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Analog Devices Inc. LT1776CN8#PBF
- Part No.:
- LT1776CN8#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 8-DIP (0.300", 7.62mm)
- Datasheet:
-
LT1776CN8#PBF.pdf
- Description:
- IC REG BUCK ADJ 550MA 8PDIP
- Quantity:
- Payment:
- Shipping:
Inventory:1,834
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Product details
Overview
LT1776CN8#PBF from Analog Devices (formerly Linear Technology) is a monolithic, wide-input-range, current-mode buck switching regulator IC. It accepts 7.4V–40V input, delivers up to 700mA peak switch current, operates at fixed 200kHz (synchronizable to 400kHz), and features adaptive switch drive for high-efficiency operation across light-to-heavy loads in automotive DC/DC converters.
For engineers reviewing the LT1776CN8#PBF datasheet, LT1776CN8#PBF pinout, LT1776CN8#PBF application, or LT1776CN8#PBF equivalent, key selection criteria include its 60V transient tolerance, true current-mode control architecture, VCC-powered biasing for reduced VIN quiescent draw, shutdown current of 30µA, and PDIP-8 package compatibility with legacy through-hole layouts.
Technical Context
The LT1776CN8#PBF implements a proprietary bipolar output switch stage with dual lateral PNP drivers (Q3/Q4) and explicit turn-off transistor Q5, enabling high dV/dt slew during heavy-load continuous conduction mode while reducing rise time under light-load discontinuous mode via boost-comparator gating. Its internal oscillator slows to ~30kHz during short-circuit conditions when FB voltage drops below ~0.83V, preserving cycle-by-cycle current limiting.
Control is fully current-mode: the VC pin serves as both feedback amplifier output and current comparator input, with transconductance of 400–1000 µmho and clamp voltage of 2.0V. The SHDN pin provides programmable undervoltage lockout (UVLO) that logically ANDs with the internal 6.7V threshold, allowing user-defined minimum input voltage without lowering the base UVLO point.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 7.4V to 40V continuous; withstands 60V transients - enables direct connection to 24V/36V automotive rails with surge margin. |
| Switch Current Limit | 0.55A to 1.0A (typ. 0.7A) - sets maximum deliverable output power and short-circuit current foldback level. |
| Switching Frequency | 180–220kHz (fixed 200kHz); synchronizable to 250–400kHz - balances EMI, inductor size, and efficiency in space-constrained designs. |
| Reference Voltage | 1.225–1.255V (typ. 1.240V) - defines output regulation accuracy; used with external resistor divider to set VOUT. |
| Shutdown Current | 30–75µA - ensures ultra-low system standby power in battery-backed or always-on applications. |
| VCC Supply Current | 3.2–5.0mA - powers internal circuitry from output rail, minimizing VIN supply loading and improving full-load efficiency. |
| Minimum On-Time | 300ns (tested), ~350ns practical limit - constrains minimum achievable duty cycle and thus lowest viable VOUT at high VIN/fOSC. |
Pinout & Package
LT1776CN8#PBF is housed in an 8-lead plastic DIP (PDIP-8) package with 0.3-inch body width and through-hole mounting. Thermal resistance θJA = 130°C/W. Pin 1 is SHDN; pin 8 is VC. All pins are electrically and thermally optimized for high-voltage buck converter layout.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| SHDN (Pin 1) | Shutdown control input | Pulls regulator into <30µA shutdown when ≤0.3V; enables user-programmable UVLO above 6.7V via resistor divider. |
| VCC (Pin 2) | Bias supply input | Powers internal circuitry from regulated output rail - reduces VIN quiescent draw and improves efficiency above ~2.9V output. |
| VSW (Pin 3) | Switch emitter node | High-dI/dt, high-dV/dt node connected to inductor; requires short, low-inductance PCB routing to minimize EMI and voltage overshoot. |
| GND (Pin 4) | Analog and power ground reference | Common return for FB divider, VC compensation network, and internal reference - must be isolated from high-current ground paths. |
| VIN (Pin 5) | Main input supply | Supplies output switch and startup bias; rated for 60V transients; requires low-ESR, high-ripple-current input capacitor. |
| SYNC (Pin 6) | Oscillator synchronization input | Accepts logic-level external clock (250–400kHz); automatically disabled during short-circuit oscillator slowdown. |
| FB (Pin 7) | Inverting feedback input | Compares output divider voltage against 1.24V internal reference; modulates oscillator frequency downward if voltage falls below ~0.83V. |
| VC (Pin 8) | Control voltage output | Feedback amplifier output and current comparator input; connects to RC compensation network for loop stability. |
Key Features
| Feature | Design Value |
|---|---|
| Adaptive switch drive | Reduces rise time at light loads to avoid pulse skipping while maintaining fast switching at full load - eliminates audible noise and improves light-load efficiency without external circuitry. |
| True current-mode control | Uses VC pin as unified control node for both error amplification and peak-current sensing - provides inherent line regulation, cycle-by-cycle current limiting, and simplified loop compensation. |
| VCC-powered biasing | Draws control power from regulated output instead of VIN after startup - cuts quiescent supply current by >80% compared to VIN-powered controllers at high input voltages. |
| Short-circuit protection | Automatically reduces switching frequency to ~30kHz when FB voltage drops below 2/3 of nominal - maintains controllable current limiting even during sustained output shorts. |
| 60V transient tolerance | Withstands 60V spikes on VIN and VSW without damage - eliminates need for external TVS clamping in 24V/36V automotive and industrial systems. |
Applications
| Automotive Infotainment Power | Industrial Sensor Node DC/DC |
|---|---|
Use Scenario: Powering 5V/400mA infotainment head-unit modules from a 12V–36V vehicle battery with cold-crank and load-dump transients. IC Role / Device Role / Timing Role: Primary step-down regulator with integrated switch, providing regulated 5V rail with 60V transient immunity and thermal derating management. Use Value: Eliminates need for external transient suppressors and discrete MOSFET drivers - reduces BOM count and PCB area while meeting ISO 7637-2 pulse 5a requirements. | Use Scenario: Generating stable 5V supply for low-power industrial IoT sensors operating from 24V factory bus with wide temperature range (-40°C to +125°C). IC Role / Device Role / Timing Role: High-reliability buck controller delivering precise 5V output with ±1.2% reference accuracy and guaranteed operation over full industrial temperature range. Use Value: Maintains regulation accuracy and current-limit integrity across -40°C to +125°C ambient - avoids recalibration or derating in uncontrolled environments. |
| IEEE 1394 Port Converter | Cellular Baseband Charger Interface |
Use Scenario: Converting 12V–40V IEEE 1394 (FireWire) bus power to 3.3V for PHY and link-layer ICs in docking stations. IC Role / Device Role / Timing Role: Fixed-frequency (200kHz) buck regulator with SYNC input for EMI reduction in mixed-signal systems sharing common clock domains. Use Value: Enables deterministic EMI placement via external clock synchronization - simplifies FCC/CE compliance testing in high-speed digital interfaces. | Use Scenario: Providing 5V charging interface power from variable-input USB-OTG or wall adapters in portable cellular accessories. IC Role / Device Role / Timing Role: Wide-input buck regulator supporting 7.4V–40V input with low 30µA shutdown current for battery-backed standby modes. Use Value: Extends accessory battery life during idle periods - achieves >100-hour standby with typical 100mAh backup cell. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar buck regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3631EMSE#PBF | 40V max input, 100mA output, MSOP-10 package; integrates power MOSFETs but lower current rating. | Suitable for low-power auxiliary rails where board space is critical but 700mA peak is not required. | Select when footprint minimization and integrated FETs outweigh need for 700mA output capability. |
| LM5088MHX/NOPB | 60V max input, 5A peak switch current, SO-8 package; requires external MOSFETs and more complex compensation. | Targeted at higher-current (>1A) applications with greater thermal design flexibility and adjustable frequency. | Select when output current exceeds 700mA or when external FET selection is preferred for thermal or cost optimization. |
Compared with LTC3631EMSE#PBF, LT1776CN8#PBF delivers 7× higher peak output current in the same pin count but lacks integrated high-side FETs; compared with LM5088MHX/NOPB, it offers simpler layout and lower component count for sub-1A designs but trades off maximum current scalability and frequency adjustability.
Availability
LT1776CN8#PBF is available at Aetrix Electronics and suitable for automotive infotainment systems, industrial sensor nodes, and IEEE 1394 power interfaces requiring stable component supply, long-term lifecycle support, and guaranteed traceable sourcing.
Supply support for LT1776CN8#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 continues to manufacture and support its high-performance analog and power management portfolio.
The LT1776 belongs to Linear's legacy high-voltage buck regulator family, designed specifically for robust, wide-input DC/DC conversion in automotive, industrial, and telecom infrastructure where reliability under voltage transients is critical.
FAQ
What is the absolute maximum input voltage rating for the LT1776CN8#PBF?
The LT1776CN8#PBF has an absolute maximum input voltage rating of 60V on both VIN and VSW pins. This rating is based on semiconductor junction breakdown limits and allows the device to survive automotive load-dump transients without external protection. However, continuous operation above 40V is thermally limited and depends on output current, switching frequency, and PCB copper area - refer to the Thermal Considerations section of the datasheet for derating curves.
Does the LT1776CN8#PBF require an external freewheeling diode, and what type is recommended?
Yes, the LT1776CN8#PBF requires an external freewheeling diode. A Schottky diode is strongly recommended - such as the MBR160 shown in the典型 application - due to its low forward voltage drop and absence of reverse recovery charge. Ultrafast recovery diodes are discouraged because their reverse recovery can cause severe VSW overshoot and RFI, potentially damaging the LT1776CN8#PBF or adjacent circuitry.
Can the LT1776CN8#PBF be synchronized to an external clock, and what is the valid frequency range?
Yes, the LT1776CN8#PBF can be synchronized to an external clock via the SYNC pin. The valid synchronization range is 250kHz to 400kHz, with minimum sync amplitude of 1.5V (typ. 2.2V). The internal oscillator automatically disables sync functionality when FB voltage drops below ~0.83V - ensuring reliable short-circuit protection remains active even during forced synchronization.
What is the purpose of the VCC pin on the LT1776CN8#PBF, and how should it be connected?
The VCC pin on the LT1776CN8#PBF supplies power to the internal control circuitry. It should be connected directly to the output capacitor's positive terminal. This configuration reduces VIN supply current by >80% after startup, significantly improving efficiency - especially at high input voltages. If the output capacitor is located >25mm from the VCC pin, a local 0.1µF ceramic bypass capacitor to ground is required at the VCC pin.
How does the LT1776CN8#PBF handle short-circuit conditions, and what protection mechanisms are built-in?
The LT1776CN8#PBF handles short-circuits using two coordinated mechanisms: first, true current-mode control limits peak switch current via the VC pin clamp (2.0V); second, when FB voltage falls below ~0.83V, the internal oscillator frequency automatically reduces from 200kHz down to ~30kHz. This slower switching preserves minimum on-time margin and maintains controllable current limiting - preventing unbounded current ramp-up during sustained shorts.
LT1776CN8#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 8-DIP (0.300", 7.62mm)
- Packaging:
- Tube
- 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:
- Through Hole
- Supplier Device Package:
- 8-PDIP
LT1776CN8#PBF FAQ
1.How can I place an order for LT1776CN8#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT1776CN8#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 LT1776CN8#PBF reliable?
The price and inventory of LT1776CN8#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT1776CN8#PBF is usually 5 days.
3.What payment methods are accepted for LT1776CN8#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT1776CN8#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT1776CN8#PBF?
LT1776CN8#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT1776CN8#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 LT1776CN8#PBF?
For technical support, including LT1776CN8#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT1776CN8#PBF requirements.
6.How does Aetrix verify that LT1776CN8#PBF is sourced from the original manufacturer or authorized distributors?
All LT1776CN8#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 LT1776CN8#PBF meets industry standards.
7.What is the process for return or replacement of LT1776CN8#PBF?
All LT1776CN8#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT1776CN8#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 LT1776CN8#PBF part is unused and in its original packaging.
Return procedure for LT1776CN8#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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