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Texas Instruments LM2794BL
- Part No.:
- LM2794BL
- Manufacturer:
- Texas Instruments
- Category:
- LED Drivers
- Package:
- 14-WFBGA, DSBGA
- Datasheet:
-
LM2794BL.pdf
- Description:
- IC LED DRV RGLTR PWM 14DSBGA
- Quantity:
- Payment:
- Shipping:
Inventory:2,834
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Product details
Overview
LM2794BL from Texas Instruments is a current-regulated switched-capacitor white LED driver IC with analog and PWM brightness control, delivering up to 20mA per output across four matched current sources (±0.5% matching), operating from 2.7V–5.5V input, and featuring 325kHz minimum switching frequency for EMI-controlled operation in portable RF devices.
For engineers reviewing the LM2794BL datasheet, LM2794BL pinout, LM2794BL application, or LM2794BL equivalent, this page provides verified technical context on its 1.5×/1× charge-pump architecture, DSBGA-14 package mapping, BRGT/SD dual-dimming interface, ISET-based current programming, and thermal shutdown behavior - all critical for backlight design in Li-ion-powered handhelds.
Technical Context
The LM2794BL implements a fractional CMOS charge pump with automatic mode switching: it operates in 1.5× boost mode below ~4.7V input and transitions to pass-through (1×) mode above that threshold, minimizing power loss while maintaining regulated current. Its internal current mirror uses a 10:1 ratio referenced to RSET, enabling precise LED current setting independent of VIN or VLED variations.
Brightness control is implemented via two orthogonal paths: analog dimming through a 0–3.0V voltage applied to BRGT (with 240kΩ input resistance), and digital dimming via PWM on the active-low SD pin - where duty cycle directly modulates average LED current without altering regulation accuracy. Thermal protection engages at TJ = 150°C (typ.) and releases at 140°C (typ.).
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 2.7V to 5.5V - supports full Li-ion battery discharge curve without external regulation |
| Max Output Current per Channel | 20mA - sufficient for driving standard white LEDs at full brightness with margin |
| Current Matching Accuracy | ±0.5% - ensures uniform brightness across multiple LEDs in display/keypad backlights |
| Switching Frequency | 325kHz (min.) - places noise spectrum outside sensitive RF bands (e.g., GSM, Bluetooth) |
| Shutdown Current | 2.3µA (typ.) - enables ultra-low-power standby in battery-critical applications |
| Charge-Pump Gain | 1.5× (boost) / 1× (pass) - dynamically selects optimal conversion mode based on VIN to maximize efficiency |
| Headroom Voltage Coefficient | 20mV/mA (typ.) - defines minimum POUT-to-LED voltage drop required for stable current regulation |
Pinout & Package
LM2794BL is housed in a Thin DSBGA package measuring 2.08mm × 2.403mm × 0.600mm, optimized for space-constrained portable designs. The 14-ball array follows JEDEC-standard bottom-view numbering.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| A1 (C1+) | Charge-pump flying capacitor positive terminal | Connects to C1 anode; forms half of 1.5× charge-pump stage with C1− |
| B2 (C1−) | Charge-pump flying capacitor negative terminal | Completes C1 loop; critical for charge transfer timing and efficiency |
| C1 (VIN) | Main power supply input | Accepts 2.7–5.5V; powers internal circuitry and feeds charge-pump input |
| D2 (GND) | Power ground reference | Common return for all currents; must be low-impedance for stability |
| E1 (C2−) | Second flying capacitor negative terminal | Part of auxiliary charge-pump path; improves ripple suppression |
| E3/E5/E7/D6 (D1–D4) | Regulated current source outputs | Directly drive LED anodes; each delivers matched current up to 20mA |
| C7 (ISET) | Current sense reference input | Connects external 1% resistor to GND; sets base current for 10:1 mirrored outputs |
| B6 (BRGT) | Analog brightness control input | 0–3.0V linear control; internal 0.385× scaling + 0.188V offset determines final LED current |
| A7 (SD) | Active-low shutdown input | LOW disables device and reduces IQ to 2.3µA; no internal pull-up (LM2794 variant) |
| A5 (C2+) | Second flying capacitor positive terminal | Completes C2 loop; works with C2− to stabilize POUT rail |
| A3 (POUT) | Unregulated charge-pump output rail | Provides ~1.5×VIN; usable for auxiliary loads (e.g., keypad LEDs) with ballast resistors |
Key Features
| Feature | Design Value |
|---|---|
| Four matched ±0.5% current sources | Enables consistent brightness across multi-LED displays without binning or calibration |
| 1.5×/1× auto-switching charge pump | Eliminates need for inductor while maintaining >80% efficiency across full battery range |
| Independent analog (BRGT) and PWM (SD) dimming | Supports hybrid brightness control schemes - e.g., coarse analog + fine PWM for flicker-free UI |
| DSBGA-14 package (2.08mm × 2.403mm) | Reduces PCB area by >60% vs. comparable QFN packages; compatible with fine-pitch assembly |
| Thermal shutdown (150°C engage / 140°C release) | Prevents permanent damage during transient overloads or poor thermal layout |
Applications
| White LED Display Backlight | White LED Keypad Backlight |
|---|---|
Use Scenario: Driving 4 parallel white LEDs behind a small TFT LCD in a handheld medical device powered by single-cell Li-ion. IC Role / Device Role / Timing Role: LM2794BL acts as constant-current source with integrated 1.5× charge pump, regulating current independently per LED to maintain luminance uniformity despite VLED variation. Use Value: Eliminates need for discrete current-setting resistors and inductor-based boost converters, reducing BOM count and board area by 35%. |
Use Scenario: Illuminating alphanumeric keypad in industrial PDA operating across −30°C to +85°C ambient range. IC Role / Device Role / Timing Role: LM2794BL supplies matched current to 2–4 keypad LEDs using D1–D4 outputs, with BRGT pin accepting microcontroller DAC output for programmable dimming. Use Value: ±0.5% current matching ensures consistent key visibility under varying temperature and battery voltage, avoiding user-perceived brightness drift. |
| 1-Cell Li-Ion Portable Equipment | RF-Sensitive Handheld Devices |
Use Scenario: Powering backlight in cellular phone with dynamic battery voltage (4.2V → 2.7V) and strict power budget. IC Role / Device Role / Timing Role: LM2794BL switches between 1.5× boost and 1× pass modes automatically, minimizing quiescent current (5.5mA typ.) and shutdown current (2.3µA typ.) to extend runtime. Use Value: Delivers stable LED current across full battery discharge without requiring system-level voltage regulation or firmware intervention. |
Use Scenario: Backlighting UI elements in Bluetooth headset where conducted EMI must avoid 2.4GHz band. IC Role / Device Role / Timing Role: LM2794BL's fixed 325kHz min. switching frequency ensures fundamental and harmonics remain below 2.4GHz, preventing interference with RF receiver sensitivity. Use Value: Meets CISPR-22 Class B emissions requirements without additional EMI filtering components, saving cost and layout space. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar LED driver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LM2795BL | Identical functionality except active-high SD pin with internal VIN pull-up; no external pull required for open-drain control | Suitable when host MCU GPIO lacks pull-down capability or requires simplified shutdown logic | Select LM2795BL if system uses open-drain drivers or needs guaranteed high-Z SD state during reset |
| TPS61160DRVR | Inductor-based boost converter with I²C interface; higher max output voltage (28V) but larger solution size and no current-matching guarantee | Better suited for high-VF LED strings (>4.5V) or systems requiring digital brightness control and fault reporting | Choose TPS61160DRVR only when >20mA per channel or >4.5V LED forward voltage is required |
Compared with LM2795BL, LM2794BL offers simpler active-low shutdown integration with standard GPIOs; compared with TPS61160DRVR, LM2794BL provides superior current matching and smaller footprint but lower output voltage headroom - making it optimal for compact, cost-sensitive single-cell LED backlighting.
Availability
LM2794BL is available at Aetrix Electronics and suitable for white LED display backlights, keypad illumination, and 1-cell Li-ion portable equipment requiring stable component supply, consistent current matching, and minimal EMI impact.
Supply support for LM2794BL 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 precision analog ICs.
The LM2794BL belongs to TI's LED backlight driver product line, engineered specifically for space- and power-constrained portable electronics requiring high-current matching, inductorless operation, and robust RF coexistence.
FAQ
What is the maximum total output current supported by the LM2794BL?
The LM2794BL supports up to 20mA per channel across D1–D4, for a maximum total regulated current of 80mA. This assumes sufficient headroom voltage (VPOUT − VDX ≥ kHR × IDX, where kHR = 20mV/mA typ.) and accounts for POUT loading. When driving four 3.6V white LEDs from 3.6V input, typical total current remains within 60–70mA due to charge-pump droop and thermal limits. LM2794BL maintains regulation integrity only when headroom conditions are met.
How does the BRGT pin control LED brightness in the LM2794BL?
The BRGT pin accepts a 0–3.0V analog voltage that linearly scales the LED current via an internal resistor network (0.385× scaling) and offset (0.188V). For example, with RSET = 124Ω, BRGT = 0V yields ~15mA per channel, while BRGT = 3.0V yields ~20mA. Voltages above 3.0V provide no additional current increase. LM2794BL's BRGT interface enables smooth, flicker-free dimming without PWM timing constraints.
Can the LM2794BL drive LEDs directly from the POUT pin?
Yes, the POUT pin provides an unregulated ~1.5×VIN rail usable for auxiliary LED loads, but current must be limited externally via ballast resistors. Because POUT voltage drops with total load current (VPOUT = 1.5×VIN − ITOTAL × ROUT, ROUT ≈ 3.0Ω), brightness matching is not guaranteed. LM2794BL documentation recommends POUT for non-critical functions like keypad LEDs - not primary display backlights - where absolute current matching is unnecessary.
What is the purpose of the ISET pin on the LM2794BL?
The ISET pin connects to a precision resistor (e.g., 124Ω for 15mA/channel) that sets the reference current for LM2794BL's internal 10:1 current mirror. The resulting mirrored current flows through D1–D4 outputs. Using a 1% tolerance resistor ensures accurate and repeatable LED current programming. ISET does not sink or source current - it develops a voltage proportional to the desired output current, which LM2794BL internally converts and replicates.
Does the LM2794BL include thermal protection?
Yes, the LM2794BL integrates thermal shutdown that disables operation when junction temperature exceeds 150°C (typ.), re-enabling automatically when temperature falls below 140°C (typ.). This protects against permanent damage during sustained overload, poor PCB thermal design, or high ambient conditions. The feature is fully internal - no external components or configuration are required for activation. LM2794BL's DSBGA package relies on proper copper pour and vias for effective heat dissipation to sustain rated performance.
LM2794BL Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- -
- Package/Case:
- 14-WFBGA, DSBGA
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Obsolete
- Type:
- DC DC Regulator
- Topology:
- Switched Capacitor (Charge Pump)
- Internal Switch(s):
- Yes
- Number of Outputs:
- 4
- Voltage - Supply (Min):
- 2.7V
- Voltage - Supply (Max):
- 5.5V
- Voltage - Output:
- 3.8V
- Current - Output / Channel:
- 20mA
- Frequency:
- 515kHz
- Dimming:
- Analog, PWM
- Applications:
- Backlight
- Operating Temperature:
- -30°C ~ 85°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 14-DSBGA
LM2794BL FAQ
1.How can I place an order for LM2794BL through Aetrix?
Please submit a Request for Quotation (RFQ) for LM2794BL 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 LM2794BL reliable?
The price and inventory of LM2794BL are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LM2794BL is usually 5 days.
3.What payment methods are accepted for LM2794BL?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LM2794BL transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LM2794BL?
LM2794BL orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM2794BL 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 LM2794BL?
For technical support, including LM2794BL datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM2794BL requirements.
6.How does Aetrix verify that LM2794BL is sourced from the original manufacturer or authorized distributors?
All LM2794BL 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 LM2794BL meets industry standards.
7.What is the process for return or replacement of LM2794BL?
All LM2794BL units undergo pre-shipment inspection (PSI). If there is an issue with LM2794BL, 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 LM2794BL part is unused and in its original packaging.
Return procedure for LM2794BL:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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