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Analog Devices Inc. LTC1649CS
- Part No.:
- LTC1649CS
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 16-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
LTC1649CS.pdf
- Description:
- IC REG CTRLR BUCK 16SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:2,793
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Product details
Overview
LTC1649CS from Analog Devices (formerly Linear Technology) is a high-efficiency, voltage-mode PWM step-down switching regulator controller optimized for 3.3V input and 1.26V–2.5V output at up to 20A. It uses dual N-channel external MOSFETs, provides integrated 5V gate drive via internal charge pump, and achieves ±1% output regulation over line, load, and temperature. It targets low-voltage microprocessor core supplies in industrial and embedded systems.
For engineers reviewing the LTC1649CS datasheet, LTC1649CS pinout, LTC1649CS application, or LTC1649CS equivalent, key selection considerations include its 200kHz fixed-frequency operation, no external sense resistor requirement, shutdown quiescent current <25µA, 16-lead SO package compatibility, and synchronous buck architecture supporting bidirectional output current capability.
Technical Context
The LTC1649CS implements voltage-mode PWM control with a precision 1.265V internal reference and transconductance error amplifier (gm = 650 µmho). Its dual-driver architecture delivers complementary G1/G2 outputs with 25ns–250ns non-overlap timing and 80ns–250ns rise/fall times, enabling robust synchronous buck operation without shoot-through.
It integrates a 700kHz internal charge pump generating regulated 5V at CPOUT, supports PVCC1 bootstrapping from the switching node, and features MIN/MAX comparators (±3% of VREF) for fast transient fault response independent of the main feedback loop. Current limiting uses Q1's RDS(ON) as a sensing element, eliminating discrete sense resistors.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 2.7V to 5V - Enables direct use with 3.3V system rails without pre-regulation. |
| Output Voltage Range | 1.26V to 2.5V - Set by external resistor divider on FB pin; supports modern low-voltage logic and CPU cores. |
| Max Output Current | 20A - Achieved with external N-MOSFETs; requires careful thermal design and layout for sustained loads. |
| Switching Frequency | 200kHz (typ) - Fixed frequency minimizes EMI filtering complexity and enables predictable inductor sizing. |
| Feedback Accuracy | ±1% over line/load/temp - Ensures stable core voltage under dynamic processor load changes. |
| Shutdown Current | <25µA - Enables low-power standby modes in battery-backed or energy-sensitive systems. |
| Charge Pump Output | 5.0V ±2% at CPOUT - Powers both PVCC2 and VCC; eliminates need for external 5V bias supply. |
Pinout & Package
Package: 16-lead narrow SOIC (SO-16), RoHS-compliant, rated for 0°C to 70°C operating temperature (C-grade).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| G1 (Pin 1) | Upper MOSFET gate driver output | Swings from PVCC1 to GND; drives Q1 gate; disabled during shutdown. |
| PVCC1 (Pin 2) | Power supply for G1 driver | Must be ≥ VIN + 5V; typically bootstrapped from switching node using external diode/capacitor. |
| GND (Pin 3) | System ground reference | Low-impedance connection point for power and signal grounds; critical for noise immunity and stability. |
| FB (Pin 4) | Output voltage feedback input | Connects to resistor divider; sets VOUT = 1.265V × (1 + R1/R2); high-impedance input. |
| SHDN (Pin 5) | Active-low shutdown control | TTL-compatible; >50µs low pulse forces shutdown mode with <25µA quiescent current. |
| SS (Pin 6) | Soft-start timing and compensation node | External capacitor controls startup ramp rate and stabilizes current limit loop dynamics. |
| VIN (Pin 7) | Main input supply input | 2.7V–5V primary power source; powers internal charge pump and bias circuits. |
| C– (Pin 8) | Flying capacitor negative terminal | Connects to 1µF ceramic cap between C– and C+; essential for internal charge pump operation. |
| C+ (Pin 9) | Flying capacitor positive terminal | Completes charge pump flying cap circuit; referenced to C– for 5V generation at CPOUT. |
| CPOUT (Pin 10) | Regulated 5V charge pump output | Supplies PVCC2 and VCC; requires ≥10µF reservoir capacitance; remains active in shutdown. |
| COMP (Pin 11) | Error amplifier output / loop compensation | Connects to RC network for stability tuning; directly interfaces with PWM comparator. |
| IMAX (Pin 12) | Current limit threshold set point | Internal 12µA pull-down; external resistor or voltage defines peak current trip level. |
| IFB (Pin 13) | Current sense input | Monitors switched-node voltage across Q1's RDS(ON); tolerant to 18V transient. |
| VCC (Pin 14) | Internal analog/feedback supply | Powered from CPOUT; requires RC filter (e.g., 22Ω + 10µF) for noise rejection. |
| PVCC2 (Pin 15) | Power supply for G2 driver | Typically tied to CPOUT; supplies 5V gate drive to lower MOSFET Q2. |
| G2 (Pin 16) | Lower MOSFET gate driver output | Swings from PVCC2 to GND; complements G1 with non-overlap timing; sinks current in shutdown. |
Key Features
| Feature | Design Value |
|---|---|
| No external current sense resistor | Uses RDS(ON) of upper MOSFET Q1 for current limiting - reduces BOM count, PCB area, and power loss in high-current paths. |
| Synchronous buck architecture | Replaces freewheeling diode with actively controlled Q2 - improves efficiency >90% at 10A and enables bidirectional output current capability. |
| Integrated 5V gate drive from 3.3V input | On-chip charge pump generates stable 5V at CPOUT - eliminates need for auxiliary 5V rail when using standard logic-level N-MOSFETs. |
| ±1% output regulation accuracy | Maintains tight voltage tolerance across full line/load/temperature range - meets stringent requirements of microprocessor core supplies. |
| Fixed 200kHz switching frequency | Enables consistent EMI profile and simplifies filter design - avoids variable-frequency jitter and allows optimal inductor selection (1–5µH typical). |
Applications
| Microprocessor Core Supply | Distributed Power System Local Regulation |
|---|---|
Use Scenario: Providing stable 2.5V/15A power to an FPGA or ASIC core in a telecom baseband board with tight thermal constraints. IC Role / Device Role / Timing Role: Primary step-down controller managing high-current DC/DC conversion with fast transient response and precise voltage setpoint. Use Value: Delivers >90% efficiency at full load while maintaining ±1% regulation, reducing heat sink size and improving system power density. | Use Scenario: Generating localized 1.8V/12A rails from a 3.3V backplane in a modular industrial PLC rack. IC Role / Device Role / Timing Role: Local point-of-load (POL) regulator ensuring low-noise, dynamically responsive voltage for I/O modules. Use Value: Synchronous operation enables bidirectional current flow, supporting reactive loads and improving transient recovery during rapid load steps. |
| Low-Voltage Logic Power | High-Efficiency Embedded Power |
Use Scenario: Powering 1.26V DDR memory interface in a medical imaging subsystem requiring ultra-low ripple and EMI compliance. IC Role / Device Role / Timing Role: Precision voltage-mode controller with MIN/MAX comparators for sub-100ns fault correction during memory burst access. Use Value: Eliminates external sense resistor and leverages MOSFET RDS(ON), reducing component count and parasitic inductance in high-dI/dt paths. | Use Scenario: Supplying 2.2V/18A to a real-time DSP in an automotive ADAS camera module with strict thermal and reliability requirements. IC Role / Device Role / Timing Role: High-power buck controller with shutdown mode (<25µA) for sleep-state power management. Use Value: 16-pin SOIC package enables compact layout; fixed 200kHz frequency simplifies EMI filtering for automotive CISPR-25 compliance. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar high-efficiency synchronous buck controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3703-5 | Higher VIN range (4.5V–38V); supports 5V output; no integrated charge pump - requires external 5V gate drive supply. | Better suited for higher-input industrial or automotive systems; not drop-in for 3.3V-only designs. | Select LTC3703-5 only if input exceeds 5V or 5V auxiliary rail is already available. |
| MP2315 | Integrated power stage (MOSFETs built-in); max 15A output; fixed 500kHz frequency; no IMAX/IFB current-sense flexibility. | Reduces external component count but limits peak current and thermal design freedom vs. controller-only LTC1649CS. | Choose MP2315 for space-constrained, medium-power designs where 15A suffices and layout simplicity outweighs configurability. |
Compared with LTC3703-5 and MP2315, the LTC1649CS uniquely combines 3.3V-native operation, no external sense resistor, and full external MOSFET control - making it optimal for high-current, low-input-voltage POL applications demanding efficiency, flexibility, and thermal manageability.
Availability
LTC1649CS is available at Aetrix Electronics and suitable for microprocessor core supplies, distributed power system local regulation, low-voltage logic power, and high-efficiency embedded power applications requiring stable component supply across production lifecycles.
Supply support for LTC1649CS 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 semiconductor leader specializing in high-performance analog, mixed-signal, and digital signal processing technologies. Formerly Linear Technology, ADI acquired Linear in 2017 and maintains its legacy of precision power management ICs.
The LTC1649CS belongs to the Linear Technology LTC® high-efficiency DC/DC controller product line, designed specifically for low-input-voltage, high-output-current synchronous buck applications in computing, industrial, and communications infrastructure.
FAQ
What is the maximum output current supported by the LTC1649CS?
The LTC1649CS supports up to 20A output current when paired with appropriately rated external N-channel MOSFETs, inductors, and thermal management. Actual achievable current depends on layout, ambient temperature, and component selection - e.g., IRF7801 or Si4410DY MOSFETs with ≤0.03Ω RDS(ON) are commonly used. The controller itself does not limit current; the external power stage defines the ceiling.
Does the LTC1649CS require an external current sense resistor?
No, the LTC1649CS eliminates the need for an external current sense resistor by using the RDS(ON) of the upper external N-channel MOSFET (Q1) as the current sensing element. The IFB pin monitors the voltage drop across Q1 during conduction, and the IMAX pin sets the trip threshold. This reduces component count, PCB area, and power loss in high-current paths.
What package type is the LTC1649CS supplied in?
The LTC1649CS is supplied in a 16-lead narrow SOIC (SO-16) package, compliant with JEDEC MS-012AC, with operating temperature range of 0°C to 70°C. This surface-mount package supports automated assembly and offers proven thermal performance for high-current DC/DC applications when properly laid out with adequate copper pour.
Can the LTC1649CS operate from a 3.3V input to generate 1.26V output?
Yes, the LTC1649CS is explicitly optimized for 3.3V input operation and supports output voltages as low as 1.26V via the FB resistor divider (VOUT = 1.265V × (1 + R1/R2)). Its internal 1.265V reference, ±1% regulation accuracy, and 200kHz fixed-frequency control ensure stable, efficient conversion across the full 1.26V–2.5V range at up to 20A.
How does the LTC1649CS provide 5V gate drive when powered from only 3.3V?
The LTC1649CS integrates an internal charge pump that boosts the 3.3V VIN supply to a regulated 5V output at the CPOUT pin. This 5V rail powers PVCC2 (for G2 driver) and VCC (for internal circuitry). For the upper MOSFET (Q1), a second external bootstrap charge pump - using CPOUT, a Schottky diode, and a capacitor tied to Q1's source - generates PVCC1 ≥ VIN + 5V, enabling full enhancement of standard 5V logic-level N-MOSFETs.
LTC1649CS Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 16-SOIC (0.154", 3.90mm Width)
- Packaging:
- Tube
- Product Status:
- Active
- Output Type:
- Transistor Driver
- Function:
- Step-Down
- Output Configuration:
- Positive
- Topology:
- Buck
- Number of Outputs:
- 1
- Output Phases:
- 1
- Voltage - Supply (Vcc/Vdd):
- 2.7V ~ 5V
- Frequency - Switching:
- 200kHz
- Duty Cycle (Max):
- 93%
- Synchronous Rectifier:
- Yes
- Clock Sync:
- No
- Serial Interfaces:
- -
- Control Features:
- Current Limit, Enable, Soft Start
- Operating Temperature:
- 0°C ~ 70°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 16-SO
LTC1649CS FAQ
1.How can I place an order for LTC1649CS through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC1649CS 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 LTC1649CS reliable?
The price and inventory of LTC1649CS are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC1649CS is usually 5 days.
3.What payment methods are accepted for LTC1649CS?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC1649CS transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC1649CS?
LTC1649CS orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC1649CS 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 LTC1649CS?
For technical support, including LTC1649CS datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC1649CS requirements.
6.How does Aetrix verify that LTC1649CS is sourced from the original manufacturer or authorized distributors?
All LTC1649CS 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 LTC1649CS meets industry standards.
7.What is the process for return or replacement of LTC1649CS?
All LTC1649CS units undergo pre-shipment inspection (PSI). If there is an issue with LTC1649CS, 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 LTC1649CS part is unused and in its original packaging.
Return procedure for LTC1649CS:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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