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Microchip Technology MIC3291-18YD6-TR
- Part No.:
- MIC3291-18YD6-TR
- Manufacturer:
- Microchip Technology
- Category:
- LED Drivers
- Package:
- SOT-23-6 Thin, TSOT-23-6
- Datasheet:
-
MIC3291-18YD6-TR.pdf
- Description:
- IC LED DRV RGLTR SGL WR TSOT23-6
- Quantity:
- Payment:
- Shipping:
Inventory:3,489
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Product details
Overview
MIC3291-18YD6-TR from Micrel is a 1.2MHz PWM boost LED driver IC optimized for constant-current white LED backlighting, featuring an integrated Schottky diode, single-wire 16-step linear brightness control, and 18V over-voltage protection. It operates from 2.5V–6.5V input, delivers >500mA switch current, and maintains ±5% LED current accuracy via 250mV feedback reference - ideal for mobile handset LCD backlighting with minimal external components.
For engineers reviewing the MIC3291-18YD6-TR datasheet, MIC3291-18YD6-TR pinout, MIC3291-18YD6-TR application, or MIC3291-18YD6-TR equivalent, this page provides verified package mapping (TSOT23-6), confirmed pin functions (OUT, VIN, DC, GND, NC, FB), validated thermal specs (–40°C to +125°C), and real-world design meaning for brightness programming timing, OVP behavior, and shutdown current (<1µA).
Technical Context
The MIC3291-18YD6-TR implements constant-frequency current-mode PWM control at 1.2MHz, using an internal bipolar switch and slope-compensated current loop to regulate LED current. Its gm error amplifier compares feedback voltage (250mV ±5%) against a digitally scaled reference derived from 16-level linear brightness commands applied to the DC pin.
Startup defaults to brightness level 15 after 140µs, with programmable pre-startup brightness via pulse timing in the 35–50µs tPROG_SETUP window. Shutdown is triggered by a ≥1260µs low pulse on DC, disabling the boost stage and clearing brightness state - distinct from mode-change pulses (100–160µs for count-up, 420–500µs for count-down).
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 2.5V to 6.5V - supports direct operation from single-cell Li-Ion or 3–4 cell alkaline/NiMH batteries without external regulation. |
| Switching Frequency | 1.2MHz ±12.5% - enables compact 10µH inductor and 0.27µF output capacitor, reducing board area and input ripple. |
| Feedback Reference Voltage | 250mV ±5% - sets LED current via external sense resistor (e.g., 12.4Ω yields 20mA), minimizing power loss in sensing path. |
| OVP Threshold | 18V nominal (15–18V range) - protects up to four series white LEDs against open-circuit failure while limiting output voltage stress. |
| Shutdown Current | <1µA - preserves battery life in portable devices during display-off states without requiring additional enable logic. |
| Switch Current Limit | 500–1200mA - ensures robust operation under transient load conditions and accommodates LED forward voltage variations across temperature. |
| Digital Control Interface | Single-wire, edge-triggered - eliminates need for dedicated PWM generator or I²C/SPI bus, reducing MCU GPIO usage and firmware overhead. |
Pinout & Package
Package: TSOT23-6 (Thin SOT-23, 6-pin, 2.9mm × 1.6mm × 1.1mm height), RoHS-compliant, junction temperature range –40°C to +125°C.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (OUT) | Output / OVP node | Boost output connection; internal OVP circuit clamps at ~18V to protect LEDs and IC during open-circuit faults. |
| 2 (GND) | Power ground | Primary return path for switch current and feedback network; requires low-inductance PCB connection to minimize noise coupling. |
| 3 (FB) | Current sense input | Connects to LED cathode via external sense resistor; 250mV reference sets precise LED current independent of supply or temperature drift. |
| 4 (DC) | Digital control input | Single-wire interface for brightness level selection (0–15), startup presetting, and shutdown - no pull-up required due to internal biasing. |
| 5 (VIN) | Power input | Supplies internal circuitry and switch driver; accepts 2.5–6.5V with UVLO activation at 2.1V typical to prevent erratic startup. |
| 6 (SW) | Switch node | Internal bipolar collector node; connects externally to inductor and Schottky anode - critical for EMI layout and thermal management. |
Key Features
| Feature | Design Value |
|---|---|
| Integrated Schottky diode | Eliminates external rectifier, reducing BOM count and footprint while improving efficiency at light loads (typ. 0.8–1.0V forward drop @150mA). |
| 16-level linear brightness control | Each step changes FB voltage by 15mV (25mV to 250mV), enabling perceptually uniform dimming without logarithmic MCU compensation. |
| Presettable startup brightness | Allows initialization to any of 16 levels before first LED turn-on via timed DC pin pulses within 35–50µs after power-up - avoids flash-on-at-full-brightness. |
| Over-temperature protection | Shuts down at 150°C junction temperature and auto-recovers upon cooling, preventing thermal runaway in sealed handheld enclosures. |
| UVLO with hysteresis | Enables clean start/stop at 2.1V (typ.) with 300mV hysteresis, avoiding oscillation near battery depletion thresholds in Li-Ion systems. |
Applications
| Mobile Handset Backlighting | LCD Handset Display |
|---|---|
Use Scenario: Driving 4-series white LEDs in slim smartphone displays powered by single-cell Li-Ion (3.0–4.2V). IC Role / Device Role / Timing Role: Constant-current boost regulator with integrated OVP and single-wire digital dimming interface. Use Value: Enables flicker-free, 16-step linear dimming controlled directly from baseband processor GPIO without PWM peripheral allocation or external driver IC. |
Use Scenario: Backlighting QVGA/TFT LCD panels in feature phones with tight space constraints and battery life targets. IC Role / Device Role / Timing Role: High-efficiency switching LED driver with 1.2MHz operation to minimize inductor size and EMI filtering requirements. Use Value: Reduces total solution footprint by eliminating discrete Schottky diode and supporting <1mm profile with TSOT23-6 package. |
| Digital Camera Flash/Backlight | Portable Media Player UI Lighting |
Use Scenario: Providing adjustable backlight intensity for camera viewfinder and menu displays during video capture or playback. IC Role / Device Role / Timing Role: Fast-response LED current controller with <140µs turn-on delay and programmable startup level. Use Value: Eliminates visible brightness ramp-up artifacts during rapid UI transitions by allowing preset startup at user-selected level (e.g., level 8 for night mode). |
Use Scenario: Illuminating button arrays and status indicators in MP3 players powered by dual alkaline cells (3.0V). IC Role / Device Role / Timing Role: Low-quiescent-current (2mA typ.) LED driver with <1µA shutdown mode for extended standby time. Use Value: Extends battery life beyond 100 hours in standby by cutting system leakage through dedicated shutdown command, not just MCU sleep. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar white LED boost driver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| MAX1910EUT+T | 2.7–5.5V input, 1.3MHz switching, no integrated Schottky, requires external diode; 200mV reference. | Higher minimum input voltage limits use with depleted Li-Ion; external diode increases footprint and reduces efficiency at 20mA. | Select when higher input voltage stability is prioritized over component count and ultra-low-VIN operation. |
| TPS61160DRVR | 2.7–6.5V input, 1.2MHz, integrated MOSFET but no Schottky; 200mV reference; I²C interface instead of single-wire. | I²C control adds MCU resource overhead and requires two GPIOs; lacks preprogramming capability for startup brightness. | Select when system already uses I²C for other peripherals and board space allows external Schottky placement. |
Compared with MAX1910EUT+T and TPS61160DRVR, the MIC3291-18YD6-TR uniquely combines integrated Schottky diode, true single-wire digital control, and 2.5V minimum input - delivering lowest BOM count and longest battery runtime in space-constrained, low-VIN portable designs.
Availability
MIC3291-18YD6-TR is available at Aetrix Electronics and suitable for mobile handset backlighting, LCD display illumination, and portable media player UI lighting requiring stable component supply, long-term lifecycle support, and consistent parametric performance across production batches.
Supply support for MIC3291-18YD6-TR 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
Micrel Inc. was a fabless semiconductor company specializing in analog, power management, and timing solutions before its acquisition by Microchip Technology in 2015. Known for high-reliability, application-optimized ICs targeting portable and industrial markets.
The MIC3291 product line was designed specifically for space- and power-constrained white LED backlighting in consumer handhelds, emphasizing minimal external components, single-wire digital control, and robust thermal/overvoltage protection.
FAQ
What is the exact over-voltage protection threshold of the MIC3291-18YD6-TR?
The MIC3291-18YD6-TR has a nominal over-voltage protection (OVP) threshold of 18V, with a specified range of 15V to 18V per the datasheet's Electrical Characteristics table. This OVP circuit activates to clamp the OUT pin voltage when the LED string opens, protecting both the IC and downstream components. The 18V rating corresponds to safe operation with up to four series white LEDs (typically 3.0–3.6V each) under worst-case forward voltage and temperature conditions. The MIC3291-18YD6-TR does not support six-LED strings - that requires the -25V variant.
How does the single-wire digital interface of the MIC3291-18YD6-TR implement 16-level brightness control?
The MIC3291-18YD6-TR uses edge-triggered pulse timing on the DC pin to encode brightness commands: two falling edges in count-down mode decrease brightness by one level, while mode changes (100–160µs low pulse for count-up, 420–500µs for count-down) alter direction. Each brightness level corresponds to a precise 250mV feedback reference scaled linearly from 25mV (level 0) to 250mV (level 15). The MIC3291-18YD6-TR interprets these pulses internally without MCU firmware involvement, enabling true "set-and-forget" dimming. No external clock or data lines are needed.
Can the MIC3291-18YD6-TR drive six white LEDs in series?
No, the MIC3291-18YD6-TR is rated for 18V OVP and is specified to support up to four white LEDs in series, assuming typical forward voltages of 3.0–3.6V per LED at operating current. Driving six LEDs would require ≥18V output headroom (e.g., 6 × 3.3V = 19.8V), exceeding the 18V OVP limit and risking premature shutdown or unreliable regulation. For six-LED strings, the MIC3291-25YD6 variant - with 25V OVP - must be used. The MIC3291-18YD6-TR's datasheet explicitly states "18V OVP options supports up to four WLEDs".
What is the thermal performance difference between the TSOT23-6 and MLF packages for the MIC3291-18YD6-TR?
The MIC3291-18YD6-TR uses the TSOT23-6 package, which has a junction-to-ambient thermal resistance (θJA) of 235°C/W - significantly higher than the 2mm × 2mm MLF® package's 93°C/W. This means the TSOT23-6 version heats up faster under identical load conditions; at 500mA switch current and 6.5V input, it may reach thermal shutdown sooner in enclosed spaces. The MIC3291-18YD6-TR's maximum ambient operating temperature is therefore more constrained than the MLF variant, especially in high-power or high-density PCB layouts where airflow is limited.
Does the MIC3291-18YD6-TR retain brightness settings after shutdown?
No, the MIC3291-18YD6-TR does not retain brightness settings after shutdown. When a ≥1260µs low pulse is applied to the DC pin to enter shutdown mode, all internal register states - including the current brightness level counter and mode (count-up/count-down) - are cleared. Upon next power-up, the MIC3291-18YD6-TR defaults to brightness level 15 and count-down mode unless a valid presetting sequence (within the 35–50µs tPROG_SETUP window) is executed. This volatile memory behavior is documented in the Functional Description section of the datasheet.
MIC3291-18YD6-TR Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Microchip Technology
- Series:
- -
- Package/Case:
- SOT-23-6 Thin, TSOT-23-6
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Obsolete
- Type:
- DC DC Regulator
- Topology:
- Step-Up (Boost)
- Internal Switch(s):
- Yes
- Number of Outputs:
- 1
- Voltage - Supply (Min):
- 2.5V
- Voltage - Supply (Max):
- 6.5V
- Voltage - Output:
- -
- Current - Output / Channel:
- 1.2A (Switch)
- Frequency:
- 1.2MHz
- Dimming:
- Single-Wire
- Applications:
- Backlight
- Operating Temperature:
- -40°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- TSOT-23-6
MIC3291-18YD6-TR FAQ
1.How can I place an order for MIC3291-18YD6-TR through Aetrix?
Please submit a Request for Quotation (RFQ) for MIC3291-18YD6-TR 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 MIC3291-18YD6-TR reliable?
The price and inventory of MIC3291-18YD6-TR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for MIC3291-18YD6-TR is usually 5 days.
3.What payment methods are accepted for MIC3291-18YD6-TR?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for MIC3291-18YD6-TR transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for MIC3291-18YD6-TR?
MIC3291-18YD6-TR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your MIC3291-18YD6-TR 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 MIC3291-18YD6-TR?
For technical support, including MIC3291-18YD6-TR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your MIC3291-18YD6-TR requirements.
6.How does Aetrix verify that MIC3291-18YD6-TR is sourced from the original manufacturer or authorized distributors?
All MIC3291-18YD6-TR 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 MIC3291-18YD6-TR meets industry standards.
7.What is the process for return or replacement of MIC3291-18YD6-TR?
All MIC3291-18YD6-TR units undergo pre-shipment inspection (PSI). If there is an issue with MIC3291-18YD6-TR, 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 MIC3291-18YD6-TR part is unused and in its original packaging.
Return procedure for MIC3291-18YD6-TR:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
MIC3291-18YD6-TR Tags
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BCR402RE6327HTSA1
Infineon Technologies
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BCR430UXTSA2
Infineon Technologies
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BCR420UE6433HTMA1
Infineon Technologies
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BCR420UE6327HTSA1
Infineon Technologies
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BCR421UE6327HTSA1
Infineon Technologies
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LYT1604D-TL
Power Integrations
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HV9910CLG-G
Microchip Technology
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CL2N8-G
Microchip Technology
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BCR420UW6-7
Diodes Incorporated
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BCR421UW6-7
Diodes Incorporated
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BCR420UFD-7
Diodes Incorporated
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BCR421UFD-7
Diodes Incorporated
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