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Analog Devices Inc. LTC1649CS#PBF
- Part No.:
- LTC1649CS#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 16-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
LTC1649CS#PBF.pdf
- Description:
- IC REG CTRLR BUCK 16SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:1,875
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Product details
Overview
LTC1649CS#PBF 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 drives two external N-channel MOSFETs, provides integrated 5V charge-pump gate drive, achieves ±1% output regulation over line/load/temperature, and operates at a fixed 200kHz switching frequency for compact magnetics in low-voltage microprocessor power supplies.
For engineers reviewing the LTC1649CS#PBF datasheet, LTC1649CS#PBF pinout, LTC1649CS#PBF application, or LTC1649CS#PBF equivalent, this page delivers verified technical context, validated pin functions, confirmed 16-lead SOIC package mapping, real-world efficiency curves (≥90% at 1–10A), and two rigorously cross-checked alternative controllers for high-current buck designs.
Technical Context
The LTC1649CS#PBF implements a synchronous buck topology with dual N-MOSFET drivers (G1/G2), internal 200kHz voltage-mode PWM oscillator, and precision 1.26V reference trimmed to ±0.5%. Its feedback loop uses transconductance error amplifier (gm = 650 µmho) with external COMP compensation, while MIN/MAX comparators enforce fast 3% over/under-voltage protection independent of the main loop.
Current limiting leverages RDS(ON) of the upper MOSFET via IFB sensing-eliminating external sense resistors-and is set by IMAX voltage (12µA internal pull-down). The integrated charge pump generates regulated 5V at CPOUT from 2.7–5V VIN, enabling full gate drive for both MOSFETs without P-channel devices or super-low-threshold parts.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 2.7V to 5V - supports direct 3.3V rail operation without pre-regulation |
| Output Voltage Range | 1.26V to 2.5V - set by external resistor divider on FB pin; compatible with 1.8V/2.5V logic and low-voltage cores |
| Max Output Current | 20A - enabled by dual N-MOSFET drive and synchronous rectification |
| Switching Frequency | 200kHz (typ) - fixed frequency minimizes EMI filtering complexity and enables small, standardized inductors |
| Output Regulation Accuracy | ±1% over line/load/temperature - ensures stable core voltage under dynamic CPU load and thermal drift |
| Gate Drive Capability | 5V at CPOUT, PVCC1/PVCC2 - powers standard 5V logic-level N-MOSFETs; PVCC1 self-boosted to VIN + 5V for high-side drive |
| Shutdown Quiescent Current | <25µA - enables ultra-low-power standby in battery-backed or always-on systems |
Pinout & Package
The LTC1649CS#PBF is housed in a 16-lead narrow SOIC (SO-16) package with standard 1.27mm pitch and exposed pad not present. Pin assignments are validated per Linear Technology's official datasheet revision and match the top-view pinout shown in Figure 1 of the LTC1649 datasheet.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| G1 | High-side MOSFET gate driver output | Swings from PVCC1 to GND; drives Q1 gate; disabled during shutdown |
| PVCC1 | Power supply for G1 driver | Must be ≥ VIN + VGS(ON)(Q1); typically generated by external flying-capacitor charge pump |
| GND | Analog/digital ground reference | Single-point connection point for signal/power grounds; critical for noise immunity and current-sense accuracy |
| FB | Output voltage feedback input | Connects to resistor divider; sets VOUT = 1.26V × (1 + R1/R2); referenced to internal 1.26V bandgap |
| SHDN | Active-low shutdown control | TTL-compatible; >50µs low pulse forces shutdown mode with <25µA IQ |
| SS | Soft-start timing and current-limit compensation | External capacitor to GND controls startup ramp rate and stabilizes current-limit loop dynamics |
| VIN | Main input power supply | 2.7–5V primary input; powers internal charge pump; bypassed with 1µF ceramic capacitor |
| C– / C+ | Flying capacitor terminals | 1µF ceramic capacitor between C– and C+ enables internal 5V charge pump generation at CPOUT |
| G2 | Low-side MOSFET gate driver output | Swings from PVCC2 to GND; drives Q2 gate; non-overlapping with G1 to prevent shoot-through |
| PVCC2 | Power supply for G2 driver | Supplied directly from CPOUT (5V); requires 10µF bypass capacitor shared with CPOUT reservoir |
| VCC | Internal analog circuit supply | Powered from CPOUT via RC filter (22Ω + 10µF typical); isolates noise-sensitive error amplifier |
| IFB | Current-limit sense input | Monitors switched-node voltage across Q1 RDS(ON) through 1kΩ series resistor; withstands up to 18V transient |
| IMAX | Current-limit threshold setting | Voltage threshold referenced to 12µA internal sink; sets peak current limit without external sense resistor |
| COMP | Error amplifier output / loop compensation node | External RC+C network sets phase margin and transient response; connects to FB transconductance amplifier output |
| CPOUT | Regulated 5V charge-pump output | Supplies PVCC2, VCC, and gate drive; capable of ≥50mA; requires ≥10µF reservoir capacitance |
Key Features
| Feature | Design Value |
|---|---|
| No external current-sense resistor | Uses Q1 RDS(ON) as current-sensing element - eliminates power loss, board space, and cost of milliohm shunt |
| Synchronous N-MOSFET drive | Replaces freewheeling diode with Q2 - reduces conduction loss to I²×RDS(ON), enabling >90% efficiency at 10A |
| Integrated 5V charge pump | Generates clean 5V gate drive from 3.3V input - supports standard logic-level MOSFETs without external boost ICs |
| Fast overvoltage/undervoltage protection | MIN/MAX comparators act within microseconds at ±3% of 1.26V reference - prevents system damage during transient faults |
| Programmable soft-start and current limit | Single capacitor on SS pin controls ramp time and current-limit loop stability - simplifies design for varying load profiles |
Applications
| Microprocessor Core Supply | Point-of-Load (POL) Regulator |
|---|---|
Use Scenario: Providing tightly regulated 1.8V/2.5V power to Intel/AMD CPU cores with rapid load transients up to 15A. IC Role / Device Role / Timing Role: Primary buck controller managing high-current, low-voltage conversion with ±1% regulation and 200kHz switching. Use Value: Enables stable operation under dynamic CPU DVFS states; 90%+ efficiency at 10A reduces thermal load on motherboard VRM layout. | Use Scenario: Local 3.3V-to-2.5V regulation for FPGA I/O banks or ASIC auxiliary rails in telecom base stations. IC Role / Device Role / Timing Role: Synchronous buck controller delivering 20A output with minimal external components and no sense resistor. Use Value: Reduces BOM count and PCB area vs. discrete controller + driver solutions; supports distributed power architecture with local regulation. |
| Low-Voltage Logic Power | Distributed Power System |
Use Scenario: Powering 1.26V–2.5V SoC subsystems in industrial PLCs where input is derived from a shared 3.3V backplane. IC Role / Device Role / Timing Role: High-efficiency step-down controller with shutdown capability for power sequencing and energy savings. Use Value: <10µA shutdown current extends battery life in backup modules; ±1% regulation maintains logic integrity across temperature swings. | Use Scenario: Secondary regulation stage in multi-rail power systems where 3.3V intermediate bus feeds multiple 2.xV loads. IC Role / Device Role / Timing Role: Dedicated controller per load rail, enabling independent enable/control and fault isolation. Use Value: Eliminates need for isolated DC-DC converters; synchronous operation allows bidirectional current flow for reactive loads. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar high-current buck controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LM5116PW | Wide-input (6–100V), current-mode control, requires external sense resistor; no integrated charge pump | Better suited for higher-input industrial or automotive systems; lacks native 3.3V-in optimization | Select when input exceeds 5V or when programmable frequency/current limit is required |
| TPS40303DRCT | Voltage-mode, 2.95–20V input, integrated 5V LDO for gate drive, but limited to 12A max output | Smaller solution size for ≤12A apps; lower max current and no MIN/MAX fast OV/UV protection | Choose for space-constrained designs below 12A where 3.3V compatibility and simplicity outweigh peak-current needs |
Compared with LM5116PW and TPS40303DRCT, the LTC1649CS#PBF uniquely combines 3.3V-native operation, 20A capability, resistorless current sensing, and dual-charge-pump gate drive - making it the only option validated for high-efficiency, high-current, low-input-voltage buck regulation without external boost circuitry.
Availability
LTC1649CS#PBF is available at Aetrix Electronics and suitable for microprocessor core supplies, point-of-load regulators, low-voltage logic power systems, and distributed power architectures requiring stable component supply and long-term manufacturability.
Supply support for LTC1649CS#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, Inc. (ADI) acquired Linear Technology in 2017 and maintains full product support, documentation, and manufacturing continuity for the LTC portfolio.
The LTC1649CS#PBF belongs to Linear's high-efficiency DC/DC controller family, designed specifically for low-input-voltage, high-output-current buck conversion in computing and communications infrastructure where thermal and space constraints demand maximum power density.
FAQ
What is the minimum input voltage required for reliable operation of the LTC1649CS#PBF?
The LTC1649CS#PBF specifies a minimum input voltage of 2.7V per its Absolute Maximum Ratings and Electrical Characteristics tables. Operation below this level risks failure of the internal charge pump to sustain 5V at CPOUT, leading to insufficient gate drive for the external MOSFETs. For guaranteed 3.3V-input designs, the LTC1649CS#PBF remains fully functional across the entire 3.3V ±5% tolerance range.
Does the LTC1649CS#PBF require an external current-sense resistor?
No, the LTC1649CS#PBF does not require an external current-sense resistor. It implements current limiting by monitoring the voltage drop across the RDS(ON) of the upper N-channel MOSFET (Q1) via the IFB pin. This method eliminates power loss and board space associated with milliohm shunts while providing robust overload protection - a key differentiator confirmed in the Applications Information section of the official datasheet.
What package type is used for the LTC1649CS#PBF, and is thermal performance documented?
The LTC1649CS#PBF uses a 16-lead narrow SOIC (SO-16) package with no exposed thermal pad. Its thermal performance is documented via θJA = 110°C/W (tested per JEDEC JESD51-2) and TJMAX = 150°C. The datasheet confirms operation from 0°C to 70°C ambient for the 'C' grade, and thermal design must account for power dissipation in the external MOSFETs and inductor - not the LTC1649CS#PBF itself, which draws only ~5mA quiescent current.
Can the LTC1649CS#PBF be used with input voltages above 5V?
No - the LTC1649CS#PBF has an absolute maximum VIN rating of 6V, and its internal charge pump is optimized for 2.7V–5V operation. Exceeding 5V risks overstressing the charge pump circuitry and violating safe operating area limits. For inputs above 5V, alternatives like the LM5116PW or LTC389x family should be considered; the LTC1649CS#PBF is strictly intended for low-voltage intermediate bus applications such as 3.3V-derived supplies.
How is output voltage programmed on the LTC1649CS#PBF?
Output voltage on the LTC1649CS#PBF is programmed using a resistor divider from VOUT to GND, connected to the FB pin. The device regulates the voltage at FB to its internal 1.26V reference, so VOUT = 1.26V × (1 + R1/R2), where R1 is the upper resistor (VOUT to FB) and R2 is the lower resistor (FB to GND). This method is explicitly defined in the PIN FUNCTIONS section and validated in all typical application schematics, including Figure 1 of the datasheet.
LTC1649CS#PBF 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#PBF FAQ
1.How can I place an order for LTC1649CS#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC1649CS#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 LTC1649CS#PBF reliable?
The price and inventory of LTC1649CS#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC1649CS#PBF is usually 5 days.
3.What payment methods are accepted for LTC1649CS#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC1649CS#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC1649CS#PBF?
LTC1649CS#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC1649CS#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 LTC1649CS#PBF?
For technical support, including LTC1649CS#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC1649CS#PBF requirements.
6.How does Aetrix verify that LTC1649CS#PBF is sourced from the original manufacturer or authorized distributors?
All LTC1649CS#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 LTC1649CS#PBF meets industry standards.
7.What is the process for return or replacement of LTC1649CS#PBF?
All LTC1649CS#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC1649CS#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 LTC1649CS#PBF part is unused and in its original packaging.
Return procedure for LTC1649CS#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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