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Analog Devices Inc. LT3487EDD#TRPBF
- Part No.:
- LT3487EDD#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 10-WFDFN Exposed Pad
- Datasheet:
-
LT3487EDD#TRPBF.pdf
- Description:
- IC REG BST CHG PUMP ADJ DL 10DFN
- Quantity:
- Payment:
- Shipping:
Inventory:1,232
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Product details
Overview
LT3487EDD#TRPBF from Analog Devices (formerly Linear Technology) is a dual-channel, 2MHz constant-frequency switching regulator optimized for CCD, TFT LCD, and OLED bias generation. It delivers +15V at 45mA and –8V at 90mA from a 2.3V–16V input, features internal Schottky diodes, output disconnect, and intelligent sequencing where the positive channel reaches regulation before negative channel startup. It is used in high-precision imaging sensor power supplies.
For engineers reviewing the LT3487EDD#TRPBF datasheet, LT3487EDD#TRPBF pinout, LT3487EDD#TRPBF application, or LT3487EDD#TRPBF equivalent, key selection criteria include dual-rail sequencing behavior, ±8V to ±28V programmable outputs, 10-lead DFN package thermal performance, soft-start capacitor programmability, and VBAT/VIN separation for independent power/control sourcing.
Technical Context
The LT3487EDD#TRPBF integrates two independent current-mode regulators: a boost converter (positive channel) and an inverting buck-boost (negative channel), both operating at a fixed 2MHz switching frequency. Each channel uses internal Schottky diodes and features dedicated feedback pins (FBP/FBN) with 25µA precision reference current and 1.23V/0V regulation thresholds.
It implements output disconnect via an internal PNP transistor controlled by CAP–VBAT differential voltage, with automatic shutdown when CAP falls ≤1.2V above VBAT. Sequencing is enforced by internal circuitry that disables the negative channel until FBP reaches ≥87% of final regulated value, ensuring VPOS + VNEG remains positive during startup.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Switching Frequency | 2MHz ±15% - enables use of ultra-small inductors & ceramic capacitors; reduces EMI filtering burden. |
| Positive Output Range | Up to +28V - supports high-voltage CCD bias rails; set via single resistor R1 referenced to 1.23V FBP threshold. |
| Negative Output Range | Down to –32V - accommodates wide-range OLED and op-amp rail generation; set via single resistor R2 referenced to 0V FBN threshold. |
| Input Voltage Range | 2.3V to 16V - compatible with Li-ion (3.0–4.2V), 5V, 12V, and automotive pre-regulated rails. |
| Output Disconnect Threshold | CAP – VBAT ≤ 1.2V (typ.) - ensures coordinated shutdown; prevents negative rail collapse before positive rail decays. |
| Quiescent Current | 3.7mA (active), 5µA (shutdown) - minimizes battery drain in portable imaging systems during standby. |
| Thermal Performance | θJA = 43°C/W - requires exposed pad soldered to PCB ground plane for reliable 125°C junction operation. |
Pinout & Package
LT3487EDD#TRPBF is housed in a 10-lead, 3mm × 3mm plastic DFN package with exposed thermal pad (Pin 11 = GND). The package is RoHS-compliant and lead-free (#PBF suffix).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| CAP (Pin 1) | Boost intermediate node / Disconnect PNP emitter | Intermediate positive rail; connects to boost output capacitor; controls disconnect activation via voltage relative to VBAT. |
| SWP (Pin 2) | Positive channel switch node / Schottky anode | Connects to boost inductor; internal Schottky cathode tied to CAP; carries peak switch current up to 920mA. |
| VBAT (Pin 3) | Battery/inductor supply return | Provides return path for disconnect drive current; sets disconnect shutdown threshold (CAP – VBAT); allows separate inductor power source. |
| SWN (Pin 4) | Negative channel switch node | Connects to inverter input inductor and flying capacitor; supports peak switch current up to 1090mA. |
| DN (Pin 5) | Inverter Schottky anode | Internal Schottky anode for inverting channel; connects to flying cap and output inductor; forward drop ≤980mV @ 600mA. |
| VIN (Pin 6) | Control circuitry supply | Powers internal logic, oscillators, and error amplifiers; must be bypassed locally with X5R/X7R ceramic capacitor. |
| FBN (Pin 7) | Negative channel feedback input | Senses VNEG via R2; regulated at 0V; bias current = 25µA (±0.6µA); line regulation = 0.001mV/V. |
| RUN/SS (Pin 8) | Enable & soft-start control | 1.4µA current source charges external capacitor; 160mV threshold initiates startup; 100mV threshold forces shutdown. |
| FBP (Pin 9) | Positive channel feedback input | Senses VPOS or CAP via R1; regulated at 1.23V (±40mV); bias current = 25µA (±0.6µA); line regulation = 0.007%/V. |
| VPOS (Pin 10) | Positive regulated output | Collector of internal disconnect PNP; load connected here; requires ≥0.1µF bypass cap between VPOS and CAP for stability. |
Key Features
| Feature | Design Value |
|---|---|
| Independent dual-rail sequencing | Guarantees VPOS reaches ≥87% of target before VNEG begins switching - prevents net-negative rail sum during startup. |
| Single-capacitor soft-start | One capacitor on RUN/SS pin programs ramp time for both channels while preserving order: VPOS ramps first, then VNEG follows. |
| Integrated Schottky diodes | Eliminates 4 external diodes; DP forward drop ≤1045mV @ 400mA, DN ≤980mV @ 600mA - reduces BOM count and board area. |
| Output disconnect | Internal PNP pass transistor with <210mV saturation drop @ 50mA - blocks VIN-to-VPOS DC path during shutdown, preventing load backfeed. |
| VBAT/VIN separation | Enables independent sourcing: VIN powers control logic, VBAT powers inductors - supports mixed-rail systems (e.g., 3.3V logic + 12V inductors). |
Applications
| CCD Imaging Sensor Bias | TFT LCD Panel Bias |
|---|---|
|
Use Scenario: Powering interline-transfer CCD image sensors requiring tightly sequenced +15V and –8V bias rails from a single Li-ion cell. IC Role / Device Role / Timing Role: Dual-channel DC/DC controller generating isolated, sequenced high-voltage rails with output disconnect to prevent sensor latch-up during power-down. Use Value: Eliminates need for discrete boost + inverter + sequencing logic; 2MHz operation allows sub-3mm inductors and low-profile ceramics. |
Use Scenario: Supplying gate-on (+20V) and gate-off (–10V) voltages for active-matrix TFT LCD source/gate drivers. IC Role / Device Role / Timing Role: Programmable dual-output regulator delivering stable, low-noise bias rails with soft-start to avoid panel flash or gate driver stress. Use Value: Single-chip solution replaces two discrete converters; internal Schottky diodes reduce heat and footprint vs. external diode designs. |
| OLED Display Anode/Cathode Bias | Op-Amp Dual-Rail Generation |
|
Use Scenario: Generating +18V anode and –5V cathode bias for high-brightness OLED microdisplays in AR/VR headsets. IC Role / Device Role / Timing Role: High-efficiency inverting/boost regulator with low quiescent current (5µA shutdown) and fast transient response for pulsed display operation. Use Value: Enables compact, battery-efficient bias supply; VBAT pin allows direct connection to main battery while VIN runs from low-noise LDO. |
Use Scenario: Providing ±12V rails for precision instrumentation op-amps in portable data acquisition systems powered by 3.3V or 5V sources. IC Role / Device Role / Timing Role: Compact dual-rail generator with tight output regulation (±1.2% FBP, ±0.3% FBN) and low noise for analog signal chains. Use Value: Replaces transformer-based or charge-pump solutions with higher efficiency, lower EMI, and better load regulation. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar dual-output boost/inverting regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT3471EDD#TRPBF | Higher switch current limits (1.3A pos/neg), 1.2MHz switching, no VBAT pin, no output disconnect. | Preferred for >60mA negative loads or where lower EMI is critical; unsuitable where load isolation during shutdown is required. | Select LT3471EDD#TRPBF when higher output current or lower switching frequency is needed; avoid if VBAT-controlled disconnect or strict sequencing is mandatory. |
| LT3463AEDD#TRPBF | Lower max output voltage (±40V), 250mA switch current, integrated Schottkys, no VBAT or disconnect, 1.2MHz. | Targeted at lower-power portable devices; lacks sequencing control and CAP–VBAT disconnect logic. | Choose LT3463AEDD#TRPBF for cost-sensitive, low-current (<30mA) dual-rail apps; not suitable for CCD bias requiring guaranteed startup ordering. |
Compared with LT3487EDD#TRPBF, LT3471EDD#TRPBF trades sequencing and disconnect for higher current and lower frequency, while LT3463AEDD#TRPBF sacrifices rail coordination and protection for smaller size and lower cost-making LT3487EDD#TRPBF uniquely suited for imaging sensor bias where startup behavior and isolation are non-negotiable.
Availability
LT3487EDD#TRPBF is available at Aetrix Electronics and suitable for CCD imaging systems, TFT LCD bias modules, and portable OLED display power supplies requiring stable component supply, long-term lifecycle support, and traceable sourcing.
Supply support for LT3487EDD#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 acquired Linear Technology in 2017 and maintains full technical and manufacturing continuity for all Linear power products. Linear was renowned for high-performance analog ICs with rigorous characterization and application-focused design.
The LT3487 belongs to Linear's precision switching regulator product line, engineered specifically for imaging and display bias applications demanding accurate dual-rail sequencing, low-noise outputs, and robust fault handling in space-constrained portable systems.
FAQ
What is the function of the VBAT pin on the LT3487EDD#TRPBF?
The VBAT pin on the LT3487EDD#TRPBF serves as the return path for the internal output disconnect PNP's drive current and sets the shutdown threshold based on the CAP–VBAT voltage difference. When CAP falls to ≤1.2V above VBAT, the disconnect transistor turns off, isolating the VPOS load. This pin also allows independent powering of the inductors (from a higher-voltage source) while VIN supplies only the control circuitry - a key feature for mixed-rail system architectures.
How does the LT3487EDD#TRPBF ensure proper startup sequencing between its positive and negative outputs?
The LT3487EDD#TRPBF enforces startup sequencing through internal circuitry that monitors the FBP pin voltage: the negative channel remains disabled until FBP reaches ≥87% of its final regulated value (i.e., 1.23V × 0.87 ≈ 1.07V). This guarantees VPOS stabilizes before VNEG begins switching, ensuring the sum VPOS + VNEG stays positive - a critical requirement for CCD sensor integrity and to prevent latch-up in bias-sensitive imaging circuits.
Can the LT3487EDD#TRPBF generate output voltages beyond +15V and –8V?
Yes, the LT3487EDD#TRPBF supports programmable outputs up to +28V on the positive channel and down to –32V on the negative channel. Output voltage is set using one external resistor per channel: R1 = (VPOS − 1.23V)/25µA for the boost channel, and R2 = |VNEG|/25µA for the inverter channel. The device maintains regulation across its full input range (2.3V–16V) and load conditions, provided external components (inductors, capacitors) are rated accordingly.
What is the purpose of the CAP pin on the LT3487EDD#TRPBF, and how does it differ from VPOS?
The CAP pin on the LT3487EDD#TRPBF is the intermediate boost node - the emitter of the internal disconnect PNP and cathode of the internal Schottky diode. It sits at a higher voltage than VPOS due to VCE(SAT) drop (≤280mV). Feedback can be taken from either CAP (for tighter output voltage setting, but no disconnect compensation) or VPOS (to regulate actual load voltage, though short-circuit events may cause CAP overvoltage). Stability requires ≥0.1µF ceramic capacitance between CAP and VPOS.
Does the LT3487EDD#TRPBF require external Schottky diodes?
No, the LT3487EDD#TRPBF integrates all necessary Schottky diodes: DP (anode at SWP, cathode at CAP) for the boost channel and DN (anode at DN, cathode at SWN) for the inverting channel. These are rated for ≤1045mV forward drop at 400mA (DP) and ≤980mV at 600mA (DN). External diodes are optional - only recommended for high-current inverter applications (>70mA) where efficiency gains outweigh added complexity and board area.
LT3487EDD#TRPBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 10-WFDFN Exposed Pad
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Function:
- Step-Up, Step-Up/Step-Down
- Output Configuration:
- Positive and Negative (Dual Rail)
- Topology:
- Boost, Charge Pump, Cuk
- Output Type:
- Adjustable
- Number of Outputs:
- 2
- Voltage - Input (Min):
- 2.3V
- Voltage - Input (Max):
- 16V
- Voltage - Output (Min/Fixed):
- 1.23V
- Voltage - Output (Max):
- 28V
- Current - Output:
- 750mA (Switch), 900mA (Switch)
- Frequency - Switching:
- 2MHz
- Synchronous Rectifier:
- No
- Operating Temperature:
- -40°C ~ 85°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 10-DFN (3x3)
LT3487EDD#TRPBF FAQ
1.How can I place an order for LT3487EDD#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3487EDD#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 LT3487EDD#TRPBF reliable?
The price and inventory of LT3487EDD#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3487EDD#TRPBF is usually 5 days.
3.What payment methods are accepted for LT3487EDD#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3487EDD#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3487EDD#TRPBF?
LT3487EDD#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3487EDD#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 LT3487EDD#TRPBF?
For technical support, including LT3487EDD#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3487EDD#TRPBF requirements.
6.How does Aetrix verify that LT3487EDD#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT3487EDD#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 LT3487EDD#TRPBF meets industry standards.
7.What is the process for return or replacement of LT3487EDD#TRPBF?
All LT3487EDD#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3487EDD#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 LT3487EDD#TRPBF part is unused and in its original packaging.
Return procedure for LT3487EDD#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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