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Analog Devices Inc. LT3909EMSE#TRPBF
- Part No.:
- LT3909EMSE#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- LED Drivers
- Package:
- 12-TSSOP (0.118", 3.00mm Width) Exposed Pad
- Datasheet:
-
LT3909EMSE#TRPBF.pdf
- Description:
- IC LED DRV RGLTR PWM 50MA 12MSOP
- Quantity:
- Payment:
- Shipping:
Inventory:2,796
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Product details
Overview
LT3909EMSE#TRPBF from Analog Devices (formerly Linear Technology) is a 2-string, 60mA per string, fixed-frequency 2MHz step-up LED driver IC with ±2% current matching and integrated 40V/1A power switch and Schottky diode. It regulates LED current via high-side constant-current sources, adapts VOUT to LED forward voltage for optimal efficiency, and supports analog dimming (10:1) and ultra-high-ratio PWM dimming (up to 40,000:1 at 100Hz). It is used in automotive instrument clusters requiring precise dual-string brightness control under wide input voltage (2.9V–40V).
For engineers reviewing the LT3909EMSE#TRPBF datasheet, LT3909EMSE#TRPBF pinout, LT3909EMSE#TRPBF application, or LT3909EMSE#TRPBF equivalent, key selection criteria include its 2MHz switching frequency, ±2% inter-string current matching (typical ±0.3%), programmable 10–60mA LED current via single ISET resistor, fault-flag diagnostics for open-LED and LED-short-to-GND, and thermal regulation with junction temperature limiting.
Technical Context
The LT3909EMSE#TRPBF integrates a peak-current-mode boost converter with two independent high-side current sources, each regulated by a dedicated feedback loop monitoring VOUT–LEDx differential voltage (target 1.3V). Its internal 2MHz oscillator enables compact magnetics and low EMI, while slope compensation ensures stability above 50% duty cycle.
It features dual protection architecture: GM1 loop maintains optimal VOUT during normal operation by regulating the lower of the two VOUT–LEDx voltages; GM2 loop activates during faults or PWM off-time to regulate FB and clamp VOUT at a user-programmable OVP level (via RFB1/RFB2), preventing overvoltage damage when strings disconnect/reconnect.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Switching Frequency | Fixed 2MHz - enables use of small inductors (e.g., 3.3–10µH) and reduces output ripple without increasing EMI filtering complexity. |
| LED Current Range | 10mA to 60mA per string - set precisely with one external resistor (RISET), eliminating need for matched current-sense resistors or DACs. |
| Current Matching | ±2% (typical ±0.3%) - ensures consistent brightness across dual LED strings without optical calibration, critical for automotive display uniformity. |
| PWM Dimming Ratio | Up to 40,000:1 at 100Hz - achieved via VOUT regulation during PWM off-time, eliminating droop from Schottky leakage and enabling fast current recovery. |
| Input Voltage Range | 2.9V to 40V - supports direct connection to automotive battery (cold-crank to load-dump) and industrial 24V rails without pre-regulation. |
| Integrated Switch | 400mΩ, 40V, 1A DMOS FET - reduces BOM count and PCB area; eliminates external MOSFET layout sensitivity and gate-drive design effort. |
| Thermal Protection | Internal junction temperature regulation - dynamically derates LED current above threshold to prevent thermal runaway, extending reliability in sealed enclosures. |
Pinout & Package
LT3909EMSE#TRPBF is housed in a 12-lead plastic MSOP package (3mm × 4.9mm) with exposed pad (Pin 13) for thermal enhancement. The exposed pad must be soldered to a continuous PCB ground plane to achieve θJA = 40°C/W and ensure stable operation at full load.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| INTVCC (1) | Internal 3.0V regulator output | Supplies gate driver and control circuits; bypass with ≥1µF ceramic capacitor; max 100µA external load allowed. |
| VIN (2) | Main input supply | Accepts 2.9V–40V; requires local ceramic bypass capacitor; powers INTVCC regulator and switch driver. |
| EN/UVLO (3) | Enable and input undervoltage lockout | Accurate 1.215V falling threshold; resistor divider from VIN sets system UVLO with 30mV hysteresis. |
| ISET (4) | LED current programming input | Single resistor to GND sets identical current for both strings (10–60mA); no trimming required. |
| CTRL (5) | Analog dimming and fault latch-off control | Voltage <80mV disables LEDs; 0.1V–1.0V provides 10:1 analog dimming; supports NTC-based thermal derating. |
| FB (6) | Output voltage regulation feedback | Programs OVP level (e.g., 36V) during faults; sampled during PWM on-time to maintain VOUT during off-time. |
| PWM (7) | Digital dimming control | Active-low signal; controls high-side current sources directly; enables 40,000:1 dimming without VOUT droop. |
| FAULT (8) | Open-LED / short-to-GND flag | Active-low open-drain output; asserts when VOUT–LEDx <0.3V (open) or VLEDx <6.0V (short); other string remains regulated. |
| LED1 / LED2 (9,10) | High-side LED current source outputs | Each delivers regulated current to LED string anode; cathodes connect to GND; pins may be paralleled for >60mA total. |
| VOUT (11) | Boost converter output | Drives LED strings; connects to output capacitor; voltage adapts dynamically to lowest required level for LED VF. |
| SW (12) | Internal switch drain / Schottky anode | Connects to inductor; carries peak switch current; minimize trace area to reduce EMI radiation. |
| Exposed Pad (13) | Thermal ground | Must be soldered to solid copper ground plane; primary path for heat dissipation; electrically GND. |
Key Features
| Feature | Design Value |
|---|---|
| Integrated Schottky diode | Eliminates external diode, saving 2–3mm² PCB area and reducing bill-of-materials in space-constrained displays. |
| ±2% inter-string current matching | Ensures luminance uniformity between left/right instrument cluster segments without post-manufacturing calibration. |
| Programmable VOUT overvoltage protection | Prevents LED overvoltage stress during hot-plug events or intermittent string disconnection using standard FB resistor divider. |
| Internal soft-start and compensation | Removes need for external compensation network or soft-start timing capacitor-reduces design iteration time. |
| Accurate EN/UVLO threshold | Enables robust system-level brown-out protection with <1% tolerance, supporting automotive cold-crank (4.5V) and load-dump (40V) compliance. |
| Micropower shutdown | Draws only 0.3µA at VIN=12V when disabled-critical for always-on vehicle modules meeting ISO 16750 quiescent current limits. |
Applications
| Automotive Instrument Clusters | High-Contrast GPS Displays |
|---|---|
|
Use Scenario: Dual-row TFT backlight driving in digital dashboards with variable ambient lighting conditions. IC Role / Device Role / Timing Role: Dual high-side current source LED driver with adaptive VOUT regulation and synchronized PWM dimming. Use Value: Maintains consistent color and brightness across temperature (-40°C to 125°C) and input voltage transients (load dump), meeting UNECE R128 photometric requirements. |
Use Scenario: Compact handheld GPS units requiring sunlight-readable display with minimal power draw. IC Role / Device Role / Timing Role: Fixed-frequency boost LED driver with 40,000:1 PWM dimming and micropower shutdown. Use Value: Enables seamless transition from indoor (low-brightness) to outdoor (high-brightness) modes while extending battery life via ultra-low shutdown current (0.3µA). |
| Industrial HMI Panels | Avionics Status Indicators |
|
Use Scenario: Ruggedized human-machine interface panels in factory automation with wide input voltage (12–36V DC). IC Role / Device Role / Timing Role: Fault-tolerant dual-string LED driver with open-LED detection and thermal foldback. Use Value: Continues operation of one LED string during failure of the other, providing fail-operational status indication per IEC 61508 SIL2 requirements. |
Use Scenario: Red/green status annunciators in cockpit displays requiring EMI resilience and deterministic response. IC Role / Device Role / Timing Role: 2MHz-switching LED driver with internal slope compensation and low-noise regulation. Use Value: Meets DO-160 Section 20 radiated emissions limits without added ferrite beads or shielding, simplifying avionics certification. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar dual-string LED driver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT3965EFE#TRPBF | 4-channel, 150mA/channel, 3MHz switching, 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 28-lead TSSOP package. | Select when digital addressability, per-channel fault reporting, or >2 strings are required; not drop-in due to different pinout and control interface. |
| TPS61165DRVR | Single-string, 40mA, 1.2MHz, no integrated switch or Schottky; requires external MOSFET and diode; ±5% current matching. | Lower cost for single-string applications; lacks dual-string matching, fault flag, and thermal regulation. | Select only for cost-sensitive single-string designs where ±5% matching and absence of thermal foldback are acceptable. |
Compared with LT3909EMSE#TRPBF, LT3965EFE#TRPBF offers greater flexibility for complex lighting systems but increases layout complexity and component count, while TPS61165DRVR reduces integration and precision at the expense of fault resilience and thermal safety-making LT3909EMSE#TRPBF optimal for dual-string automotive displays demanding robustness and accuracy.
Availability
LT3909EMSE#TRPBF is available at Aetrix Electronics and suitable for automotive instrument clusters, industrial HMI panels, and avionics status indicators requiring stable component supply, long-term lifecycle support, and AEC-Q200-aligned reliability.
Supply support for LT3909EMSE#TRPBF 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. (acquired Linear Technology in 2017) is a global leader in high-performance analog, mixed-signal, and power management semiconductors, serving automotive, industrial, communications, and aerospace markets.
The LT3909 belongs to Linear's high-reliability LED driver product line, designed specifically for automotive-grade dual-string backlighting with emphasis on current matching, fault tolerance, and thermal robustness in harsh environments.
FAQ
What is the maximum LED string voltage supported by the LT3909EMSE#TRPBF?
The LT3909EMSE#TRPBF supports up to 36V of total LED forward voltage per string. Its internal 40V-rated switch and Schottky diode, combined with adaptive VOUT regulation that tracks the minimum required voltage above LED VF, enable efficient operation across wide VF ranges (e.g., 10 white LEDs at ~3.2V each). Absolute maximum VOUT is limited to 40V per absolute ratings.
How does the LT3909EMSE#TRPBF achieve 40,000:1 PWM dimming without VOUT droop?
The LT3909EMSE#TRPBF samples the FB pin voltage during the PWM high period to capture the optimal VOUT level needed for LED regulation, then actively regulates VOUT to that stored value during the PWM low period-even with leakage from the internal Schottky diode. This closed-loop VOUT hold function prevents droop and ensures instantaneous LED current recovery at the next PWM rising edge, enabling the full 40,000:1 ratio at 100Hz.
Can the LT3909EMSE#TRPBF drive a single LED string at 120mA?
Yes-the LT3909EMSE#TRPBF allows paralleling of LED1 and LED2 pins to combine both high-side current sources. With RISET set for 60mA per string, paralleling yields 120mA total into one string. Thermal performance must be verified: the MSOP package's θJA = 40°C/W requires adequate copper area on the exposed pad to maintain TJ < 125°C at full load and ambient up to 85°C.
What protection features does the LT3909EMSE#TRPBF provide for open-LED and short-to-GND faults?
The LT3909EMSE#TRPBF continuously monitors VOUT–LEDx (open-LED threshold: <0.3V) and VLEDx (short-to-GND threshold: <6.0V). Upon detection, it asserts the active-low FAULT pin and disables only the affected string-leaving the other string fully regulated. During dual-string faults, it clamps VOUT at a user-programmed OVP level via the FB resistor divider to protect downstream components.
Is the LT3909EMSE#TRPBF pin-compatible with other variants in the LT3909 family?
Yes-the LT3909EMSE#TRPBF shares identical pinout and functionality with LT3909EDD#TRPBF (DFN), LT3909IMSE#TRPBF (industrial-temp MSOP), and LT3909IDD#TRPBF (industrial-temp DFN). All use the same 12-pin configuration, including exposed pad (Pin 13), and require identical external components; only package type and temperature grade differ.
LT3909EMSE#TRPBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 12-TSSOP (0.118", 3.00mm Width) Exposed Pad
- Packaging:
- Tape & Reel (TR)
- 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-MSOP-EP
LT3909EMSE#TRPBF FAQ
1.How can I place an order for LT3909EMSE#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3909EMSE#TRPBF 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 LT3909EMSE#TRPBF reliable?
The price and inventory of LT3909EMSE#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3909EMSE#TRPBF is usually 5 days.
3.What payment methods are accepted for LT3909EMSE#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3909EMSE#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3909EMSE#TRPBF?
LT3909EMSE#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3909EMSE#TRPBF 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 LT3909EMSE#TRPBF?
For technical support, including LT3909EMSE#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3909EMSE#TRPBF requirements.
6.How does Aetrix verify that LT3909EMSE#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT3909EMSE#TRPBF 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 LT3909EMSE#TRPBF meets industry standards.
7.What is the process for return or replacement of LT3909EMSE#TRPBF?
All LT3909EMSE#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3909EMSE#TRPBF, 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 LT3909EMSE#TRPBF part is unused and in its original packaging.
Return procedure for LT3909EMSE#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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