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Analog Devices Inc. LT3482IUD#PBF
- Part No.:
- LT3482IUD#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 16-WFQFN Exposed Pad
- Datasheet:
-
LT3482IUD#PBF.pdf
- Description:
- IC REG BST CHARGE PUMP ADJ 16QFN
- Quantity:
- Payment:
- Shipping:
Inventory:5,455
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Product details
Overview
LT3482IUD#PBF from Analog Devices (formerly Linear Technology) is a fixed-frequency current-mode boost DC/DC converter with integrated voltage doubler and high-side APD current monitor, designed specifically for biasing avalanche photodiodes in optical receivers. It delivers up to 90V output, supports 2.5V–16V input, integrates a 48V/280mA power switch and Schottky diodes, and achieves better than 10% relative accuracy over four decades (250nA–2.5mA) of APD current monitoring.
For engineers reviewing the LT3482IUD#PBF datasheet, LT3482IUD#PBF pinout, LT3482IUD#PBF application, or LT3482IUD#PBF equivalent, key selection criteria include APD bias voltage stability, high-side current monitor linearity across temperature, switching frequency selection (650kHz/1.1MHz), internal compensation, and QFN thermal performance under continuous 90V output load.
Technical Context
The LT3482IUD#PBF employs constant-frequency current-mode control with an internal 1.235V reference and externally adjustable CTRL pin interface, enabling precise APD voltage regulation via feedback loop modulation. Its functional block includes a PWM comparator with ramp compensation, error amplifier (EAMP), high-side APD current mirror (5:1 ratio), and integrated charge pump circuitry using internal Schottky diodes.
Operation relies on synchronous voltage doubling between VOUT1 and VOUT2 pins, where PUMP and SW form a flying-capacitor topology; MONIN accepts up to 90V supply while MON outputs 20% of APD current as a proportional current source. The device operates across –40°C to 125°C and features soft-start via SHDN pin voltage ramping (1.5V–2V).
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Voltage | Up to 90V - enables direct biasing of high-gain APDs used in long-haul fiber optic receivers. |
| Input Voltage Range | 2.5V to 16V - supports single-cell Li-ion, 3.3V/5V/12V rails without pre-regulation. |
| Switch Current Limit | 280mA typical - sets maximum energy transfer per cycle; limits inrush and short-circuit stress. |
| APD Monitor Accuracy | Better than ±10% over –40°C to 125°C - ensures stable gain calibration for low-light optical signal measurement. |
| Switching Frequency | 650kHz or 1.1MHz selectable via fSET pin - balances EMI, inductor size, and efficiency in space-constrained modules. |
| Feedback Reference | 1.235V internal or 0–1.2V external via CTRL pin - allows digital or analog adjustment of APD bias without polarity inversion. |
| Shutdown Current | <1µA - preserves battery life in portable optical test equipment during standby. |
Pinout & Package
LT3482IUD#PBF is housed in a thermally enhanced 16-lead 3mm × 3mm plastic QFN package with exposed pad (Pin 17) soldered to PCB ground for optimal thermal dissipation (θJC = 4.2°C/W). The package supports reflow assembly and meets JEDEC MO-220 WEED-2 outline standards.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| APD (Pin 2) | High-side APD cathode connection | Direct interface to photodiode cathode; voltage swing up to 90V; requires series 20Ω resistor for short-circuit protection. |
| MONIN (Pin 3) | APD monitor supply input | Accepts 10V–90V bias; powers internal current mirror; external RC filter reduces supply ripple affecting monitor accuracy. |
| VOUT2 (Pin 4) | Voltage doubler output node | Forms cascaded output with VOUT1; requires 50V-rated capacitor to VOUT1 for charge-pump operation above 45V. |
| VOUT1 (Pin 5) | Main boost output | Primary regulated output; connects to output capacitor; minimized trace length critical for EMI and stability. |
| PUMP (Pin 6) | Flying capacitor node | Completes voltage-doubling path with SW and internal Schottky diodes; requires low-ESR 50V bypass capacitor. |
| SW (Pins 7, 8) | Power switch drain terminals | Drives external inductor; dual-pin layout reduces parasitic inductance and improves thermal spreading. |
| GND (Pins 9, 10) | Power and signal ground | Internally connected; both pins must be tied to low-impedance PCB ground plane for noise immunity and thermal relief. |
| VIN (Pin 11) | Input supply | 2.5V–16V input; requires local 1µF ceramic decoupling placed adjacent to pin for transient response. |
| SHDN (Pin 12) | Enable/soft-start control | Logic-high (>1.5V) enables operation; voltage ramp between 1.5V–2V controls startup dV/dt to limit inrush. |
| CTRL (Pin 13) | Reference override input | Sets FB threshold from 0–1.2V; enables dynamic APD voltage tuning without changing resistor divider. |
| FB (Pin 14) | Feedback sense input | Monitors resistor divider output; 30nA bias current minimizes divider loading error. |
| fSET (Pin 15) | Frequency selection | GND selects 650kHz; ≥1.5V selects 1.1MHz - determines inductor/capacitor sizing trade-off between size and efficiency. |
| MON (Pin 16) | APD current monitor output | Sources 20% of APD current; open-circuit clamped at 11.5V; converts to voltage via external R3 for closed-loop control. |
| Exposed Pad (Pin 17) | Thermal ground | Must be soldered to PCB ground plane; primary thermal path for junction-to-board conduction (θJA = 68°C/W). |
Key Features
| Feature | Design Value |
|---|---|
| Integrated voltage doubler | Enables 90V output from 16V input using only two external capacitors (C1, C2), eliminating need for transformer-based topologies. |
| High-side APD current monitor | Delivers 20% mirrored current with <10% error over –40°C to 125°C and 250nA–2.5mA range - supports precision optical gain control. |
| Internal compensation | Eliminates external compensation network; simplifies design for stable operation across all output voltages and loads. |
| Adjustable switching frequency | 650kHz/1.1MHz selection optimizes component size vs. efficiency - e.g., 1.1MHz allows 6.8µH inductor instead of 10µH at 650kHz. |
| Soft-start via SHDN pin | Ramp-enabled startup prevents output overshoot and inductor saturation during cold start or hot-plug conditions. |
| Low shutdown current | <1µA quiescent draw extends battery runtime in handheld optical test instruments and field-deployable modules. |
Applications
| Optical Receiver Biasing | PIN Diode Bias Supply |
|---|---|
|
Use Scenario: Biasing APDs in 10G/25G SFP+ and QSFP transceivers for coherent detection in metro and access networks. IC Role / Device Role / Timing Role: Provides regulated, low-noise 70–90V bias with real-time current monitoring for automatic gain control (AGC) loops. Use Value: Maintains APD responsivity within ±5% over temperature via 10% accurate current mirror, reducing need for factory recalibration. |
Use Scenario: Supplying reverse-bias voltage to PIN photodiodes in optical power meters and OTDR modules. IC Role / Device Role / Timing Role: Delivers stable 30–60V output with fast transient response (<500ns step recovery) to track rapid optical input changes. Use Value: Integrated Schottky diodes and internal switch eliminate discrete BOM items, shrinking solution footprint by 40% vs. discrete boost + doubler. |
| Fiber Optic Network Equipment | Industrial Laser Monitoring |
|
Use Scenario: Powering APD arrays in passive optical network (PON) OLT receivers requiring multi-channel synchronized bias. IC Role / Device Role / Timing Role: Generates tightly regulated outputs across multiple channels using shared CTRL/FB architecture for inter-channel matching. Use Value: Constant-frequency operation yields predictable EMI spectrum, easing FCC Class B compliance in dense line-card layouts. |
Use Scenario: Biasing APDs in laser safety interlock circuits and LIDAR time-of-flight sensors operating in harsh industrial environments. IC Role / Device Role / Timing Role: Operates reliably from –40°C to 125°C junction temperature; MON output feeds FPGA-based fault detection logic. Use Value: 125°C max junction rating and QFN thermal pad enable conduction-cooled mounting on metal-core PCBs without heatsinks. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar APD bias converter applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT3461AEDD#PBF | Max output 38V; no voltage doubler; 3MHz switching; 300mA switch; no APD monitor | Suitable for lower-voltage PIN diodes or pre-amplifier bias, not for 70–90V APD operation | Select when output ≤38V and current monitoring is unnecessary; smaller 8-lead DFN package saves area. |
| LTC3873EMS#TRPBF | External MOSFET controller; no integrated switch/diodes; supports >100V output; no APD monitor | Used in custom high-efficiency, high-reliability APD supplies where thermal management and layout control are critical | Choose for designs requiring >90V or >500mA output, or where discrete FET selection enables optimized RDS(on)/Qg trade-offs. |
Compared with LT3482IUD#PBF, LT3461AEDD#PBF offers higher frequency but lacks voltage doubling and monitoring, limiting it to sub-40V applications; LTC3873EMS#TRPBF provides scalability beyond 90V but demands additional components and layout effort for APD-specific functionality.
Availability
LT3482IUD#PBF is available at Aetrix Electronics and suitable for optical receiver biasing, fiber optic network equipment, industrial laser monitoring, and PIN diode power supplies requiring stable component supply across extended temperature ranges and long production lifecycles.
Supply support for LT3482IUD#PBF 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 acquired Linear Technology in 2017 and maintains full product support, documentation, and manufacturing continuity for legacy Linear parts including the LT3482 series.
The LT3482IUD#PBF belongs to Linear's precision high-voltage DC/DC converter family, engineered specifically for low-noise, temperature-stable biasing of avalanche photodiodes in optical communication and sensing systems.
FAQ
What is the maximum output voltage capability of the LT3482IUD#PBF?
The LT3482IUD#PBF supports up to 90V output using its integrated voltage doubler architecture. This is achieved by cascading VOUT1 and VOUT2 with appropriate external capacitors (e.g., two 0.47µF/50V ceramics), enabling direct biasing of high-gain APDs without external transformers or multi-stage converters. Output voltage is set via resistor divider on FB pin or dynamically adjusted using the CTRL pin.
How does the APD current monitor in the LT3482IUD#PBF achieve accuracy over temperature?
The LT3482IUD#PBF uses a matched high-side current mirror with trimming and process compensation to maintain better than ±10% relative accuracy across –40°C to 125°C. Its MONIN pin accepts up to 90V, and MON output sources exactly 20% of APD current - verified over four decades (250nA to 2.5mA) - enabling stable AGC loop performance without recalibration in optical modules.
Can the LT3482IUD#PBF operate from a 3.3V input to generate 85V output?
Yes, the LT3482IUD#PBF supports input voltages from 2.5V to 16V and can generate up to 90V output regardless of input rail. A typical 3.3V-to-85V design uses 10µH inductor, 0.47µF output capacitors, and 1.1MHz switching (fSET = VIN) to minimize size. Efficiency remains >50% at 2.5mA APD load, as confirmed in Figure 3482 TA02b of the datasheet.
What is the purpose of the exposed pad (Pin 17) on the LT3482IUD#PBF QFN package?
The exposed pad (Pin 17) on the LT3482IUD#PBF is electrically and thermally connected to GND and must be soldered to a PCB ground plane. It provides the primary thermal conduction path from die to board (θJC = 4.2°C/W), enabling reliable operation at full 90V/280mA load in industrial temperature ranges. Omitting this connection risks thermal shutdown or parametric drift.
Does the LT3482IUD#PBF require external compensation components?
No, the LT3482IUD#PBF features fully internal compensation, eliminating the need for external Type-II or Type-III compensation networks. This simplifies design, reduces BOM count, and ensures stable loop response across all operating conditions - including varying input voltage, output voltage, and load current - without manual tuning.
LT3482IUD#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 16-WFQFN Exposed Pad
- Packaging:
- Tube
- Product Status:
- Active
- Function:
- Step-Up
- Output Configuration:
- Positive
- Topology:
- Boost, Charge Pump
- Output Type:
- Adjustable
- Number of Outputs:
- 1
- Voltage - Input (Min):
- 2.5V
- Voltage - Input (Max):
- 16V
- Voltage - Output (Min/Fixed):
- 5V
- Voltage - Output (Max):
- 90V
- Current - Output:
- 280mA (Switch)
- Frequency - Switching:
- 650kHz ~ 1.1MHz
- Synchronous Rectifier:
- No
- Operating Temperature:
- -40°C ~ 85°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 16-QFN (3x3)
LT3482IUD#PBF FAQ
1.How can I place an order for LT3482IUD#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3482IUD#PBF 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 LT3482IUD#PBF reliable?
The price and inventory of LT3482IUD#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3482IUD#PBF is usually 5 days.
3.What payment methods are accepted for LT3482IUD#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3482IUD#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3482IUD#PBF?
LT3482IUD#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3482IUD#PBF 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 LT3482IUD#PBF?
For technical support, including LT3482IUD#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3482IUD#PBF requirements.
6.How does Aetrix verify that LT3482IUD#PBF is sourced from the original manufacturer or authorized distributors?
All LT3482IUD#PBF 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 LT3482IUD#PBF meets industry standards.
7.What is the process for return or replacement of LT3482IUD#PBF?
All LT3482IUD#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3482IUD#PBF, 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 LT3482IUD#PBF part is unused and in its original packaging.
Return procedure for LT3482IUD#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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