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Texas Instruments LM27951SDX/NOPB
- Part No.:
- LM27951SDX/NOPB
- Manufacturer:
- Texas Instruments
- Category:
- LED Drivers
- Package:
- 14-WFDFN Exposed Pad
- Datasheet:
-
LM27951SDX/NOPB.pdf
- Description:
- IC LED DRV RGLTR PWM 30MA 14WSON
- Quantity:
- Payment:
- Shipping:
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Product details
Overview
LM27951SDX/NOPB from Texas Instruments is a switched-capacitor white LED driver IC with adaptive 1.5×/1× charge pump architecture, four matched current sources (±0.2% typical matching), 30 mA max per channel, and fixed 750 kHz switching frequency. It operates from 2.8 V to 5.5 V input and drives up to four display backlight LEDs with uniform brightness in space-constrained portable devices.
For engineers reviewing the LM27951SDX/NOPB datasheet, LM27951SDX/NOPB pinout, LM27951SDX/NOPB application, or LM27951SDX/NOPB equivalent, key selection criteria include regulated current source matching, gain-mode transition threshold (500 mV headroom), shutdown current (<1 µA), PWM-controlled brightness without charge-pump cycling, and WSON-14 package thermal resistance (RθJA = 42.5 °C/W).
Technical Context
The LM27951SDX/NOPB implements an adaptive gain-selecting CMOS charge pump that dynamically switches between 1× and 1.5× modes based on real-time VOUT–VDX headroom (threshold = 500 mV), enabling peak efficiency (>85%) across varying LED forward voltages (2.5–3.9 V) and input rails (2.8–5.5 V). Its constant-frequency pre-regulation minimizes conducted EMI.
Four independent, tightly matched current sources are controlled via a single external RSET resistor connected to ISET (1.25 V reference), delivering programmable output current (10–30 mA) with 200× scaling factor. The dedicated PWM pin modulates current sources while keeping the charge pump continuously active-reducing input ripple versus EN-based PWM control.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 2.8 V to 5.5 V - supports single-cell Li-ion (3.0–4.2 V) and USB-powered systems without LDO pre-regulation. |
| Max Output Current per Channel | 30 mA - enables full-brightness drive for four standard white LEDs (e.g., 3.2 V @ 20 mA) from 3 V input. |
| Current Matching Accuracy | ±0.2% typical - ensures uniform luminance across multi-LED displays without per-channel trimming. |
| Switching Frequency | 750 kHz (±30%) - balances capacitor size (1 µF flying caps), EMI profile, and efficiency in portable designs. |
| Shutdown Supply Current | <1 µA - preserves battery life during display-off states in handheld devices. |
| Charge Pump Output Resistance | 3.3 Ω - determines voltage droop at VOUT; used with Equation VOUT = G × VIN – ROUT × IOUT for headroom margining. |
| Headroom Requirement | 240–360 mV - minimum VOUT–VDX needed for regulation; lower at 20 mA (240 mV), higher at 30 mA (360 mV). |
Pinout & Package
LM27951SDX/NOPB uses a 14-pin WSON package (4.00 mm × 3.00 mm, no-pullback), thermally enhanced with exposed die-attach pad tied to GND.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| C2+, C2− | Flying capacitor terminals | Connect 1 µF ceramic capacitor (C2) to implement 1.5× charge pump stage; polarity-sensitive layout required. |
| C1+, C1− | Flying capacitor terminals | Connect second 1 µF ceramic capacitor (C1) for 1×/1.5× mode switching; forms dual-stage flying cap network. |
| VIN | Main power input | Accepts 2.8–5.5 V supply; requires 3.3 µF low-ESR ceramic input capacitor (CIN) close to pin. |
| VOUT | Pre-regulated charge-pump output | Loosely regulated node (≈4.5 V typical); supplies all four current sources; requires 3.3 µF output capacitor (COUT). |
| D1–D4 | Regulated current source outputs | Four independent, matched sinks; each delivers programmed current (via RSET) to cathode of white LED. |
| ISET | Current programming input | 1.25 V reference node; RSET from ISET to GND sets LED current: ILED = 200 × (1.25 V / RSET). |
| EN | Enable logic input | Active-high (VIH ≥1 V); internal 150 kΩ pulldown ensures default shutdown; controls global charge-pump activation. |
| PWM | Brightness control input | Active-high logic input (VIH ≥1 V); modulates D1–D4 current sources without disabling charge pump - reduces input ripple. |
| GND | Power ground | Primary return path; die-attach pad must be soldered to PCB ground plane for thermal and electrical performance. |
Key Features
| Feature | Design Value |
|---|---|
| Adaptive 1.5×/1× gain selection | Automatically transitions based on VOUT–VDX headroom (500 mV threshold), maximizing efficiency across input and LED VF variations. |
| Four matched current sources | 0.2% typical matching ensures ≤1.5% worst-case current deviation across D1–D4 - critical for consistent display luminance. |
| No-inductor architecture | Uses only four low-cost, small-footprint ceramic capacitors (CIN, COUT, C1, C2); eliminates EMI and size penalties of inductive solutions. |
| Dedicated PWM brightness control | Enables flicker-free dimming (100–1000 Hz) while maintaining active charge pump - avoids input current spikes seen with EN-based PWM. |
| Thermal protection | Shuts down at TJ ≥150°C (typical) and recovers at TJ ≤140°C - prevents damage under sustained high-power or poor PCB thermal design. |
Applications
| Smartphone Display Backlight | Tablet Keypad Illumination |
|---|---|
Use Scenario: Driving four parallel white LEDs behind a 4.3-inch TFT LCD panel in a battery-powered smartphone. IC Role / Device Role / Timing Role: Adaptive switched-capacitor current driver providing uniform 20 mA per LED with automatic gain selection to maintain efficiency as battery discharges from 4.2 V to 3.0 V. Use Value: Eliminates inductor, reduces BOM cost and board area by >30% vs. inductive boost drivers, while sustaining >85% efficiency across full battery range. |
Use Scenario: Illuminating segmented rubber keypad LEDs on an industrial tablet operating in ambient temperatures from –20°C to 70°C. IC Role / Device Role / Timing Role: Four-channel constant-current source delivering 15 mA per LED with ±0.2% matching to prevent visible brightness gradients across keys. Use Value: Maintains consistent visual feedback across temperature extremes due to matched current sources and stable 1.25 V ISET reference. |
| Portable Medical Device Indicator | Wearable Fitness Tracker UI |
Use Scenario: Powering status indicator LEDs (red/green/blue) on a handheld pulse oximeter with strict EMC limits. IC Role / Device Role / Timing Role: Low-EMI switched-capacitor driver using fixed 750 kHz frequency and pre-regulation to minimize conducted noise on shared 3.3 V rail. Use Value: Meets CISPR-22 Class B emissions without ferrite beads or shielding - simplifies compliance testing and reduces system cost. |
Use Scenario: Driving two parallel white LEDs for OLED status display in a wrist-worn fitness tracker with 120-day battery life target. IC Role / Device Role / Timing Role: Ultra-low-quiescent-current LED driver (0.1 µA shutdown) with PWM dimming to extend battery runtime while preserving display visibility. Use Value: Enables 200+ hours of continuous backlight use on a 120 mAh coin cell via <1 µA shutdown and efficient 1× mode operation at 3.6 V input. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar white LED current driver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| TPS61165DRVR | Inductive boost topology; 1.2 MHz switching; requires external inductor and diode; higher peak efficiency (90%) but larger solution size. | Better suited for higher LED string voltages (>16 V) or single-LED strings where inductor size is acceptable. | Choose TPS61165DRVR when driving >4 LEDs in series or needing >16 V output; avoid if board space or EMI sensitivity is critical. |
| MAX1910ETE+ | Fixed 1.5× charge pump; no adaptive gain; 1.25% current matching; 1.2 MHz switching; 16-pin TQFN package. | Lacks dynamic gain selection - less efficient below 4.0 V input; tighter thermal limits (RθJA = 55 °C/W). | Choose MAX1910ETE+ only for legacy designs requiring pin-compatible replacement with relaxed efficiency requirements above 4.0 V. |
Compared with TPS61165DRVR and MAX1910ETE+, the LM27951SDX/NOPB uniquely combines adaptive gain selection, ultra-tight current matching (0.2%), and inductorless operation - making it optimal for compact, multi-LED, battery-sensitive display backlighting where input voltage varies widely.
Availability
LM27951SDX/NOPB is available at Aetrix Electronics and suitable for smartphone display backlights, tablet keypad illumination, and portable medical device indicators requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.
Supply support for LM27951SDX/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 company specializing in analog, embedded processing, and digital signal processing technologies, with leadership in power management ICs for portable and industrial applications.
The LM27951SDX/NOPB belongs to TI's white LED driver product line, engineered specifically for space-constrained, battery-powered display backlighting where uniform brightness, high efficiency across varying input voltage, and minimal EMI are critical.
FAQ
What is the recommended capacitor type and value for LM27951SDX/NOPB flying capacitors C1 and C2?
The LM27951SDX/NOPB requires two 1 µF X7R or X5R multilayer ceramic capacitors (MLCCs) for C1 and C2, rated ≥6.3 V. These must have low ESR (<20 mΩ) and tight tolerance (±10%). Y5V/Z5U types are prohibited due to severe capacitance loss over temperature and bias - a nominal 1 µF Y5V may drop to 0.1 µF, causing regulation failure. TI recommends TDK C1608X7R1C105K.
How does the LM27951SDX/NOPB determine when to switch between 1× and 1.5× charge pump gain modes?
The LM27951SDX/NOPB monitors headroom voltage (VHR = VOUT − VDX) across each current source. When VHR falls below 500 mV (typical), it triggers transition from 1× to 1.5× mode to maintain regulation. This adaptive decision occurs in real time and is independent of external control - ensuring optimal efficiency across input voltage (2.8–5.5 V) and LED forward voltage (2.5–3.9 V) variations.
Can multiple output pins (e.g., D1 and D2) of the LM27951SDX/NOPB be paralleled to drive a single high-current LED?
Yes - D1–D4 outputs can be paralleled to increase per-LED current. For a 60 mA single-LED load, configure RSET to deliver 15 mA per channel (since 4 × 15 mA = 60 mA). All electrical specifications - including current matching, headroom, and thermal limits - remain valid in this configuration. No additional components or layout changes are required beyond connecting pins externally.
What is the function of the ISET pin on the LM27951SDX/NOPB, and how is LED current calculated?
The ISET pin on the LM27951SDX/NOPB is a precision 1.25 V reference node. Connecting RSET between ISET and GND sets total LED current via ILED = 200 × (1.25 V / RSET). For example, RSET = 12.5 kΩ yields 20 mA per channel (200 × 0.0001 A). This scaling factor (200×) is laser-trimmed and ensures predictable, resistor-programmable current without calibration.
Does the LM27951SDX/NOPB support analog dimming, or is brightness control limited to PWM?
The LM27951SDX/NOPB supports only PWM-based brightness control via the dedicated PWM pin. It does not support analog dimming - there is no ISET voltage adjustment or current-scaling interface for linear dimming. PWM frequency must be 100–1000 Hz to avoid visible flicker and audible noise; minimum ON time must exceed 30 µs to ensure regulation loop stability.
LM27951SDX/NOPB Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- -
- Package/Case:
- 14-WFDFN Exposed Pad
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Type:
- DC DC Regulator
- Topology:
- Switched Capacitor (Charge Pump)
- Internal Switch(s):
- Yes
- Number of Outputs:
- 4
- Voltage - Supply (Min):
- 2.8V
- Voltage - Supply (Max):
- 5.5V
- Voltage - Output:
- 2.5V ~ 3.9V
- Current - Output / Channel:
- 30mA
- Frequency:
- 750kHz
- Dimming:
- PWM
- Applications:
- Backlight
- Operating Temperature:
- -40°C ~ 85°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 14-WSON (4x3)
LM27951SDX/NOPB FAQ
1.How can I place an order for LM27951SDX/NOPB through Aetrix?
Please submit a Request for Quotation (RFQ) for LM27951SDX/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 LM27951SDX/NOPB reliable?
The price and inventory of LM27951SDX/NOPB are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LM27951SDX/NOPB is usually 5 days.
3.What payment methods are accepted for LM27951SDX/NOPB?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LM27951SDX/NOPB transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LM27951SDX/NOPB?
LM27951SDX/NOPB orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM27951SDX/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 LM27951SDX/NOPB?
For technical support, including LM27951SDX/NOPB datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM27951SDX/NOPB requirements.
6.How does Aetrix verify that LM27951SDX/NOPB is sourced from the original manufacturer or authorized distributors?
All LM27951SDX/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 LM27951SDX/NOPB meets industry standards.
7.What is the process for return or replacement of LM27951SDX/NOPB?
All LM27951SDX/NOPB units undergo pre-shipment inspection (PSI). If there is an issue with LM27951SDX/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 LM27951SDX/NOPB part is unused and in its original packaging.
Return procedure for LM27951SDX/NOPB:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
LM27951SDX/NOPB Tags
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