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Texas Instruments LM3503SQ-44/NOPB
- Part No.:
- LM3503SQ-44/NOPB
- Manufacturer:
- Texas Instruments
- Category:
- LED Drivers
- Package:
- 16-WFQFN Exposed Pad
- Datasheet:
-
LM3503SQ-44/NOPB.pdf
- Description:
- IC LED DRV RGLTR PWM 16WQFN
- Quantity:
- Payment:
- Shipping:
Inventory:3,338
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Product details
Overview
LM3503SQ-44/NOPB from Texas Instruments is a dual-display constant-current white LED driver IC with analog brightness control, 44 V over-voltage protection, 1 MHz switching frequency, and support for up to 10 LEDs (5 per display). It operates from 2.5 V to 5.5 V input and delivers >80% peak efficiency in portable backlighting applications.
For engineers reviewing the LM3503SQ-44/NOPB datasheet, LM3503SQ-44/NOPB pinout, LM3503SQ-44/NOPB application, or LM3503SQ-44/NOPB equivalent, key selection considerations include its dual-string enable logic (En1/En2), Cntrl-pin-based analog dimming, 44 V OVP threshold, thermal shutdown, and compatibility with low-profile WQFN and DSBGA packages.
Technical Context
The LM3503SQ-44/NOPB implements an asynchronous current-mode PWM controller with cycle-by-cycle current limiting, dedicated OVP (40.5–43.5 V on-threshold), UVP (2.4–2.5 V on-threshold), and internal soft-start. Its dual-FET architecture integrates separate PMOS (VOUT1) and NMOS (VOUT2) switches to independently manage MAIN and SUB LED strings.
Control is achieved via analog voltage on the Cntrl pin (0.2–3.5 V), which linearly adjusts feedback reference (VFb = 0.156 × VCntrl), enabling precise LED current regulation without external DACs. The device supports both continuous and discontinuous conduction modes and includes light-load PFM operation to maintain regulation at low currents.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output OVP Threshold | 40.5–43.5 V (on-threshold); prevents damage during LED open-circuit or removal in 44 V variant |
| Switching Frequency | 0.8–1.2 MHz (typ. 1 MHz); enables compact magnetics and reduces EMI filtering burden |
| Input Voltage Range | 2.5 V to 5.5 V; compatible with single-cell Li-ion and multi-cell alkaline battery rails |
| LED Current Control | Analog Cntrl pin (0.2–3.5 V); sets VFb = 0.156 × VCntrl for direct DC dimming without PWM filtering |
| Peak Efficiency | >80% (measured at VIN = 4.2 V, 10 mA LED current, 8-LED load); minimizes thermal stress in space-constrained handhelds |
| Enable Logic | En1 ≥1.4 V enables MAIN display; En2 ≥1.4 V enables SUB display; both ≤0.3 V forces shutdown |
| Thermal Protection | Internal thermal shutdown at TJ = +150 °C; ensures reliability under sustained high-current or high-ambient conditions |
Pinout & Package
LM3503SQ-44/NOPB is packaged in a 16-pin WQFN (RGH0016A) with 0.4 mm pitch and <1 mm height. The exposed die attach pad (DAP) must be soldered to PCB ground for thermal dissipation.
| 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 | Drain of internal NMOS power switch (N1) | Connects to inductor; trace must be short/wide to reduce switching losses and radiated noise |
| En1 | PMOS FET (P1) enable for MAIN display | Logic-high (≥1.4 V) disables MAIN string; internal pull-down holds default OFF state |
| En2 | NMOS FET (N2) enable for SUB display | Logic-high (≥1.4 V) disables SUB string; floating or grounded if VOUT2 unused |
| Fb | Feedback voltage sensing node | Monitors regulated output; connects to resistor divider from VOUT2 for current-sense loop |
| Cntrl | Analog brightness control input | 0.2–3.5 V input sets VFb; enables smooth DC dimming without flicker or audible noise |
| AGND | Analog ground reference | Must tie directly to PGND to avoid noise coupling into feedback path |
| PGND | Power ground return | High-current return for Sw, VOUT1, VOUT2; connect to solid ground plane under DAP |
| VOUT1 | OVP sense node & PMOS source (P1) | Connects to cathode of main LED string; OVP comparator monitors this pin for 44 V threshold |
| VOUT2 | Drain of NMOS (N2) & PMOS (P1) switches | Forms SUB string between VOUT2 and Fb; 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-enabling flexible UI backlight partitioning |
| 44 V over-voltage protection | Hardware-enforced OVP threshold prevents catastrophic failure during LED string disconnection or open-circuit faults |
| 1 MHz fixed-frequency PWM | Stable switching frequency simplifies EMI filter design and avoids audible noise in portable audio-sensitive environments |
| Analog brightness control | Cntrl pin accepts DC voltage (not PWM) for flicker-free dimming-eliminates need for RC filters or external DACs |
| Integrated soft-start | Gradually ramps current limit at startup to suppress inrush current-protects input capacitors and battery sources |
| Low-profile WQFN package | 16-pin 3 mm × 3 mm × 0.8 mm WQFN enables ultra-thin designs in smartphones and PDAs |
Applications
| Cellular Phone Main/Sub Display Backlight | PDA Dual-Screen UI Illumination |
|---|---|
Use Scenario: Simultaneous illumination of primary LCD and secondary status OLED in clamshell or slider phones. IC Role / Device Role / Timing Role: Constant-current driver managing two independent LED strings with dynamic brightness scaling via Cntrl pin. Use Value: Enables differentiated brightness levels per display using single analog control signal-reducing BOM count and layout complexity. | Use Scenario: Powering main touchscreen and auxiliary keypad/backlight in handheld PDAs with limited board area. IC Role / Device Role / Timing Role: Dual-channel boost converter with independent enable logic (En1/En2) for selective display activation. Use Value: Eliminates need for two discrete LED drivers-saving PCB space and reducing system power-up sequencing overhead. |
| Portable Media Player Dual-Panel Lighting | Industrial Handheld Terminal Display Stack |
Use Scenario: Driving front-panel main screen and rear-panel battery/status indicator in MP3/video players. IC Role / Device Role / Timing Role: Analog-dimmable dual-output LED driver supporting 2–5 LEDs per channel with 44 V fault tolerance. Use Value: Sustains full brightness across varying battery voltage (2.5–5.5 V) while maintaining tight current matching (<±5%) between channels. | Use Scenario: Backlighting stacked LCD layers (e.g., main display + overlay touch panel) in ruggedized industrial terminals. IC Role / Device Role / Timing Role: High-reliability constant-current source with thermal shutdown and OVP protecting against field-induced LED failures. Use Value: Ensures uninterrupted display operation in extended-temperature (-40°C to +85°C ambient) and vibration-prone 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 |
|---|---|---|---|
| LM3503SQ-25/NOPB | 25 V OVP threshold (vs. 44 V); identical pinout, control interface, and package | Suitable for lower-voltage LED strings (≤20 V); not safe for 44 V fault conditions | Select when output voltage headroom is constrained and maximum string voltage remains below 22 V |
| TPS61165DRVR | Single-output, 40 V OVP, I²C programmable; no En1/En2 dual-control logic | Lacks hardware-based MAIN/SUB enable separation; requires MCU firmware coordination | Choose when digital control and higher integration (I²C, fault reporting) outweigh need for independent analog enable signals |
Compared with LM3503SQ-25/NOPB and TPS61165DRVR, the LM3503SQ-44/NOPB uniquely combines 44 V hardware OVP, dual independent enable pins, and analog Cntrl-based dimming in one WQFN package-making it optimal for space-limited dual-display systems requiring robust fault protection and minimal MCU interaction.
Availability
LM3503SQ-44/NOPB is available at Aetrix Electronics and suitable for cellular phone backlighting, PDA dual-screen illumination, and portable media player display stacks requiring stable component supply, long-term lifecycle support, and consistent parametric performance across production batches.
Supply support for LM3503SQ-44/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 delivering analog, embedded processing, and connectivity solutions for industrial, automotive, and personal electronics markets.
The LM3503 product line was designed specifically for dual-display white LED backlighting in ultra-thin portable devices-emphasizing analog dimming simplicity, dual-string flexibility, and integrated protection for battery-powered applications.
FAQ
What is the over-voltage protection threshold for LM3503SQ-44/NOPB?
The LM3503SQ-44/NOPB features a hardware-defined over-voltage protection threshold of 40.5 V (minimum), 42 V (typical), and 43.5 V (maximum) on the VOUT1 pin. This 44 V-rated OVP circuit disables switching when the output exceeds the threshold, safeguarding external LEDs and capacitors during open-circuit or string-failure events. The LM3503SQ-44/NOPB's OVP is factory-trimmed and does not require external components.
How does analog brightness control work on LM3503SQ-44/NOPB?
Analog brightness control on the LM3503SQ-44/NOPB is implemented via the Cntrl pin, which accepts a DC voltage from 0.2 V to 3.5 V. This voltage linearly scales the internal feedback reference: VFb = 0.156 × VCntrl. As VFb changes, the error amplifier adjusts LED current to maintain regulation-enabling flicker-free, noiseless dimming without PWM filtering. The LM3503SQ-44/NOPB does not require external DACs or RC networks for basic analog dimming.
Can LM3503SQ-44/NOPB drive both MAIN and SUB displays simultaneously?
Yes, the LM3503SQ-44/NOPB can drive both MAIN and SUB displays simultaneously by setting En1 ≥1.4 V and En2 ≥1.4 V. In this configuration, the PMOS (P1) and NMOS (N2) switches are both disabled, allowing current to flow through the full LED string from VOUT1 → MAIN LEDs → VOUT2 → SUB LEDs → Fb. The LM3503SQ-44/NOPB regulates total current across the combined string, supporting up to 10 LEDs (5+5) with matched brightness.
What package type is used for LM3503SQ-44/NOPB?
The LM3503SQ-44/NOPB uses a 16-pin WQFN package (TI designation RGH0016A), measuring 3 mm × 3 mm × 0.8 mm with 0.4 mm pitch. It features an exposed die attach pad (DAP) that must be soldered to the PCB ground plane for thermal performance. This low-profile package meets stringent height requirements in smartphones and PDAs-unlike the 10-bump DSBGA option offered in other LM3503 variants.
Does LM3503SQ-44/NOPB support PWM dimming in addition to analog control?
Yes, the LM3503SQ-44/NOPB supports PWM dimming via RC-filtered signals applied to the Cntrl pin. TI recommends using a PWM frequency at least 10× the RC filter's cutoff frequency (e.g., 500 Hz PWM with 50 Hz RC bandwidth). A 1–2 ms delay between Cntrl signal activation and En1 assertion is advised to prevent flicker-especially with short SUB strings (2 LEDs or fewer). The LM3503SQ-44/NOPB's analog path remains fully functional alongside PWM-derived DC equivalents.
LM3503SQ-44/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:
- 44V
- 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-44/NOPB FAQ
1.How can I place an order for LM3503SQ-44/NOPB through Aetrix?
Please submit a Request for Quotation (RFQ) for LM3503SQ-44/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 LM3503SQ-44/NOPB reliable?
The price and inventory of LM3503SQ-44/NOPB are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LM3503SQ-44/NOPB is usually 5 days.
3.What payment methods are accepted for LM3503SQ-44/NOPB?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LM3503SQ-44/NOPB transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LM3503SQ-44/NOPB?
LM3503SQ-44/NOPB orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM3503SQ-44/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 LM3503SQ-44/NOPB?
For technical support, including LM3503SQ-44/NOPB datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM3503SQ-44/NOPB requirements.
6.How does Aetrix verify that LM3503SQ-44/NOPB is sourced from the original manufacturer or authorized distributors?
All LM3503SQ-44/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 LM3503SQ-44/NOPB meets industry standards.
7.What is the process for return or replacement of LM3503SQ-44/NOPB?
All LM3503SQ-44/NOPB units undergo pre-shipment inspection (PSI). If there is an issue with LM3503SQ-44/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 LM3503SQ-44/NOPB part is unused and in its original packaging.
Return procedure for LM3503SQ-44/NOPB:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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