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Analog Devices Inc. LT1777IS#TRPBF
- Part No.:
- LT1777IS#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 16-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
LT1777IS#TRPBF.pdf
- Description:
- IC REG BUCK ADJ 550MA 16SO
- Quantity:
- Payment:
- Shipping:
Inventory:1,307
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Product details
Overview
LT1777IS#TRPBF from Analog Devices (formerly Linear Technology) is a low-noise, current-mode synchronous step-down DC/DC regulator IC designed for EMI-sensitive applications. It features programmable dI/dt limiting via external sense inductor, internally controlled dV/dt slew rates, 48V max input voltage, 700mA peak switch rating, and fixed 100kHz switching frequency with synchronization capability up to 250kHz.
For engineers reviewing the LT1777IS#TRPBF datasheet, LT1777IS#TRPBF pinout, LT1777IS#TRPBF application, or LT1777IS#TRPBF equivalent, key selection considerations include its integrated dI/dt and dV/dt control architecture, SO-16 fused-lead thermal package, true current-mode operation for line rejection and short-circuit protection, and VCC-powered control circuitry for improved efficiency.
Technical Context
The LT1777IS#TRPBF implements true current-mode control using an internal transconductance error amplifier (400–1500 µmho), reference voltage of 1.24 V ±1.2%, and switch current limit trimmed to 0.55–1.0 A over temperature. Its proprietary output stage includes both ±dI/dt limiting (via external sense inductor + VD pin) and –dV/dt limiting (via internal Darlington clamp), enabling controlled turn-on and turn-off transitions.
It operates with VIN from 6.7 V to 48 V, delivers regulated output via feedback at FB pin referenced to internal 1.24 V bandgap, and supports shutdown (SHDN threshold 0.2–0.8 V) and external synchronization (SYNC input compatible with 130–250 kHz, 1.5–2.2 V amplitude). The VCC pin powers internal logic independently from VIN, reducing input supply current draw during normal operation.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 6.7 V to 48 V - Supports wide industrial and automotive input rails without pre-regulation. |
| Switch Current Limit | 0.55 A to 1.0 A - Programmable dI/dt via external sense inductor enables noise optimization per application. |
| Switching Frequency | 90–115 kHz (fixed) - Enables compact magnetics; synchronizable to 130–250 kHz for EMI spreading. |
| Reference Voltage | 1.225–1.255 V - Tight 1.24 V ±1.2% bandgap reference ensures stable output regulation accuracy. |
| Shutdown Current | 30–75 µA - Ultra-low quiescent draw preserves battery life in always-on systems. |
| Thermal Resistance θJA | 50 °C/W - Achieved via fused-lead SO-16 package with four corner GND pins connected to die paddle. |
| Operating Junction Temp | –40°C to 125°C - Qualified for extended industrial and automotive under-hood environments. |
Pinout & Package
LT1777IS#TRPBF is housed in a 16-pin plastic SOIC (SO-16) package with fused-lead construction. Four corner pins (1, 8, 9, 16) are electrically and thermally connected to the internal die paddle for enhanced heat sinking. Pins 2, 11, and 15 are unconnected (NC).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| GND (1, 8, 9, 16) | Signal & Thermal Ground | Electrically tied to die substrate; must be connected to local ground plane for reference stability and thermal dissipation. |
| SHDN (3) | Shutdown Control Input | Pull below 0.5 V to enter ultra-low-IQ shutdown mode; high-impedance input requires 100 pF bypass if left floating. |
| VCC (4) | Internal Logic Power Supply | Powered from output rail to reduce VIN current draw; enables higher efficiency vs VIN-powered controllers. |
| VD (5) | dI/dt Sense Reference | Connects to cathode of freewheeling diode; forms sensing node with VSW to trigger ±dI/dt limiting. |
| VSW (6) | Switch Emitter Node | High-current emitter output of internal NPN switch; requires short, low-inductance PCB routing to minimize EMI. |
| SGND (7) | Signal Ground Reference | Reference point for FB amplifier and internal bias; must be isolated from power ground currents. |
| SYNC (12) | External Clock Input | Logic-compatible sync input (130–250 kHz); disabled automatically if FB voltage drops below 2/3 of nominal. |
| FB (13) | Feedback Input | Inverting input of transconductance amplifier; compares output voltage against 1.24 V reference. |
| VC (14) | Control Voltage Output | Error amplifier output and current comparator input; used for loop compensation with R/C network to ground. |
| VIN (10) | Main Power Input | Supplies output switch and startup logic; requires high-ripple-current input capacitor due to pulsed current draw. |
Key Features
| Feature | Design Value |
|---|---|
| Programmable dI/dt Limiting | Enabled via external sense inductor between VSW and diode cathode; allows user-tuned trade-off between EMI and efficiency. |
| Internally Controlled dV/dt | Turn-on and turn-off voltage slew rates limited by internal –dV/dt limiter and Q2/Q1 capacitance; reduces high-frequency E-field emissions. |
| True Current-Mode Control | Provides inherent cycle-by-cycle current limiting, excellent line transient rejection, and simplified loop compensation. |
| Fused-Lead SO-16 Package | Four corner GND pins bonded to die paddle yield θJA = 50 °C/W - enables 700 mA operation without heatsink in typical layouts. |
| VCC-Powered Internal Circuitry | Reduces VIN supply current to 620–900 µA (vs multi-mA in VIN-powered controllers), improving overall system efficiency. |
Applications
| Automotive GPS Receivers | Industrial Instrumentation |
|---|---|
Use Scenario: Powering sensitive RF front-end stages in vehicle-mounted GPS modules where conducted and radiated EMI must meet CISPR 25 Class 5 limits. IC Role / Device Role / Timing Role: Low-noise buck regulator providing clean 3.3 V or 5 V rail; dI/dt and dV/dt control suppresses harmonics above 30 MHz that interfere with L1-band reception. Use Value: Eliminates need for additional LC filters or shielding, reducing BOM cost and board area while ensuring signal integrity in noisy automotive environments. | Use Scenario: Generating precision analog supply rails (e.g., ±15 V, +5 V) for data acquisition systems in factory-floor PLCs and sensor transmitters. IC Role / Device Role / Timing Role: Primary DC/DC converter delivering stable, low-ripple output; current-mode control maintains regulation during rapid load transients from ADC sampling bursts. Use Value: Maintains <±0.5% output accuracy across –40°C to 125°C and rejects >60 dB of input line ripple - critical for 16-bit+ measurement fidelity. |
| Telecom Base Station Power | Medical Diagnostic Equipment |
Use Scenario: Intermediate bus conversion in remote radio units (RRUs), stepping down 48 V backplane to 12 V or 5 V for FPGA, SerDes, and clock IC supplies. IC Role / Device Role / Timing Role: High-input-voltage buck controller supporting 48 V telecom standard; SYNC pin enables phase alignment with system clock to avoid beat frequencies. Use Value: Synchronization capability reduces spectral peak energy by >10 dB at fundamental and harmonics - easing compliance with EN 55022 Class A conducted emissions. | Use Scenario: Powering low-noise analog signal chains (e.g., EEG amplifiers, ultrasound beamformers) where switching noise could corrupt microvolt-level bio-signals. IC Role / Device Role / Timing Role: Primary power stage with dI/dt-limited switching; fused-lead SO-16 package minimizes thermal resistance to prevent drift in temperature-sensitive analog circuits. Use Value: Achieves >25 dB reduction in 10 MHz spectral energy vs standard buck converters (with 2.2 µH sense inductor), meeting IEC 60601-1 EMI requirements without added filtering. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar step-down regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3631EMSE#PBF | 42 V max input, 1.2 A switch, 3 mm × 4 mm MSOP-10, no dI/dt programming; uses constant-frequency current mode with internal compensation. | Higher current, smaller footprint, but lacks programmable dI/dt and fused-lead thermal design - less suitable for ultra-low-EMI analog rails. | Select when board space is constrained and EMI requirements are moderate; verify thermal performance at 700 mA in target layout. |
| TPS54332DR | 28 V max input, 3.5 A switch, SO-8, no dV/dt control; includes integrated high-side FET and soft-start, but no external dI/dt adjustment. | Higher output current and integrated MOSFET simplify design, yet lacks dedicated EMI mitigation features - requires external snubbers or filters for noise-sensitive loads. | Prefer for cost-sensitive, high-current digital rail applications where EMI is managed at system level rather than IC level. |
Compared with LTC3631EMSE#PBF and TPS54332DR, the LT1777IS#TRPBF uniquely combines programmable dI/dt, intrinsic dV/dt limiting, and fused-lead thermal packaging - making it the only option among the three qualified for demanding low-EMI analog power delivery without external suppression components.
Availability
LT1777IS#TRPBF is available at Aetrix Electronics and suitable for automotive GPS receivers, industrial instrumentation, telecom base station power, and medical diagnostic equipment requiring stable component supply across extended temperature ranges and long production lifecycles.
Supply support for LT1777IS#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. (ADI) is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, serving industrial, automotive, communications, and healthcare markets.
The LT1777IS#TRPBF belongs to ADI's legacy Linear Technology power management portfolio, specifically engineered for low-noise, high-reliability DC/DC conversion in EMI-critical analog and RF systems - emphasizing controlled switching transitions over raw efficiency.
FAQ
What is the maximum input voltage rating for the LT1777IS#TRPBF?
The LT1777IS#TRPBF has an absolute maximum input voltage rating of 48 V on the VIN pin. Operation is specified from 6.7 V to 48 V, with minimum input voltage degrading slightly over temperature (e.g., 6.4 V at 125°C). Exceeding 48 V risks permanent damage per Absolute Maximum Ratings.
How does the dI/dt limiting function work on the LT1777IS#TRPBF?
The LT1777IS#TRPBF implements dI/dt limiting using an external sense inductor placed between the VSW pin and the cathode of the freewheeling diode. The VD pin connects to that cathode, forming a sensing node. When the voltage across the sense inductor reaches ±2×VBE (~1.0–1.4 V), internal circuitry adjusts base drive to the output transistor to clamp the current slew rate - enabling user-defined noise/efficiency trade-offs.
Can the LT1777IS#TRPBF be synchronized to an external clock source?
Yes, the LT1777IS#TRPBF supports external synchronization via the SYNC pin (Pin 12). It accepts logic-level signals with 10–90% duty cycle across a 130–250 kHz range and requires ≥1.5 V amplitude. The internal oscillator disables sync functionality automatically if the FB pin voltage falls below ~0.83 V, preserving short-circuit protection behavior.
What is the purpose of the VCC pin on the LT1777IS#TRPBF?
The VCC pin on the LT1777IS#TRPBF powers the internal oscillator, logic, and error amplifier circuitry - decoupling control-stage supply from the high-current VIN path. This reduces total VIN supply current to 620–900 µA (vs several mA in VIN-powered controllers), improving overall efficiency. During startup, internal circuitry draws from VIN until VCC reaches regulation.
Is the LT1777IS#TRPBF pin-compatible with other members of the LT1777 family?
Yes, the LT1777IS#TRPBF shares identical pinout and electrical characteristics with LT1777CS#TRPBF and LT1777HS#TRPBF. The suffix denotes temperature grade: 'C' (0°C to 125°C), 'I' (–40°C to 125°C), and 'H' (–40°C to 150°C). All variants use the same SO-16 fused-lead package and require identical PCB layout and external components.
LT1777IS#TRPBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 16-SOIC (0.154", 3.90mm Width)
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Function:
- Step-Down
- Output Configuration:
- Positive
- Topology:
- Buck
- Output Type:
- Adjustable
- Number of Outputs:
- 1
- Voltage - Input (Min):
- 7.4V
- Voltage - Input (Max):
- 48V
- Voltage - Output (Min/Fixed):
- 1.24V
- Voltage - Output (Max):
- 30V
- Current - Output:
- 550mA (Switch)
- Frequency - Switching:
- 100kHz
- Synchronous Rectifier:
- No
- Operating Temperature:
- -40°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 16-SO
LT1777IS#TRPBF FAQ
1.How can I place an order for LT1777IS#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT1777IS#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 LT1777IS#TRPBF reliable?
The price and inventory of LT1777IS#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT1777IS#TRPBF is usually 5 days.
3.What payment methods are accepted for LT1777IS#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT1777IS#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT1777IS#TRPBF?
LT1777IS#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT1777IS#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 LT1777IS#TRPBF?
For technical support, including LT1777IS#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT1777IS#TRPBF requirements.
6.How does Aetrix verify that LT1777IS#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT1777IS#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 LT1777IS#TRPBF meets industry standards.
7.What is the process for return or replacement of LT1777IS#TRPBF?
All LT1777IS#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT1777IS#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 LT1777IS#TRPBF part is unused and in its original packaging.
Return procedure for LT1777IS#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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