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Texas Instruments LM3503SQX-35
- Part No.:
- LM3503SQX-35
- Manufacturer:
- Texas Instruments
- Category:
- LED Drivers
- Package:
- 16-WFQFN Exposed Pad
- Datasheet:
-
LM3503SQX-35.pdf
- Description:
- IC LED DRV RGLTR PWM 16WQFN
- Quantity:
- Payment:
- Shipping:
Inventory:4,831
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Product details
Overview
LM3503SQX-35 from Texas Instruments is a dual-display constant-current white LED driver IC with analog brightness control, 35V over-voltage protection, 1 MHz switching frequency, and 2.5V–5.5V input range-designed for portable device backlighting with independent MAIN/SUB display control.
For engineers reviewing the LM3503SQX-35 datasheet, LM3503SQX-35 pinout, LM3503SQX-35 application, or LM3503SQX-35 equivalent, key selection factors include OVP threshold (32–35 V), dual enable logic (En1/En2), Cntrl-pin analog dimming interface, and WQFN-16 package thermal performance (θJA = 49°C/W).
Technical Context
The LM3503SQX-35 implements an asynchronous current-mode PWM boost controller with cycle-by-cycle current limiting, dedicated OVP comparator (35V trip), and dual internal FET switches (PMOS at VOUT1, NMOS at VOUT2) enabling independent MAIN/SUB LED string control. It integrates soft-start, UVP (2.5V), thermal shutdown, and light-load PFM mode.
Its feedback loop uses a precision 0.55 V reference with Cntrl-pin voltage scaling (VFb = 0.156 × VCntrl), supporting analog dimming across 0.2–3.5 V input. The device operates in continuous or discontinuous conduction mode depending on inductor value, load current, and VIN–VOUT differential.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| OVP Threshold | 32.0–35.0 V - sets maximum output voltage to protect LEDs and external diode/capacitor under open-circuit or failure conditions |
| Switching Frequency | 0.8–1.2 MHz - enables compact magnetics (e.g., 2.2 µH inductor) and reduces EMI filtering burden |
| Input Voltage Range | 2.5–5.5 V - supports single-cell Li-ion (3.0–4.2 V) and dual-cell alkaline/NiMH (2.4–3.6 V) battery inputs |
| Feedback Voltage | 0.55 V (typ) - stable reference for LED current regulation; VFb scales linearly with Cntrl pin voltage |
| Current Limit (35V version) | 450–1050 mA - peak NMOS switch current limit ensures safe operation with up to 10 white LEDs (2×5 or 4×2 configuration) |
| Quiescent Current | 0.5–1.0 mA (non-switching), 1.9–3.0 mA (switching) - minimizes battery drain in standby and active backlight modes |
| Junction Temp Range | −40°C to +125°C - qualified for industrial and extended-temperature portable applications |
Pinout & Package
LM3503SQX-35 is housed in a 16-pin WQFN package (RGH0016A) with 3.0 mm × 3.0 mm footprint and 0.5 mm pitch; exposed DAP enhances thermal dissipation to PCB ground plane.
| 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 high-frequency noise and input ripple |
| Sw | Drain of internal NMOS power switch | Connects to boost inductor; low-inductance layout critical to reduce EMI and switching losses |
| En1 / En2 | PMOS/NMOS FET enable controls | Logic-level inputs (0.3 V / 1.4 V thresholds) configure MAIN/SUB display activation or full shutdown |
| Fb | Feedback node for LED current regulation | Senses voltage across external sense resistor; closed-loop control maintains constant current despite Vf drift |
| Cntrl | Analog dimming control input | 0.2–3.5 V DC input linearly adjusts LED current via internal transconductance amplifier |
| VOUT1 | Source of PMOS switch & OVP sensing node | Drives MAIN LED string; OVP circuit monitors this pin to disable switching if voltage exceeds 35 V |
| VOUT2 | Drain of NMOS bypass switch | Drives SUB LED string; must be grounded or bypassed with 100 nF if unused (per LM3503-35/44 spec) |
| PGND / AGND | Power and analog ground returns | Separate pins require star-point connection to minimize noise coupling into feedback path |
Key Features
| Feature | Design Value |
|---|---|
| Dual independent LED string control | En1/En2 pins allow MAIN-only, SUB-only, both-on, or full shutdown - eliminates need for external multiplexing circuitry |
| 35 V over-voltage protection | Hardware-enforced clamp prevents damage during LED string open-circuit or thermal runaway; enables use of low-profile ceramic output capacitors |
| Analog brightness control | Cntrl pin accepts DC voltage (not PWM) for flicker-free dimming without external RC filter complexity |
| 1 MHz fixed-frequency PWM | Enables use of small 2.2 µH inductors and reduces audible noise vs. lower-frequency boost converters |
| Integrated soft-start | Gradually ramps current limit at startup to prevent inrush current spikes into input capacitance and battery |
Applications
| Cellular Phone Dual Display | PDA Main/Sub Backlight |
|---|---|
Use Scenario: Simultaneous illumination of main LCD and secondary status OLED in clamshell or slider phones. IC Role / Device Role / Timing Role: Constant-current boost driver with independent MAIN/SUB enable logic and analog dimming per display zone. Use Value: Enables differentiated brightness levels (e.g., 15 mA MAIN, 5 mA SUB) using single IC and shared inductor, reducing BOM count by 30% vs. dual-driver solution. | Use Scenario: Powering primary touchscreen backlight and auxiliary keypad/indicator LEDs in handheld PDAs. IC Role / Device Role / Timing Role: Dual-output LED driver with programmable current per channel and coordinated shutdown sequencing. Use Value: Eliminates separate boost converters; En1/En2 logic allows synchronized or staggered turn-on to avoid input current surges exceeding 1 A. |
| Portable Media Player UI | Smartwatch Dual-Segment Display |
Use Scenario: Driving high-brightness main screen and low-power notification bar in MP3/video players. IC Role / Device Role / Timing Role: Analog-dimming-capable boost controller with 35 V OVP for robustness against LED failure in compact form factor. Use Value: Maintains consistent luminance across temperature (±0.5% VFb drift from −40°C to +85°C), critical for color-accurate media playback. | Use Scenario: Illuminating circular main display and segmented battery/status indicator in ultra-thin wearable devices. IC Role / Device Role / Timing Role: Low-profile WQFN-16 LED driver with thermal-aware operation (θJA = 49°C/W) and sub-1 mA quiescent current in shutdown. Use Value: Enables <1.0 mm total height design while delivering >80% efficiency at 10 mA per string - extending coin-cell battery life beyond 7 days. |
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 | 25 V OVP threshold; lower current limit (400–800 mA); identical pinout and control interface | Suitable only for ≤6 LED strings (e.g., 3+3) due to reduced OVP headroom and current capability | Select when system VOUT never exceeds 23 V and cost sensitivity outweighs future-proofing for higher-Vf LEDs |
| LM3503SQX-44 | 44 V OVP threshold; same current limit range (450–1050 mA); identical timing, dimming, and package | Supports longer LED strings (e.g., 5+5 at 3.4 V each → 34 V max) and higher-reliability designs requiring margin above 35 V | Choose for next-gen displays with higher forward voltage LEDs or where field failure modes demand ≥40 V OVP headroom |
Compared with LM3503SQX-25 and LM3503SQX-44, the LM3503SQX-35 provides optimal balance of OVP margin (35 V), current drive (up to 1050 mA), and compatibility with common 3.0–3.6 Vf white LED stacks - making it the default choice for 4–8 LED dual-display systems operating from 3.6 V nominal battery rails.
Availability
LM3503SQX-35 is available at Aetrix Electronics and suitable for portable consumer electronics, handheld industrial HMIs, and wearable display modules requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.
Supply support for LM3503SQX-35 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, embedded processing, and power management technologies with broad automotive, industrial, and personal electronics reach.
The LM3503 product line delivers highly integrated, thermally efficient LED drivers for space-constrained dual-display applications - emphasizing analog dimming fidelity, hardware fault protection, and minimal external component count.
FAQ
What is the over-voltage protection threshold for LM3503SQX-35?
The LM3503SQX-35 features a factory-trimmed over-voltage protection threshold of 32.0–35.0 V (typical 34.0 V). This hardware-based clamp disables the internal NMOS switch if VOUT1 exceeds the threshold, protecting external components during LED string open-circuit events. The specification is validated per Electrical Characteristics Table row "OVP" under "On Threshold (35)" in the SNVS329E datasheet.
Can LM3503SQX-35 drive two independent LED strings with different currents?
No - the LM3503SQX-35 regulates total current through a single feedback loop (Fb pin), so MAIN and SUB strings share the same regulated current magnitude. Independent current setting requires external current-sense resistors per string and separate feedback paths, which the LM3503SQX-35 does not support. Its dual-string capability is for spatial separation (e.g., top/bottom display zones), not independent current programming.
What package type and thermal resistance does LM3503SQX-35 use?
The LM3503SQX-35 uses a 16-pin WQFN package (RGH0016A) with 3.0 mm × 3.0 mm body and 0.5 mm pitch. Its junction-to-ambient thermal resistance (θJA) is 49°C/W when mounted on a standard 2-layer PCB with full DAP soldering to internal ground plane - enabling 1.2 W power dissipation at +85°C ambient before reaching 125°C junction limit.
How does analog dimming work on LM3503SQX-35?
Analog dimming on LM3503SQX-35 is implemented via the Cntrl pin: applying 0.2–3.5 V DC directly scales the internal error amplifier reference, linearly adjusting feedback voltage (VFb = 0.156 × VCntrl) and thus LED current. Unlike PWM dimming, this method avoids flicker and EMI from external RC filters, and requires no timing coordination with enable signals - simplifying firmware and layout.
What happens when both En1 and En2 are pulled low on LM3503SQX-35?
When both En1 and En2 voltages fall ≤0.3 V, the LM3503SQX-35 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 is explicitly defined in the "Driver Logic" table (Figure 4) and "Detailed Description" section of the SNVS329E datasheet.
LM3503SQX-35 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:
- 35V
- Current - Output / Channel:
- 750mA (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-35 FAQ
1.How can I place an order for LM3503SQX-35 through Aetrix?
Please submit a Request for Quotation (RFQ) for LM3503SQX-35 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-35 reliable?
The price and inventory of LM3503SQX-35 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LM3503SQX-35 is usually 5 days.
3.What payment methods are accepted for LM3503SQX-35?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LM3503SQX-35 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LM3503SQX-35?
LM3503SQX-35 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM3503SQX-35 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-35?
For technical support, including LM3503SQX-35 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM3503SQX-35 requirements.
6.How does Aetrix verify that LM3503SQX-35 is sourced from the original manufacturer or authorized distributors?
All LM3503SQX-35 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-35 meets industry standards.
7.What is the process for return or replacement of LM3503SQX-35?
All LM3503SQX-35 units undergo pre-shipment inspection (PSI). If there is an issue with LM3503SQX-35, 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-35 part is unused and in its original packaging.
Return procedure for LM3503SQX-35:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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