 2.3 2.4 2.5

ON Threshold 15 15.5 16

(LM3501-16)

Output Overvoltage Protection
(LM3501-21)

V

Leakage Current

OUT

(LM3501-16)

V

Leakage Current

OUT

(LM3501-21)

PMOS Switch Leakage Current
(LM3501-16)

PMOS Switch Leakage Current
(LM3501-21)

OFF Threshold 14 14.6 15

ON Threshold 20 20.5 21

OFF Threshold 19 19.5 20

V

= 15V, SHDN = 1.5V

OUT

V

= 20V, SHDN = 1.5V

OUT

V

= 15V, VSW=0V

OUT

= 20V, VSW=0V

V

OUT

260 400

300 460

0.01 3

0.01 3

LED power off 75

LED power on 125

SHDN low

SHDN High

<

V

IN

OUT

, and the ambient temperature, TA. See the Thermal Properties section for the thermal resistance. The maximum allowable power dissipation at any

JA

D

>

.IfV

V

IN

(MAX) = (T

JA

, a voltage greater than VIN+ 0.3V should not be applied to the V

OUT

J(MAX)−TA

) is highly application and board-layout dependent. The 75oC/W figure provided was measured on a 4-layer test

)/θJA. Exceeding the maximum allowable power dissipation will cause excessive die temperature.

1.1 0.65

0.65 0.3

or VSWpins.

OUT

, the junction-to-ambient thermal

J(MAX)

LM3501

Units

Ω

%

µASHDN = 2.7V

µA

µA

V

V

µA

µA

mV

V

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Typical Performance Characteristics

LM3501

Switching Quiescent Current vs. V

IN

Non-Switching Quiescent Current vs. V

IN

2 LED Efficiency vs. Load Current

L = Coilcraft DT1608C-223,

Efficiency = 100*(P

IN

/(2V

LED*ILED

4 LED Efficiency vs. Load Current

L = Coilcraft DT1608C-223,

Efficiency = 100*(P

IN

/(4V

LED*ILED

20065355

20065356

3 LED Efficiency vs. Load Current

L = Coilcraft DT1608C-223,

))

20065357 20065358

))

Efficiency = 100*(PIN/(3V

Output Power vs. V

LED*ILED

))

IN

(LM3501-16, L = Coilcraft DT1608C-223)

20065359 20065386

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