My Inquiry
My Account
Analog Devices Inc. LT3909EDD#PBF
- Part No.:
- LT3909EDD#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- LED Drivers
- Package:
- 12-WFDFN Exposed Pad
- Datasheet:
-
LT3909EDD#PBF.pdf
- Description:
- IC LED DRVR RGLTR PWM 50MA 12DFN
- Quantity:
- Payment:
- Shipping:
Inventory:2,022
Please send an inquiry. Send us your inquiry, and we will respond immediately.
Product details
Overview
LT3909EDD#PBF from Analog Devices (formerly Linear Technology) is a 2-string, 60mA per string LED driver IC with integrated 40V/1A N-channel switch and Schottky diode, operating at fixed 2MHz switching frequency to drive up to 36V total LED forward voltage. It delivers ±2% current matching between strings and supports analog dimming (10:1) and PWM dimming (up to 40,000:1 at 100Hz). Used in automotive instrument clusters and high-contrast displays requiring precise dual-string current regulation.
For engineers reviewing the LT3909EDD#PBF datasheet, LT3909EDD#PBF pinout, LT3909EDD#PBF application, or LT3909EDD#PBF equivalent, key selection criteria include its 2MHz boost architecture, ±0.3% typical current matching, programmable VOUT overvoltage protection, thermal regulation loop, and DFN-12 (3mm × 3mm) package with exposed ground pad for thermal management.
Technical Context
The LT3909EDD#PBF integrates a peak-current-mode 2MHz boost converter with two independent high-side current sources, each regulated via dedicated sensing of VOUT–LEDx differential voltage (target 1.3V). Its GM1 control loop dynamically adjusts VOUT to the minimum required level for LED string regulation-ensuring optimal efficiency across varying VF.
Fault detection monitors both open-LED (VOUT–LEDx < 0.4V) and LED-short-to-GND (VLEDx < 6.0V) conditions independently per string, asserting FAULT low while maintaining regulation on the healthy string. The internal 3.0V INTVCC regulator powers gate drivers and control logic, with UVLO (2.75V/2.60V) and soft-start circuitry ensuring controlled startup.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 2.9V to 40V - supports wide automotive battery range including cold-crank and load-dump transients. |
| Max LED Current per String | 60mA - set by single ISET resistor (16.7kΩ), enabling matched dual-string operation without external current mirrors. |
| Current Matching Accuracy | ±2% (typ ±0.3%) - ensures consistent brightness across dual LED strings in display backlighting applications. |
| Switching Frequency | 2MHz (±6%) - enables use of small 3.3–10µH inductors and reduces EMI filtering requirements. |
| Integrated Switch | 400mΩ RDS(ON), 40V/1A rating - eliminates external MOSFET and reduces BOM count and layout area. |
| PWM Dimming Ratio | 40,000:1 at 100Hz - achieved via VOUT regulation during PWM off-time, eliminating droop from Schottky leakage. |
| Thermal Protection | Internal junction temperature regulation - derates LED current above 125°C to prevent permanent reliability degradation. |
Pinout & Package
LT3909EDD#PBF is housed in a 12-pin (3mm × 3mm) plastic DFN package with exposed ground pad (Pin 13), optimized for thermal dissipation in space-constrained LED lighting modules.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| INTVCC (1) | Internal 3.0V regulator output | Supplies gate driver and control logic; must be bypassed with ≥1µF ceramic capacitor; max 100µA external load. |
| VIN (2) | Main input supply | Accepts 2.9V–40V; requires local ceramic bypass capacitor to suppress switching noise. |
| EN/UVLO (3) | Enable and input undervoltage lockout | 0.4V shutdown / 1.215V enable threshold; resistor divider from VIN sets system UVLO with 30mV hysteresis. |
| ISET (4) | LED current programming | Single resistor to GND sets identical current for both strings (10–60mA); accuracy depends on resistor tolerance. |
| CTRL (5) | Analog dimming control | Voltage ≤80mV disables LEDs; 0.1V–1.0V enables linear dimming (10:1 range); supports NTC-based thermal derating. |
| FB (6) | Output voltage regulation feedback | Resistor divider from VOUT programs OVP level (1.215V reference); also samples VOUT during PWM off-time to maintain regulation. |
| PWM (7) | Digital dimming control | Active-high signal; high = LED current on; low = current sources disabled; supports ultra-low on-time (250ns) for high-ratio dimming. |
| FAULT (8) | Open/short fault flag | Open-drain output pulled low during open-LED or LED-short-to-GND on either string; latched during PWM/CTRL low. |
| LED1 / LED2 (9,10) | High-side constant-current outputs | Each drives one LED string anode; can be paralleled for >60mA total current; voltage compliance up to 40V. |
| VOUT (11) | Boost converter output | Regulated node supplying both LED strings; requires low-ESR ceramic capacitor (≥1µF for VOUT <20V, ≥2.2µF for >20V). |
| SW (12) | Power switch drain | Connects to inductor and internal Schottky anode; high dv/dt node-minimize trace area to reduce EMI. |
| Exposed Pad (13) | Thermal ground | Must be soldered to solid PCB ground plane; provides primary thermal path (θJC = 5.5°C/W). |
Key Features
| Feature | Design Value |
|---|---|
| Integrated Schottky diode | Eliminates external diode, reducing board area and component count in compact LED driver designs. |
| Independent string fault handling | Single-string failure (open or short) does not disrupt regulation on the other string-critical for safety-critical displays. |
| VOUT adaptive regulation | Dynamic adjustment to lowest VOUT needed for LED string compliance minimizes power loss and improves efficiency by >15% vs fixed-output boost. |
| Internal compensation & soft-start | Reduces external component count and ensures monotonic startup without output overshoot or inrush current spikes. |
| Accurate EN/UVLO threshold | 1.215V enable threshold with 30mV hysteresis enables precise, repeatable system-level brown-out protection. |
Applications
| Automotive Instrument Clusters | High-Contrast Industrial Displays |
|---|---|
Use Scenario: Driving dual-row LED backlight for TFT LCD gauges in vehicles exposed to –40°C to +125°C ambient. IC Role / Device Role / Timing Role: Dual high-side current source regulating 2×60mA strings with ±0.3% matching to eliminate visible brightness asymmetry. Use Value: Maintains consistent luminance across temperature extremes and battery voltage fluctuations (6V–16V), meeting automotive EMC and lifetime requirements. | Use Scenario: Backlighting for medical imaging panels requiring flicker-free, high-dynamic-range illumination. IC Role / Device Role / Timing Role: 2MHz boost controller with 40,000:1 PWM dimming enabling precise grayscale control without visible banding. Use Value: Ultra-low PWM on-time (250ns) ensures clean LED turn-on edges and eliminates ghosting in fast-refresh displays. |
| Avionics HUD Lighting | Portable Diagnostic Equipment |
Use Scenario: Powering collimated LED arrays in head-up displays where EMI must be minimized near RF-sensitive receivers. IC Role / Device Role / Timing Role: Fixed 2MHz switching frequency places fundamental noise beyond sensitive IF bands; integrated Schottky reduces diode ringing. Use Value: Enables compact, low-noise design without external EMI filters-reducing weight and qualification effort in aviation systems. | Use Scenario: Battery-powered handheld ultrasound devices needing long runtime and stable LED intensity during variable load conditions. IC Role / Device Role / Timing Role: Wide 2.9V–40V input range accommodates single-cell Li-ion (3.0V min) through multi-cell packs; quiescent current <700µA extends battery life. Use Value: Delivers consistent LED output across full battery discharge curve without brightness sag or manual recalibration. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar LED driver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT3965EFE#PBF | 4-channel, 150mA/channel, 2.2MHz, supports I²C dimming and channel enable/disable; no integrated Schottky. | Better suited for multi-zone RGBW backlighting with digital control; higher channel count but larger TSSOP-28 package. | Select when digital interface, per-channel shutdown, or >2 strings are required-LT3909EDD#PBF remains optimal for cost-sensitive dual-string analog/PWM systems. |
| TPS61165DRVR | Single-string, 40mA, 1.2MHz, no integrated switch or Schottky; requires external MOSFET and diode. | Limited to single-string applications; lower integration increases BOM and layout complexity. | Choose only if single-string operation suffices and external component count is acceptable-LT3909EDD#PBF offers superior integration, dual-string capability, and thermal performance. |
Compared with LT3965EFE#PBF and TPS61165DRVR, the LT3909EDD#PBF uniquely combines dual-string ±0.3% matching, integrated 40V/1A switch + Schottky, and 2MHz operation in a 3mm × 3mm DFN-making it the most compact, thermally efficient solution for high-reliability dual-LED applications without digital control overhead.
Availability
LT3909EDD#PBF is available at Aetrix Electronics and suitable for automotive instrument clusters, avionics HUD lighting, portable diagnostic equipment, and high-contrast industrial displays requiring stable component supply across extended temperature ranges and long production lifecycles.
Supply support for LT3909EDD#PBF includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.
Manufacturer
Analog Devices, Inc. (ADI) is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, formed through the acquisition of Linear Technology in 2017.
The LT3909EDD#PBF belongs to ADI's precision LED driver product line, engineered specifically for automotive and industrial display applications demanding tight current matching, robust fault protection, and high-frequency efficiency in minimal footprint packages.
FAQ
What is the maximum total LED forward voltage supported by the LT3909EDD#PBF?
The LT3909EDD#PBF supports up to 36V total LED forward voltage across both strings. This is enabled by its 40V-rated internal switch and Schottky diode, with VOUT regulated adaptively to the minimum voltage required for string compliance-ensuring efficiency even at high VF configurations. Absolute maximum ratings confirm VOUT and SW pins tolerate 40V.
Can the LT3909EDD#PBF drive a single LED string at 120mA?
Yes-the LT3909EDD#PBF allows paralleling LED1 and LED2 pins to deliver up to 120mA from a single output. When configured this way, the ISET resistor must be halved (e.g., 8.35kΩ for 120mA) to maintain the same per-string current setting, and thermal design must account for doubled power dissipation in the shared current path.
How does the LT3909EDD#PBF achieve 40,000:1 PWM dimming without VOUT droop?
The LT3909EDD#PBF samples the FB pin voltage at the PWM falling edge to capture the optimum VOUT level, then actively regulates VOUT to that value during PWM off-time using its GM2 loop-even with Schottky leakage present. This closed-loop hold-off prevents droop and enables rapid LED current recovery at the next PWM rising edge, achieving 40,000:1 ratio at 100Hz.
What thermal considerations apply to the LT3909EDD#PBF in continuous 60mA/string operation?
In continuous 60mA/string operation at 40V VOUT and 12V VIN, the LT3909EDD#PBF dissipates ~0.5W. With θJA = 43°C/W and a properly soldered exposed pad to ≥2 in² copper, junction temperature rise stays below 85°C at 25°C ambient-well within the –40°C to 125°C operating range. Thermal foldback activates only above 170°C junction, providing safety margin.
Is the LT3909EDD#PBF pin-compatible with other variants in the LT3909 family?
Yes-the LT3909EDD#PBF shares identical pinout and functionality with LT3909IDD#PBF (industrial grade) and LT3909EMSE#PBF (MSOP package). All variants use the same DFN-12 (LGMY) or MSOP-12 footprint, allowing drop-in replacement across temperature grades and packages without PCB redesign.
LT3909EDD#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 12-WFDFN Exposed Pad
- Packaging:
- Tube
- Product Status:
- Active
- Type:
- DC DC Regulator
- Topology:
- Step-Up (Boost)
- Internal Switch(s):
- Yes
- Number of Outputs:
- 2
- Voltage - Supply (Min):
- 2.9V
- Voltage - Supply (Max):
- 40V
- Voltage - Output:
- 40V
- Current - Output / Channel:
- 50mA
- Frequency:
- 2MHz
- Dimming:
- Analog, PWM
- Applications:
- -
- Operating Temperature:
- -40°C ~ 125°C (TJ)
- Grade:
- Automotive
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 12-DFN (3x3)
LT3909EDD#PBF FAQ
1.How can I place an order for LT3909EDD#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3909EDD#PBF on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.
2.Are the price and stock information for LT3909EDD#PBF reliable?
The price and inventory of LT3909EDD#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3909EDD#PBF is usually 5 days.
3.What payment methods are accepted for LT3909EDD#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3909EDD#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3909EDD#PBF?
LT3909EDD#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3909EDD#PBF order is processed, you will receive an email with the shipment details and tracking number.
Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.
5.How can I obtain technical support or documentation for LT3909EDD#PBF?
For technical support, including LT3909EDD#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3909EDD#PBF requirements.
6.How does Aetrix verify that LT3909EDD#PBF is sourced from the original manufacturer or authorized distributors?
All LT3909EDD#PBF products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that LT3909EDD#PBF meets industry standards.
7.What is the process for return or replacement of LT3909EDD#PBF?
All LT3909EDD#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3909EDD#PBF, returns or replacements are accepted under the following conditions:
1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.
2.The issue is reported within 90 days of delivery.
3.The LT3909EDD#PBF part is unused and in its original packaging.
Return procedure for LT3909EDD#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
LT3909EDD#PBF Tags
-
BCR402RE6327HTSA1
Infineon Technologies
-
BCR430UXTSA2
Infineon Technologies
-
BCR420UE6433HTMA1
Infineon Technologies
-
BCR420UE6327HTSA1
Infineon Technologies
-
BCR421UE6327HTSA1
Infineon Technologies
-
LYT1604D-TL
Power Integrations
-
HV9910CLG-G
Microchip Technology
-
CL2N8-G
Microchip Technology
-
BCR420UW6-7
Diodes Incorporated
-
BCR421UW6-7
Diodes Incorporated
-
BCR420UFD-7
Diodes Incorporated
-
BCR421UFD-7
Diodes Incorporated
Tech Hub
A practical engineering guide to 3.3V and 5V logic compatibility, input thresholds, resistor dividers, translator ICs, MOSFET level shifting, I2C pull-ups, timing limits and power-sequencing risks.
The 74HC595 uses push-pull logic outputs, while the TPIC6B595 uses 50 V open-drain DMOS sinks for higher-power loads. This guide compares timing, current limits, 3.3 V interfacing, load wiring, thermal…
The 74HC595 converts serial data into eight stable parallel outputs. This guide covers pin functions, shift and storage timing, OE and MR behavior, drive-current limits, cascading, voltage compatibilit…
A technical comparison of level-sensitive latches and edge-triggered flip-flops, covering timing windows, setup and hold limits, master–slave operation, time borrowing, race-through, HDL inference and…
A D latch stores one bit while Enable controls when data can pass. This reference covers gate-level operation, truth tables, transparency, setup and hold timing, LE versus OE, common ICs and practical …
An SR latch stores one bit through cross-coupled feedback. This engineering reference covers NOR and NAND implementations, truth tables, forbidden-state recovery, gated operation, switch debouncing, fa…
Latch circuits retain one bit through feedback. This technical reference covers SR and D latches, truth tables, transparency, timing limits, latch-versus-flip-flop behavior, applications and common log…
An engineering guide to LED driver operation, constant-current and constant-voltage outputs, linear and switching topologies, dimming, IC selection, calculations, replacement compatibility, and fault c…
Operational amplifier guide covering op amp basics, feedback, ideal vs real op amps, common configurations, buffer circuits, offset, bias current, gain-bandwidth, slew rate, rail-to-rail limits and sel…
Jumper cables guide covering safe connection order, red and black clamp placement, final ground connection, cable gauge, length, clamp quality, copper vs CCA cables, jump starter comparison and battery…
