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Texas Instruments LM3503SQX-25/NOPB
- Part No.:
- LM3503SQX-25/NOPB
- Manufacturer:
- Texas Instruments
- Category:
- LED Drivers
- Package:
- 16-WFQFN Exposed Pad
- Datasheet:
-
LM3503SQX-25/NOPB.pdf
- Description:
- IC LED DRV RGLTR PWM 16WQFN
- Quantity:
- Payment:
- Shipping:
Inventory:3,472
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Product details
Overview
LM3503SQX-25/NOPB from Texas Instruments is a dual-display constant-current white LED driver IC with analog brightness control, 25V over-voltage protection, 1 MHz switching frequency, and 2.5–5.5 V input range-designed for portable device backlighting with independent MAIN/SUB display control.
For engineers reviewing the LM3503SQX-25/NOPB datasheet, LM3503SQX-25/NOPB pinout, LM3503SQX-25/NOPB application, or LM3503SQX-25/NOPB equivalent, this page delivers verified technical context, package-specific pin functions, real-world dimming behavior, OVP threshold accuracy, and validated alternative options for dual-LED-string backlight systems.
Technical Context
The LM3503SQX-25/NOPB implements an asynchronous current-mode PWM boost controller with integrated dual FET switches (PMOS at VOUT1, NMOS at VOUT2) to drive two independent white LED strings-MAIN (VOUT1–VOUT2) and SUB (VOUT2–Fb)-each configurable for 2–5 LEDs. It uses cycle-by-cycle current limiting and dedicated UVP/OVP comparators.
Its analog brightness control operates via Cntrl pin voltage (0.2–3.5 V), which linearly sets feedback reference (VFb = 0.156 × VCntrl), enabling precise LED current regulation without external DACs. Soft-start prevents inrush, and thermal shutdown activates above +150°C junction temperature.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output OVP Threshold | 22.5–25.5 V (on-threshold); enables safe operation with 25 V-rated output capacitors and protects against open-string faults |
| Switching Frequency | 0.8–1.2 MHz (typ. 1 MHz); allows compact external inductor (e.g., 2.2 µH) and reduces EMI filtering burden |
| Input Voltage Range | 2.5–5.5 V; supports single-cell Li-ion (3.0–4.2 V) and USB-powered systems without pre-regulation |
| LED Current Control | Cntrl pin voltage (0.2–3.5 V) → VFb = 0.156 × VCntrl → ILED = VFb / RSET; enables smooth analog dimming |
| Efficiency Peak | >80% (at 15 mA, VIN = 3.6 V, 4 LEDs); minimizes thermal load in space-constrained handheld PCBs |
| Enable Logic Thresholds | En1/En2 high-threshold ≥1.4 V (ON), low-threshold ≤0.3 V (OFF); supports direct GPIO control from 1.8/3.3 V MCUs |
| Junction Temp Range | −40°C to +125°C; qualified for industrial and extended-temperature portable applications |
Pinout & Package
LM3503SQX-25/NOPB is packaged in a 16-pin WQFN (RGH0016A) with 3.5 mm × 3.5 mm footprint and <1 mm height. The exposed DAP must be soldered to PCB ground for thermal performance (θJA = 49°C/W).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VIN | Input power supply connection | Accepts 2.5–5.5 V; requires local 4.7 µF ceramic capacitor to minimize input ripple and EMI |
| Sw | Power NMOS switch drain | Connects to inductor and Schottky diode anode; high dv/dt node requiring short, wide trace routing |
| En1 | MAIN display PMOS switch enable | Drives MAIN string (VOUT1–VOUT2); ≤0.3 V disables MAIN, ≥1.4 V enables MAIN |
| En2 | SUB display NMOS switch enable | Drives SUB string (VOUT2–Fb); ≤0.3 V disables SUB, ≥1.4 V enables SUB |
| Fb | Feedback voltage sensing node | Monitors regulated output voltage; connects to resistor divider from VOUT2 for closed-loop control |
| Cntrl | Analog brightness control input | DC voltage (0.2–3.5 V) sets VFb and thus LED current; compatible with RC-filtered PWM signals |
| AGND | Analog ground reference | Must be tied directly to PGND near device to avoid noise coupling into feedback path |
| PGND | Power ground return | High-current return path for Sw, VOUT1, VOUT2; requires low-impedance connection to DAP |
| VOUT1 | OVP sense node & PMOS source | Connects to cathodes of MAIN LEDs; OVP comparator monitors this pin for 25 V fault detection |
| VOUT2 | Drain of internal PMOS/NMOS switches | Interconnect node between MAIN and SUB strings; 100 nF capacitor required if unused |
Key Features
| Feature | Design Value |
|---|---|
| Dual independent LED string control | Separate En1/En2 pins allow MAIN and SUB displays to be enabled/disabled independently-enabling split-screen UI modes |
| 25 V over-voltage protection | Hardware-comparator-based OVP triggers at 22.5–25.5 V on VOUT1, preventing damage during LED open-circuit conditions |
| Analog brightness interface | Cntrl pin accepts DC voltage or filtered PWM signal (≥10× RC bandwidth), eliminating need for external DAC or microcontroller PWM peripherals |
| Internal soft-start | Gradually ramps current limit at startup to suppress inrush current into output capacitors and LED strings |
| Thermal shutdown | Halts switching when junction temperature exceeds +150°C, protecting IC and adjacent components during sustained overload |
| 1 MHz fixed-frequency operation | Enables use of small, low-profile inductors (e.g., DO1608C-223) and simplifies EMI filter design vs. variable-frequency PFM schemes |
Applications
| Smartphone Dual-Display Backlight | Tablet Secondary Screen Driver |
|---|---|
|
Use Scenario: Driving MAIN (top half) and SUB (bottom half) white LED strings in foldable smartphones with independent brightness zones. IC Role / Device Role / Timing Role: Constant-current boost driver with dual-switch architecture and hardware-enforced 25 V OVP. Use Value: Enables localized dimming without MCU intervention; OVP prevents catastrophic failure during hinge-related LED disconnection. |
Use Scenario: Powering auxiliary status display (e.g., e-ink companion screen) alongside primary LCD backlight in tablets. IC Role / Device Role / Timing Role: Dual-output LED driver with independent enable logic and shared analog dimming control. Use Value: Reduces BOM count by replacing two discrete drivers; En2 pin allows SUB display to remain active while MAIN is off. |
| Portable Medical Device UI | Industrial Handheld Terminal |
|
Use Scenario: Illuminating high-reliability diagnostic display panels where LED open-circuit must not damage driver or system. IC Role / Device Role / Timing Role: Fault-tolerant LED driver with UVP, OVP, thermal shutdown, and cycle-by-cycle current limiting. Use Value: 25 V OVP threshold matches common 20–24 V LED string configurations; eliminates need for external protection circuitry. |
Use Scenario: Backlighting ruggedized front-panel displays operating across −40°C to +85°C ambient range. IC Role / Device Role / Timing Role: Wide-input, thermally robust LED driver with guaranteed operation from −40°C to +125°C junction. Use Value: Maintains >80% efficiency at 15 mA even at −40°C, ensuring consistent brightness in cold storage or outdoor environments. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar dual-display LED driver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LM3503SQX-16/NOPB | 16 V OVP threshold; lower maximum output voltage capability | Suitable only for ≤12 V LED strings; cannot replace LM3503SQX-25/NOPB in 20+ V configurations | Select only when system-level OVP margin permits lower threshold and LED string voltage is ≤14 V |
| LM3503SQX-44/NOPB | 44 V OVP threshold; identical pinout, timing, and control interface | Supports longer LED strings (up to 10 LEDs @ 3.2 V each); higher output capacitance tolerance | Drop-in replacement where higher OVP headroom is needed; same layout, no firmware changes required |
Compared with LM3503SQX-16/NOPB, LM3503SQX-25/NOPB provides 9 V higher OVP headroom for robustness in variable-string-length designs; compared with LM3503SQX-44/NOPB, it offers tighter OVP tolerance (±1.5 V vs ±2.5 V) for improved precision in mid-voltage applications.
Availability
LM3503SQX-25/NOPB is available at Aetrix Electronics and suitable for smartphone backlighting, medical display illumination, and industrial handheld terminals requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.
Supply support for LM3503SQX-25/NOPB 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 leader specializing in analog and embedded processing technologies, with decades of expertise in power management and LED lighting solutions.
The LM3503 product line was engineered specifically for dual-display portable electronics, delivering integrated dual-FET switching, analog dimming, and hardware fault protection in ultra-low-profile packages.
FAQ
What is the exact over-voltage protection threshold for LM3503SQX-25/NOPB?
The LM3503SQX-25/NOPB has a guaranteed OVP on-threshold of 22.5–25.5 V and off-threshold of 21.5–24.5 V on the VOUT1 pin. This 25 V rating is factory-trimmed and applies across −40°C to +125°C junction temperature, enabling reliable open-string fault response without external clamping.
Can LM3503SQX-25/NOPB drive both MAIN and SUB displays simultaneously?
Yes, LM3503SQX-25/NOPB can drive both MAIN and SUB displays simultaneously when En1 ≥1.4 V and En2 ≥1.4 V. In this state, the internal PMOS (P1) and NMOS (N2) switches conduct, routing current through both LED segments-verified in the Operational Characteristics Table (Figure 4) and supported by typical application schematics.
What is the minimum Cntrl pin voltage required to achieve zero LED current with LM3503SQX-25/NOPB?
Applying VCntrl = 0 V does not guarantee zero LED current due to internal amplifier offsets in LM3503SQX-25/NOPB. To ensure full LED turn-off, both En1 and En2 must be driven ≤0.3 V to place the device in shutdown mode-where leakage is limited to 0.1–3 µA per VOUT pin.
Does LM3503SQX-25/NOPB require external compensation components?
No, LM3503SQX-25/NOPB operates with no external compensation. Its current-mode PWM architecture, cycle-by-cycle current limiting, and integrated error amplifier eliminate the need for loop compensation networks-reducing BOM count and layout sensitivity versus voltage-mode boost controllers.
What thermal resistance value applies to LM3503SQX-25/NOPB in its WQFN package?
LM3503SQX-25/NOPB in the 16-pin WQFN (RGH0016A) package has a junction-to-ambient thermal resistance (θJA) of 49°C/W when mounted on a standard 4-layer PCB with the DAP fully soldered to an internal ground plane-per TI's SNVS329E datasheet, Section 6.5.
LM3503SQX-25/NOPB Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- -
- Package/Case:
- 16-WFQFN 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):
- 2.5V
- Voltage - Supply (Max):
- 5.5V
- Voltage - Output:
- 25V
- Current - Output / Channel:
- 600mA (Switch)
- Frequency:
- 1MHz
- Dimming:
- Analog, PWM
- Applications:
- Backlight
- Operating Temperature:
- -40°C ~ 85°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 16-WQFN (4x4)
LM3503SQX-25/NOPB FAQ
1.How can I place an order for LM3503SQX-25/NOPB through Aetrix?
Please submit a Request for Quotation (RFQ) for LM3503SQX-25/NOPB 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 LM3503SQX-25/NOPB reliable?
The price and inventory of LM3503SQX-25/NOPB are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LM3503SQX-25/NOPB is usually 5 days.
3.What payment methods are accepted for LM3503SQX-25/NOPB?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LM3503SQX-25/NOPB transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LM3503SQX-25/NOPB?
LM3503SQX-25/NOPB orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM3503SQX-25/NOPB 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 LM3503SQX-25/NOPB?
For technical support, including LM3503SQX-25/NOPB datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM3503SQX-25/NOPB requirements.
6.How does Aetrix verify that LM3503SQX-25/NOPB is sourced from the original manufacturer or authorized distributors?
All LM3503SQX-25/NOPB 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 LM3503SQX-25/NOPB meets industry standards.
7.What is the process for return or replacement of LM3503SQX-25/NOPB?
All LM3503SQX-25/NOPB units undergo pre-shipment inspection (PSI). If there is an issue with LM3503SQX-25/NOPB, 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 LM3503SQX-25/NOPB part is unused and in its original packaging.
Return procedure for LM3503SQX-25/NOPB:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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