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Texas Instruments LM3503SQX-16
- Part No.:
- LM3503SQX-16
- Manufacturer:
- Texas Instruments
- Category:
- LED Drivers
- Package:
- 16-WFQFN Exposed Pad
- Datasheet:
-
LM3503SQX-16.pdf
- Description:
- IC LED DRV RGLTR PWM 16WQFN
- Quantity:
- Payment:
- Shipping:
Inventory:4,287
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Product details
Overview
LM3503SQX-16 from Texas Instruments is a dual-display constant-current white LED driver IC with analog brightness control, 16 V over-voltage protection, 1 MHz switching frequency, and 2.5–5.5 V input range-designed for portable device backlighting driving up to 10 LEDs across MAIN and SUB segments.
For engineers reviewing the LM3503SQX-16 datasheet, LM3503SQX-16 pinout, LM3503SQX-16 application, or LM3503SQX-16 equivalent, this page delivers verified technical context, package mapping, real-world use cases, and validated alternative options for dual-string LED backlight designs requiring stable current regulation and independent display enable control.
Technical Context
The LM3503SQX-16 implements an asynchronous current-mode PWM boost controller with integrated NMOS power switch (N1), PMOS bypass switch (P1), and NMOS segment switch (N2). It regulates LED current via feedback voltage (VFb = 0.55 V typ) controlled by an external DC voltage on the Cntrl pin (0.2–3.5 V range).
It features dual enable logic (En1/En2) for independent MAIN/SUB display activation, cycle-by-cycle current limiting (450–750 mA typ for 16 V version), internal soft start, and dedicated protection blocks including under-voltage lockout (UVP: 2.5 V on-threshold) and over-voltage protection (OVP: 15.5 V on-threshold).
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 2.5 V to 5.5 V - supports single-cell Li-ion or 3.3 V/5 V system rails without external LDO. |
| Output OVP Threshold | 15.5 V (typ) - protects against open-circuit LED failure or string removal in 16 V variant. |
| Switching Frequency | 1 MHz (±20%) - enables compact external components (e.g., 2.2 µH inductor, 1 µF ceramic output cap). |
| Feedback Voltage | 0.55 V (typ) - sets regulated LED current via external sense resistor (ILED = VFb / RSENSE). |
| Current Limit (ICL) | 450–750 mA (typ) - peak NMOS switch current limit ensures safe operation with 2–5 LEDs per string. |
| Efficiency | >80% (peak) - achieved at typical loads (e.g., 15 mA × 4 LEDs @ VIN = 3.6 V). |
| Enable Thresholds | En1/En2 high-level ≥1.4 V, low-level ≤0.3 V - compatible with standard GPIO outputs without level-shifting. |
Pinout & Package
LM3503SQX-16 is housed in a 16-pin WQFN package (RGH0016A) with 0.4 mm pitch and <1 mm height, featuring exposed thermal pad (DAP) soldered to PCB ground plane for enhanced thermal dissipation.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VIN | Input supply connection | Accepts 2.5–5.5 V; requires local 4.7 µF ceramic capacitor between VIN and PGND. |
| Sw | Drain of internal NMOS power switch (N1) | Connects to inductor and Schottky diode anode; minimize trace length/width to reduce EMI. |
| En1 | PMOS FET (P1) control for MAIN display | ≥1.4 V enables MAIN segment; ≤0.3 V disables MAIN; internal pull-down defaults to OFF. |
| En2 | NMOS FET (N2) control for SUB display | ≥1.4 V enables SUB segment; ≤0.3 V disables SUB; internal pull-down defaults to OFF. |
| Fb | Feedback voltage sensing node | Monitors output current via external resistor; regulated at 0.55 V (typ) for precise ILED control. |
| Cntrl | Analog brightness control input | DC voltage (0.2–3.5 V) sets VFb linearly; enables smooth analog dimming without PWM filtering. |
| AGND | Analog ground reference | Must be connected directly to PGND to avoid noise coupling into feedback path. |
| PGND | Power ground return | High-current return path for Sw, VOUT1, VOUT2; connect to PCB ground plane with multiple vias. |
| VOUT1 | OVP sense & PMOS source (P1) | Connects to MAIN LED string cathode; OVP circuit monitors this node for 16 V threshold. |
| VOUT2 | Drain of NMOS/NMOS switches (N2/P1) | Connects to SUB LED string cathode; unused pin requires 100 nF capacitor to PGND for stability. |
| L | Inductor connection point | Not a pin - label on schematic indicating inductor placement between Sw and VOUT1/VOUT2. |
| D | Diode anode connection | Not a pin - label on schematic indicating Schottky diode anode tied to Sw, cathode to VOUT1. |
Key Features
| Feature | Design Value |
|---|---|
| Dual independent display control | Separate En1/En2 pins allow MAIN and SUB LED strings to be enabled/disabled independently - essential for clamshell phones or dual-screen PDAs. |
| Analog brightness control | Cntrl pin accepts 0.2–3.5 V DC to linearly scale LED current without external RC filtering - eliminates PWM flicker and EMI from dimming signals. |
| Integrated protection suite | Includes UVP (2.5 V), OVP (15.5 V), thermal shutdown, soft-start, and cycle-by-cycle current limiting - reduces BOM count and improves field reliability. |
| Compact 16-pin WQFN | 16-lead WQFN (3 mm × 3 mm, 0.4 mm pitch) with DAP enables high-density layout in space-constrained handhelds. |
| High-efficiency boost topology | Asynchronous current-mode architecture achieves >80% peak efficiency driving 4–10 white LEDs - extends battery life in portable applications. |
Applications
| Clamshell Mobile Phone Backlight | Handheld PDA Dual-Screen Lighting |
|---|---|
Use Scenario: Simultaneous or selective illumination of inner and outer displays in flip-style mobile phones. IC Role / Device Role / Timing Role: Constant-current LED driver managing two independent LED strings (MAIN: inner screen; SUB: outer screen) with independent enable control. Use Value: Enables zero-flicker analog dimming per display and dynamic power gating - reducing average current draw by up to 50% when only one display is active. | Use Scenario: Powering front and rear LCD panels in enterprise PDAs used for inventory scanning and data entry. IC Role / Device Role / Timing Role: Dual-output boost driver regulating current for two separate LED arrays, each with 2–5 series-connected white LEDs. Use Value: Eliminates need for two discrete drivers; single IC supports flexible UI modes (e.g., main screen only, secondary screen only, or both) via GPIO-controlled En1/En2. |
| Portable Media Player Display | Smart Remote Control Backlight |
Use Scenario: Driving high-brightness backlight for color TFT display while maintaining battery runtime in audio/video players. IC Role / Device Role / Timing Role: High-efficiency boost converter delivering stable 15–20 mA per LED across 4–6 series LEDs with analog dimming. Use Value: >80% efficiency at 3.6 V input minimizes heat generation and extends playback time - critical for thermally constrained plastic enclosures. | Use Scenario: Illuminating segmented button backlight in RF-enabled smart remotes with dual-zone visual feedback. IC Role / Device Role / Timing Role: Low-quiescent-current LED driver (0.1 µA shutdown) enabling always-on IR functionality with periodic backlight activation. Use Value: Ultra-low shutdown current preserves coin-cell battery life for years; fast wake-up (<100 µs) ensures responsive user interface. |
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-25 | Higher OVP threshold (24 V typ); same pinout, package, and control logic. | Suitable for longer LED strings (up to 8 LEDs per segment) or higher forward-voltage displays. | Select when VOUT exceeds 16 V under worst-case LED VF drift and temperature variation. |
| TPS61165DRVR | Single-output, 40-V OVP, I²C programmable, no En2/En1 dual-enable logic. | Requires external logic or MCU firmware to emulate dual-string control; lacks native SUB/MAN enable separation. | Choose only if system already uses I²C infrastructure and can implement software-based dual-string sequencing. |
Compared with LM3503SQX-25 and TPS61165DRVR, the LM3503SQX-16 provides native hardware-level dual-display enable control and optimal OVP margin for 4–6 LED strings - simplifying design, reducing firmware overhead, and eliminating external logic gates required by alternatives.
Availability
LM3503SQX-16 is available at Aetrix Electronics and suitable for portable consumer electronics, handheld industrial terminals, and medical display devices requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.
Supply support for LM3503SQX-16 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 delivering analog, embedded processing, and connectivity solutions for industrial, automotive, and personal electronics markets.
The LM3503 product line was engineered specifically for dual-display LED backlighting in space- and power-constrained portable devices - emphasizing analog dimming fidelity, independent segment control, and robust protection for unattended operation.
FAQ
What is the maximum number of LEDs the LM3503SQX-16 can drive per string?
The LM3503SQX-16 supports 2 to 5 white LEDs per string in MAIN or SUB configuration, for a total of up to 10 LEDs. This is determined by its 16 V over-voltage protection threshold and typical white LED forward voltage (3.0–3.6 V per diode), allowing up to five 3.2 V LEDs (16 V ÷ 3.2 V ≈ 5) in series without triggering OVP during normal operation.
How does the Cntrl pin control LED brightness in the LM3503SQX-16?
The Cntrl pin accepts a DC voltage from 0.2 V to 3.5 V, which linearly scales the internal feedback reference (VFb = 0.156 × VCntrl). Since LED current is calculated as ILED = VFb / RSENSE, adjusting VCntrl directly modulates ILED - enabling smooth, flicker-free analog dimming without external PWM filtering or microcontroller intervention.
What happens when both En1 and En2 are pulled low on the LM3503SQX-16?
When both En1 and En2 are ≤0.3 V, the LM3503SQX-16 enters full shutdown mode: all internal switches (N1, P1, N2) turn off, quiescent current drops to 0.1–3 µA, and the output capacitor discharges through the LED string and feedback resistor. This state ensures zero LED current and minimal battery drain - critical for standby operation in portable devices.
Can the LM3503SQX-16 operate with only the MAIN display active?
Yes. To activate only the MAIN display, apply ≥1.4 V to En1 and ≤0.3 V to En2. This configures the LM3503SQX-16 to turn on the PMOS switch (P1) while keeping the NMOS switch (N2) off - routing current exclusively through the MAIN LED string connected between VOUT1 and PGND. The SUB string remains electrically isolated.
Is an external Schottky diode required for the LM3503SQX-16, and what are its key specs?
Yes, an external Schottky diode is mandatory between Sw and VOUT1. TI recommends the B150-13 (150 V, 1 A, low VF ~0.45 V) or equivalent. It must be placed as close as possible to the LM3503SQX-16's Sw and VOUT1 pins to minimize trace inductance and EMI - critical for stable 1 MHz switching and efficient energy transfer to the LED load.
LM3503SQX-16 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:
- 16V
- Current - Output / Channel:
- 400mA (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-16 FAQ
1.How can I place an order for LM3503SQX-16 through Aetrix?
Please submit a Request for Quotation (RFQ) for LM3503SQX-16 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-16 reliable?
The price and inventory of LM3503SQX-16 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LM3503SQX-16 is usually 5 days.
3.What payment methods are accepted for LM3503SQX-16?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LM3503SQX-16 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LM3503SQX-16?
LM3503SQX-16 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM3503SQX-16 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-16?
For technical support, including LM3503SQX-16 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM3503SQX-16 requirements.
6.How does Aetrix verify that LM3503SQX-16 is sourced from the original manufacturer or authorized distributors?
All LM3503SQX-16 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-16 meets industry standards.
7.What is the process for return or replacement of LM3503SQX-16?
All LM3503SQX-16 units undergo pre-shipment inspection (PSI). If there is an issue with LM3503SQX-16, 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-16 part is unused and in its original packaging.
Return procedure for LM3503SQX-16:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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