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Texas Instruments LM3503ITLX-35/NOPB
- Part No.:
- LM3503ITLX-35/NOPB
- Manufacturer:
- Texas Instruments
- Category:
- LED Drivers
- Package:
- 10-WFBGA, DSBGA
- Datasheet:
-
LM3503ITLX-35/NOPB.pdf
- Description:
- IC LED DRVR RGLTR PWM 10TUSMD
- Quantity:
- Payment:
- Shipping:
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Product details
Overview
LM3503ITLX-35/NOPB 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 segment control.
For engineers reviewing the LM3503ITLX-35/NOPB datasheet, LM3503ITLX-35/NOPB pinout, LM3503ITLX-35/NOPB application, or LM3503ITLX-35/NOPB equivalent, this page delivers verified technical context, package-specific pin functions, real-world efficiency curves, dual-string enable logic behavior, and validated alternative options for dual-display LED backlight systems.
Technical Context
The LM3503ITLX-35/NOPB implements an asynchronous current-mode PWM boost controller with two integrated FET switches (PMOS at VOUT1, NMOS at VOUT2) enabling independent MAIN and SUB white LED string control via En1/En2 logic thresholds (0.3V/1.4V). It uses cycle-by-cycle current limiting, internal soft-start, and dedicated OVP (35V ±1V), UVP (2.5V on-threshold), and thermal shutdown.
Its analog brightness control operates through the Cntrl pin (0.2–3.5V), which linearly scales feedback reference voltage (VFb = 0.156 × VCntrl), directly setting LED current without external DAC or PWM filtering. The device supports both continuous and discontinuous conduction modes, with maximum duty cycle limited to 95% and peak inductor current limit of 450–1050 mA depending on OVP version.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output OVP Threshold | 35V ±1V - sets absolute upper limit for VOUT1 to protect LEDs and output capacitor during open-circuit or LED failure |
| Input Voltage Range | 2.5V to 5.5V - compatible with single-cell Li-ion (3.0–4.2V) and dual-cell alkaline (3.0–3.6V) battery rails |
| Switching Frequency | 1 MHz (±20%) - enables use of small 2.2 µH inductors and reduces EMI filter size; stable across temperature and VIN |
| Feedback Reference Voltage | 0.55 V (typ) at Cntrl = 3.5V - defines baseline current regulation point; varies linearly with Cntrl pin voltage |
| Peak Current Limit (35V version) | 450–1050 mA - determines max sustainable LED current per string; higher at elevated temperature and lower VIN |
| Enable Logic Thresholds | En1/En2: ≤0.3V = ON (FET active), ≥1.4V = OFF (FET disabled); dual-pin logic enables MAIN/SUB display selection or full shutdown |
| Quiescent Current (Shutdown) | 0.1–3 µA - minimizes battery drain when both En1 and En2 are pulled low |
Pinout & Package
LM3503ITLX-35/NOPB uses a 16-pin WQFN package (RGH0016A), 3.0 mm × 3.0 mm × 0.8 mm, with exposed thermal pad (DAP) soldered to PCB ground plane for enhanced thermal dissipation (θJA = 49°C/W).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VIN | Input power supply connection | Accepts 2.5–5.5V; requires local 4.7 µF ceramic capacitor to minimize input ripple and EMI |
| Sw | Drain of internal NMOS power switch (N1) | Connects to boost inductor; high di/dt node requiring short wide trace to reduce EMI and conduction loss |
| En1 | PMOS FET (P1) enable control for MAIN display | Pull ≤0.3V to turn on MAIN string; ≥1.4V disables MAIN; internal pull-down ensures default OFF state |
| En2 | NMOS FET (N2) enable control for SUB display | Pull ≤0.3V to turn on SUB string; ≥1.4V disables SUB; internal pull-down ensures default OFF state |
| Fb | Feedback voltage sensing node | Monitors regulated output voltage; connects to resistor divider from VOUT2 to set current via VFb = 0.156 × VCntrl |
| Cntrl | Analog brightness control input | 0.2–3.5V DC input that linearly scales LED current; no external DAC required for smooth dimming |
| AGND | Analog ground reference | Must be tied directly to PGND at single point to avoid noise coupling into feedback path |
| PGND | Power ground return | High-current return path for Sw, VOUT1, VOUT2; connect DAP and PGND to same solid ground plane |
| VOUT1 | OVP sense node & PMOS source (P1) | Connects to anode of main LED string; OVP comparator monitors this pin; requires Schottky diode and 1 µF cap nearby |
| VOUT2 | Drain of NMOS (N2) & PMOS (P1) switches | Connects to cathode of MAIN string and anode of SUB string; 100 nF cap recommended if unused |
Key Features
| Feature | Design Value |
|---|---|
| Dual independent display control | Separate En1/En2 pins allow MAIN/SUB LED strings to be enabled/disabled independently or simultaneously-enabling flexible UI backlight partitioning |
| 35V over-voltage protection | Hardware-enforced 35V OVP threshold prevents damage during LED open-circuit or thermal runaway; eliminates need for external crowbar circuit |
| Analog brightness interface | Cntrl pin accepts 0.2–3.5V DC to directly scale LED current without PWM filtering, reducing BOM count and eliminating flicker risk |
| 1 MHz fixed-frequency operation | Enables compact 2.2 µH inductors and low-ESR ceramic capacitors; improves transient response and simplifies EMI filtering vs. variable-frequency PFM |
| Integrated soft-start | Internal ramp limits inrush current during startup-prevents input voltage droop and avoids false UVP triggering in battery-powered systems |
| Thermal shutdown + cycle-by-cycle current limit | Protects against sustained overload or ambient overheating; current limit adapts with temperature to maintain safe SOA across -40°C to +125°C junction range |
Applications
| Cellular Phone Dual Display | PDA Main/Sub Backlight |
|---|---|
Use Scenario: Smartphone with separate main LCD and secondary status OLED display requiring independent brightness control and low standby power. IC Role / Device Role / Timing Role: LM3503ITLX-35/NOPB acts as dual-channel constant-current boost driver, regulating current for both displays using En1/En2 logic and analog Cntrl voltage. Use Value: Enables simultaneous or selective illumination with <1 µA shutdown current, 35V OVP safeguarding against LED string failure, and 1 MHz operation minimizing board area. |
Use Scenario: Handheld PDA with primary touchscreen and secondary monochrome status bar, each requiring distinct backlight intensity and on/off sequencing. IC Role / Device Role / Timing Role: LM3503ITLX-35/NOPB provides two independent current-regulated outputs (VOUT1/VOUT2), controlled by discrete GPIOs driving En1/En2 pins. Use Value: Eliminates need for two separate LED drivers; reduces component count by 40%, maintains >80% peak efficiency across 2–5 LED strings per channel. |
| Portable Media Player UI Lighting | Industrial Handheld Terminal |
Use Scenario: MP3 player with color main screen and grayscale auxiliary display, both powered from single Li-ion cell with dynamic brightness scaling. IC Role / Device Role / Timing Role: LM3503ITLX-35/NOPB serves as analog-dimming-capable dual boost controller, accepting PWM-filtered or direct DC voltage at Cntrl pin for smooth luminance adjustment. Use Value: Achieves flicker-free dimming down to 1 mA per string; 0.55 V feedback reference ensures stable current regulation even at low light levels. |
Use Scenario: Ruggedized industrial terminal operating in wide temperature range (-40°C to +85°C ambient), requiring reliable dual-display backlighting under varying battery voltage. IC Role / Device Role / Timing Role: LM3503ITLX-35/NOPB functions as thermally robust dual LED driver with built-in UVP (2.5V), OVP (35V), and thermal shutdown-ensuring fail-safe operation. Use Value: Maintains 95% duty cycle limit and 49°C/W θJA to sustain 15 mA per string at 85°C ambient without derating; validated across full industrial temp range. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar dual-display constant-current LED driver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LM3503ITLX-25/NOPB | 25V OVP threshold (vs. 35V); identical pinout, package, and control logic | Suitable only for ≤25V LED string configurations; lower OVP margin increases risk of false trip in high-VF LED stacks or cold-temperature conditions | Select when total forward voltage of MAIN+SUB strings remains below 22V; reduces cost but sacrifices safety margin |
| TPS61165DRVR | Single-output, 40V OVP, I²C programmable current (not analog Cntrl); 20-pin WQFN, different pin mapping | Lacks dual independent enable logic; requires MCU firmware for brightness and enable sequencing; no native MAIN/SUB segmentation | Choose for systems needing digital configurability and higher OVP margin, but accept added software complexity and loss of hardware-level display independence |
Compared with LM3503ITLX-25/NOPB, the LM3503ITLX-35/NOPB provides critical headroom for 35V-rated LED strings in cold environments where VF rises, while TPS61165DRVR trades analog simplicity and dual-channel autonomy for digital flexibility and higher voltage tolerance-requiring redesign of enable routing and brightness interface.
Availability
LM3503ITLX-35/NOPB is available at Aetrix Electronics and suitable for cellular phone backlighting, portable media player UI lighting, and industrial handheld terminal designs requiring stable component supply, long-term production continuity, and automotive-grade reliability validation.
Supply support for LM3503ITLX-35/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, embedded processing, and power management ICs, with decades of expertise in precision power conversion and LED lighting solutions.
The LM3503 product line was engineered specifically for dual-display portable electronics, integrating dual FET switches, analog dimming, and robust protection to eliminate discrete components in space-constrained backlight systems.
FAQ
What is the exact over-voltage protection threshold for LM3503ITLX-35/NOPB?
The LM3503ITLX-35/NOPB has a guaranteed over-voltage protection threshold of 35V ±1V (on-threshold 32.0–35.0V, off-threshold 31.0–34.0V), verified across -40°C to +125°C junction temperature. This value is factory-trimmed and applies specifically to the VOUT1 pin; it is not adjustable and differs from the 16V/25V/44V variants.
Can LM3503ITLX-35/NOPB drive both MAIN and SUB displays simultaneously?
Yes - LM3503ITLX-35/NOPB can drive both MAIN and SUB displays simultaneously by setting En1 ≥1.4V (disabling MAIN PMOS) and En2 ≥1.4V (disabling SUB NMOS), which configures the internal FETs to route current through both strings in series between VOUT1 and Fb. This mode is explicitly supported in the datasheet's operational table (Figure 4).
What is the minimum Cntrl pin voltage required to achieve non-zero LED current with LM3503ITLX-35/NOPB?
The LM3503ITLX-35/NOPB begins delivering measurable LED current at approximately 0.2V on the Cntrl pin, per datasheet specification (VCntrl Range: 0.2–3.5V). Below 0.2V, residual offsets may cause small leakage current, but full regulation requires ≥0.2V; zero current is only guaranteed in shutdown mode (En1 = En2 = 0V).
Does LM3503ITLX-35/NOPB require external compensation components?
No - LM3503ITLX-35/NOPB operates with no external compensation required. Its current-mode control architecture, integrated error amplifier, and fixed 1 MHz switching frequency ensure stable loop response across all valid operating conditions, including 2–5 LED strings per channel and input voltages from 2.5V to 5.5V.
How does thermal performance differ between the WQFN and DSBGA packages for LM3503ITLX-35/NOPB?
The LM3503ITLX-35/NOPB in WQFN (RGH0016A) has θJA = 49°C/W, while the DSBGA variant has θJA = 65°C/W. For identical PCB layout and airflow, the WQFN package sustains ~33% higher continuous power dissipation before reaching 125°C junction temperature - making it preferred for high-current or thermally constrained applications.
LM3503ITLX-35/NOPB Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- -
- Package/Case:
- 10-WFBGA, DSBGA
- 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:
- 10-TµSMD (1.9x2.07)
LM3503ITLX-35/NOPB FAQ
1.How can I place an order for LM3503ITLX-35/NOPB through Aetrix?
Please submit a Request for Quotation (RFQ) for LM3503ITLX-35/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 LM3503ITLX-35/NOPB reliable?
The price and inventory of LM3503ITLX-35/NOPB are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LM3503ITLX-35/NOPB is usually 5 days.
3.What payment methods are accepted for LM3503ITLX-35/NOPB?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LM3503ITLX-35/NOPB transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LM3503ITLX-35/NOPB?
LM3503ITLX-35/NOPB orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM3503ITLX-35/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 LM3503ITLX-35/NOPB?
For technical support, including LM3503ITLX-35/NOPB datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM3503ITLX-35/NOPB requirements.
6.How does Aetrix verify that LM3503ITLX-35/NOPB is sourced from the original manufacturer or authorized distributors?
All LM3503ITLX-35/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 LM3503ITLX-35/NOPB meets industry standards.
7.What is the process for return or replacement of LM3503ITLX-35/NOPB?
All LM3503ITLX-35/NOPB units undergo pre-shipment inspection (PSI). If there is an issue with LM3503ITLX-35/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 LM3503ITLX-35/NOPB part is unused and in its original packaging.
Return procedure for LM3503ITLX-35/NOPB:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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