DC2176A Step-Up (Boost) LED Drivers by Analog Devices

Step-Up (Boost) LED Drivers
Status: Production
Series: LT3909
RoHS: Compliant
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The LT3909 is a 2-string × 60mA LED driver with a fixed 2MHz step-up DC/DC converter capable of driving up to 36V of LEDs. Each LED string contains an accurate high-side current source with ±2% current matching. Output voltage adapts to variations in LED VF for optimum efficiency.Maximum LED current can be programmed from 10mA to 60mA per string using a single resistor. LED brightness can be reduced with analog dimming (up to 10:1) or with PWM dimming (up to 40,000:1 at 100Hz, up to 160:1 at 25kHz) (independent of leakage at VOUT). The LED pins can be paralleled for higher LED current.Additional features include: programmable maximum VOUT for open LED protection, a fault flag to indicate open-LED or LED-short-to-GND and an internal regulation loop to safely limit junction temperature. The LT3909 also includes internal compensation, internal soft-start and micropower shutdown. The LT3909 is available in the 12-pin (3mm × 3mm) DFN and 12-pin MSOP packages.

Where to Buy

Prices starting from US$169.48

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Analog Devices
from US$176.55
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Features

Up to 36V of LEDs, 2-String × 60mA LED Driver
Wide Input Range: 2.9V to 40V
Up to 40,000:1 PWM Dimming (250ns LED On-Time) (Independent of Leakage at VOUT)
±2% LED Current Matching (Typ ±0.3%)
Integrated Schottky Diode
Internal 400mΩ, 40V, 1A Switch
Single Resistor Sets LED Current (10mA to 60mA) for Both High-Side Current Sources
Output Adapts to LED VF for Optimum Efficiency
LED Current Regulated Even for VIN > VOUT
Fault Flag + Protection for Open-LED and LED-Short-to- GND (Other String Remains in Regulation)
Programmable Maximum VOUT (Regulated)
Internal Compensation, Soft-Start and Thermal Regulation
Accurate EN/UVLO Threshold
Fixed 2MHz Switching Frequency

Alternative Descriptions

LT3909EDD Demo Board - 7V # VI | Analog Devices
SEMICONDUCTOR DESIGNER KIT | Richardson RFPD

DC2176A Development Boards & Evaluation Kits by Linear Technology

DEMO BOARD LT3909 BOOST LED DRIVER

Education Maker & Hobbyist Electronics>Development Boards & Evaluation Kits>Lighting Development Kits
Status: Unknown
Series: -
RoHS: Unknown
Download Datasheet Visit Manufacturer Site View Pricing & Stock
Demonstration circuit 2176A features the LT®3909, a 2-string × 50mA, 2MHz step-up LED driver with ±1.8% current matching. The LT3909 precisely regulates two LED strings for equal current, supports LED dimming that reduces brightness down to a 1/40,000 ratio, protects against faults and also reports faults. The LT3909 consists of a step-up converter with a fixed 2MHz switching frequency and current sources for the LED strings. The operating voltage range for DC2176A is from 7V to 36V. The maximum current in each LED string is 40mA and is programmed by 24.9kΩ ISET resistor R1. The ISET resistor can be changed to 20.0kΩ to program the string current to 50mA – see the data sheet for an application example with 50mA string current. The LT3909 utilizes voltage feedback during PWM dimming and when there are faults on both LED strings. Voltage feedback resistors R2 and R3 on DC2176A optimize operation for LEDs that are 35V maximum. Efficiency is 86% at 12V input, 35V for the LED string forward voltages and 40mA per string. LED current can be reduced by an external voltage applied to the CTRL terminal. Resistor R8 pulls up CTRL to the INTVCC voltage of the LT3909 so the LED current is at the 40mA maximum when there is no external CTRL voltage applied. There are placeholders to add voltage dividers either from VIN or INTVCC to the CTRL pin. A voltage divider from VIN to the CTRL pin can be used to reduce LED current at low input voltages. A resistor divider from INTVCC to CTRL allows an NTC to reduce LED current at high temperatures. There are placeholders for an RC filter between the CTRL terminal and the CTRL pin. The RC filter limits the ramp time of the CTRL pin and prevent false faults when CTRL ramps too quickly. The FAULT terminal is pulled up by 100kΩ R6 to VIN, but there is a placeholder to pull up FAULT to INTVCC instead. Resistor divider R4 and R5 from the input to the EN/UVLO pin programs the circuit to turn off when VIN decreases below 5V with 0.9V of hysteresis. The circuit can also be turned off by connecting the EN/UVLO terminal to ground. An external voltage must be applied to the PWM terminal in order for DC2176A to operate. The external voltage can be a DC level or an appropriate PWM dimming signal. A common frequency for PWM dimming is 100Hz. There is a placeholder for a resistor to pull up PWM to INTVCC so an external voltage on PWM for operation is unnecessary. There is a placeholder that allows an external diode to be placed in parallel with the internal LT3909 rectifier for higher current capability. DC2176A uses an inductor that is optimized for high efficiency, and the input supply for power to the inductor can be separated from the LT3909 VIN pin to allow operation from two input sources. Ceramic capacitors are used at the input, output and for INTVCC. A 50V tantalum polymer capacitor protects the input from ringing that may occur when the input is hot-plugged using long leads. There are placeholders occupied by 0805 size 0Ω jumpers on the back of the PCB for two LED strings and also placeholders for SOD323 diodes to clamp the LED1 and LED2 voltages from ringing below ground. 2-string operation, close current matching, an extremely wide dimming range and fault protection make the LT3909 ideal for functionally advanced back lighting and illumination circuits. DC2176A features the LT3909EDD in a thermally enhanced 12-lead 3mm × 3mm DFN package. The LT3909 data sheet must be read in conjunction with this demo manual to properly use or modify DC2176A.

Features

Specifications

Device Topology Boost (Step Up)
No. of Outputs 2Outputs
Output Current 40mA
Output Voltage 35V
Input Voltage Min 7V
Input Voltage Max 36V
Core Chip LT3909
Dimming Control Type PWM
Kit Contents Demo Board LT3909
Product Range -
SVHC No SVHC (15-Jan-2018)

Frequently Asked Questions

Where can I find additional details, specifications and documents for a DC2176A?

Additional datasheets, footprints and schematics for DC2176A are listed on our Part Details page. You can also find images and similar parts to DC2176A on this page.

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What category does DC2176A fall under?

The DC2176A is listed under Step-Up (Boost) LED Drivers.

Can I view similar or alternative parts?

You can view similar parts to DC2176A when available in the Step-Up (Boost) LED Drivers range under the specifications section at the bottom of the details page.

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Is the DC2176A RoHS compliant?

Yes. This part has been flagged as RoHS Compliant by Analog Devices.

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Authorised distributors including Analog Devices and Richardson RFPD have stock available or on a lead time for DC2176A.

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