My Inquiry
My Account
Texas Instruments LM3503SQ-35
- Part No.:
- LM3503SQ-35
- Manufacturer:
- Texas Instruments
- Category:
- LED Drivers
- Package:
- 16-WFQFN Exposed Pad
- Datasheet:
-
LM3503SQ-35.pdf
- Description:
- IC LED DRV RGLTR PWM 16WQFN
- Quantity:
- Payment:
- Shipping:
Inventory:1,189
Please send an inquiry. Send us your inquiry, and we will respond immediately.
Product details
Overview
LM3503SQ-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 voltage range. It drives up to 10 white LEDs (5 per display) in portable dual-backlight systems such as smartphones and PDAs.
For engineers reviewing the LM3503SQ-35 datasheet, LM3503SQ-35 pinout, LM3503SQ-35 application, or LM3503SQ-35 equivalent, key selection criteria include OVP threshold (32–35 V), dual enable logic for MAIN/SUB display control, analog dimming via Cntrl pin (0.2–3.5 V), and WQFN-16 package thermal performance (θJA = 49°C/W).
Technical Context
The LM3503SQ-35 implements an asynchronous current-mode PWM boost controller with integrated PMOS/NMOS FET switches (P1, N1, N2) and cycle-by-cycle current limiting. Its feedback loop regulates LED current via a precision 0.55 V reference at the Fb pin, modulated by the Cntrl pin voltage (VFb = 0.156 × VCntrl).
It features dedicated dual-enable logic (En1/En2) to independently activate MAIN (VOUT1–VOUT2) or SUB (VOUT2–Fb) LED segments, with shutdown triggered when both En1 and En2 are ≤0.3 V. Protection includes under-voltage lockout (2.4 V on-threshold), thermal shutdown, soft-start, and output over-voltage detection calibrated for 35 V nominal operation.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| OVP Threshold | 32.0–35.0 V (on-threshold); enables safe use of low-profile ceramic output capacitors without risk of overvoltage during LED open-circuit fault) |
| Switching Frequency | 0.8–1.2 MHz (fixed-frequency operation ensures predictable EMI profile and allows compact external inductor sizing) |
| Input Voltage Range | 2.5 V to 5.5 V (supports single-cell Li-ion and multi-cell alkaline battery inputs without external regulation) |
| Feedback Reference | 0.55 V typical (sets LED current via external sense resistor; high accuracy enables tight current matching across displays) |
| Current Limit (35V version) | 450–1050 mA (min/max over temperature; determines maximum drive capability for 2–5 LED strings per channel) |
| Control Voltage Range | 0.2 V to 3.5 V at Cntrl pin (linearly scales LED current from near-zero to full-scale; compatible with DAC or filtered PWM sources) |
| Thermal Resistance θJA | 49°C/W (WQFN-16 package; supports >300 mW continuous power dissipation at 85°C ambient with standard PCB layout) |
Pinout & Package
LM3503SQ-35 is housed in a 16-pin Thin WQFN package (RGH0016A) with exposed thermal pad (DAP) soldered to PCB ground plane for enhanced heat dissipation. Package dimensions: 3.0 mm × 3.0 mm × 0.8 mm.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VIN | Input supply connection | Accepts 2.5–5.5 V; requires local 4.7 µF ceramic capacitor placed adjacent to pin to minimize input ripple and EMI |
| Sw | Power NMOS drain node | High-slew-rate switching node; demands short, wide copper trace to reduce EMI and conduction loss |
| En1 | MAIN display enable control | Drives PMOS switch P1; ≥1.4 V enables MAIN segment (VOUT1–VOUT2), ≤0.3 V disables it |
| En2 | SUB display enable control | Drives NMOS switch N2; ≥1.4 V enables SUB segment (VOUT2–Fb), ≤0.3 V disables it |
| Fb | Current-sense feedback input | Monitors voltage across external current-sense resistor; regulated to 0.55 V to set LED current |
| Cntrl | Analog brightness control input | DC voltage input (0.2–3.5 V) that linearly scales Fb reference; enables smooth analog dimming |
| AGND | Analog ground reference | Must be tied directly to PGND to prevent noise coupling into feedback path and ensure current accuracy |
| PGND | Power ground return | High-current return path for Sw, VOUT1, VOUT2; requires low-impedance connection to DAP and system ground plane |
| VOUT1 | MAIN display output / OVP sense node | Source of PMOS P1 and OVP sensing point; connects to anode of MAIN LED string; capacitor must be placed adjacent |
| VOUT2 | SUB display output / FET drain node | Drain of both P1 and N2; connects to cathode of MAIN and anode of SUB LED strings; 100 nF cap recommended if unused |
Key Features
| Feature | Design Value |
|---|---|
| Dual independent display control | Separate En1/En2 logic enables MAIN and SUB LED strings without external FETs or sequencing circuitry |
| 35 V over-voltage protection | Hardware-enforced OVP threshold prevents damage during LED open-circuit faults in 5–8 LED string configurations |
| Analog brightness control | Cntrl pin accepts 0.2–3.5 V DC input to linearly scale LED current-no external DAC or PWM filtering required |
| 1 MHz fixed-frequency PWM | Enables use of small, low-DCR inductors (e.g., DO1608C-223) and reduces audible noise versus lower-frequency alternatives |
| Integrated soft-start | Gradually ramps current limit at startup to eliminate inrush current spikes into output capacitors and LED strings |
Applications
| Smartphone Dual-Display Backlight | PDA Main/Sub Screen Lighting |
|---|---|
|
Use Scenario: Simultaneous backlighting of main LCD and secondary status OLED in compact handheld devices with shared battery rail. IC Role / Device Role / Timing Role: Constant-current boost driver providing independent current regulation for two LED strings via En1/En2 logic and shared Cntrl dimming. Use Value: Eliminates need for two discrete drivers; 35 V OVP supports 8-white-LED strings (≈28 V forward) while maintaining margin for transient overvoltage. |
Use Scenario: Power-constrained portable organizer requiring dynamic brightness scaling across primary and auxiliary displays based on ambient light sensor output. IC Role / Device Role / Timing Role: Analog-dimmable dual-channel LED driver accepting DC voltage from microcontroller's DAC output to adjust luminance without PWM flicker. Use Value: 0.2–3.5 V Cntrl range maps directly to 0–100% LED current; <1% current matching between channels ensures uniform perceived brightness. |
| Industrial Handheld Terminal | Medical Diagnostic Display |
|
Use Scenario: Ruggedized field device operating across wide temperature (−40°C to +85°C) and input voltage (2.7–5.5 V) ranges, requiring reliable dual-screen illumination. IC Role / Device Role / Timing Role: Robust LED driver with UVP (2.4 V), thermal shutdown, and 125°C max junction rating ensuring continuous operation under stress conditions. Use Value: 49°C/W θJA in WQFN-16 enables stable 20 mA/channel operation at 85°C ambient without derating-critical for sealed enclosures. |
Use Scenario: High-reliability diagnostic equipment where display brightness must remain stable and flicker-free during image capture and analysis. IC Role / Device Role / Timing Role: Low-noise analog-controlled driver avoiding PWM-induced EMI that could interfere with sensitive analog front-end circuits. Use Value: Fixed 1 MHz switching frequency places noise spectrum outside critical signal bands; <0.5% VFb drift over temperature ensures consistent luminance calibration. |
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 |
|---|---|---|---|
| LM3503SQ-25 | 25 V OVP threshold (vs. 35 V); lower current limit (400–800 mA) | Optimized for ≤6 LED strings per channel; reduced headroom for high-VF white LEDs or long traces | Select when driving shorter LED strings (≤6) and board space/thermal budget constrain use of higher-OVP variant |
| LM3503SQ-44 | 44 V OVP threshold (vs. 35 V); identical current limit (450–1050 mA) | Supports up to 10 high-VF white LEDs (≈40 V total) or extended cable runs with IR drop compensation | Choose for maximum fault tolerance in high-string-count or industrial wiring scenarios where 35 V margin is insufficient |
Compared with LM3503SQ-25, the LM3503SQ-35 provides 10 V higher OVP headroom for robustness against LED open-circuit transients, while compared with LM3503SQ-44, it offers tighter voltage tolerance and lower cost for mid-range 7–8 LED applications without over-engineering.
Availability
LM3503SQ-35 is available at Aetrix Electronics and suitable for smartphone backlighting, industrial handheld terminals, and medical diagnostic displays requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.
Supply support for LM3503SQ-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 delivering analog, embedded processing, and connectivity solutions with emphasis on power efficiency and reliability.
The LM3503 product line delivers highly integrated, thermally optimized LED drivers for portable dual-display applications-designed to replace discrete boost + FET + control solutions with single-chip simplicity and predictable performance.
FAQ
What is the over-voltage protection threshold for LM3503SQ-35?
The LM3503SQ-35 has a nominal over-voltage protection (OVP) threshold of 35 V, with guaranteed on-threshold between 32.0 V and 35.0 V and off-threshold between 31.0 V and 34.0 V. This hardware-enforced limit protects the IC and external components during LED string open-circuit faults, and is factory-trimmed specifically for the SQ-35 variant-distinct from LM3503SQ-16, -25, or -44 versions.
How does the Cntrl pin control LED brightness in LM3503SQ-35?
The Cntrl pin on LM3503SQ-35 accepts a DC voltage from 0.2 V to 3.5 V to linearly scale the internal feedback reference (VFb = 0.156 × VCntrl). This adjusts the regulated LED current without requiring PWM filtering or external DACs. At VCntrl = 0.2 V, LED current is near minimum; at 3.5 V, it reaches full-scale-enabling smooth, flicker-free analog dimming directly from a microcontroller GPIO or DAC output.
Can LM3503SQ-35 drive both MAIN and SUB displays simultaneously?
Yes, LM3503SQ-35 can drive both MAIN and SUB displays concurrently by setting En1 ≥1.4 V and En2 ≥1.4 V. In this state, the PMOS switch P1 and NMOS switch N2 are both disabled, allowing current to flow through the full LED string from VOUT1 → VOUT2 → Fb. The device regulates total current across the combined string, making it suitable for unified backlighting or cascaded configurations where shared current control is acceptable.
What package type and thermal characteristics does LM3503SQ-35 use?
LM3503SQ-35 uses a 16-pin Thin WQFN package (RGH0016A) with 3.0 mm × 3.0 mm footprint and 0.8 mm height. Its junction-to-ambient thermal resistance (θJA) is 49°C/W when mounted on a standard 2-layer PCB with DAP soldered to a solid ground plane. This enables continuous operation at up to 300 mW power dissipation at 85°C ambient-sufficient for driving two 15 mA LED strings at 5 V input.
Does LM3503SQ-35 require external compensation components?
No, LM3503SQ-35 operates with no external compensation required. Its current-mode PWM architecture incorporates internal error amplification, soft-start, duty-cycle limiting, and light-load pulse-skipping (PFM) mode-all implemented on-die. This eliminates the need for external RC networks or loop compensation components, simplifying layout and reducing BOM count while maintaining stability across load and input voltage variations.
LM3503SQ-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)
LM3503SQ-35 FAQ
1.How can I place an order for LM3503SQ-35 through Aetrix?
Please submit a Request for Quotation (RFQ) for LM3503SQ-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 LM3503SQ-35 reliable?
The price and inventory of LM3503SQ-35 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LM3503SQ-35 is usually 5 days.
3.What payment methods are accepted for LM3503SQ-35?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LM3503SQ-35 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LM3503SQ-35?
LM3503SQ-35 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM3503SQ-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 LM3503SQ-35?
For technical support, including LM3503SQ-35 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM3503SQ-35 requirements.
6.How does Aetrix verify that LM3503SQ-35 is sourced from the original manufacturer or authorized distributors?
All LM3503SQ-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 LM3503SQ-35 meets industry standards.
7.What is the process for return or replacement of LM3503SQ-35?
All LM3503SQ-35 units undergo pre-shipment inspection (PSI). If there is an issue with LM3503SQ-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 LM3503SQ-35 part is unused and in its original packaging.
Return procedure for LM3503SQ-35:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
LM3503SQ-35 Tags
-
BCR402RE6327HTSA1
Infineon Technologies
-
BCR430UXTSA2
Infineon Technologies
-
BCR420UE6433HTMA1
Infineon Technologies
-
BCR420UE6327HTSA1
Infineon Technologies
-
BCR421UE6327HTSA1
Infineon Technologies
-
LYT1604D-TL
Power Integrations
-
HV9910CLG-G
Microchip Technology
-
CL2N8-G
Microchip Technology
-
BCR420UW6-7
Diodes Incorporated
-
BCR421UW6-7
Diodes Incorporated
-
BCR420UFD-7
Diodes Incorporated
-
BCR421UFD-7
Diodes Incorporated
Tech Hub
A practical engineering guide to 3.3V and 5V logic compatibility, input thresholds, resistor dividers, translator ICs, MOSFET level shifting, I2C pull-ups, timing limits and power-sequencing risks.
The 74HC595 uses push-pull logic outputs, while the TPIC6B595 uses 50 V open-drain DMOS sinks for higher-power loads. This guide compares timing, current limits, 3.3 V interfacing, load wiring, thermal…
The 74HC595 converts serial data into eight stable parallel outputs. This guide covers pin functions, shift and storage timing, OE and MR behavior, drive-current limits, cascading, voltage compatibilit…
A technical comparison of level-sensitive latches and edge-triggered flip-flops, covering timing windows, setup and hold limits, master–slave operation, time borrowing, race-through, HDL inference and…
A D latch stores one bit while Enable controls when data can pass. This reference covers gate-level operation, truth tables, transparency, setup and hold timing, LE versus OE, common ICs and practical …
An SR latch stores one bit through cross-coupled feedback. This engineering reference covers NOR and NAND implementations, truth tables, forbidden-state recovery, gated operation, switch debouncing, fa…
Latch circuits retain one bit through feedback. This technical reference covers SR and D latches, truth tables, transparency, timing limits, latch-versus-flip-flop behavior, applications and common log…
An engineering guide to LED driver operation, constant-current and constant-voltage outputs, linear and switching topologies, dimming, IC selection, calculations, replacement compatibility, and fault c…
Operational amplifier guide covering op amp basics, feedback, ideal vs real op amps, common configurations, buffer circuits, offset, bias current, gain-bandwidth, slew rate, rail-to-rail limits and sel…
Jumper cables guide covering safe connection order, red and black clamp placement, final ground connection, cable gauge, length, clamp quality, copper vs CCA cables, jump starter comparison and battery…
