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Analog Devices Inc. LTC1649IS#PBF
- Part No.:
- LTC1649IS#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 16-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
LTC1649IS#PBF.pdf
- Description:
- IC REG CTRLR BUCK 16SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:3,081
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Product details
Overview
LTC1649IS#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 200kHz fixed frequency for compact magnetics. It is used in local regulation for low-voltage microprocessor power domains.
For engineers reviewing the LTC1649IS#PBF datasheet, LTC1649IS#PBF pinout, LTC1649IS#PBF application, or LTC1649IS#PBF equivalent, key selection considerations include its 16-lead SOIC package, shutdown quiescent current <25µA, IMAX-adjustable current limit without sense resistor, soft-start capacitor control, and synchronous buck architecture enabling >90% efficiency at 15A in 3.3V-to-2.5V conversion.
Technical Context
The LTC1649IS#PBF implements voltage-mode PWM control with a fixed 200kHz oscillator and internal 1.26V reference trimmed to ±0.5%. Its feedback loop uses an error amplifier (gm = 650 µmho) and external RC compensation at COMP to stabilize the output under dynamic load transients.
It integrates dual gate drivers (G1/G2) with non-overlap timing (25–250 ns), internal charge pump (CPOUT = 5V ±2%, fCP = 700 kHz), and three independent protection loops: MIN/MAX comparators (±3% of VREF) for fast over/under-voltage response, and ILIM amplifier (gm = 1300 µmho) that senses Q1 RDS(ON) to enforce current limit without external sense resistor.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 2.7V to 5V - supports direct 3.3V rail operation with margin for droop; absolute max VIN = 6V. |
| Output Voltage Range | 1.26V to 2.5V - set by external resistor divider on FB; VFB = 1.265V ±15mV ensures tight regulation. |
| Max Output Current | 20A - enabled by synchronous N-MOSFET topology and 5V gate drive; requires proper external FET selection and thermal design. |
| Switching Frequency | 200kHz (typ) - fixed internal oscillator minimizes EMI spread and allows predictable inductor sizing (e.g., 1.2µH for 3.3V→2.5V/15A). |
| Regulation Accuracy | ±1% over line, load, temperature - achieved via precision bandgap reference and gm error amplifier, critical for CPU core voltage stability. |
| Shutdown Current | <25µA - enables ultra-low-power standby in systems requiring rapid wake-up from deep sleep modes. |
| Charge Pump Output | CPOUT = 5.0V ±0.25V - powers PVCC2 and VCC; supplies up to 50mA, sufficient for gate drive of multiple logic-level MOSFETs. |
Pinout & Package
Package: 16-lead narrow SOIC (SO-16), RoHS-compliant, rated for –40°C to +85°C operating temperature.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| G1 | Upper MOSFET gate driver output | Swings from PVCC1 to GND; drives Q1 gate; disabled in shutdown. |
| PVCC1 | Power supply for G1 driver | Must be ≥ VIN + 5V; generated externally via charge pump from switching node. |
| GND | System ground reference | Low-impedance connection point for signal/power grounds; single-point star grounding required. |
| FB | Output voltage feedback input | Connects to resistor divider; sets VOUT = 1.265V × (1 + R1/R2); high-impedance input. |
| SHDN | Active-low shutdown control | TTL-compatible; <0.8V disables regulators; >2.4V enables; 50µs delay ensures clean state transition. |
| SS | Soft-start timing and current-limit compensation | Capacitor to GND sets startup ramp time and stabilizes ILIM loop during overload recovery. |
| VIN | Main input power supply | 2.7V–5V primary input; powers internal charge pump; bypass with 1µF ceramic near pin. |
| C– / C+ | Flying capacitor terminals | 1µF ceramic between C– and C+ forms charge pump stage for CPOUT generation. |
| G2 | Lower MOSFET gate driver output | Swings from PVCC2 to GND; drives Q2 gate; complementary to G1 with non-overlap timing. |
| PVCC2 | Power supply for G2 driver | Supplied directly from CPOUT (5V); bypass with 10µF capacitor shared with CPOUT reservoir. |
| VCC | Internal analog/digital supply | Powered from CPOUT via RC filter (22Ω + 10µF typical); decouples noise from gate drivers. |
| IFB | Current-sense input | Monitors switched-node voltage across Q1 RDS(ON); protected to 18V; requires 1kΩ series resistor. |
| IMAX | Current-limit threshold set | Internal 12µA pull-down; external resistor or voltage defines peak current trip point. |
| COMP | Error amplifier output / loop compensation | External RC network sets dominant pole-zero; determines transient response and phase margin. |
| CPOUT | Regulated 5V charge-pump output | Stable 5V supply for PVCC2/VCC; requires ≥10µF reservoir capacitance; can power small external circuitry. |
Key Features
| Feature | Design Value |
|---|---|
| No external current-sense resistor | Uses RDS(ON) of upper MOSFET Q1 for current limiting - eliminates power loss, board space, and cost of shunt resistor. |
| Synchronous buck architecture | Replaces freewheeling diode with lower-RDS(ON) Q2 - enables >90% efficiency at 15A and allows bidirectional output current (sink/source). |
| Integrated 5V charge pump | Generates regulated 5V gate drive from 3.3V input - permits use of standard 5V logic-level N-MOSFETs instead of expensive P-channel or ultra-low-VGS(th) devices. |
| Triple-loop protection | Combines main FB loop (±1%), fast MIN/MAX comparators (±3%), and ILIM amplifier - prevents output collapse during load transients and overcurrent faults. |
| 16-pin SOIC package | Industry-standard footprint with thermal pad option (not present in IS grade) - supports automated assembly and thermal management up to 20A continuous load. |
Applications
| High-Performance CPU Core Supply | Industrial FPGA I/O Bank Regulator |
|---|---|
Use Scenario: Providing tightly regulated 1.8V/15A to a multicore x86 processor under dynamic DVFS load steps. IC Role / Device Role / Timing Role: Primary step-down controller managing power delivery network (PDN) impedance, transient response, and current limit coordination with VRM telemetry. Use Value: ±1% regulation and 200kHz switching enable sub-100mV output deviation during 10A/µs load steps; synchronous operation reduces thermal stress on PCB layout. | Use Scenario: Delivering stable 2.5V/12A to configurable I/O banks of a Xilinx Kintex Ultrascale+ FPGA in factory automation equipment. IC Role / Device Role / Timing Role: Local point-of-load (POL) regulator with fast transient recovery and robust overcurrent protection in harsh industrial environments. Use Value: Shutdown current <25µA supports energy-efficient sleep modes; wide –40°C to +85°C rating ensures reliability in uncontrolled enclosures. |
| Telecom Baseband ASIC Power | Distributed Power System Local Regulator |
Use Scenario: Generating 1.26V/18A for a 5G baseband SoC in a macrocell radio unit with strict EMI limits. IC Role / Device Role / Timing Role: High-efficiency buck controller operating from intermediate 3.3V bus; interfaces with system PMIC for sequencing and fault reporting. Use Value: Fixed 200kHz frequency simplifies EMI filter design; no sense resistor avoids parasitic inductance that degrades high-frequency transient response. | Use Scenario: Local regulation of 2.0V/10A from a 3.3V backplane in modular server blade architecture. IC Role / Device Role / Timing Role: Standalone POL controller supporting hot-swap and redundancy requirements in distributed power architectures. Use Value: Dual gate drivers with non-overlap timing prevent shoot-through; IMAX-adjustable current limit enables scalable protection across blade variants. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar high-current step-down controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3728CUH#PBF | Higher VIN range (4.5V–38V), supports 2-phase interleaving, no integrated charge pump - requires external 5V bias supply for gate drive. | Targeted at higher-input industrial/motor drives; lacks native 3.3V-input optimization and synchronous sensing. | Select when input exceeds 5V or multi-phase scalability is required; not drop-in for 3.3V-only designs. |
| MP2918GL-Z | Monolithic 20A buck converter (integrated MOSFETs), 2.7V–6V input, 0.6V–3.3V output - no external FETs needed but fixed 500kHz switching. | Preferred for space-constrained designs where integration outweighs efficiency tuning; limited thermal headroom at 20A continuous. | Choose for simplified BOM and layout; avoid when discrete FET selection (e.g., Si4410DY) or 200kHz EMI profile is mandatory. |
Compared with LTC3728CUH#PBF and MP2918GL-Z, the LTC1649IS#PBF uniquely combines native 3.3V-input operation, integrated 5V charge pump, and external FET flexibility - making it optimal for high-efficiency, thermally managed, low-voltage POL applications where gate drive overhead and sense-resistor loss must be eliminated.
Availability
LTC1649IS#PBF is available at Aetrix Electronics and suitable for high-reliability embedded computing, industrial FPGA power, and telecom baseband ASIC supply requiring stable component supply across extended temperature ranges and long production lifecycles.
Supply support for LTC1649IS#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) is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, formed through the acquisition of Linear Technology in 2017.
The LTC1649IS#PBF belongs to ADI's legacy Linear Technology Power Management product line, specifically designed for high-efficiency, low-input-voltage DC/DC controller applications in computing, communications, and industrial systems.
FAQ
What is the operating temperature range for the LTC1649IS#PBF?
The LTC1649IS#PBF is specified for operation from –40°C to +85°C ambient temperature. This industrial-grade rating makes it suitable for deployment in factory automation, telecom infrastructure, and outdoor embedded systems where environmental extremes are expected. The device's thermal performance is validated under full 20A load conditions within this range, and its SOIC package provides adequate thermal dissipation when mounted on standard FR-4 PCBs with appropriate copper pour.
Can the LTC1649IS#PBF operate from a 2.7V input supply?
Yes, the LTC1649IS#PBF supports a minimum input voltage of 2.7V per its Absolute Maximum Ratings and Electrical Characteristics tables. At 2.7V input, the internal charge pump maintains CPOUT at 5V to sustain gate drive for external MOSFETs, and the controller continues regulating down to 1.26V output. However, maximum duty cycle is reduced at low VIN, limiting achievable output voltage - for example, at 2.7V input, the highest regulated output is approximately 2.0V due to DCMAX constraints.
How does the LTC1649IS#PBF implement current limiting without a sense resistor?
The LTC1649IS#PBF uses the RDS(ON) of the upper external N-channel MOSFET (Q1) as an intrinsic current-sensing element. During the on-time of G1, the IFB pin monitors the voltage drop across Q1's channel via a 1kΩ series resistor. When this voltage falls below the threshold set at the IMAX pin (via external resistor or voltage source), the ILIM amplifier pulls current from the SS capacitor, reducing duty cycle. This method eliminates sense-resistor losses while providing robust short-circuit protection - though accuracy varies with MOSFET temperature and unit-to-unit RDS(ON) tolerance.
What is the purpose of the C– and C+ pins on the LTC1649IS#PBF?
The C– and C+ pins form the flying capacitor interface for the internal charge pump that generates the regulated 5V CPOUT supply. A 1µF ceramic capacitor is connected between C– and C+, and the charge pump uses this capacitor to step up the VIN voltage to 5V. This architecture enables the LTC1649IS#PBF to deliver 5V gate drive even when powered from a 3.3V or 2.7V input - a critical capability for driving standard logic-level N-MOSFETs without requiring external boost circuitry.
Is the LTC1649IS#PBF pin-compatible with the LTC1649CS#PBF?
Yes, the LTC1649IS#PBF and LTC1649CS#PBF share identical pinout, package (16-lead SOIC), and electrical functionality. The only difference is their guaranteed operating temperature range: the 'C' grade is rated for 0°C to +70°C, while the 'I' grade (LTC1649IS#PBF) extends to –40°C to +85°C. Both versions use the same internal silicon die and undergo identical functional testing - interchangeability is supported in designs where extended temperature operation is required, provided thermal derating and qualification protocols are followed.
LTC1649IS#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:
- -40°C ~ 85°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 16-SO
LTC1649IS#PBF FAQ
1.How can I place an order for LTC1649IS#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC1649IS#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 LTC1649IS#PBF reliable?
The price and inventory of LTC1649IS#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC1649IS#PBF is usually 5 days.
3.What payment methods are accepted for LTC1649IS#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC1649IS#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC1649IS#PBF?
LTC1649IS#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC1649IS#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 LTC1649IS#PBF?
For technical support, including LTC1649IS#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC1649IS#PBF requirements.
6.How does Aetrix verify that LTC1649IS#PBF is sourced from the original manufacturer or authorized distributors?
All LTC1649IS#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 LTC1649IS#PBF meets industry standards.
7.What is the process for return or replacement of LTC1649IS#PBF?
All LTC1649IS#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC1649IS#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 LTC1649IS#PBF part is unused and in its original packaging.
Return procedure for LTC1649IS#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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