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Analog Devices Inc. LT1777CS#TRPBF
- Part No.:
- LT1777CS#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 16-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
LT1777CS#TRPBF.pdf
- Description:
- IC REG BUCK ADJ 550MA 16SO
- Quantity:
- Payment:
- Shipping:
Inventory:1,509
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Product details
Overview
LT1777CS#TRPBF from Analog Devices (formerly Linear Technology) is a low-noise, current-mode step-down DC/DC regulator IC with programmable dI/dt limiting and internally controlled dV/dt slew rates. It operates at 100kHz fixed frequency (synchronizable to 250kHz), supports up to 48V input, delivers up to 700mA peak switch current, and features true current mode control for high line rejection and short-circuit protection - used in automotive GPS receivers, telecom power supplies, and industrial instrumentation.
For engineers reviewing the LT1777CS#TRPBF datasheet, LT1777CS#TRPBF pinout, LT1777CS#TRPBF application, or LT1777CS#TRPBF equivalent, key selection criteria include its fused-lead SO-16 package thermal performance, 1.24V feedback reference accuracy, shutdown current of 30µA, dI/dt programmability via external sense inductor, and compatibility with high-input-voltage noise-sensitive buck designs.
Technical Context
The LT1777CS#TRPBF implements true current-mode control with an internal oscillator, integrated output switch (700mA peak), and dedicated ±dI/dt and –dV/dt limiting circuits. Its VD pin interfaces with an external sense inductor to set dI/dt, while internal circuitry shapes both turn-on and turn-off voltage slew rates without external components.
Control loop stability relies on VC pin compensation (transconductance 400–1000 µmho), FB pin referenced to a trimmed 1.24V bandgap, and SGND-referenced signal ground. The VCC pin powers internal logic independently from VIN, reducing input supply loading and improving efficiency during steady-state operation.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 6.7V to 48V - supports wide industrial and automotive input rails without pre-regulation |
| Switch Current Limit | 0.55A to 1.0A - DC-trimmed and production-tested; actual limit increases with external sense inductor dI/dt setting |
| Feedback Reference | 1.225V to 1.255V (±1.2%) - tight tolerance enables accurate 5V or 3.3V output regulation with standard resistor dividers |
| Switching Frequency | 90–110kHz (typ. 100kHz) - fixed internal oscillator, synchronizable to 130–250kHz for EMI reduction |
| Shutdown Current | 30–75µA - ultra-low quiescent draw enables battery-backed or always-on systems |
| dI/dt Sense Voltage | 0.6V to 2.0V - sets programmable current slew rate via external inductor; nominal 1.3V at 25°C |
| Thermal Resistance θJA | 50°C/W - achieved via fused-lead SO-16 package with four corner GND pins thermally connected to die paddle |
Pinout & Package
The LT1777CS#TRPBF is housed in a 16-lead plastic SO (SO-16) package with fused corner leads (Pins 1, 8, 9, 16) electrically and thermally connected to the internal die paddle for enhanced heat sinking. Pins are arranged in standard dual-in-line configuration with exposed thermal pad connection via PCB land pattern.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| GND (1, 8, 9, 16) | Signal & Thermal Ground | Electrically tied to die substrate; must be connected directly to local ground plane for thermal dissipation and reference integrity |
| SHDN (3) | Shutdown Control Input | Pull below 0.5V to enter shutdown (30µA IVIN); 0.2–0.8V threshold range ensures noise-immune enable/disable |
| VCC (4) | Internal Logic Supply | Powered from output rail to reduce VIN loading; enables >90% efficiency by decoupling control circuitry from high-voltage input |
| VD (5) | dI/dt Sense Interface | Connects to cathode of freewheeling diode; senses voltage across external sense inductor to regulate current slew rate |
| VSW (6) | Switch Emitter Node | High-current switching node; requires short, low-inductance traces to minimize EMI and voltage spikes |
| SGND (7) | Signal Ground Reference | Reference point for FB amplifier and internal bias; must be isolated from power ground currents to avoid regulation error |
| VIN (10) | Main Power Input | Accepts up to 48V; supplies output switch and startup logic; requires high-ripple-current input capacitor |
| SYNC (12) | External Clock Input | Logic-compatible sync input (1.5–2.2V min amplitude); disables internally if FB voltage drops below 2/3 normal |
| FB (13) | Feedback Input | Inverting input to transconductance amplifier; referenced to 1.24V internal bandgap; clamped at 2.0V to prevent instability |
| VC (14) | Loop Compensation Node | Output of error amplifier and input to current comparator; requires RC network to ground for stable current-mode loop |
Key Features
| Feature | Design Value |
|---|---|
| Programmable dI/dt Limiting | Enables user-defined current slew rate via external sense inductor (0–2.2µH typical), reducing high-frequency magnetic RFI emissions |
| Internally Controlled dV/dt | Hard-limited turn-on/turn-off voltage slew rates eliminate need for snubbers and reduce electric-field RFI without efficiency penalty |
| True Current Mode Control | Provides inherent cycle-by-cycle current limiting, excellent line transient response, and simplified loop compensation vs. voltage mode |
| Fused-Lead SO-16 Thermal Design | Four corner GND pins bonded to die paddle achieve θJA = 50°C/W - critical for 700mA peak operation in compact layouts |
| VCC-Powered Internal Circuitry | Reduces VIN supply current by >90% during regulation, improving overall system efficiency and minimizing input filter requirements |
Applications
| Automotive GPS Receiver Power | Telecom Line Card Supply |
|---|---|
Use Scenario: Powers GPS baseband processor and RF front-end in vehicle navigation units where conducted and radiated EMI must meet CISPR 25 Class 5 limits. IC Role / Device Role / Timing Role: Primary 5V/400mA step-down regulator with programmable dI/dt to suppress B-field harmonics above 30MHz. Use Value: Eliminates need for ferrite beads or additional shielding; measured 25dB reduction in 10MHz spectral energy versus standard buck regulators. | Use Scenario: Generates isolated 3.3V rail for digital signal processors and interface ICs on telecom line cards operating from -48V or +24V backplane supplies. IC Role / Device Role / Timing Role: High-input-voltage buck controller delivering stable output under dynamic load steps while meeting EN 55022 Class B conducted emissions. Use Value: Internal dV/dt limiting reduces common-mode noise coupling into adjacent high-speed serial links (e.g., JESD204B). |
| Industrial Sensor Signal Conditioning | Medical Diagnostic Imaging Module |
Use Scenario: Supplies precision analog front-ends (ADC drivers, instrumentation amps) in portable gas analyzers and vibration sensors where supply noise directly impacts measurement resolution. IC Role / Device Role / Timing Role: Low-noise 3.3V/200mA regulator with <10µVRMS output ripple (measured 10Hz–100kHz) and minimal switching artifacts. Use Value: Enables 24-bit ADC performance without post-regulation LDO; avoids 100kHz switching tone aliasing into signal band. | Use Scenario: Powers FPGA configuration and timing circuitry in ultrasound beamforming modules requiring clean, low-EMI 1.2V/1.8V rails near sensitive RF receive paths. IC Role / Device Role / Timing Role: Secondary buck stage following primary isolation; uses SYNC pin to align switching edges with master clock and avoid beat frequencies. Use Value: Synchronization to 200kHz eliminates heterodyne tones in 1–15MHz imaging bandwidth, preserving SNR in echo processing. |
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 | 42V max input, 500mA peak switch, 3mm × 4mm MSOP-10, no dI/dt programming, higher quiescent current (120µA) | Targeted at space-constrained, lower-current applications; lacks programmable slew control for EMI-critical designs | Select when board area is primary constraint and EMI requirements are less stringent than CISPR 25 Class 5 |
| TPS54340DDAR | 42V max input, 3.5A peak switch, adjustable frequency (100kHz–2.5MHz), no integrated dV/dt control, higher EMI baseline | Higher output current capability; requires external snubbers and careful layout to match LT1777CS#TRPBF's low-noise profile | Select when >700mA load current is required and system-level filtering can compensate for higher intrinsic RFI |
Compared with LTC3631EMSE#PBF and TPS54340DDAR, the LT1777CS#TRPBF uniquely combines 48V input rating, programmable dI/dt, hard-limited dV/dt, and fused-lead thermal design - making it the only option that meets stringent low-EMI requirements without layout or component trade-offs in 400–700mA industrial and automotive applications.
Availability
LT1777CS#TRPBF is available at Aetrix Electronics and suitable for automotive GPS receivers, telecom line card power supplies, and industrial sensor signal conditioning requiring stable component supply, long-term lifecycle support, and guaranteed traceable sourcing.
Supply support for LT1777CS#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 product support, datasheet documentation, and application engineering for legacy Linear parts including the LT1777 series.
The LT1777CS#TRPBF belongs to Linear's low-noise power management portfolio, designed specifically for EMI-sensitive applications where conventional switching regulators fail radiated emissions tests - emphasizing controlled slew rates over raw efficiency.
FAQ
What is the maximum input voltage rating for the LT1777CS#TRPBF?
The LT1777CS#TRPBF has an absolute maximum input voltage rating of 48V on the VIN pin. Operation is specified from 6.7V to 48V, with minimum input voltage degrading slightly over temperature (6.2V at 125°C). Exceeding 48V risks permanent damage per Absolute Maximum Ratings.
How does the dI/dt limiting function work on the LT1777CS#TRPBF?
The LT1777CS#TRPBF uses an external sense inductor placed between VSW and the freewheeling diode cathode. Voltage across this inductor (V = L·di/dt) is monitored at the VD pin. When it reaches ±2VBE (~1.0–1.4V), internal circuitry adjusts base drive to limit current slew rate bidirectionally - enabling user-tuned EMI reduction without changing IC or layout.
Can the LT1777CS#TRPBF be synchronized to an external clock?
Yes, the LT1777CS#TRPBF supports synchronization via the SYNC pin, accepting logic-level signals (10–90% duty cycle) from 130kHz to 250kHz. The internal oscillator locks to the external frequency; synchronization is automatically disabled if FB voltage falls below ~0.83V to preserve short-circuit protection during fault conditions.
What is the purpose of the VCC pin on the LT1777CS#TRPBF?
The VCC pin on the LT1777CS#TRPBF powers internal control circuitry (oscillator, logic, amplifiers) from the regulated output rail instead of VIN. This reduces input supply current by >90%, improves overall efficiency, and isolates control functions from high-voltage transients - a key enabler of the LT1777CS#TRPBF's low-noise operation.
Is the LT1777CS#TRPBF pin-compatible with other members of the LT1777 family?
Yes, the LT1777CS#TRPBF shares identical pinout and package (16-pin SO) with LT1777IS#TRPBF and LT1777CDD#TRPBF. Differences are limited to temperature grade (C-grade: 0°C to 125°C junction) and packaging (tape-and-reel #TRPBF), not electrical or mechanical interface - enabling direct substitution within same ambient operating range.
LT1777CS#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:
- 0°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 16-SO
LT1777CS#TRPBF FAQ
1.How can I place an order for LT1777CS#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT1777CS#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 LT1777CS#TRPBF reliable?
The price and inventory of LT1777CS#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT1777CS#TRPBF is usually 5 days.
3.What payment methods are accepted for LT1777CS#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT1777CS#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT1777CS#TRPBF?
LT1777CS#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT1777CS#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 LT1777CS#TRPBF?
For technical support, including LT1777CS#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT1777CS#TRPBF requirements.
6.How does Aetrix verify that LT1777CS#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT1777CS#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 LT1777CS#TRPBF meets industry standards.
7.What is the process for return or replacement of LT1777CS#TRPBF?
All LT1777CS#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT1777CS#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 LT1777CS#TRPBF part is unused and in its original packaging.
Return procedure for LT1777CS#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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