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Analog Devices Inc. LT1268CQ#PBF
- Part No.:
- LT1268CQ#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- TO-263-6, D2PAK (5 Leads + Tab), TO-263BA
- Datasheet:
-
LT1268CQ#PBF.pdf
- Description:
- IC REG BUCK BST ADJ 7.5A DDPAK-5
- Quantity:
- Payment:
- Shipping:
Inventory:187
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Product details
Overview
LT1268CQ#PBF from Analog Devices (formerly Linear Technology) is a monolithic 7.5A, 150kHz current-mode switching regulator IC in a 5-lead TO-220 package. It integrates a high-current switch, oscillator, error amplifier, and protection circuitry, enabling buck, boost, flyback, and inverting topologies. Designed for high-efficiency DC/DC conversion with 3.5V–30V input and ±1% output accuracy using external 0.1% resistors, it serves in battery upconverters and PC multi-rail power supplies.
For engineers reviewing the LT1268CQ#PBF datasheet, LT1268CQ#PBF pinout, LT1268CQ#PBF application, or LT1268CQ#PBF equivalent, key selection considerations include its 7.5A internal switch current limit at ≤100°C, 150kHz fixed switching frequency, adaptive anti-saturation drive, 7mA quiescent current, and shutdown mode drawing only 100µA - all critical for thermally constrained industrial and embedded power designs.
Technical Context
The LT1268CQ#PBF employs current-mode control with an integrated transconductance error amplifier (gm = 3000–6000 µmho) and adaptive anti-saturation switch drive to maintain efficiency across wide load ranges. Its reference voltage is tightly specified (1.224V–1.264V for LT1268 variant), enabling ±1% output regulation when paired with precision feedback resistors.
It supports external synchronization via the VC pin and includes built-in overload protection, thermal shutdown, and undervoltage lockout. The device operates from 3.5V to 30V input, delivers up to 7.5A switch current (derated above 100°C), and features a maximum duty cycle of 92% - enabling high step-up ratios in boost configurations without external current sensing.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Switch Current Limit | 7.5A at ≤100°C; enables single-chip 3.75A boost converters (e.g., 4.7–5.3V input to 5.3V±1% @ 3.75A) |
| Switching Frequency | 150kHz typical; balances EMI, inductor size, and efficiency for medium-power DC/DC designs |
| Input Voltage Range | 3.5V to 30V; supports wide-input industrial rails and battery-powered systems (e.g., 12V nominal with brownout margin) |
| Quiescent Current | 7mA typical; minimizes no-load power loss in always-on applications like standby power supplies |
| Reference Voltage | 1.244V typical (±9mV for LT1268B); ensures ±1% output accuracy with 0.1% external resistor dividers |
| Shutdown Current | 100µA typical; allows low-power standby mode without auxiliary LDOs or external disconnect switches |
| Switch RDS(on) | 0.12Ω typical at TJ ≤100°C; limits conduction loss to <0.34W at 5A, easing thermal design in TO-220 package |
Pinout & Package
LT1268CQ#PBF is housed in a 5-lead TO-220 package (T package) with case-connected drain for direct heatsinking. Pin 1 (VIN) accepts 3.5–30V input; Pin 2 (VSW) connects to external inductor/switch node; Pin 3 (GND) is power ground; Pin 4 (FB) senses output voltage via resistor divider; Pin 5 (VC) controls duty cycle and enables shutdown.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VIN (Pin 1) | Input supply connection | Accepts unregulated 3.5–30V; must be bypassed with ≥220µF low-ESR capacitor near package |
| VSW (Pin 2) | Switch node output | Drives external inductor; carries high di/dt; requires short, low-inductance PCB routing |
| GND (Pin 3) | Power ground reference | Return path for switch current and feedback network; must be star-connected to minimize noise coupling |
| FB (Pin 4) | Feedback input | Senses divided output voltage; high-impedance (≤750nA bias) - sensitive to PCB leakage and noise |
| VC (Pin 5) | Control voltage / shutdown | Duty cycle control input; <0.25V disables switch (100µA IQ); >1.08V enables full operation |
Key Features
| Feature | Design Value |
|---|---|
| Integrated 7.5A switch | Eliminates external MOSFET and driver, reducing BOM count and layout complexity in ≤40W converters |
| Current-mode control | Provides inherent cycle-by-cycle current limiting and stable operation without external compensation components |
| Adaptive anti-saturation drive | Maintains high efficiency (>85%) across 0.1A–3.75A load range by dynamically optimizing gate drive |
| External synchronization capability | Allows VC pin to accept external clock signal, enabling noise-sensitive designs to avoid EMI bands |
| Self-protected overload handling | Combines thermal shutdown, current limiting, and UVLO to survive sustained shorts without external fusing |
Applications
| High-Efficiency Boost Converter | PC Power Supply with Multiple Outputs |
|---|---|
Use Scenario: Generating stable 12V from 5V USB-C PD source in portable test equipment. IC Role / Device Role / Timing Role: Primary switching regulator controlling inductor current and output voltage via FB/VC loop. Use Value: Delivers 1.5A at 90% efficiency with only 5 external parts - eliminating need for secondary controllers or discrete FETs. |
Use Scenario: Providing +5V and +12V rails from a single 12V input in compact industrial PCs. IC Role / Device Role / Timing Role: Configured as dual-output flyback controller with coupled inductor and independent feedback paths. Use Value: Achieves ±1% regulation on both outputs using single IC, reducing board area versus dual-regulator solutions. |
| Battery Upconverter | Negative-to-Positive Converter |
Use Scenario: Boosting Li-ion battery voltage (3.0–4.2V) to 5.0V for USB peripherals in handheld medical devices. IC Role / Device Role / Timing Role: Synchronous boost controller managing energy transfer during charge/discharge cycles. Use Value: Maintains >87% efficiency down to 3.0V input, extending runtime while meeting IEC 60601 leakage requirements. |
Use Scenario: Converting –5V rail to +5V in legacy instrumentation requiring bipolar analog front-ends. IC Role / Device Role / Timing Role: Inverting topology regulator generating regulated positive output from negative input supply. Use Value: Enables single-supply op-amp biasing without isolated DC/DC modules - reducing cost and EMI footprint. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar high-current switching regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3789EFE#PBF | 4-switch synchronous buck-boost controller; requires external MOSFETs; supports 4–36V input; no integrated switch | Used in higher-efficiency (>94%), higher-power (>60W) applications where thermal management justifies added complexity | Select when efficiency >92% and input voltage may exceed 30V - but expect +8 BOM items and layout sensitivity |
| LM5118MH/NOPB | 100kHz–1MHz adjustable-frequency controller; 5.5–100V input; external N-channel MOSFET driver; no integrated switch | Preferred for ultra-wide VIN (e.g., 24V automotive with load dump) and programmable frequency EMI compliance | Choose when input exceeds 30V or frequency tuning is required - but note higher component count and compensation effort |
Compared with LTC3789EFE#PBF and LM5118MH/NOPB, the LT1268CQ#PBF offers lowest system-level BOM count and fastest time-to-function for ≤40W boost/flyback designs, trading off programmability and ultra-wide VIN for simplicity and proven ruggedness in industrial environments.
Availability
LT1268CQ#PBF is available at Aetrix Electronics and suitable for battery upconverters, PC multi-rail power supplies, and industrial boost regulators requiring stable component supply, long-term lifecycle support, and traceable sourcing.
Supply support for LT1268CQ#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 maintains its high-reliability analog and power management portfolio. Linear's legacy products emphasize robustness, ease-of-use, and application-ready performance in harsh environments.
The LT1268CQ#PBF belongs to Linear's monolithic switching regulator family designed for medium-power DC/DC conversion where integration, thermal resilience, and minimal external components are prioritized over programmability - targeting industrial, medical, and test equipment power stages.
FAQ
What is the maximum continuous output current achievable with the LT1268CQ#PBF in a boost configuration?
The LT1268CQ#PBF supports up to 3.75A output current in a typical 4.7–5.3V to 5.3V±1% boost converter, as validated in the datasheet's TA02 application circuit. This assumes 100°C junction temperature, 40% duty cycle, and proper heatsinking on the TO-220 case. At higher ambient temperatures or longer duty cycles, the 7.5A switch current limit derates per the thermal resistance curve - limiting practical output to ~2.5A on a single-sided PCB without forced air.
Does the LT1268CQ#PBF require an external Schottky diode in boost topology, and what is the recommended part?
Yes, the LT1268CQ#PBF requires an external Schottky diode in boost configurations to conduct inductor current during switch-off periods. The datasheet specifies MBR1035 (10A, 35V) for the 3.75A TA02 circuit. For lower-current designs (<1.5A), MBR1020 or SS10P4 are valid alternatives - all must exhibit ≤0.5V forward drop at peak load current and sufficient surge rating to handle inductive kickback.
Can the LT1268CQ#PBF be synchronized to an external clock, and how is this implemented?
Yes, the LT1268CQ#PBF can be externally synchronized via its VC pin, as noted in the "Can Be Externally Synchronized" feature and referenced to the LT1072 datasheet. A clean TTL- or CMOS-compatible square wave applied to VC overrides the internal 150kHz oscillator. Duty cycle must remain below 92%, and the external clock must not exceed 180kHz to ensure reliable switching edge alignment and avoid subharmonic oscillation.
What is the purpose of the VC pin on the LT1268CQ#PBF beyond shutdown control?
Beyond enabling shutdown (<0.25V), the VC pin on the LT1268CQ#PBF serves as the control voltage input for duty cycle modulation. Applying 0.9–1.4V sets proportional on-time, allowing analog dimming in LED drivers or variable output voltage control. Its transconductance is 12A/V, meaning a 100mV change adjusts switch current by ~1.2A - useful for precision current limiting or soft-start ramping.
How does the LT1268CQ#PBF achieve ±1% output voltage accuracy, and what external components are critical?
The LT1268CQ#PBF achieves ±1% output voltage accuracy using its 1.244V reference (±9mV for LT1268B variant) and high-impedance FB pin. Critical external components are the feedback resistor divider - requiring 0.1% tolerance on both R1 and R2 - and separate grounding of the GND pin to output ground (not input ground) to avoid load-induced errors. Layout must minimize trace capacitance on FB to prevent instability.
LT1268CQ#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- TO-263-6, D2PAK (5 Leads + Tab), TO-263BA
- Packaging:
- Tube
- Product Status:
- Active
- Function:
- Step-Up, Step-Down, Step-Up/Step-Down
- Output Configuration:
- Positive or Negative
- Topology:
- Buck, Boost, Flyback
- Output Type:
- Adjustable
- Number of Outputs:
- 1
- Voltage - Input (Min):
- 3.5V
- Voltage - Input (Max):
- 30V
- Voltage - Output (Min/Fixed):
- 1.244V
- Voltage - Output (Max):
- 60V (Switch)
- Current - Output:
- 7.5A (Switch)
- Frequency - Switching:
- 150kHz
- Synchronous Rectifier:
- No
- Operating Temperature:
- 0°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- DDPAK-5
LT1268CQ#PBF FAQ
1.How can I place an order for LT1268CQ#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT1268CQ#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 LT1268CQ#PBF reliable?
The price and inventory of LT1268CQ#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT1268CQ#PBF is usually 5 days.
3.What payment methods are accepted for LT1268CQ#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT1268CQ#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT1268CQ#PBF?
LT1268CQ#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT1268CQ#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 LT1268CQ#PBF?
For technical support, including LT1268CQ#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT1268CQ#PBF requirements.
6.How does Aetrix verify that LT1268CQ#PBF is sourced from the original manufacturer or authorized distributors?
All LT1268CQ#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 LT1268CQ#PBF meets industry standards.
7.What is the process for return or replacement of LT1268CQ#PBF?
All LT1268CQ#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT1268CQ#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 LT1268CQ#PBF part is unused and in its original packaging.
Return procedure for LT1268CQ#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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