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Texas Instruments LM27951SD
- Part No.:
- LM27951SD
- Manufacturer:
- Texas Instruments
- Category:
- LED Drivers
- Package:
- 14-WFDFN Exposed Pad
- Datasheet:
-
LM27951SD.pdf
- Description:
- IC LED DRV RGLTR PWM 30MA 14WSON
- Quantity:
- Payment:
- Shipping:
Inventory:2,540
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Product details
Overview
LM27951SD from Texas Instruments is a white LED adaptive 1.5×/1× switched-capacitor current driver IC designed for display backlighting. It delivers up to 30 mA per channel across four tightly matched regulated current sources (0.2% typical matching), operates from 2.8 V to 5.5 V input, and uses a fixed 750-kHz charge-pump switching frequency with no inductor required. It is deployed in compact portable displays requiring uniform brightness and low EMI.
For engineers reviewing the LM27951SD datasheet, LM27951SD pinout, LM27951SD application, or LM27951SD equivalent, key selection criteria include its adaptive gain transition (1×/1.5× based on LED forward voltage), PWM-controlled brightness without charge-pump cycling, <1 µA shutdown current, 360 mV headroom requirement at 30 mA, and WSON-14 package thermal resistance of 42.5°C/W.
Technical Context
The LM27951SD implements an adaptive CMOS charge pump with closed-loop VOUT regulation (~4.5 V typical) and automatic 1×/1.5× gain selection triggered by falling headroom voltage (500 mV threshold). Its four independent current sources share a single ISET pin, where LED current is set via external RSET using the formula IDx = 200 × (1.25 V / RSET).
It features dual logic control: EN enables/disables the entire IC (150 kΩ internal pulldown), while PWM modulates only the current sources-keeping the charge pump active to minimize input ripple. Startup time is 330 µs typical due to integrated soft-start, and thermal shutdown activates at 150°C junction temperature.
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 - sufficient for driving four standard white LEDs (3.0–3.6 VF) at full brightness in parallel configuration. |
| Current Matching | 0.2% typical - ensures uniform luminance across multi-LED displays, critical for aesthetic consistency in consumer UIs. |
| Switching Frequency | 750 kHz (±30%) - high enough to allow small ceramic capacitors (1 µF flying, 3.3 µF input/output), low enough to avoid RF interference. |
| Shutdown Current | <1 µA - enables ultra-low-power standby in battery-critical handheld devices like feature phones or wearables. |
| Headroom Voltage | 360 mV at 30 mA - defines minimum VOUT–VDX differential needed for stable current regulation; impacts minimum usable LED forward voltage. |
| Charge Pump Output Resistance | 3.3 Ω - determines output droop under load; used to calculate max sustainable current given VIN, VLED, and number of LEDs. |
Pinout & Package
LM27951SD is housed in a 4.00 mm × 3.00 mm, 14-pin no-pullback WSON package with exposed die-attach pad connected to GND for thermal dissipation.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| C1+, C1−, C2+, C2− | Flying capacitor connections | Interface with external 1 µF ceramic capacitors to implement 1× or 1.5× charge-pump gain stages; polarity-sensitive layout required. |
| VIN | Main power input | Accepts 2.8–5.5 V supply; feeds charge pump and internal circuitry; requires 3.3 µF low-ESR ceramic bypass capacitor. |
| VOUT | Pre-regulated charge-pump output | Loosely regulated ~4.5 V node supplying all four current sources; must maintain ≥360 mV headroom above highest LED cathode voltage. |
| D1–D4 | Regulated current source outputs | Four independent constant-current sinks (up to 30 mA each); may be paralleled for higher single-LED drive (e.g., D1+D2 for 60 mA). |
| ISET | Current programming reference | Internal 1.25 V reference; RSET from ISET to GND sets all LED currents via IDx = 200 × (1.25 V / RSET). |
| EN | Global enable input | Active-high logic input (150 kΩ internal pulldown); <0.4 V disables entire IC, reducing supply current to <1 µA. |
| PWM | Brightness modulation input | Active-high logic input (no internal pull); toggling this pin ON/OFF modulates LED current without restarting charge pump-reducing input ripple. |
| GND | Power ground | Primary return path; die-attach pad is electrically and thermally tied to GND-must be soldered to large PCB copper area. |
Key Features
| Feature | Design Value |
|---|---|
| Adaptive 1×/1.5× gain selection | Automatically switches between 1× and 1.5× charge-pump modes based on real-time LED forward voltage to maximize efficiency across input range. |
| Four matched current sources | 0.2% typical current matching ensures consistent brightness across all four LEDs-critical for seamless display backlight uniformity. |
| PWM-only brightness control | Enables flicker-free dimming (100 Hz–1 kHz) while keeping charge pump continuously active-eliminates input current spikes seen when PWM-ing EN. |
| No-inductor architecture | Relies solely on four low-cost, miniature ceramic capacitors (CIN, COUT, C1, C2), reducing BOM cost, board area, and EMI vs inductive boost solutions. |
| Thermal protection | Shuts down at 150°C junction temperature and recovers at 140°C-prevents permanent damage during sustained high-current or poor heatsinking conditions. |
Applications
| Smartphone Display Backlight | Feature Phone Keypad Illumination |
|---|---|
|
Use Scenario: Driving four white LEDs behind a 2.4-inch TFT LCD panel in a cost-sensitive smartphone. IC Role / Device Role / Timing Role: Adaptive switched-capacitor current driver providing matched 20 mA per LED with dynamic gain selection to maintain efficiency as battery voltage drops from 4.2 V to 3.2 V. Use Value: Eliminates inductor, reduces solution size by >40%, and achieves >85% peak efficiency across battery discharge cycle-extending talk time. |
Use Scenario: Uniform keypad backlighting for a dual-SIM GSM handset with limited PCB space and strict BOM cost targets. IC Role / Device Role / Timing Role: Four-channel constant-current sink delivering 15 mA per LED with 0.2% matching, controlled via baseband processor's GPIO-driven PWM signal. Use Value: Ensures consistent key illumination intensity across all 12 keys without optical diffusers; <1 µA shutdown current preserves standby battery life >1 month. |
| Portable Medical Device Indicator | Industrial HMI Status Panel |
|
Use Scenario: Powering status LEDs on a handheld pulse oximeter requiring reliable, low-noise illumination under varying ambient temperatures. IC Role / Device Role / Timing Role: Regulated current source maintaining 25 mA per LED despite input voltage sag to 2.8 V and junction temperature shifts from –40°C to +85°C. Use Value: Delivers stable visual feedback without brightness drift; thermal shutdown prevents malfunction during extended operation in warm environments. |
Use Scenario: Backlighting a 4×4 LED array on an industrial control panel powered from a 5 V rail with stringent EMC requirements. IC Role / Device Role / Timing Role: Low-EMI switched-capacitor driver operating at 750 kHz with minimal input ripple, enabling compliance with CISPR-22 Class B emissions limits. Use Value: Avoids magnetic field coupling from inductors; ceramic-only design simplifies layout and passes conducted emissions testing without ferrite beads or shielding. |
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 |
|---|---|---|---|
| TPS61160DRVR | Inductor-based boost converter; fixed 1.2 MHz switching; supports up to 40 mA per channel; requires external diode. | Higher peak efficiency (>90%) at low VIN but generates magnetic EMI; larger solution size due to inductor and diode. | Choose TPS61160DRVR when maximum efficiency at 2.5–3.0 V input is critical and board area allows inductor placement. |
| MAX1910ETE+ | Switched-capacitor driver with 1×/2× gain; 28 mA max per channel; 1.2 MHz switching; 16-pin TQFN package (4×4 mm). | Higher gain flexibility but lower current matching (±3%); lacks adaptive gain logic-requires manual mode selection. | Choose MAX1910ETE+ when driving higher-VF LEDs (e.g., blue/green) where 2× gain is mandatory, and moderate matching suffices. |
Compared with LM27951SD, TPS61160DRVR trades inductor-related EMI and size for higher efficiency at low input voltages, while MAX1910ETE+ offers wider gain range but sacrifices precision matching and adaptive control-making LM27951SD optimal for cost-sensitive, space-constrained white LED backlighting where uniformity and low noise are prioritized.
Availability
LM27951SD is available at Aetrix Electronics and suitable for smartphone display backlights, feature phone keypad illumination, and portable medical device indicators requiring stable component supply, long-term lifecycle support, and traceable sourcing.
Supply support for LM27951SD 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 ICs for portable electronics.
The LM27951SD belongs to TI's white LED driver product line, engineered specifically for high-efficiency, low-EMI backlighting in space-constrained mobile displays-emphasizing current matching, adaptive gain, and capacitor-only design.
FAQ
What is the recommended capacitor type and value for LM27951SD flying capacitors?
LM27951SD 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 voltage-potentially causing regulation failure or instability in the LM27951SD charge pump operation.
How does LM27951SD achieve adaptive 1×/1.5× gain switching?
LM27951SD monitors the headroom voltage (VOUT − VDX) across its current sources. When this voltage falls below 500 mV, it automatically transitions from 1× to 1.5× charge-pump gain to maintain regulation. This real-time adjustment maximizes efficiency across the 2.8–5.5 V input range and varying LED forward voltages-without requiring external control or configuration in the LM27951SD.
Can multiple LM27951SD outputs be paralleled to drive a single high-current LED?
Yes-D1 through D4 outputs of the LM27951SD can be wired in parallel to drive one or two LEDs at higher current. For a single 60 mA LED, configure RSET so each channel delivers 15 mA (i.e., RSET = 200 × 1.25 V / 15 mA ≈ 16.7 kΩ). All electrical specifications-including headroom, matching, and thermal limits-remain valid for this configuration of the LM27951SD.
What is the minimum PWM frequency supported by LM27951SD for brightness control?
The LM27951SD supports PWM dimming from 100 Hz to 1 kHz. Frequencies below 100 Hz risk visible flicker; above 1 kHz may interfere with internal regulation or generate audible noise. The LM27951SD also requires a minimum ON time of 30 µs per cycle-so at 1 kHz, duty cycles below 3% are not recommended to ensure stable current regulation in the LM27951SD.
Does LM27951SD require an external resistor on the EN pin for proper operation?
No-the LM27951SD integrates a 150 kΩ pulldown resistor between EN and GND, so no external resistor is needed for default shutdown behavior. A logic-high signal (>1 V) applied directly to EN enables the IC. This internal pulldown ensures fail-safe shutdown during MCU reset or floating control lines-enhancing system reliability in the final LM27951SD implementation.
LM27951SD Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- -
- Package/Case:
- 14-WFDFN Exposed Pad
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Not For New Designs
- 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)
LM27951SD FAQ
1.How can I place an order for LM27951SD through Aetrix?
Please submit a Request for Quotation (RFQ) for LM27951SD 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 LM27951SD reliable?
The price and inventory of LM27951SD are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LM27951SD is usually 5 days.
3.What payment methods are accepted for LM27951SD?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LM27951SD transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LM27951SD?
LM27951SD orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM27951SD 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 LM27951SD?
For technical support, including LM27951SD datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM27951SD requirements.
6.How does Aetrix verify that LM27951SD is sourced from the original manufacturer or authorized distributors?
All LM27951SD 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 LM27951SD meets industry standards.
7.What is the process for return or replacement of LM27951SD?
All LM27951SD units undergo pre-shipment inspection (PSI). If there is an issue with LM27951SD, 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 LM27951SD part is unused and in its original packaging.
Return procedure for LM27951SD:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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