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Analog Devices Inc. LT3571EUD#TRPBF
- Part No.:
- LT3571EUD#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 16-WFQFN Exposed Pad
- Datasheet:
-
LT3571EUD#TRPBF.pdf
- Description:
- IC REG BOOST ADJ 370MA 16QFN
- Quantity:
- Payment:
- Shipping:
Inventory:2,326
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Product details
Overview
LT3571EUD#TRPBF from Analog Devices (formerly Linear Technology) is a 75V current-mode step-up DC/DC converter optimized for avalanche photodiode (APD) biasing in optical receivers. It integrates a 75V/370mA power switch, Schottky diode, and high-side APD current monitor with ±10% accuracy across 250nA–2.5mA, enabling constant-current or constant-voltage regulation up to 70V output. Its 3mm × 3mm QFN package supports compact fiber-optic module designs.
For engineers reviewing the LT3571EUD#TRPBF datasheet, LT3571EUD#TRPBF pinout, LT3571EUD#TRPBF application, or LT3571EUD#TRPBF equivalent, key selection criteria include APD current monitoring accuracy, programmable switching frequency (250kHz–2MHz), integrated protection features (programmable current limit, internal soft-start), and compatibility with low-noise biasing requirements in optical receiver front-ends.
Technical Context
The LT3571EUD#TRPBF employs a constant-frequency current-mode control architecture with dual feedback loops: a voltage loop regulating FB to 1V (or externally set via CTRL) and a current loop using MONIN–APD sensing to enforce fixed 5V voltage drop across the APD. The two loops operate competitively-whichever demands lower peak switch current determines operating mode.
Its integrated high-side current monitor delivers 20% mirrored output current at MON pin with better than 10% relative accuracy over four decades of dynamic range and –40°C to 125°C. The device supports synchronization (SYNC pin), adjustable frequency (RT resistor), and digitally programmable output voltage without polarity inversion via the CTRL pin.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Max Output Voltage | 70V - Enables biasing of high-breakdown APDs used in long-haul fiber optics. |
| Switch Rating | 75V / 370mA - Supports robust operation under transient overvoltage and load-step conditions. |
| APD Current Monitor Accuracy | ±10% over –40°C to 125°C - Ensures stable photodiode gain control across industrial temperature range. |
| Switching Frequency Range | 250kHz to 2MHz - Allows EMI optimization and inductor size reduction in space-constrained modules. |
| Input Voltage Range | 2.7V to 20V - Compatible with single-cell Li-ion, USB, and intermediate bus rails. |
| Feedback Reference | 1.00V ±1.5% - Provides precise output voltage regulation when using internal reference. |
| Shutdown Current | <1μA - Enables ultra-low-power standby in battery-operated optical sensors. |
Pinout & Package
The LT3571EUD#TRPBF is housed in a 16-lead 3mm × 3mm plastic QFN (UD package) with exposed thermal pad (Pin 17) that must be soldered to PCB ground for thermal and electrical performance. Pin 1 is marked by notch or chamfer; top-side marking is "LDTN".
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| APD (Pin 2) | APD cathode connection | Direct interface to photodiode cathode; enables high-side current sensing with fixed 5V monitor drop. |
| MONIN (Pin 3) | Current sense amplifier inverting input | Serves as both supply rail for monitor circuit and sense node; accepts up to 75V and sets current limit via RSENSE. |
| VOUT (Pin 4) | Boost converter output | Delivers regulated high-voltage bias; connects to APD anode and output capacitor; also non-inverting input of current sense amp. |
| SW (Pins 5,6) | Power switch drain | High-frequency switching node; requires minimal trace length to reduce EMI and voltage spikes. |
| GND (Pins 7,10) | Power and signal ground | Dual ground pins reduce impedance; both must connect to low-impedance PCB ground plane. |
| SYNC (Pin 8) | External clock input | Enables deterministic switching alignment; RT must be set for 20% lower free-running frequency. |
| RT (Pin 9) | Oscillator timing resistor | Resistor-to-ground sets switching frequency; open-circuit or capacitive loading causes malfunction. |
| VIN (Pin 11) | Main input supply | Accepts 2.7V–20V; requires local 1μF ceramic bypass capacitor placed adjacent to pin. |
| SHDN (Pin 12) | Enable/disable & soft-start control | Logic-high (>1.5V) enables operation; RC filter on this pin controls startup slew rate. |
| VREF (Pin 13) | 1.222V precision reference output | Supplies up to 100μA; used for external biasing or CTRL voltage generation; requires ≥10nF bypass. |
| CTRL (Pin 14) | Feedback reference override | Externally sets FB threshold from 0V to 1V; allows real-time APD voltage adjustment without polarity inversion. |
| FB (Pin 15) | Voltage feedback input | Compares against CTRL or internal 1V reference; connects to resistor divider from VOUT for output regulation. |
| MON (Pin 16) | Current monitor output | Sources 20% of APD current; clamped to 11.5V for open-circuit protection; used for closed-loop gain control. |
| NC (Pin 1) | No connect | Not internally bonded; must remain unconnected. |
Key Features
| Feature | Design Value |
|---|---|
| Integrated Schottky diode | Eliminates external diode, reduces BOM count and board area in APD bias supplies. |
| High-side APD current monitor | Fixed 5V voltage drop between MONIN and APD pins ensures accurate, temperature-stable current sensing. |
| Constant-current + constant-voltage regulation | Dual-loop architecture automatically transitions between modes based on load demand-critical for APD stability during signal transients. |
| Programmable current limit protection | RSENSE between VOUT and MONIN sets APD current limit with 200mV threshold-enables safe start-up and fault limiting. |
| CTRL pin voltage override | Allows dynamic output voltage adjustment from 0V to 1V at FB pin-supports temperature compensation and digital calibration. |
Applications
| Optical Receiver Front-End | Fiber Optic Transceiver Module |
|---|---|
Use Scenario: Biasing APDs in 10G/25G SFP+ and QSFP modules where low-noise, stable gain is required for weak optical signal detection. IC Role / Device Role / Timing Role: Primary high-voltage DC/DC converter providing regulated bias voltage and real-time APD current monitoring for automatic gain control (AGC). Use Value: Integrated current monitor with ±10% accuracy eliminates need for external op-amps and precision resistors, reducing component count and layout sensitivity. | Use Scenario: Powering multiple APDs in multi-channel DWDM line cards requiring synchronized, low-ripple bias voltages up to 70V. IC Role / Device Role / Timing Role: High-efficiency boost regulator with SYNC capability enabling channel-to-channel switching alignment to minimize system-level EMI. Use Value: 250kHz–2MHz adjustable frequency allows optimization for EMI compliance while maintaining small magnetics footprint. |
| PIN Diode Bias Supply | Low-Power Optical Sensor |
Use Scenario: Generating stable 30–60V bias for PIN photodiodes in portable OTDR or optical power meters. IC Role / Device Role / Timing Role: Compact, integrated boost converter delivering precise voltage with shutdown current <1μA for battery longevity. Use Value: Internal soft-start and programmable current limit prevent inrush damage to sensitive photodiodes during power-up. | Use Scenario: Ultra-low-power APD bias in IoT-connected environmental sensors requiring long-life coin-cell operation. IC Role / Device Role / Timing Role: Standby-capable DC/DC controller with SHDN pin enabling microcontroller-driven on-demand bias activation. Use Value: 1.7mA quiescent current in active mode and sub-μA shutdown current extend operational life in intermittent-readout applications. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar APD bias converter applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT3482EUD#TRPBF | Lower max output (48V/90V dual-output), no integrated Schottky, ±15% current monitor accuracy, 650kHz/1.1MHz fixed frequencies. | Targeted at dual-rail APD/PIN bias; lacks single-rail flexibility and tighter current sensing needed for high-gain optical receivers. | Select LT3571EUD#TRPBF when 70V single-output, ±10% current accuracy, and integrated diode are required for compact, high-performance APD bias. |
| LT3461AEFE#TRPBF | 38V max output, 0.3A switch, no APD current monitor, SC70-6 package, higher quiescent current (2.8mA). | Suitable only for low-voltage PIN diode bias; cannot support APD biasing above ~40V or provide closed-loop current feedback. | Choose LT3571EUD#TRPBF for applications demanding >40V APD bias, integrated monitoring, and QFN thermal performance. |
Compared with LT3482EUD#TRPBF and LT3461AEFE#TRPBF, the LT3571EUD#TRPBF provides superior APD-specific integration-including 70V capability, ±10% current monitoring, and integrated Schottky-making it the only option among the three qualified for high-gain, single-rail optical receiver designs requiring tight bias stability.
Availability
LT3571EUD#TRPBF is available at Aetrix Electronics and suitable for optical receiver front-ends, fiber optic transceiver modules, and low-power optical sensors requiring stable component supply, full industrial temperature range (–40°C to 125°C), and lead-free RoHS-compliant packaging.
Supply support for LT3571EUD#TRPBF 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
Analog Devices, Inc. (acquired Linear Technology in 2017) is a global leader in high-performance analog, mixed-signal, and power management semiconductors, serving precision instrumentation, communications, and industrial markets.
The LT3571EUD#TRPBF belongs to Linear's specialized high-voltage DC/DC converter product line, engineered specifically for photodetector biasing-emphasizing low-noise operation, accurate current monitoring, and compact integration for optical infrastructure applications.
FAQ
What is the maximum output voltage supported by the LT3571EUD#TRPBF?
The LT3571EUD#TRPBF supports a maximum output voltage of 70V, as specified in its features and typical applications. This rating enables reliable biasing of avalanche photodiodes used in long-reach optical receivers. Absolute maximum ratings allow up to 75V at VOUT and APD pins, but sustained operation above 70V is not guaranteed per datasheet specifications. Designers should maintain margin below 70V for stable regulation and lifetime reliability.
How does the LT3571EUD#TRPBF achieve APD current monitoring accuracy?
The LT3571EUD#TRPBF achieves better than ±10% relative accuracy in APD current monitoring over –40°C to 125°C by integrating a high-side current sense amplifier with a fixed 5V voltage drop between MONIN and APD pins. Its design uses a precision current mirror with 5:1 ratio and internal clamping (11.5V at MON), validated across four decades of dynamic range (250nA to 2.5mA). No external calibration is required-the accuracy is inherent to the monolithic implementation.
Can the LT3571EUD#TRPBF operate in both constant-current and constant-voltage modes?
Yes, the LT3571EUD#TRPBF combines a traditional voltage feedback loop (via FB pin) and a dedicated current feedback loop (via MONIN–APD sensing) to operate seamlessly in either constant-current or constant-voltage mode. Whichever loop demands the lower peak switch current takes precedence-enabling automatic transition during load transients. This dual-loop architecture is explicitly designed for APD biasing, where stable current control is essential during low-light conditions and voltage control dominates at saturation.
What is the role of the CTRL pin in the LT3571EUD#TRPBF?
The CTRL pin in the LT3571EUD#TRPBF allows external adjustment of the FB reference voltage between 0V and 1V, enabling real-time programming of the output voltage without polarity inversion. When CTRL is held above 1.2V (e.g., tied to VREF), the internal 1V reference is used. When CTRL is between 0V and 1V, the FB pin regulates to match that voltage-supporting temperature compensation networks or DAC-based calibration. This feature is central to the LT3571EUD#TRPBF's use in adaptive optical receiver designs.
Is the LT3571EUD#TRPBF pin-compatible with other Linear Technology QFN converters?
No, the LT3571EUD#TRPBF has a unique 16-pin QFN pinout optimized for APD biasing-including dedicated APD, MONIN, and MON pins-not shared with general-purpose boost converters like LT3461A or LT3482. Its pin functions (e.g., APD cathode interface, high-side monitor inputs) are application-specific. Substituting with other QFN parts requires full schematic and layout revision due to incompatible pin mapping, functionality, and internal architecture.
LT3571EUD#TRPBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 16-WFQFN Exposed Pad
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Function:
- Step-Up
- Output Configuration:
- Positive
- Topology:
- Boost
- Output Type:
- Adjustable
- Number of Outputs:
- 1
- Voltage - Input (Min):
- 2.7V
- Voltage - Input (Max):
- 20V
- Voltage - Output (Min/Fixed):
- 2.7V
- Voltage - Output (Max):
- 75V (Switch)
- Current - Output:
- 370mA (Switch)
- Frequency - Switching:
- 250kHz ~ 2MHz
- Synchronous Rectifier:
- No
- Operating Temperature:
- -40°C ~ 125°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 16-QFN (3x3)
LT3571EUD#TRPBF FAQ
1.How can I place an order for LT3571EUD#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3571EUD#TRPBF 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 LT3571EUD#TRPBF reliable?
The price and inventory of LT3571EUD#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3571EUD#TRPBF is usually 5 days.
3.What payment methods are accepted for LT3571EUD#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3571EUD#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3571EUD#TRPBF?
LT3571EUD#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3571EUD#TRPBF 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 LT3571EUD#TRPBF?
For technical support, including LT3571EUD#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3571EUD#TRPBF requirements.
6.How does Aetrix verify that LT3571EUD#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT3571EUD#TRPBF 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 LT3571EUD#TRPBF meets industry standards.
7.What is the process for return or replacement of LT3571EUD#TRPBF?
All LT3571EUD#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3571EUD#TRPBF, 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 LT3571EUD#TRPBF part is unused and in its original packaging.
Return procedure for LT3571EUD#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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