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Part: LM3501TL-16EV
Category:
Description: Synchronous Step-up DC/DC Converter For White Led Applications
Company: National Semiconductor Corporation
Datasheet: Download LM3501TL-16EV datasheet File size : 1064 kB
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Datasheet text preview:
Synchronous Step-up DC/DC Converter for White LED Applications
December 2003
LM3501 Synchronous Step-up DC/DC Converter for White LED Applications
General Description
The LM3501 is a fixed frequency synchronous step-up DC/DC converter in a small 8-bump thin micro SMD package. The LM3501 is ideal for white LED applications for cellular phone back-lighting requiring low current and high efficiency. Its fixed 1MHz operating frequency allows the use of small, low ESR capacitors as well as a more predictable frequency spectrum, which is important in cellular phone applications. The LM3501 can drive 2 to 4 white LEDs in series from a single Li-Ion battery or 3 cell NiMH with no external rectification diode. For white LED applications, a single external resistor is used to set the maximum LED current. The white LED current can easily be adjusted using an external voltage signal from a DAC or micro-controller. The LM3501 uses special protection circuitry on the output to prevent an overvoltage event if the primary white LED network should be disconnected eliminating the need of an extra protection Zener diode. In shutdown, the LM3501 disconnects the input and output creating a true isolation preventing any LED light from emitting over the full input operating voltage range and temperature.
Features
n Synchronous rectification, high efficiency and no external schottky diode required n Uses small surface mount components n Can drive up to 3 (or 4 low VF) white LEDs in series 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 Output overvoltage protection, no external zener diode required n Requires only a small 16V ceramic capacitor at the output n Thermal Shutdown n 0.1µA shutdown current n Small 8-bump thin micro SMD package
Applications
n n n n n LCD Bias Supplies White LED Back-Lighting Handheld Devices Digital Cameras Portable Applications
Typical Application Circuit
20065301
FIGURE 1. Typical 3 LED Application
© 2003 National Semiconductor Corporation
DS200653
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LM3501
Connection Diagram
Top View
20065302
TJ(MAX)
8-bump micro SMD = 125°C, JA = 220°C/W (Note 3)
Ordering Information
Order Number LM3501TL-16 LM3501TLX-16 Package Type micro SMD micro SMD NSC Package Drawing TL08SSA TL08SSA Top Mark C19 C19 Supplied As 250 Units, Tape and Reel 3000 Units, Tape and Reel
Pin Description/Functions
Pin A1 B1 C1 C2 C3 B3 A3 A2 Name AGND VIN VOUT VSW GND FB CNTRL SHDN Analog ground. Analog and Power supply input. PMOS source connection for synchronous rectification. Switch pin. Drain connections of both NMOS and PMOS power devices. Power Ground. Output voltage feedback connection. Analog LED current control. 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 125mV will begin to regulate the LED current. Decreasing the voltage below 75mV 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. Function
AGND(pin A1): Analog ground pin. The analog ground pin should tie directly to the GND pin. VIN(pin B1): Analog and Power supply pin. Bypass this pin with a capacitor, as close to the device as possible, connected between the VIN and GND pins. VOUT(pin C1): Source connection of internal PMOS power device. Connect the output capacitor between the VOUT and GND pins as close as possible to the device. VSW(pin C2): Drain connection of internal NMOS and PMOS 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.
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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. VIN VOUT(Note 2) VSW(Note 2) FB Voltage SHDN Voltage CNTRL Maximum Junction Temperature Lead Temperature (Soldering 10 sec.) Vapor Phase (60 sec.) Infrared (15 sec.) -0.3V to 7.5V -0.3V to 16V -0.3V to VOUT+0.3V -0.3V to 7.5V -0.3V to VIN+0.3V -0.3V to 7.5V 150°C 300°C 215°C 220°C
ESD Ratings (Note 4) Human Body Model Machine Model 2kV 200V
Operating Conditions
Junction Temperature (Note 5) Supply Voltage CNTRL Max. -40°C to +125°C 2.7V to 7V 2.7V
Thermal Properties
Junction to Ambient Thermal Resistance (JA), 8-pin micro SMD package (Note 3) 220°C/W
Electrical Characteristics
Specifications in standard type face are for TA = 25°C and those in boldface type apply over the Operating Temperature Range of TA = -10°C to +85°C. Unless otherwise specified VIN = 2.7V. Symbol IQ Parameter Quiescent Current, Device Not Switching Quiescent Current, Device Switching Shutdown VFB FeedbackVoltage Conditions FB > 0.54V FB = 0V SHDN = 0V CNTRL = 2.7V, VIN = 2.7V to 7V CNTRL = 1V, VIN = 2.7V to 7V VFB ICL FeedbackVoltage Line Regulation Switch Current Limit VIN = 2.7V to 7V VIN = 2.7V, Duty Cycle = 80% VIN = 3.0V, Duty Cycle = 70% IB VIN RDSON DLimit FSW ISD FB Pin Bias Current Input Voltage Range NMOS Switch RDSON PMOS Switch RDSON Duty Cycle Limit Switching Frequency SHDN Pin Current (Note 8) SHDN = 5.5V SHDN = 2.7V SHDN = GND ICNTRL IL UVP CNTRL Pin Current (Note 8) Switch Leakage Current Input Undervoltage Lockout VCNTRL = 2.7V VCNTRL = 1V VSW = 15V ON Threshold OFF Threshold 2.4 2.3 VIN = 2.7V, ISW = 300mA VOUT = 6V, ISW = 300mA FB = 0V 80 0.85 1.3 87 1.0 1.8 1 0.1 10 4 0.01 2.5 2.4 20 15 0.5 2.6 2.5 µA µA V 1.15 4 2.5 µA FB = 0.5V (Note 7) 2.7 0.485 0.14 Min (Note 5) Typ (Note 6) 0.95 2 0.1 0.515 0.19 0.1 275 255 400 400 45 Max (Note 5) 1.2 mA 2.5 2 0.545 V 0.24 0.5 480 mA 530 200 7.0 0.43 2.3 nA V % MHz %/V µA Units
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