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Allegro MicroSystems A6277ELWTR-T
- Part No.:
- A6277ELWTR-T
- Manufacturer:
- Allegro MicroSystems
- Category:
- LED Drivers
- Package:
- 20-SOIC (0.295", 7.50mm Width)
- Datasheet:
-
A6277ELWTR-T.pdf
- Description:
- IC LED DRVR LINEAR 120MA 20SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:2,017
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Product details
Overview
A6277ELWTR-T from Allegro MicroSystems is an 8-bit serial-input constant-current latched LED driver in a 20-pin SOICW package, featuring eight NPN constant-current sink outputs, CMOS shift register and latch logic, and HIGH/LOW current select (100% or 50% of programmed value). It supports up to 20 MHz serial data input at 5 V logic supply and enables inter-digit blanking via active-low OUTPUT ENABLE - used in multiplexed LED displays requiring precise per-bit current control.
For engineers reviewing the A6277ELWTR-T datasheet, A6277ELWTR-T pinout, A6277ELWTR-T application, or A6277ELWTR-T equivalent, key selection criteria include output current programmability via REXT, thermal derating behavior in SOICW (RθJA = 90°C/W), dual serial data outputs for daisy-chaining, and compatibility with microprocessor-based display controllers operating at 4.5–5.5 V.
Technical Context
The A6277ELWTR-T integrates a serial-shift register followed by parallel latches, allowing asynchronous data loading and synchronous output update on LATCH ENABLE high. Its output drivers are NPN bipolar transistors with user-defined current via external resistor REXT connected to pin 19, supporting 34–140 mA per channel depending on REXT and VCE.
It features two CMOS serial data outputs (SDO1 on rising clock edge, SDO2 on falling edge), undervoltage lockout (VDD(UV) = 4.3 V min), and separate logic ground (pin 1) and power ground (pins 6 & 15) to minimize noise coupling. The HIGH/LOW pin (pin 5) provides hardware-selectable 50% or 100% current scaling without software intervention.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Configuration | Eight NPN constant-current sink drivers, each programmable via single REXT (pin 19) |
| Max Output Current | 150 mA per output (continuous, at TA = 25°C, VCE = 1.0 V, REXT = 160 Ω) |
| Logic Supply Range | 4.5–5.5 V - compatible with standard 5 V microcontroller I/O without level shifting |
| Serial Data Rate | Up to 20 MHz - enables fast refresh in high-resolution LED matrices |
| Propagation Delay | <1000 ns (CLOCK-to-OUTn, LATCH-to-OUTn, ENABLE-to-OUTn) - ensures tight timing control in multiplexed systems |
| Thermal Resistance | RθJA = 90°C/W (SOICW package on 1-layer PCB) - requires thermal-aware layout above ~50 mA average per output |
| Undervoltage Lockout | Triggers below 4.3 V - prevents erratic operation during brown-out conditions |
Pinout & Package
Package: 20-pin SOICW (suffix LW), RoHS-compliant, 100% matte-tin leadframe plating, surface-mount.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 | LOGIC GROUND | Reference for all digital inputs (CLK, DATA IN, LATCH, OE, HIGH/LOW); must be isolated from power ground to avoid noise-induced latch errors |
| 2 | SERIAL DATA IN | CMOS-compatible serial data input to shift register; accepts 0–5 V logic levels |
| 3 | CLOCK | Rising-edge-triggered shift clock; minimum pulse width 50 ns; max transition time 10 µs |
| 4 | LATCH ENABLE | Active-high strobe; transfers shift register contents to output latches; latching occurs while high |
| 5 | HIGH/LOW (CURRENT) | Selects 100% (logic low) or 50% (logic high) of REXT-programmed current - enables hardware dimming |
| 6, 15 | POWER GROUND | Return path for all eight output drivers; must connect to low-impedance power plane |
| 7–14 | OUT0–OUT7 | Constant-current sink outputs; each delivers identical current set by REXT; VCE(sat) ≤ 1.0 V at 122 mA |
| 16 | OUTPUT ENABLE | Active-low global blanking; disables all outputs when high (open-collector compatible) |
| 17 | SERIAL OUT2 | CMOS output; data shifted out on clock falling edge - for cascading to next device |
| 18 | SERIAL OUT1 | CMOS output; data shifted out on clock rising edge - alternate cascade path |
| 19 | REXT | Connection point for external current-setting resistor; sets identical current for all eight outputs |
| 20 | LOGIC SUPPLY (VDD) | 5 V ±10% CMOS logic supply; powers shift register, latches, and input buffers |
Key Features
| Feature | Design Value |
|---|---|
| Dual serial data outputs (SDO1/SDO2) | Enables flexible daisy-chaining topologies - SDO1 for rising-edge sync, SDO2 for falling-edge sync |
| HIGH/LOW current select pin | Hardware-based 2× dimming ratio without firmware changes or PWM modulation |
| Separate logic and power grounds | Prevents latch corruption from switching noise on shared ground paths in high-current LED arrays |
| Undervoltage lockout (UVLO) | Guarantees clean reset and disables outputs below 4.3 V - eliminates partial activation during power ramp-up |
| CMOS-compatible 20 MHz input rate | Supports >1 kHz refresh rates even in 128×8 segment displays with minimal microcontroller overhead |
Applications
| LED Matrix Displays | Alphanumeric Segment Drivers |
|---|---|
|
Use Scenario: Driving 8×8 or 16×8 red/green LED dot-matrix panels in industrial HMIs and signage. IC Role / Device Role / Timing Role: Constant-current sink driver with serial-to-parallel conversion; handles multiplexed column scanning at ≥1 kHz refresh. Use Value: Eliminates per-LED current-setting resistors; ensures uniform brightness across all 64 segments using one REXT. |
Use Scenario: Driving 7-segment or 14-segment alphanumeric displays in test equipment and panel meters. IC Role / Device Role / Timing Role: Latched LED driver with inter-digit blanking; synchronizes digit updates via LATCH ENABLE and blanks unused digits via OUTPUT ENABLE. Use Value: Reduces microcontroller GPIO count from 14+ to 4 (DATA, CLK, LATCH, OE) while maintaining flicker-free display. |
| LED Bar Graph Drivers | Industrial Status Indicators |
|
Use Scenario: Driving linear 10- or 20-segment LED bar graphs in audio level meters and process monitoring systems. IC Role / Device Role / Timing Role: Serial-input current-sink array with hardware dimming; HIGH/LOW pin adjusts full-scale intensity without PWM. Use Value: Enables analog-like intensity control via simple logic level change - avoids EMI from high-frequency PWM switching. |
Use Scenario: Driving discrete status LEDs (power, fault, comms) in PLC modules and motor drives where reliability and current stability are critical. IC Role / Device Role / Timing Role: Robust constant-current sink with UVLO and thermal-aware design; operates continuously over –40°C to +85°C ambient. Use Value: Maintains ±6% output current matching between channels - ensures consistent LED brightness across long product lifetimes. |
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 functional block diagram and REXT-based current programming; lacks SDO2 output | No falling-edge serial output - limits daisy-chain flexibility in large arrays | Valid drop-in replacement where only SDO1 is used; verify thermal margin (RθJA = 95°C/W) |
| ON Semiconductor CAT4016 | 16-channel vs. 8-channel; I²C interface instead of SPI-like serial; no HIGH/LOW current select pin | Requires I²C master and firmware configuration; no hardware dimming mode | Better for systems needing more outputs and digital control; unsuitable for direct A6277ELWTR-T hardware replacement |
Compared with TD62715FN and CAT4016, the A6277ELWTR-T uniquely combines dual-edge serial outputs, hardware current scaling, and BiCMOS efficiency in a thermally optimized SOICW package - making it optimal for cost-sensitive, high-reliability LED display subsystems requiring minimal MCU intervention.
Availability
A6277ELWTR-T is available at Aetrix Electronics and suitable for LED matrix displays, alphanumeric segment drivers, LED bar graph indicators, and industrial status lighting requiring stable component supply and long-term production continuity.
Supply support for A6277ELWTR-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 motion-control solutions, headquartered in Worcester, Massachusetts.
The A6277ELWTR-T belongs to Allegro's constant-current LED driver product line, engineered specifically for reliable, low-noise, high-density LED display systems in industrial and commercial environments - emphasizing thermal robustness, current accuracy, and microcontroller interoperability.
FAQ
What is the maximum continuous output current per channel for the A6277ELWTR-T?
The A6277ELWTR-T supports up to 150 mA per output continuously under specified conditions: TA = 25°C, VCE = 1.0 V, and REXT = 160 Ω. At higher ambient temperatures or duty cycles, derating applies - e.g., 122 mA at 85°C with VCE = 1.0 V. Always consult the "Allowable Output Current vs. Duty Cycle" curves in the A6277ELWTR-T datasheet for thermal boundary validation.
How does the HIGH/LOW pin (pin 5) affect output current in the A6277ELWTR-T?
In the A6277ELWTR-T, the HIGH/LOW pin selects between two fixed current scales: logic low enables 100% of the REXT-programmed current, while logic high reduces output to exactly 50%. This is implemented internally via current mirror scaling - not PWM or analog attenuation - ensuring stable, ripple-free dimming without added MCU overhead or EMI.
Can the A6277ELWTR-T be used in daisy-chained configurations, and how do SDO1 and SDO2 differ?
Yes, the A6277ELWTR-T supports daisy chaining via two independent serial data outputs: SDO1 (pin 18) shifts data on the clock's rising edge, and SDO2 (pin 17) shifts on the falling edge. This allows synchronization flexibility - e.g., SDO1 can feed the next device's DATA IN while SDO2 feeds a parallel chain - enabling scalable LED driver arrays without additional clock buffering.
What is the purpose of separate LOGIC GROUND (pin 1) and POWER GROUND (pins 6 & 15) in the A6277ELWTR-T?
The A6277ELWTR-T uses split grounds to isolate sensitive CMOS logic (shift register, latches, inputs) from high-current switching noise generated by the eight NPN output drivers. Connecting LOGIC GROUND to the microcontroller's ground plane and POWER GROUND to the LED return path prevents voltage spikes on the logic reference - avoiding false clocking or latch corruption, especially in dense PCB layouts.
Does the A6277ELWTR-T include protection features, and what are their thresholds?
Yes, the A6277ELWTR-T includes undervoltage lockout (UVLO) that disables operation below VDD = 4.3 V (min), preventing erratic behavior during power-up or brownout. It also features Class 2 ESD protection on all inputs. Absolute maximum ratings include VO = –0.5 to 24 V and TJ(max) = 150°C - but sustained operation above 125°C junction temperature risks parametric shift and reduced lifetime.
A6277ELWTR-T Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Allegro MicroSystems
- Series:
- -
- Package/Case:
- 20-SOIC (0.295", 7.50mm Width)
- Packaging:
- Tape & Reel (TR)
- 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
A6277ELWTR-T FAQ
1.How can I place an order for A6277ELWTR-T through Aetrix?
Please submit a Request for Quotation (RFQ) for A6277ELWTR-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 A6277ELWTR-T reliable?
The price and inventory of A6277ELWTR-T are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for A6277ELWTR-T is usually 5 days.
3.What payment methods are accepted for A6277ELWTR-T?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for A6277ELWTR-T transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for A6277ELWTR-T?
A6277ELWTR-T orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your A6277ELWTR-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 A6277ELWTR-T?
For technical support, including A6277ELWTR-T datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your A6277ELWTR-T requirements.
6.How does Aetrix verify that A6277ELWTR-T is sourced from the original manufacturer or authorized distributors?
All A6277ELWTR-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 A6277ELWTR-T meets industry standards.
7.What is the process for return or replacement of A6277ELWTR-T?
All A6277ELWTR-T units undergo pre-shipment inspection (PSI). If there is an issue with A6277ELWTR-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 A6277ELWTR-T part is unused and in its original packaging.
Return procedure for A6277ELWTR-T:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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