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Analog Devices Inc. LT3909HMSE#TRPBF
- Part No.:
- LT3909HMSE#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- LED Drivers
- Package:
- 12-TSSOP (0.118", 3.00mm Width) Exposed Pad
- Datasheet:
-
LT3909HMSE#TRPBF.pdf
- Description:
- IC LED DRV RGLTR PWM 50MA 12MSOP
- Quantity:
- Payment:
- Shipping:
Inventory:1,716
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Product details
Overview
LT3909HMSE#TRPBF from Analog Devices (formerly Linear Technology) is a 2-string, 60mA high-side LED driver IC with integrated 2MHz step-up DC/DC converter, ±2% current matching, and programmable output voltage regulation up to 36V. It delivers precise constant-current drive for automotive instrument clusters and high-contrast displays requiring stable brightness across temperature and supply variation.
For engineers reviewing the LT3909HMSE#TRPBF datasheet, LT3909HMSE#TRPBF pinout, LT3909HMSE#TRPBF application, or LT3909HMSE#TRPBF equivalent, key selection criteria include its 2MHz fixed-frequency boost architecture, dual high-side current sources with <±0.3% typical matching, 40,000:1 PWM dimming capability at 100Hz, integrated 400mΩ/40V/1A switch, and fault-flag–based open-LED/short-to-GND protection.
Technical Context
The LT3909HMSE#TRPBF integrates a peak-current-mode 2MHz boost controller with two independent high-side current sources, each regulated via internal GM1 loop to maintain VOUT–VLEDx at 1.3V for optimal efficiency. Its FB pin enables programmable OVP regulation (1.215V reference) during fault conditions or PWM off-time to prevent VOUT droop from Schottky leakage.
Operation combines analog dimming (CTRL pin, 0–1V, up to 10:1) and PWM dimming (PWM pin, 100Hz–25kHz, up to 40,000:1), with independent fault detection per string: open-LED (VOUT–VLEDx < 0.4V) and LED-short-to-GND (VLEDx < 6.0V). Thermal foldback and internal soft-start ensure robust startup and junction temperature control.
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); enables uniform brightness in dual-string configurations. |
| Current Matching Accuracy | ±2% (typ ±0.3%) - ensures consistent luminance between strings without external calibration. |
| PWM Dimming Ratio | Up to 40,000:1 at 100Hz - achieves deep black levels in display backlights with 250ns minimum on-time. |
| Switching Frequency | 2MHz (±6%) - allows compact 3.3–10µH inductors and reduces EMI filtering requirements. |
| Integrated Power Switch | 400mΩ, 40V, 1A N-channel DMOS - eliminates external MOSFET, simplifies layout, and supports up to 36V LED stack. |
| Fault Protection | Open-LED & LED-short-to-GND detection per string with active-low FAULT flag - maintains regulation in unaffected string during fault. |
Pinout & Package
LT3909HMSE#TRPBF is housed in a 12-lead plastic MSOP package (3mm × 4.9mm) with exposed pad (Pin 13) soldered to PCB ground for thermal management (θJA = 40°C/W).
| 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. |
| VIN (2) | Main input supply | Accepts 2.9–40V; requires local ceramic bypass; powers internal regulator and switch. |
| EN/UVLO (3) | Enable & undervoltage lockout input | 0.4V shutdown / 1.215V enable threshold; supports programmable UVLO with resistor divider. |
| ISET (4) | LED current programming input | Single resistor to GND sets both string currents (10–60mA); 16.7kΩ = 60mA per string. |
| CTRL (5) | Analog dimming control | 0–1V input scales LED current linearly; <80mV disables output; supports NTC-based thermal derating. |
| FB (6) | Output voltage feedback | Sets programmable OVP level (1.215V reference); samples VOUT during PWM on-time for stable off-time regulation. |
| PWM (7) | Digital dimming control | Active-high signal; controls high-side current source enable/disable; supports >40,000:1 dimming ratio. |
| FAULT (8) | Fault status flag | Open-drain, active-low output indicating open-LED or short-to-GND on either LED string. |
| LED1 / LED2 (9,10) | High-side LED current outputs | Each drives one LED string; can be paralleled for higher current; tolerate up to 40V relative to GND. |
| VOUT (11) | Boost converter output | Regulated node feeding LED strings; requires low-ESR ceramic capacitor (≥1µF for VOUT < 20V). |
| SW (12) | Power switch drain | Connects to inductor and internal Schottky anode; minimize trace area to reduce EMI. |
| GND (13, Exposed Pad) | Power and thermal ground | Exposed pad must be soldered to solid PCB ground plane for thermal performance and noise immunity. |
Key Features
| Feature | Design Value |
|---|---|
| Integrated Schottky diode | Eliminates external diode, reducing BOM count and board space while maintaining efficiency at 2MHz switching. |
| Internal compensation & soft-start | Reduces external component count; ensures controlled inrush current and stable startup without external RC networks. |
| Thermal regulation loop | Derates LED current automatically above 125°C junction temperature to prevent permanent device degradation. |
| VOUT adaptive regulation | Maintains only the minimum VOUT needed to sustain LED current, improving efficiency across VF variations and temperature. |
| Independent per-string fault handling | One string failure (open or short) does not disrupt regulation of the other string - critical for safety-critical displays. |
Applications
| Automotive Instrument Clusters | High-Contrast Display Backlighting |
|---|---|
|
Use Scenario: Driving dual-color (e.g., red/green) LED arrays behind analog gauges and digital TFT overlays in vehicle dashboards. IC Role / Device Role / Timing Role: Dual high-side constant-current source with adaptive VOUT regulation and synchronized PWM dimming. Use Value: Ensures identical brightness and color point across strings despite varying LED forward voltage and ambient temperature shifts. |
Use Scenario: Backlighting industrial HMIs and medical displays requiring deep dimming and flicker-free operation. IC Role / Device Role / Timing Role: 2MHz boost controller with 40,000:1 PWM dimming and sub-250ns on-time capability. Use Value: Enables true black-level rendering and eliminates visible PWM artifacts at 100Hz–25kHz frequencies. |
| GPS Receiver Status Indicators | PDA & Handheld Computer UI Lighting |
|
Use Scenario: Powering multi-segment LED indicators showing satellite lock status, signal strength, and navigation mode. IC Role / Device Role / Timing Role: Low-quiescent-current (600µA) LED driver with EN/UVLO hysteresis for battery-powered operation. Use Value: Extends runtime in portable GPS units while maintaining reliable fault detection during intermittent power conditions. |
Use Scenario: Illuminating keypad backlight and status LEDs in legacy PDAs operating from single-cell Li-ion or alkaline supplies. IC Role / Device Role / Timing Role: Wide-input (2.9–40V), single-resistor-programmed LED driver with analog + PWM dimming flexibility. Use Value: Simplifies firmware design by enabling brightness control via either CTRL voltage or PWM signal - no hardware change required. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar LED driver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT3909EMSE#TRPBF | Same die, same pinout, but specified for –40°C to 125°C (E-grade) vs. –40°C to 125°C (H-grade); identical electrical specs. | No functional difference; H-grade offers enhanced screening for high-reliability automotive use cases. | Select LT3909HMSE#TRPBF when AEC-Q200 qualification or extended lifetime under thermal stress is required. |
| LT3909IMSE#TRPBF | Same architecture and pinout; I-grade rated for –40°C to 125°C with tighter initial parameter tolerances (e.g., ±1.8% current matching vs. ±2%). | Better matching and stability over temperature; preferred for precision lighting where binning is impractical. | Choose LT3909IMSE#TRPBF when system-level current matching tolerance must remain ≤±1.8% across full temp range. |
Compared with LT3909EMSE#TRPBF and LT3909IMSE#TRPBF, the LT3909HMSE#TRPBF provides identical functionality and pin compatibility but is characterized for higher reliability in sustained high-temperature environments - making it optimal for under-hood automotive modules and industrial displays with long MTBF targets.
Availability
LT3909HMSE#TRPBF is available at Aetrix Electronics and suitable for automotive instrument clusters, high-contrast display backlights, and portable GPS receivers requiring stable component supply, long-term lifecycle support, and AEC-Q200–aligned reliability.
Supply support for LT3909HMSE#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 acquired Linear Technology in 2017 and maintains full technical and manufacturing continuity for all Linear products, including rigorous process control and automotive-grade qualification protocols.
The LT3909 product line was designed specifically for high-reliability, dual-string LED backlighting in automotive and industrial displays - emphasizing current matching, fault resilience, and wide-input operation without external compensation.
FAQ
What is the maximum LED string voltage supported by the LT3909HMSE#TRPBF?
The LT3909HMSE#TRPBF supports up to 36V of total LED forward voltage per string. This is enabled by its internal 40V-rated 1A switch and 40V absolute maximum ratings on LED1/LED2 pins. The output voltage (VOUT) adapts dynamically to the lowest level needed to sustain the programmed LED current, optimizing efficiency across VF variations.
Can the LT3909HMSE#TRPBF drive a single LED string at 120mA?
Yes - the LT3909HMSE#TRPBF allows paralleling of LED1 and LED2 pins to combine both 60mA current sources into a single 120mA output. When doing so, connect both pins to the anode of one LED string and program ISET for 60mA per source (i.e., 16.7kΩ), resulting in 120mA total. Ensure thermal design accommodates doubled power dissipation in the IC.
Does the LT3909HMSE#TRPBF require external compensation components?
No - the LT3909HMSE#TRPBF features fully internal compensation. Its control loops (GM1 for current-source regulation and GM2 for VOUT OVP) are factory-tuned and do not require external capacitors or resistors. This simplifies layout, reduces BOM count, and ensures consistent stability across manufacturing lots and temperature ranges.
How does the LT3909HMSE#TRPBF handle an open-LED fault on one string?
When an open-LED fault occurs on LED1 or LED2, the LT3909HMSE#TRPBF asserts the FAULT pin low and disables regulation on the faulty string, while maintaining full regulation and dimming control on the healthy string. VOUT rises until limited by the FB-set OVP threshold (1.215V reference), protecting downstream components and preserving system functionality.
What is the minimum PWM on-time achievable with the LT3909HMSE#TRPBF?
The LT3909HMSE#TRPBF supports PWM on-times as low as 250ns while maintaining accurate current delivery - verified in datasheet Figure 3909 G21. This enables 40,000:1 dimming ratio at 100Hz and ensures clean LED current recovery at the rising edge of each PWM pulse, critical for flicker-free display operation.
LT3909HMSE#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:
- Obsolete
- 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
LT3909HMSE#TRPBF FAQ
1.How can I place an order for LT3909HMSE#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3909HMSE#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 LT3909HMSE#TRPBF reliable?
The price and inventory of LT3909HMSE#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3909HMSE#TRPBF is usually 5 days.
3.What payment methods are accepted for LT3909HMSE#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3909HMSE#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3909HMSE#TRPBF?
LT3909HMSE#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3909HMSE#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 LT3909HMSE#TRPBF?
For technical support, including LT3909HMSE#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3909HMSE#TRPBF requirements.
6.How does Aetrix verify that LT3909HMSE#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT3909HMSE#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 LT3909HMSE#TRPBF meets industry standards.
7.What is the process for return or replacement of LT3909HMSE#TRPBF?
All LT3909HMSE#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3909HMSE#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 LT3909HMSE#TRPBF part is unused and in its original packaging.
Return procedure for LT3909HMSE#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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