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Allegro MicroSystems A8740EEETR-T
- Part No.:
- A8740EEETR-T
- Manufacturer:
- Allegro MicroSystems
- Category:
- LED Drivers
- Package:
- 8-UFDFN Exposed Pad
- Datasheet:
-
A8740EEETR-T.pdf
- Description:
- IC LED DRIVER OFFL 8DFN
- Quantity:
- Payment:
- Shipping:
Inventory:4,524
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Product details
Overview
A8740EEETR-T from Allegro MicroSystems is a discontinued Xenon photoflash capacitor charger IC with integrated 50 V DMOS switch and IGBT driver, designed for ultra-small mobile phone cameras operating from 1.5–5.5 V single-cell Li⁺ battery input. It delivers >75% efficiency, 31.5 V primary-side output voltage sensing, 1.5 A peak current limit, and 0.5 μA shutdown supply current.
For engineers reviewing the A8740EEETR-T datasheet, A8740EEETR-T pinout, A8740EEETR-T application, or A8740EEETR-T equivalent, this page provides verified technical context, real-world timing behavior (18 μs fixed off-time), ZVS/DCM operation modes, thermal pad layout guidance, and validated alternative options for legacy design support.
Technical Context
The A8740EEETR-T implements adaptive discontinuous conduction mode (DCM) control with two distinct charging phases: Timer mode (fixed 18 μs off-time for soft-start at low VOUT) and Fast-Charging mode (minimum-voltage switching, transitioning to true zero-voltage switching above 50 V). Its primary-side voltage sensing eliminates secondary resistive dividers and reduces leakage currents.
It integrates a self-clamping 50 V DMOS switch (RDS(on) = 0.4 Ω), an IGBT driver with internal gate resistors (RSrc = 6.6 Ω, RSnk = 50 Ω), and logic-compatible 1.3 VHIGH(min) inputs for CHARGE, TRIG, and DONE. Charge completion is signaled via open-drain DONE output.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | VBAT: 1.5–5.5 V; VIN_DRV: 2.3–5.5 V - supports direct single-cell Li⁺ battery and bias rail operation |
| Peak Switch Current Limit | 1.5 A (min 1.35 A, max 1.65 A) - sets transformer primary ramp rate and energy per cycle |
| Output Voltage Sensing | VOUTTRIP = 31.5 V (31.0–32.0 V) - determines final photoflash capacitor charge level via primary-side VSW–VVBAT |
| Shutdown Supply Current | 0.5 μA max - enables multi-week standby in camera modules without battery drain |
| Switch On/Off Timing | ton(max) = toff(max) = 18 μs - defines minimum switching period and controls initial inrush current |
| Thermal Resistance | RθJA = 49 °C/W (4-layer PCB) - requires exposed pad soldered to ground plane for safe 150°C junction limit |
| Logic Threshold Voltage | VHIGH(min) = 1.3 V - compatible with 1.8 V and 3.3 V microcontroller GPIO without level shifting |
Pinout & Package
Package: 8-contact 2 mm × 2 mm DFN/MLP (suffix EE) with 0.60 mm max height and exposed thermal pad (PAD) connected to GND for thermal dissipation.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1: ¯D¯ ¯O¯ ¯N¯ ¯E¯ | Open-drain charge-complete indicator | Pulls low when VOUT reaches target and CHARGE is high; requires external pull-up for logic-level interface |
| 2: TRIG | IGBT trigger enable input | Active-high logic input (1.3 VHIGH(min)) initiating flash discharge; internal 130 kΩ pull-down |
| 3: GATE | IGBT gate drive output | Integrated driver with 6.6 Ω source / 50 Ω sink resistance; 25 ns rise / 60 ns fall propagation delay |
| 4: GND | Power and signal ground reference | Common return for all analog and power paths; must be low-impedance connection to thermal pad |
| 5: SW | Drain of internal 50 V DMOS switch | Connects directly to transformer primary; self-clamped to 50 V with ≤0.5 μJ flyback spike energy limit |
| 6: VBAT | Battery input supply | Accepts 1.5–5.5 V Li⁺ battery; supplies internal circuitry and switch; 1 μA max leakage at full temp range |
| 7: VIN_DRV | Bias supply input | 3–5.5 V dedicated rail for IGBT driver; decoupled with 0.1 μF ceramic capacitor near pin |
| 8: CHARGE | Charge enable control | Active-high logic input (1.3 VHIGH(min)) starting charging cycle; internal 130 kΩ pull-down; 20 μs enable delay |
| PAD | Exposed thermal pad | Must be soldered to solid GND plane with ≥4 thermal vias; primary path for heat removal from DMOS and driver |
Key Features
| Feature | Design Value |
|---|---|
| Primary-side voltage sensing | Eliminates high-voltage feedback resistors on secondary side, reducing BOM count and leakage current by >90% |
| Zero-voltage switching (ZVS) | Reduces switching losses and EMI above 50 V output, enabling >75% system efficiency at full charge |
| Integrated IGBT driver | Includes matched source/sink resistors (6.6 Ω / 50 Ω) and 20 kΩ pull-down, removing 4 external components |
| Ultra-low shutdown current | 0.5 μA max draw extends camera module standby time to months on a single Li⁺ cell charge |
| Self-clamping 50 V DMOS switch | Withstands flyback spikes up to 50 V without external clamp diode, simplifying transformer design |
Applications
| Mobile Phone Camera Flash Module | Compact Digital Still Camera (DSC) |
|---|---|
Use Scenario: Charging a 100 μF/315 V photoflash capacitor from a 3.6 V Li⁺ battery in sub-20 mm² camera module footprint. IC Role / Device Role / Timing Role: Primary-side flyback controller with integrated switch and IGBT driver; manages charge timing via 18 μs off-time and VOUTTRIP-based termination. Use Value: Enables <1.5 s full-charge time with <0.5 μA quiescent drain, meeting OEM battery life targets for always-on camera subsystems. | Use Scenario: Low-profile flash charging in portable DSCs using discrete transformers and minimal external passives. IC Role / Device Role / Timing Role: Photoflash capacitor charger IC providing primary-side regulation, DONE signaling, and logic-level TRIG interface. Use Value: Reduces component count by eliminating secondary feedback network and external gate resistors, shrinking PCB area by ≥25%. |
| USB-Powered Portable Flash Unit | Industrial Inspection Flash System |
Use Scenario: Compact flash unit powered from USB 5 V supply, requiring fast recharge and low standby loss. IC Role / Device Role / Timing Role: Dual-rail controller accepting 5 V bias (VIN_DRV) and 3.3–5.5 V battery-equivalent input (VBAT). Use Value: Supports efficient operation across 2.3–5.5 V input range while maintaining 1.3 V logic compatibility for host MCU control. | Use Scenario: High-reliability flash triggering in machine vision systems where consistent charge voltage and timing are critical. IC Role / Device Role / Timing Role: Precision photoflash charger with ±0.5 V output voltage tolerance (31.0–32.0 V trip window) and open-drain DONE confirmation. Use Value: Ensures repeatable flash intensity by guaranteeing 31.5 V ±0.5 V capacitor charge level before TRIG assertion. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar photoflash capacitor charger applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| MAX8640Y | Requires external MOSFET and IGBT driver; no integrated switch or gate resistors; 2.7–5.5 V input only | Lacks primary-side sensing and ZVS; lower integration increases board area and component count | Choose when redesign allows external power stage and higher input voltage margin is acceptable |
| TPS613222A | Boost converter only (no IGBT driver or DONE signal); 2.5–5.5 V input; 30 V max output | Cannot directly drive IGBT or signal flash readiness; requires external trigger logic and voltage monitoring | Use only if photoflash function is split across separate boost + driver ICs and VOUT ≤30 V suffices |
Compared with A8740EEETR-T, MAX8640Y demands more external components and lacks integrated ZVS, while TPS613222A omits both IGBT driving and charge-complete signaling-making neither a drop-in replacement but viable alternatives when system architecture permits added complexity or reduced voltage requirements.
Availability
A8740EEETR-T is available at Aetrix Electronics and suitable for legacy mobile phone camera repair, industrial inspection flash refurbishment, and USB-powered portable flash unit sustainment requiring stable component supply and full documentation traceability.
Supply support for A8740EEETR-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 of high-performance magnetic sensors and power ICs, headquartered in Worcester, Massachusetts, with global manufacturing and support infrastructure.
The A8740 product line was developed specifically for ultra-compact, low-power Xenon photoflash charging in space-constrained mobile imaging systems, emphasizing integration, efficiency, and battery longevity.
FAQ
Is A8740EEETR-T still in production?
No, A8740EEETR-T is a discontinued product. Allegro ceased production in 2012 and no longer offers samples or new production lots. Aetrix Electronics maintains limited legacy stock for repair and sustainment use only, with full traceability and datasheet documentation for the A8740EEETR-T.
What is the maximum allowable flyback energy at the SW pin of A8740EEETR-T?
The A8740EEETR-T allows up to 0.5 μJ of repetitive flyback energy at the SW pin during each switching cycle, provided the frequency remains ≤400 kHz. This energy limit is enforced by the internal active clamp circuit, which self-limits VSW to 50 V even during transient spikes - a key specification confirmed in the Absolute Maximum Ratings table for the A8740EEETR-T.
Can A8740EEETR-T operate from a 1.5 V alkaline battery?
Yes, A8740EEETR-T supports VBAT down to 1.5 V per its guaranteed operating range (1.5–5.5 V), making it compatible with single-cell alkaline or NiMH batteries. However, charging time increases significantly below 2.5 V due to reduced di/dt and average input current - performance curves in the A8740EEETR-T datasheet confirm functional operation at 1.5 V with extended charge duration.
Does A8740EEETR-T require external gate resistors for the IGBT driver?
No, A8740EEETR-T integrates internal gate resistors: 6.6 Ω source resistance and 50 Ω sink resistance between GATE and VIN_DRV/GND. These values are optimized for standard small-signal IGBTs used in mobile flash applications and eliminate the need for external series resistors - a confirmed feature in the "Features and Benefits" section of the A8740EEETR-T datasheet.
How is output voltage regulated without secondary-side feedback in A8740EEETR-T?
A8740EEETR-T uses primary-side sensing: it monitors VSW – VVBAT to infer secondary output voltage via transformer turns ratio (VOUT ≈ 31.5 × N – Vd). The internal comparator trips at 31.5 V (31.0–32.0 V) differential, enabling precise regulation without secondary resistors - a core functional description verified in the "General Operation Overview" of the A8740EEETR-T datasheet.
A8740EEETR-T Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Allegro MicroSystems
- Series:
- -
- Package/Case:
- 8-UFDFN Exposed Pad
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Obsolete
- Type:
- AC DC Offline Switcher
- Topology:
- Flyback
- Internal Switch(s):
- No
- Number of Outputs:
- 1
- Voltage - Supply (Min):
- 1.5V
- Voltage - Supply (Max):
- 5.5V
- Voltage - Output:
- -
- Current - Output / Channel:
- -
- Frequency:
- -
- Dimming:
- -
- Applications:
- Camera Flash
- Operating Temperature:
- -40°C ~ 85°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 8-DFN (2x2)
A8740EEETR-T FAQ
1.How can I place an order for A8740EEETR-T through Aetrix?
Please submit a Request for Quotation (RFQ) for A8740EEETR-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 A8740EEETR-T reliable?
The price and inventory of A8740EEETR-T are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for A8740EEETR-T is usually 5 days.
3.What payment methods are accepted for A8740EEETR-T?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for A8740EEETR-T transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for A8740EEETR-T?
A8740EEETR-T orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your A8740EEETR-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 A8740EEETR-T?
For technical support, including A8740EEETR-T datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your A8740EEETR-T requirements.
6.How does Aetrix verify that A8740EEETR-T is sourced from the original manufacturer or authorized distributors?
All A8740EEETR-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 A8740EEETR-T meets industry standards.
7.What is the process for return or replacement of A8740EEETR-T?
All A8740EEETR-T units undergo pre-shipment inspection (PSI). If there is an issue with A8740EEETR-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 A8740EEETR-T part is unused and in its original packaging.
Return procedure for A8740EEETR-T:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
A8740EEETR-T Tags
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BCR402RE6327HTSA1
Infineon Technologies
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BCR430UXTSA2
Infineon Technologies
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BCR420UE6433HTMA1
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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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