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Texas Instruments LM3405XMKX
- Part No.:
- LM3405XMKX
- Manufacturer:
- Texas Instruments
- Category:
- LED Drivers
- Package:
- SOT-23-6 Thin, TSOT-23-6
- Datasheet:
-
LM3405XMKX.pdf
- Description:
- IC LED DRV RGLTR PWM 1A TSOT23-6
- Quantity:
- Payment:
- Shipping:
Inventory:4,191
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Product details
Overview
LM3405XMKX from Texas Instruments is a 1.6-MHz, 1-A constant-current buck LED driver in SOT-6 package, featuring 0.205-V feedback reference, 300-mΩ internal NMOS switch, and EN/DIM pin for PWM dimming. It drives up to five high-brightness LEDs in series and supports input voltages from 3 V to 15 V, making it suitable for portable LED flashlights and industrial lighting systems.
For engineers reviewing the LM3405XMKX datasheet, LM3405XMKX pinout, LM3405XMKX application, or LM3405XMKX equivalent, key selection criteria include its fixed 1.6-MHz switching frequency, thermal shutdown protection, cycle-by-cycle current limit, UVLO with 440-mV hysteresis, and ability to operate with ceramic output capacitors and small-surface-mount inductors.
Technical Context
The LM3405XMKX uses current-mode control with internal compensation, enabling stable regulation across wide input (3–15 V) and load (200 mA–1 A) ranges without external loop compensation. Its 1.6-MHz oscillator allows compact passive component selection, while the BOOST/SW bootstrap architecture sustains gate drive voltage between 2.5 V and 5.5 V for optimal RDS(ON) performance.
LED current is set by a single external resistor (R1) via the FB pin, where IF = 0.205 V / R1; minimum R1 is ~0.2 Ω for 1-A operation. The EN/DIM pin provides both enable control and PWM dimming (100 Hz–5 kHz), with 1.8-V enable threshold and 0.4-V shutdown threshold, plus 0.3-µA shutdown quiescent current at VIN = 5 V.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Switching frequency | 1.6 MHz (fixed); enables use of sub-2.2-µH inductors and 10-µF ceramic output capacitors |
| Feedback reference voltage | 0.205 V ±0.017 V; sets LED current with <0.1% line regulation error over 3–15 V input range |
| Internal NMOS RDS(ON) | 300 mΩ typical; limits conduction loss to ≤300 mW at 1-A load, supporting >90% efficiency at mid-load |
| Input voltage range | 3 V to 15 V; supports single-cell Li-ion (3.0–4.2 V) and 12-V industrial rails without pre-regulation |
| UVLO threshold | 2.95 V rising / 2.3 V falling; 440-mV hysteresis prevents oscillation during brownout conditions |
| Shutdown current | 0.3 µA typical at VIN = 5 V; enables battery-powered flashlight designs with multi-year shelf life |
| Current limit | 2 A typical cycle-by-cycle limit; protects internal switch during short-circuit or startup overload |
Pinout & Package
LM3405XMKX is housed in a thermally enhanced 6-pin SOT-6 (DDC) package measuring 2.90 mm × 1.60 mm, with exposed pad for improved thermal dissipation (RθJA = 182.9°C/W). Pin 1 is marked by a dot; device orientation follows JEDEC MO-178 standard.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| BOOST | Bootstrap supply output | Drives NMOS gate; requires external capacitor to SW; must maintain 2.5–5.5 V above SW for full RDS(ON) performance |
| GND | Signal and power ground | Reference for FB, EN/DIM, and internal circuitry; bottom resistor of feedback network must connect here |
| FB | Current-sense feedback input | Senses 0.205-V reference; connects to LED string cathode; sets IF = 0.205 V / R1 |
| EN/DIM | Enable and PWM dimming input | Logic-high (>1.8 V) enables regulator; PWM signal (100 Hz–5 kHz) controls average LED brightness |
| VIN | Main input supply | Accepts 3–15 V; requires local 1-µF ceramic bypass capacitor to GND for stability |
| SW | Power switch node | Connects to inductor, catch diode anode, and BOOST capacitor; swings from GND to VIN − IF×RDS(ON) |
Key Features
| Feature | Design Value |
|---|---|
| Internally compensated current-mode control | Eliminates need for external compensation components; ensures stable operation across all recommended operating conditions |
| 1.6-MHz fixed-frequency PWM | Reduces EMI filtering requirements and enables use of 1.0–2.2-µH shielded inductors under 3 mm height |
| 0.205-V precision feedback reference | Minimizes power loss in current-setting resistor; supports ±3% LED current accuracy with 1% R1 |
| Thermal shutdown with 15°C hysteresis | Shuts down at 165°C junction temperature; resumes operation only after cooling to ~150°C, preventing thermal runaway |
| Overcurrent protection at 328 mV FB threshold | Clamps LED current overshoot to ≤1.6× nominal during transients; complements cycle-by-cycle current limit |
Applications
| Portable LED Flashlights | Industrial Panel Lighting |
|---|---|
|
Use Scenario: High-intensity handheld illumination powered by single Li-ion cell (3.0–4.2 V). IC Role / Device Role / Timing Role: Constant-current buck regulator maintaining 1-A LED drive despite battery voltage sag. Use Value: Delivers consistent lumen output over full discharge curve; 0.3-µA shutdown current extends shelf life beyond 5 years. |
Use Scenario: DIN-rail mounted LED strip drivers in factory control panels requiring 12-V input. IC Role / Device Role / Timing Role: Primary LED current controller with EN/DIM interface for PLC-based dimming commands. Use Value: 1.6-MHz switching avoids audible noise; thermal shutdown protects against enclosure overheating in sealed enclosures. |
| Automotive Interior Lighting | Emergency Exit Signage |
|
Use Scenario: Map light and dome light modules operating from 9–16-V vehicle battery with cold-crank immunity. IC Role / Device Role / Timing Role: UVLO-protected LED driver ensuring turn-on only above 2.95 V, avoiding flicker during cranking. Use Value: 440-mV UVLO hysteresis prevents cycling during transient dips; 15-V max input withstands load-dump events. |
Use Scenario: Battery-backed exit sign with red LEDs requiring fail-safe constant current during AC outage. IC Role / Device Role / Timing Role: Primary current source during backup mode, controlled via microcontroller EN/DIM signal. Use Value: 0.3-µA shutdown current minimizes battery drain; overcurrent protection prevents LED failure during capacitor charging surges. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar constant-current LED driver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LM3404MHX/NOPB | Higher 1.6-A current capability; 1-MHz switching; SO-8 package with better thermal performance (RθJA = 62°C/W) | Preferred for >1-A LED strings or higher ambient temperature environments (>85°C) | Select when board space permits SO-8 and higher current or thermal margin is required |
| TPS92515HVDGQR | Integrated high-side current sense; 2.2-MHz operation; supports analog + PWM dimming; 3-mm × 3-mm WQFN | Enables true high-side sensing for grounded-cathode LED configurations and tighter current matching | Choose for designs requiring high-side sensing, smaller footprint, or dual dimming modes |
Compared with LM3405XMKX, LM3404MHX/NOPB offers higher current and superior thermal handling but requires larger layout area, while TPS92515HVDGQR delivers advanced dimming flexibility and compact packaging at the cost of higher BOM complexity and unit price.
Availability
LM3405XMKX is available at Aetrix Electronics and suitable for portable LED flashlights, industrial panel lighting, and automotive interior lighting requiring stable component supply, long-term lifecycle support, and traceable sourcing.
Supply support for LM3405XMKX 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
Texas Instruments is a global semiconductor company headquartered in Dallas, Texas, delivering analog and embedded processing solutions for industrial, automotive, and personal electronics markets.
The LM3405XMKX belongs to TI's LED driver product line, engineered specifically for high-efficiency, low-component-count constant-current LED regulation in space-constrained and thermally demanding applications.
FAQ
What is the maximum number of LEDs the LM3405XMKX can drive in series?
The LM3405XMKX can drive up to five high-brightness LEDs in series at 1-A forward current, assuming each LED has a typical forward voltage of ~3.7 V. With a maximum input voltage of 15 V and 0.205-V feedback reference, the total LED string voltage must not exceed approximately 14.8 V (15 V − VSW drop − diode drop). The exact count depends on individual LED VF at 1 A, as specified in the LED manufacturer's datasheet. LM3405XMKX does not regulate voltage - only current - so string voltage is determined solely by the connected LEDs.
Does the LM3405XMKX require external compensation components?
No, the LM3405XMKX features internally compensated current-mode control, eliminating the need for external compensation networks. This simplifies design, reduces BOM count, and ensures stable regulation across the full operating range (3–15 V input, 200 mA–1 A load, –40°C to 125°C junction temperature) without tuning. The internal compensation is optimized for standard ceramic output capacitors and 1.0–2.2-µH inductors used in typical LED buck applications.
What is the purpose of the BOOST pin on the LM3405XMKX?
The BOOST pin on the LM3405XMKX supplies gate drive voltage to the internal NMOS power switch. It connects to a bootstrap capacitor between BOOST and SW pins, generating a voltage 2.5–5.5 V above SW to fully enhance the switch and minimize RDS(ON). During normal operation, BOOST is charged from VIN (via D2) or VOUT, depending on circuit configuration. Proper BOOST voltage is critical for efficiency - insufficient voltage increases conduction loss, while exceeding 5.5 V risks damage. LM3405XMKX includes internal charge pump initialization to ensure reliable startup.
Can the LM3405XMKX be used with PWM dimming frequencies above 5 kHz?
No - the LM3405XMKX is characterized for reliable PWM dimming only between 100 Hz and 5 kHz. Above 5 kHz, the dimming ratio degrades significantly due to the ~100-µs delay between EN/DIM signal assertion and full LED current establishment. At 10 kHz, for example, the on-time may be too short for the internal soft-start and current-loop settling, resulting in inconsistent brightness and potential current undershoot. For high-frequency dimming (>10 kHz), consider alternatives like the TPS92515HVDGQR, which supports seamless analog + PWM dimming up to 25 kHz.
How does the LM3405XMKX handle thermal overload conditions?
The LM3405XMKX incorporates thermal shutdown that disables the internal NMOS switch when junction temperature exceeds 165°C. Operation resumes only after the die cools to approximately 150°C, providing 15°C hysteresis to prevent rapid cycling. This protection is independent of current limit and UVLO functions. In practice, with the SOT-6 package's RθJA of 182.9°C/W, continuous 1-A operation at ambient >65°C typically requires PCB copper pour or airflow. LM3405XMKX data sheet recommends ≥1 in² of 2-oz copper connected to the exposed pad for optimal thermal performance.
LM3405XMKX Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- -
- Package/Case:
- SOT-23-6 Thin, TSOT-23-6
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Discontinued at Digi-Key
- Type:
- DC DC Regulator
- Topology:
- Step-Down (Buck)
- Internal Switch(s):
- Yes
- Number of Outputs:
- 1
- Voltage - Supply (Min):
- 3V
- Voltage - Supply (Max):
- 15V
- Voltage - Output:
- 13.5V
- Current - Output / Channel:
- 1A
- Frequency:
- 1.6MHz
- Dimming:
- PWM
- Applications:
- Lighting
- Operating Temperature:
- -40°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- TSOT-23-6
LM3405XMKX FAQ
1.How can I place an order for LM3405XMKX through Aetrix?
Please submit a Request for Quotation (RFQ) for LM3405XMKX 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 LM3405XMKX reliable?
The price and inventory of LM3405XMKX are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LM3405XMKX is usually 5 days.
3.What payment methods are accepted for LM3405XMKX?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LM3405XMKX transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LM3405XMKX?
LM3405XMKX orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM3405XMKX 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 LM3405XMKX?
For technical support, including LM3405XMKX datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM3405XMKX requirements.
6.How does Aetrix verify that LM3405XMKX is sourced from the original manufacturer or authorized distributors?
All LM3405XMKX 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 LM3405XMKX meets industry standards.
7.What is the process for return or replacement of LM3405XMKX?
All LM3405XMKX units undergo pre-shipment inspection (PSI). If there is an issue with LM3405XMKX, 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 LM3405XMKX part is unused and in its original packaging.
Return procedure for LM3405XMKX:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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