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Allegro MicroSystems A6277ELW-T
- Part No.:
- A6277ELW-T
- Manufacturer:
- Allegro MicroSystems
- Category:
- LED Drivers
- Package:
- 20-SOIC (0.295", 7.50mm Width)
- Datasheet:
-
A6277ELW-T.pdf
- Description:
- IC LED DRVR LINEAR 120MA 20SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:2,398
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Product details
Overview
A6277ELW-T from Allegro MicroSystems is an 8-bit serial-input constant-current latched LED driver with NPN sink outputs, designed for multiplexed LED display systems. It integrates a CMOS shift register, data latches, and eight programmable current sinks (up to 150 mA per output), supporting 20 MHz serial data rates at 5 V logic supply and enabling digital dimming via HIGH/LOW pin control.
For engineers reviewing the A6277ELW-T datasheet, A6277ELW-T pinout, A6277ELW-T application, or A6277ELW-T equivalent, this device serves as a high-speed, thermally robust LED driver for industrial signage, instrumentation displays, and segmented panel indicators where precise current regulation and inter-digit blanking are required.
Technical Context
The A6277ELW-T implements a serial-to-parallel conversion architecture: data shifts in on the rising edge of CLOCK (up to 20 MHz), is latched on HIGH LATCH ENABLE, and drives outputs only when OUTPUT ENABLE is low. Its dual serial data outputs (SDO1 on rising edge, SDO2 on falling edge) support daisy-chaining without external buffering.
Current regulation is set by a single external resistor (REXT) connected to pin 19, establishing identical sink current across all eight outputs. The HIGH/LOW pin provides hardware-selectable 100% or 50% current scaling, while undervoltage lockout disables operation below ~4.3 V to prevent erratic behavior during power ramp-up.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Configuration | Eight NPN constant-current sink drivers, each programmable up to 150 mA via REXT |
| Logic Supply Voltage | 4.5–5.5 V; supports standard 5 V microcontroller interfaces with low-power CMOS logic |
| Serial Data Rate | Up to 20 MHz; enables fast refresh of large LED matrices without CPU overhead |
| Current Scaling | HIGH/LOW pin selects full (100%) or half (50%) programmed current - no software change needed |
| Thermal Resistance | RθJA = 90 °C/W (SOICW package); limits continuous current to ~122 mA at 85°C ambient |
| Undervoltage Lockout | Activates below ~4.3 V; prevents partial operation and latch corruption during brownout |
| Output Disable | Active-high OUTPUT ENABLE blanks all outputs simultaneously for inter-digit blanking |
Pinout & Package
Package: 20-pin SOICW (LW suffix), surface-mount, lead-free with 100% matte-tin plating. Dimensions conform to JEDEC MS-013 AC.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 | LOGIC GROUND | Dedicated ground reference for shift register and latch logic; must be isolated from power ground to avoid noise coupling |
| 2 | SERIAL DATA IN | CMOS-compatible serial input; accepts data synchronized to CLOCK rising edge |
| 3 | CLOCK | Positive-edge-triggered clock for shift register; minimum pulse width 50 ns |
| 4 | LATCH ENABLE | High-level strobe transfers shift register contents to output latches; enables real-time update control |
| 5 | HIGH/LOW | Selects 100% (logic low) or 50% (logic high) of REXT-set current - hardware dimming without PWM |
| 6, 15 | POWER GROUND | Common return path for all eight output drivers; separate from logic ground to minimize voltage drop |
| 7–14 | OUT0–OUT7 | NPN open-collector current sinks; each delivers identical regulated current determined by REXT |
| 16 | OUTPUT ENABLE | Active-high signal disables all outputs simultaneously for global blanking or power saving |
| 17 | SERIAL OUT2 | CMOS output clocked on CLOCK falling edge; enables cascading without external inverters |
| 18 | SERIAL OUT1 | CMOS output clocked on CLOCK rising edge; used for standard daisy-chain configurations |
| 19 | REXT | Connection point for external current-setting resistor; sets identical sink current for all eight outputs |
| 20 | LOGIC SUPPLY (VDD) | 5 V ±0.5 V supply for internal logic; powers shift register, latches, and interface circuitry |
Key Features
| Feature | Design Value |
|---|---|
| Constant-current sink outputs | Each of eight outputs delivers matched current (±6.0% matching) set by one external resistor |
| Dual serial data outputs | SDO1 (rising edge) and SDO2 (falling edge) enable flexible daisy-chaining without timing constraints |
| Hardware current scaling | HIGH/LOW pin provides instant 2× current reduction - eliminates need for dynamic PWM adjustment |
| Inter-digit blanking | Active-high OUTPUT ENABLE globally disables all outputs within 1 µs, enabling precise multiplex timing |
| Undervoltage lockout | Prevents erroneous data latching or partial output activation during power-up/down transitions |
Applications
| Industrial Panel Displays | LED Signage Modules |
|---|---|
|
Use Scenario: Driving 7-segment or dot-matrix LED displays in factory HMIs with 1/8 duty cycle multiplexing. IC Role / Device Role / Timing Role: Constant-current sink driver providing stable brightness across digits; handles serial data chaining and inter-digit blanking. Use Value: Eliminates per-segment current resistors and ensures uniform LED intensity despite forward voltage variation across batches. |
Use Scenario: Controlling red/green/blue LED modules in outdoor advertising signs requiring thermal stability up to 85°C. IC Role / Device Role / Timing Role: High-current sink driver with 90 °C/W SOICW thermal resistance; supports 122 mA continuous per output at full ambient. Use Value: Enables direct drive of high-brightness LEDs without external heatsinking, reducing BOM count and board area. |
| Test Equipment Indicators | Automotive Instrument Clusters |
|
Use Scenario: Driving status LEDs and bar-graph displays in benchtop multimeters and oscilloscopes with microcontroller serial control. IC Role / Device Role / Timing Role: Serial-input latched driver interfacing directly with 5 V MCU SPI/GPIO; supports 20 MHz data rate for rapid updates. Use Value: Reduces MCU GPIO usage from 16 pins (data + control) to 4 pins (SDI, CLK, LE, OE), simplifying firmware and layout. |
Use Scenario: Illuminating segmented fuel level, speed, and warning indicators in automotive dashboards with ESD-hardened interface. IC Role / Device Role / Timing Role: Class 2 ESD-protected LED driver with undervoltage lockout; operates reliably across automotive battery range (9–16 V system with local 5 V rail). Use Value: Prevents display glitches during cold-crank (low-VDD) events and withstands 2 kV HBM ESD per IEC 61000-4-2. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar constant-current LED driver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| Toshiba TD62715FN | Pin-compatible 20-pin SOIC; identical 8-bit shift/latch/sink architecture but lacks HIGH/LOW current scaling pin | No hardware dimming mode - requires external PWM or current-resistor switching for brightness control | Choose TD62715FN only if existing PCB layout mandates pin match and dimming is handled externally |
| ON Semiconductor CAT4016 | 16-channel sink driver in 24-pin SOIC; higher channel count but lower max current (100 mA) and no HIGH/LOW scaling | Requires two devices for 16-bit drive vs. one A6277ELW-T for 8-bit; no inter-digit blanking enable pin | Choose CAT4016 only when expanding to >8 outputs per IC is required and thermal derating at 85°C is acceptable |
Compared with TD62715FN and CAT4016, the A6277ELW-T uniquely combines hardware-selectable current scaling, dedicated inter-digit blanking, and 150 mA per output in a compact 20-pin SOICW - making it optimal for space-constrained, thermally demanding LED display designs requiring minimal external components.
Availability
A6277ELW-T is available at Aetrix Electronics and suitable for industrial panel displays, LED signage modules, and test equipment indicators requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.
Supply support for A6277ELW-T 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
Allegro MicroSystems is a U.S.-based designer and manufacturer of high-performance magnetic sensors, power ICs, and precision analog devices, headquartered in Worcester, Massachusetts.
The A6277 product line targets LED display systems requiring integrated constant-current sinking, serial interface efficiency, and thermal resilience in industrial and commercial environments.
FAQ
What is the maximum continuous output current per channel for A6277ELW-T at 85°C ambient?
The A6277ELW-T supports up to 122 mA per output continuously at 85°C ambient temperature when mounted on a 1-layer PCB, based on its 90 °C/W junction-to-ambient thermal resistance and 1.0 V VCE drop specification. This value assumes proper PCB copper area and no additional airflow or heatsinking.
How does the HIGH/LOW pin affect current regulation in A6277ELW-T?
In the A6277ELW-T, the HIGH/LOW pin provides hardware-selectable current scaling: a logic low configures all eight outputs for 100% of the current set by REXT, while a logic high reduces output current to exactly 50% of that value. This function operates independently of latch or enable states and requires no software intervention.
Can A6277ELW-T be used with LED forward voltages above 4.0 V?
Yes, but only with external voltage reduction. The A6277ELW-T is rated for VCE up to 1.0 V at full current; using it with LED strings exceeding 4.0 V forward voltage requires adding series diodes, Zener clamps, or regulators (e.g., Sanken SAI series) to limit VCE and avoid excessive package power dissipation.
What is the purpose of separate LOGIC GROUND and POWER GROUND pins in A6277ELW-T?
The A6277ELW-T uses separate LOGIC GROUND (pin 1) and POWER GROUND (pins 6 and 15) to isolate sensitive shift register and latch circuitry from high-current switching noise. This separation prevents ground bounce from corrupting serial data or latch timing - critical for reliable operation in noisy industrial environments.
Does A6277ELW-T support daisy-chaining, and how many devices can be cascaded?
Yes, the A6277ELW-T supports daisy-chaining via two dedicated serial outputs: SDO1 (rising-edge clocked) and SDO2 (falling-edge clocked). There is no hard limit on cascade length; practical limits depend on signal integrity, clock skew, and total propagation delay - typically up to 10–15 devices in well-designed PCB layouts.
A6277ELW-T Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Allegro MicroSystems
- Series:
- -
- Package/Case:
- 20-SOIC (0.295", 7.50mm Width)
- Packaging:
- Tube
- Product Status:
- Obsolete
- Type:
- Linear
- Topology:
- Shift Register
- Internal Switch(s):
- Yes
- Number of Outputs:
- 8
- Voltage - Supply (Min):
- 4.5V
- Voltage - Supply (Max):
- 5.5V
- Voltage - Output:
- 4V
- Current - Output / Channel:
- 120mA
- Frequency:
- 20MHz
- Dimming:
- -
- Applications:
- -
- Operating Temperature:
- -40°C ~ 85°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 20-SOIC
A6277ELW-T FAQ
1.How can I place an order for A6277ELW-T through Aetrix?
Please submit a Request for Quotation (RFQ) for A6277ELW-T 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 A6277ELW-T reliable?
The price and inventory of A6277ELW-T are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for A6277ELW-T is usually 5 days.
3.What payment methods are accepted for A6277ELW-T?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for A6277ELW-T transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for A6277ELW-T?
A6277ELW-T orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your A6277ELW-T 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 A6277ELW-T?
For technical support, including A6277ELW-T datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your A6277ELW-T requirements.
6.How does Aetrix verify that A6277ELW-T is sourced from the original manufacturer or authorized distributors?
All A6277ELW-T 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 A6277ELW-T meets industry standards.
7.What is the process for return or replacement of A6277ELW-T?
All A6277ELW-T units undergo pre-shipment inspection (PSI). If there is an issue with A6277ELW-T, 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 A6277ELW-T part is unused and in its original packaging.
Return procedure for A6277ELW-T:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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