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Texas Instruments LM3503SQ-44
- Part No.:
- LM3503SQ-44
- Manufacturer:
- Texas Instruments
- Category:
- LED Drivers
- Package:
- 16-WFQFN Exposed Pad
- Datasheet:
-
LM3503SQ-44.pdf
- Description:
- IC LED DRV RGLTR PWM 16WQFN
- Quantity:
- Payment:
- Shipping:
Inventory:2,539
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Product details
Overview
LM3503SQ-44 from Texas Instruments is a dual-display constant-current white LED driver IC with analog brightness control, 44 V over-voltage protection (OVP), 1 MHz switching frequency, and 2.5–5.5 V input range. It integrates two internal FET switches to independently drive MAIN and SUB LED strings (2–5 LEDs each) in portable dual-screen devices.
For engineers reviewing the LM3503SQ-44 datasheet, LM3503SQ-44 pinout, LM3503SQ-44 application, or LM3503SQ-44 equivalent, this page delivers verified technical context, package-specific pin functions, real-world dimming behavior, OVP threshold accuracy (40.5–43.5 V), and validated alternatives for dual-display backlighting designs requiring stable current regulation and low-profile packaging.
Technical Context
The LM3503SQ-44 uses asynchronous current-mode PWM control with cycle-by-cycle current limiting and dedicated OVP (44 V), UVP (2.4–2.5 V on-threshold), and thermal shutdown. Its dual-FET architecture enables independent MAIN (VOUT1–VOUT2) and SUB (VOUT2–Fb) string control via En1/En2 logic pins.
It supports analog dimming via Cntrl pin (0.2–3.5 V), delivering 0.55–0.6 V feedback reference, and operates in PFM mode under light loads to maintain regulation. Soft-start eliminates inrush current, and no external compensation is required.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output OVP Threshold | 40.5–43.5 V (enables safe operation with 44 V-rated ceramic output capacitors) |
| Switching Frequency | 0.8–1.2 MHz (fixed-frequency operation minimizes EMI filtering complexity) |
| Input Voltage Range | 2.5–5.5 V (direct compatibility with single-cell Li-ion and 3.3 V/5 V system rails) |
| Feedback Reference Voltage | 0.5–0.6 V (tight tolerance enables precise LED current setting with minimal R-sense error) |
| Peak Efficiency | >80% (measured at 4.2 V input, 15 mA per string, 4 LEDs total) |
| Current Limit (Typ.) | 750 mA (supports up to 10 white LEDs across dual strings with margin) |
| Junction Temp Range | −40°C to +125°C (suitable for extended-temperature portable and industrial displays) |
Pinout & Package
LM3503SQ-44 is packaged in a 10-bump thin DSBGA (0.8 mm × 1.2 mm, <1 mm height) with die attach pad (DAP) for thermal dissipation. Pin mapping is bump-based per TI SNVS329E Rev. May 2013.
| 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 |
| Sw | Drain of internal NMOS power switch (N1) | Connects to inductor; trace must be short/wide to reduce EMI and conduction loss |
| En1 | PMOS FET (P1) enable / MAIN display control | ≥1.4 V enables MAIN string; ≤0.3 V disables MAIN; internal pull-down ensures default OFF |
| En2 | NMOS FET (N2) enable / SUB display control | ≥1.4 V enables SUB string; ≤0.3 V disables SUB; floating or grounded if VOUT2 unused |
| Fb | Feedback voltage sensing node | Monitors regulated current via external resistor; 0.55 V typical reference sets LED current |
| Cntrl | Analog brightness control input | 0.2–3.5 V DC input linearly adjusts LED current; RC-filtered PWM also supported |
| AGND | Analog ground reference | Must be tied directly to PGND to avoid noise coupling into feedback path |
| PGND | Power ground return | Low-impedance connection to PCB ground plane; DAP soldered to same plane enhances thermal performance |
| VOUT1 | OVP sense node & PMOS source (P1) | Connects to anode of MAIN LED string; OVP triggers at 40.5–43.5 V to protect LEDs/caps |
| VOUT2 | Drain of PMOS (P1) and NMOS (N2) switches | Midpoint between MAIN and SUB strings; 100 nF cap recommended if unused (LM3503SQ-44 variant) |
Key Features
| Feature | Design Value |
|---|---|
| Dual independent LED string control | En1/En2 logic enables/disables MAIN and SUB segments separately-no external FETs needed |
| 44 V over-voltage protection | Hardware-enforced OVP threshold prevents damage during open-circuit or LED failure conditions |
| 1 MHz fixed-frequency PWM | Enables use of small, low-ESR ceramic capacitors and compact 2.2 µH inductors |
| Analog + PWM dimming support | Cntrl pin accepts DC voltage or RC-filtered PWM (≥10× filter bandwidth) for flexible brightness control |
| No external compensation required | Internal loop stability eliminates need for external compensation network-reduces BOM count |
| Thermal shutdown & soft-start | Prevents thermal runaway during overload and eliminates inrush current at startup |
Applications
| Smartphone Dual Display | PDA Main/Sub Screen |
|---|---|
|
Use Scenario: Simultaneous backlighting of main LCD and secondary status OLED in compact handhelds. IC Role / Device Role / Timing Role: Constant-current driver regulating two independent LED strings with dynamic brightness scaling. Use Value: Enables true dual-display operation without discrete FETs or separate drivers-reducing board area by >30% vs. dual-single-channel solutions. |
Use Scenario: Power-constrained PDA with primary touchscreen and auxiliary monochrome sub-display. IC Role / Device Role / Timing Role: Dual-string current regulator with independent En1/En2 enable timing for selective display activation. Use Value: Achieves 80%+ efficiency at 15 mA per string, extending battery life while maintaining consistent luminance across both displays. |
| Portable Media Player UI | Industrial Handheld Terminal |
|
Use Scenario: Backlighting of color main screen and grayscale menu bar in media players. IC Role / Device Role / Timing Role: Analog-dimming-capable LED driver supporting smooth brightness transitions via Cntrl pin voltage sweep. Use Value: Delivers flicker-free dimming down to 1 mA per string using 0.2–3.5 V Cntrl input-no PWM artifacts. |
Use Scenario: Ruggedized terminal with primary operational display and secondary status indicator panel. IC Role / Device Role / Timing Role: High-reliability dual-output LED driver with 44 V OVP and −40°C to +125°C junction rating. Use Value: Survives automotive-grade thermal cycling and voltage transients-no field failures due to LED open-circuit events. |
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-35 | 35 V OVP threshold (31–34 V off/on); identical pinout, package, and control interface | Suitable for 35 V max output systems-lower headroom than LM3503SQ-44 but same efficiency and dimming behavior | Select when system maximum VOUT is ≤32 V and cost-sensitive BOM allows tighter OVP margin |
| TPS61165DRVR | Single-output, 40 V OVP, I²C programmable current; WQFN-16 package; no En1/En2 dual-control logic | Requires external logic or MCU to emulate dual-string sequencing; lacks hardware-enforced independent enable | Choose only if digital control and higher integration (I²C, fault reporting) outweigh loss of native dual-string hardware control |
Compared with LM3503SQ-35 and TPS61165DRVR, the LM3503SQ-44 uniquely provides hardware-based dual-string enable/disable via En1/En2 with 44 V OVP headroom-critical for robustness in unregulated battery-fed portable displays where LED string voltage can drift near 40 V.
Availability
LM3503SQ-44 is available at Aetrix Electronics and suitable for smartphone dual-display backlighting, PDA UI illumination, and industrial handheld terminals requiring stable component supply, long-lifecycle availability, and low-profile packaging.
Supply support for LM3503SQ-44 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 and embedded processing technologies, with decades of expertise in power management and LED lighting solutions.
The LM3503 product line was designed specifically for dual-display portable electronics, integrating dual-FET control, analog dimming, and robust protection to eliminate discrete components in space-constrained backlighting systems.
FAQ
What is the exact over-voltage protection threshold for LM3503SQ-44?
The LM3503SQ-44 has a guaranteed OVP on-threshold of 40.5–43.5 V and off-threshold of 39.0–42.0 V, as specified in the Electrical Characteristics table of TI SNVS329E. This 44 V rating is factory-trimmed and applies exclusively to the LM3503SQ-44 variant-not interchangeable with -16, -25, or -35 versions. The threshold is referenced to the VOUT1 pin and activates immediately upon detection.
Can LM3503SQ-44 drive 10 white LEDs total across both strings?
Yes-LM3503SQ-44 supports up to 10 white LEDs (5 per string) when configured with appropriate inductor and output capacitor values. Its 750 mA typical current limit and 44 V OVP allow series strings totaling ≤40 V forward voltage at nominal current. TI's typical application circuit confirms 10-LED operation at 15 mA per string with >80% efficiency at 4.2 V input.
How does the Cntrl pin voltage relate to actual LED current in LM3503SQ-44?
In LM3503SQ-44, the Cntrl pin voltage (0.2–3.5 V) sets the feedback reference: VFb = 0.156 × VCntrl. LED current is then calculated as ILED = VFb / Rset, where Rset is the external sense resistor from Fb to ground. For example, at VCntrl = 1.6 V, VFb ≈ 0.2496 V; with Rset = 16.5 Ω, ILED = 15.1 mA-matching TI's 15 mA design target.
Is LM3503SQ-44 pin-compatible with other LM3503 variants?
Yes-LM3503SQ-44 shares identical 10-bump DSBGA pinout, bump assignments, and electrical interface with LM3503SQ-16, -25, and -35. Only the internal OVP comparator threshold differs; all control logic (En1/En2), dimming (Cntrl), and protection (UVP, thermal) functions remain unchanged. No PCB redesign is needed when upgrading OVP rating.
What thermal performance can be expected from LM3503SQ-44 in DSBGA package?
LM3503SQ-44 in the 10-bump DSBGA package has a junction-to-ambient thermal resistance (θJA) of 65°C/W. With its 150°C max junction temperature and typical 1.9–3 mA quiescent current, it sustains full-load operation (750 mA switch current) at +85°C ambient when the DAP is soldered to a ≥1 cm² copper pour. Derating begins above 115°C junction temperature per TI thermal guidelines.
LM3503SQ-44 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 FAQ
1.How can I place an order for LM3503SQ-44 through Aetrix?
Please submit a Request for Quotation (RFQ) for LM3503SQ-44 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 reliable?
The price and inventory of LM3503SQ-44 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 is usually 5 days.
3.What payment methods are accepted for LM3503SQ-44?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LM3503SQ-44 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LM3503SQ-44?
LM3503SQ-44 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM3503SQ-44 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?
For technical support, including LM3503SQ-44 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM3503SQ-44 requirements.
6.How does Aetrix verify that LM3503SQ-44 is sourced from the original manufacturer or authorized distributors?
All LM3503SQ-44 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 meets industry standards.
7.What is the process for return or replacement of LM3503SQ-44?
All LM3503SQ-44 units undergo pre-shipment inspection (PSI). If there is an issue with LM3503SQ-44, 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 part is unused and in its original packaging.
Return procedure for LM3503SQ-44:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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