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Analog Devices Inc. LT1776CS8#TRPBF
- Part No.:
- LT1776CS8#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 8-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
LT1776CS8#TRPBF.pdf
- Description:
- IC REG BUCK ADJ 550MA 8SO
- Quantity:
- Payment:
- Shipping:
Inventory:2,370
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Product details
Overview
LT1776CS8#TRPBF from Analog Devices (formerly Linear Technology) is a monolithic, current-mode, step-down DC/DC switching regulator IC designed for high-input-voltage automotive and industrial power conversion. It accepts 7.4V–40V input, delivers up to 700mA peak switch current, operates at 200kHz fixed frequency (synchronizable to 400kHz), and features adaptive switch drive for efficiency across load range. It is used in automotive DC/DC converters where transient tolerance and thermal robustness are critical.
For engineers reviewing the LT1776CS8#TRPBF datasheet, LT1776CS8#TRPBF pinout, LT1776CS8#TRPBF application, or LT1776CS8#TRPBF equivalent, key selection criteria include its 60V transient-tolerant VIN/VSW rating, true current-mode control architecture, VCC-biased internal circuitry for quiescent current optimization, and SO-8 package compatibility with board-level thermal management requirements.
Technical Context
The LT1776CS8#TRPBF implements a proprietary bipolar Darlington output switch with dual-mode dV/dt control: high-slew-rate "boost" mode above VC = 1.35V for heavy loads, and low-slew-rate direct-drive mode below that threshold to suppress pulse skipping at light loads. Its oscillator dynamically slows to ~30kHz when FB voltage drops below ~0.83V (2/3 × 1.24V), enabling stable short-circuit protection without external circuitry.
Internal bias regulation draws power from VCC (output rail) after startup, reducing VIN supply current to 620–900µA under normal operation and only 30–75µA in shutdown. The feedback amplifier has 1.24V reference (±1.2% over temperature), 400–1500µmho transconductance, and clamps VC at 2.0V to enforce 0.55–1.0A switch current limit depending on operating conditions.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 7.4V to 40V continuous; survives 60V transients - enables direct connection to 24V/42V automotive rails without pre-regulation. |
| Switch Current Limit | 0.55A to 1.0A (typ. 0.7A) - sets maximum deliverable output power and defines short-circuit current foldback behavior. |
| Switching Frequency | 200kHz fixed (±10%), synchronizable to 250–400kHz - balances EMI, inductor size, and efficiency for mid-power buck designs. |
| Reference Voltage | 1.240V ±1.2% (–40°C to 125°C) - determines output voltage accuracy via FB divider ratio; supports 3.3V, 5V, and custom outputs. |
| Shutdown Current | 30µA (typ.) - enables ultra-low-power standby modes in battery-backed systems without external disconnect switches. |
| Thermal Resistance θJA | 110°C/W (SO-8 package) - defines maximum power dissipation before junction exceeds 125°C at 25°C ambient; requires minimal copper area. |
| Minimum On-Time | 300ns (tested), ~350ns practical - constrains minimum achievable duty cycle; limits lowest output voltage at high VIN/frequency. |
Pinout & Package
LT1776CS8#TRPBF is housed in an 8-lead plastic SOIC (SO-8) package with standard JEDEC MS-012AC footprint, exposed pad not electrically connected, rated for –40°C to 125°C operating junction temperature.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| SHDN (Pin 1) | Shutdown enable input | Pulled below 0.2–0.8V to enter 30µA shutdown; between 0.2V–1.245V enables lockout mode (no switching); >1.26V enables full operation. |
| VCC (Pin 2) | Internal bias supply input | Powered from output rail to reduce VIN quiescent draw; supplies control logic after startup; requires local 0.1µF bypass if >1 inch from output cap. |
| VSW (Pin 3) | Switch emitter node | High-dI/dt, high-dV/dt node connecting to inductor; must be routed short and away from sensitive signals to minimize EMI and coupling. |
| GND (Pin 4) | Analog and power ground reference | Common return for FB divider, VC compensation network, and internal reference; must be star-connected near FB/VC to avoid noise injection. |
| VIN (Pin 5) | Main high-voltage input supply | Supplies output switch and startup bias; withstands 60V transients; requires low-ESR, high-ripple-current input capacitor. |
| SYNC (Pin 6) | External clock synchronization input | Accepts 1.5–2.2V logic-compatible signal (10–90% duty); disabled automatically during FB undervoltage fault to preserve short-circuit protection. |
| FB (Pin 7) | Inverting input of error amplifier | Compares output voltage (via resistor divider) against 1.24V reference; low voltage (<0.83V) triggers oscillator slowdown for short-circuit handling. |
| VC (Pin 8) | Control voltage output | Integrator output driving current comparator; compensation RC network placed here sets loop stability; clamped at 2.0V for current limiting. |
Key Features
| Feature | Design Value |
|---|---|
| Adaptive dV/dt switch drive | Switches between high-slew boost mode (>1.35V VC) and low-slew direct mode (<1.35V VC) to eliminate pulse skipping while maintaining light-load controllability. |
| VCC-powered internal bias | Reduces VIN supply current from ~800µA to ~30µA in shutdown and cuts quiescent loss by >90% vs VIN-powered controllers at high input voltages. |
| Auto-slowing oscillator | Reduces switching frequency from 200kHz to ~30kHz when FB falls below 0.83V, extending minimum on-time and preserving cycle-by-cycle current limiting during shorts. |
| True current-mode control | Uses sensed switch current directly in comparator - provides inherent line regulation, fast transient response, and simplified loop compensation vs voltage-mode. |
| 60V transient tolerance | VIN and VSW pins rated for 60V absolute max - eliminates need for external TVS or pre-regulator in 24V/42V automotive systems subject to load dump. |
Applications
| Automotive DC/DC Conversion | Industrial 24V-to-5V/3.3V Supply |
|---|---|
Use Scenario: Converting 12V/24V vehicle battery rail to stable 5V for infotainment head units under cold-crank (6.7V) and load-dump (60V) conditions. IC Role / Device Role / Timing Role: Primary step-down controller managing inductor current, feedback regulation, and transient protection via built-in 60V tolerance and auto-slowing oscillator. Use Value: Eliminates external pre-regulator and TVS diode, reduces BOM count by ≥3 components, and maintains regulation during ISO 7637-2 Pulse 5a (load dump). |
Use Scenario: Powering PLC I/O modules from unregulated 24V factory bus with wide input variation and occasional brownouts. IC Role / Device Role / Timing Role: High-efficiency buck regulator delivering 400mA at 5V with tight line/load regulation and thermal derating down to –40°C. Use Value: Achieves >85% efficiency at 24V→5V/400mA using standard 100µH inductor and MBR160 Schottky, with no external current sense or protection IC required. |
| IEEE 1394 (FireWire) Step-Down Converter | Cellular Base Station Auxiliary Supply |
Use Scenario: Generating 3.3V from 12V intermediate rail for FireWire PHY and link layer ICs requiring low-noise, tightly regulated supply. IC Role / Device Role / Timing Role: Fixed-frequency (200kHz) current-mode regulator with VC compensation enabling <1% output ripple and <50µs load transient recovery. Use Value: Meets IEEE 1394a power integrity specs without post-filtering; adaptive dV/dt prevents EMI spikes during burst-mode data transfers. |
Use Scenario: Providing isolated 12V bias for RF power amplifier bias control circuits in remote radio heads operating from 48V telecom rectifier. IC Role / Device Role / Timing Role: Robust front-end buck stage tolerant of 48V surges and capable of synchronized operation (via SYNC pin) to avoid heterodyne interference with RF carriers. Use Value: Enables deterministic 400kHz sync to baseband clock domain, suppressing beat frequencies in sensitive analog RF sections. |
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, 1.2A switch, 3mm × 4mm MSOP-10, 500kHz switching, integrated MOSFETs | Higher current, smaller footprint, but lacks 60V transient tolerance and auto-slowing short-circuit protection | Preferred for space-constrained 42V systems needing >700mA; requires external TVS for load dump immunity. |
| LM5009AMMX/NOPB | 80V max input, 500mA switch, SO-8, 500kHz, voltage-mode control, no sync or auto-slowing | Wider input range but lower peak current, no adaptive light-load drive, less robust short-circuit response | Suitable for cost-sensitive 48V telecom supplies where 60V transients are absent and light-load efficiency is secondary. |
Compared with LTC3631EMSE#PBF and LM5009AMMX/NOPB, the LT1776CS8#TRPBF uniquely combines 60V transient survival, true current-mode control with auto-slowing oscillator, and adaptive dV/dt drive - making it the only choice for automotive-grade 24V/42V buck regulators requiring guaranteed short-circuit behavior without external supervision.
Availability
LT1776CS8#TRPBF is available at Aetrix Electronics and suitable for automotive DC/DC converters, industrial 24V-to-5V supplies, and IEEE 1394 step-down converters requiring stable component supply, long-term lifecycle support, and traceable sourcing.
Supply support for LT1776CS8#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, automotive, industrial, and communications markets.
The LT1776CS8#TRPBF belongs to Linear's legacy high-voltage buck regulator product line, engineered specifically for automotive and industrial environments demanding wide-input operation, transient robustness, and self-protecting fault response without external supervision.
FAQ
What is the maximum input voltage the LT1776CS8#TRPBF can safely withstand?
The LT1776CS8#TRPBF has an absolute maximum VIN and VSW rating of 60V, meaning it can survive brief transients up to that level without damage. However, continuous operation is limited to 40V due to thermal constraints - exceeding this requires careful PCB layout, copper area, and ambient temperature control to prevent junction temperature from exceeding 125°C. Always verify thermal performance in final application conditions.
Does the LT1776CS8#TRPBF support synchronization to an external clock?
Yes, the LT1776CS8#TRPBF supports external synchronization via the SYNC pin (Pin 6), accepting logic-level signals from 250kHz to 400kHz with 1.5–2.2V amplitude. Crucially, the sync function is automatically disabled when FB voltage drops below ~0.83V - preserving the internal oscillator slowdown feature during short-circuit faults. This ensures fault protection remains active regardless of sync source status.
How does the LT1776CS8#TRPBF handle short-circuit conditions?
The LT1776CS8#TRPBF handles short circuits through three coordinated mechanisms: (1) true current-mode control enforces cycle-by-cycle peak current limiting via VC clamping at 2.0V; (2) FB voltage collapse below 0.83V triggers automatic oscillator slowdown from 200kHz to ~30kHz, extending minimum on-time to maintain control; and (3) SYNC function is disabled during this state to prevent external clock interference with fault response. No external components are needed.
What is the purpose of the VCC pin on the LT1776CS8#TRPBF?
The VCC pin (Pin 2) on the LT1776CS8#TRPBF powers the internal control circuitry from the output rail instead of VIN after startup - reducing VIN supply current from ~800µA to ~30µA in shutdown and cutting quiescent loss significantly at high input voltages. During startup, internal bias is drawn from VIN until VOUT reaches ~2.9V, then seamlessly transitions to VCC. A 0.1µF bypass capacitor is recommended if VCC routing exceeds one inch from the output capacitor.
Can the LT1776CS8#TRPBF operate efficiently at very light loads?
Yes, the LT1776CS8#TRPBF maintains controllability and avoids pulse skipping at light loads via its adaptive dV/dt switch drive: when VC falls below 1.35V, it disables the boost circuit and reverts to slower, direct PNP drive - relaxing minimum on-time requirements and enabling stable discontinuous conduction mode. Efficiency at light loads is further improved by VCC-powered biasing, which minimizes VIN current draw to just 620–900µA under normal operation.
LT1776CS8#TRPBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 8-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):
- 40V
- Voltage - Output (Min/Fixed):
- 1.24V
- Voltage - Output (Max):
- 34V
- Current - Output:
- 550mA (Switch)
- Frequency - Switching:
- 200kHz
- Synchronous Rectifier:
- No
- Operating Temperature:
- 0°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 8-SO
LT1776CS8#TRPBF FAQ
1.How can I place an order for LT1776CS8#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT1776CS8#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 LT1776CS8#TRPBF reliable?
The price and inventory of LT1776CS8#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT1776CS8#TRPBF is usually 5 days.
3.What payment methods are accepted for LT1776CS8#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT1776CS8#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT1776CS8#TRPBF?
LT1776CS8#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT1776CS8#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 LT1776CS8#TRPBF?
For technical support, including LT1776CS8#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT1776CS8#TRPBF requirements.
6.How does Aetrix verify that LT1776CS8#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT1776CS8#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 LT1776CS8#TRPBF meets industry standards.
7.What is the process for return or replacement of LT1776CS8#TRPBF?
All LT1776CS8#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT1776CS8#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 LT1776CS8#TRPBF part is unused and in its original packaging.
Return procedure for LT1776CS8#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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