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Analog Devices Inc. LTC1735CS#PBF
- Part No.:
- LTC1735CS#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 16-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
LTC1735CS#PBF.pdf
- Description:
- IC REG CTRLR BUCK 16SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:3,597
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Product details
Overview
LTC1735CS#PBF from Analog Devices (formerly Linear Technology) is a synchronous step-down switching regulator controller driving external N-channel MOSFETs in fixed-frequency current-mode operation. It delivers 0.8V to 6V output at up to 9A, supports 4V–30V input, features ±1% output voltage accuracy, OPTI-LOOP™ compensation, and Burst Mode™ for high efficiency below 10mA load. It is used in notebook DC/DC power rails requiring tight regulation and low-noise operation.
For engineers reviewing the LTC1735CS#PBF datasheet, LTC1735CS#PBF pinout, LTC1735CS#PBF application, or LTC1735CS#PBF equivalent, key selection criteria include its programmable 265–335kHz oscillator frequency (via COSC), forced continuous mode control (FCB pin), remote sense capability, foldback current limiting, and compatibility with 0.005Ω RSENSE for high-current designs.
Technical Context
The LTC1735CS#PBF implements a constant-frequency, current-mode control architecture with dual N-channel gate drivers (TG/BG), internal 5.2V INTVCC LDO, and precision 0.8V reference. Its error amplifier (ITH pin) directly controls peak inductor current via a transconductance gm of 1.3 mmho, enabling stable loop response across wide output capacitance and ESR ranges using OPTI-LOOP™ compensation.
Burst Mode™ operation-activated when FCB ≥ 0.8V-disables switching during light loads to maintain >85% efficiency at 1mA, while forced continuous mode (FCB ≤ 0.76V) eliminates subharmonic noise and supports secondary winding regulation. Overvoltage crowbar (VOVL = 0.86V) and latched short-circuit shutdown (defeatable via RUN/SS current injection) provide robust protection.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 4V to 30V operating; 36V absolute max - supports wide industrial and computing input rails. |
| Output Voltage Range | 0.8V to 6V - set by external resistor divider; compatible with core voltages of Pentium III/Mobile CPUs. |
| Oscillator Frequency | 265–335kHz (COSC = 43pF); synchronizable up to 500kHz - enables EMI control and layout optimization. |
| Output Voltage Accuracy | ±1% over temperature - ensures reliable microprocessor supply margining without external calibration. |
| Quiescent Current | 450µA normal mode; <25µA shutdown - minimizes standby loss in battery-backed systems. |
| Current Sense Threshold | 60–85mV (ΔVSENSE(MAX)) - sets peak inductor current limit with 0.005Ω RSENSE yielding ~17A peak for 9A avg. |
| Duty Cycle Max | 98–99.4% - enables ultra-low dropout operation (e.g., 5V→4.9V at full load) without external boost. |
Pinout & Package
Package: 16-lead plastic SO (SO-16), JEDEC MS-012, θJA = 110°C/W. Pin 1 marked with dot; lead finish is matte tin (RoHS-compliant).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| COSC | Oscillator timing capacitor node | Connects to ground via 43pF capacitor to set nominal 300kHz switching frequency; enables sync via FCB pin. |
| RUN/SS | Soft-start ramp & shutdown control | Capacitor-to-ground sets soft-start time (~1.25s/µF); <1.5V forces shutdown; >4.1V triggers latchoff on undervoltage. |
| ITH | Error amplifier output / current comparator threshold | Voltage (0–2.4V) directly programs peak inductor current; used for loop compensation and transient response tuning. |
| FCB | Forced continuous / sync / Burst Mode control | 0.76–0.84V threshold: tie to GND for continuous mode; to INTVCC for Burst Mode; drive with external clock for sync. |
| VOSENSE | Feedback voltage input | Receives divided output voltage; servo-controlled to 0.8V reference with ±1% accuracy and ±0.3% load regulation. |
| SENSE+, SENSE− | Current sense differential inputs | Measure voltage across RSENSE; built-in offset enables accurate current limiting independent of common-mode voltage. |
| TG, BG | Top/bottom N-MOSFET gate drivers | 3A peak drive capability; TG swings from SW to INTVCC; BG swings from PGND to INTVCC - supports discrete FETs like FDS6680A. |
| VIN, SW, BOOST, PGND, SGND, EXTVCC, INTVCC | Power and ground connections | VIN powers control logic; SW is switch node; BOOST supplies floating top driver; EXTVCC bypasses INTVCC LDO for higher efficiency. |
Key Features
| Feature | Design Value |
|---|---|
| OPTI-LOOP™ Compensation | Enables stable loop response with ceramic or polymer output capacitors from 10µF to 1000µF without external type-specific tuning. |
| Burst Mode™ Operation | Maintains >85% efficiency at 1mA load by disabling switching cycles - critical for standby power in portable computing. |
| Forced Continuous Control (FCB) | Eliminates audible noise and enables precise secondary-side regulation in multi-output flyback-derived topologies. |
| Remote Output Voltage Sense | Compensates for IR drop in PCB traces or connectors - maintains ±1% regulation at load point, not IC pins. |
| Internal Foldback Current Limit | Reduces peak current to ~25% of max when VOUT drops below 70%, preventing thermal runaway during short-circuit faults. |
| Programmable Soft-Start | External CSS capacitor prevents inrush current into bulk output caps - avoids input rail sag and MOSFET stress at startup. |
Applications
| Notebook CPU Core Supply | Industrial DC Power Distribution |
|---|---|
Use Scenario: Regulating 1.6V/9A core voltage for Intel Pentium III-M processors in space-constrained laptop motherboards. IC Role / Device Role / Timing Role: Primary synchronous buck controller managing external FETs, feedback loop, and dynamic voltage scaling interface. Use Value: ±1% output accuracy and OPTI-LOOP™ ensure stable operation under rapid load transients (0→9A in 10µs), while Burst Mode™ cuts no-load power to <10mW. |
Use Scenario: Generating 3.3V/5A auxiliary rail from 24V factory automation bus with strict EMI limits. IC Role / Device Role / Timing Role: Fixed-frequency current-mode controller synchronized to system clock (via FCB) to avoid beat frequencies in noise-sensitive PLC modules. Use Value: 300kHz sync capability and forced continuous mode suppress conducted emissions; 4V–30V input range accommodates brownout conditions. |
| Wireless Baseband Power | PDA Main System Rail |
Use Scenario: Powering LTE baseband SoC (e.g., Qualcomm MDM9200) requiring 1.2V/3A with <20mV ripple and fast load-step response. IC Role / Device Role / Timing Role: High-efficiency synchronous buck controller with remote sensing and programmable ITH compensation for SoC VDDQ stability. Use Value: 0.8V reference and ±0.3% load regulation prevent digital logic errors; 160ns minimum on-time supports high VIN/VOUT ratios (24V→1.2V). |
Use Scenario: Delivering 3.3V/2A main system rail in palm-sized PDAs with Li-ion battery input (3.0–4.2V) and aggressive thermal constraints. IC Role / Device Role / Timing Role: Wide-input buck controller with 99% duty cycle dropout support and micropower shutdown (<25µA). Use Value: Ultra-low IQ extends battery life in sleep mode; 98% max duty cycle sustains regulation down to 3.33V input - critical for end-of-discharge operation. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar synchronous buck controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT3741EFE#PBF | Integrated 4A FETs; 4–40V input; no external RSENSE required; requires different compensation network. | Targeted at isolated forward converters and LED drivers - lacks remote sense and Burst Mode™ optimization for CPU rails. | Choose LT3741EFE#PBF only if board space is constrained and integrated FETs meet current requirements; not drop-in for LTC1735CS#PBF layouts. |
| TPS54620RGYR | Integrated 6A FETs; 4.5–17V input; 2.5V–15V VDD bias; no EXTVCC option; fixed 600kHz or sync capable. | Designed for telecom/datacom POL use - lacks foldback current limiting and 0.8V reference compatibility with legacy microprocessors. | Prefer TPS54620RGYR for new designs needing smaller footprint and higher integration; verify VOUT accuracy drift vs. temperature before replacing LTC1735CS#PBF in CPU supply. |
Compared with LT3741EFE#PBF and TPS54620RGYR, the LTC1735CS#PBF offers superior flexibility in high-current discrete-FET designs, wider input range, and proven compatibility with mobile CPU voltage sequencing - making it preferred for legacy and thermally demanding embedded power systems.
Availability
LTC1735CS#PBF is available at Aetrix Electronics and suitable for notebook computing, industrial DC distribution, and wireless infrastructure applications requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.
Supply support for LTC1735CS#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 full technical support, datasheet archives, and product change notifications for all Linear-branded parts.
The LTC1735CS#PBF belongs to Linear's high-efficiency DC/DC controller family designed specifically for synchronous step-down conversion in portable and embedded systems where thermal performance, light-load efficiency, and precision regulation are critical.
FAQ
What is the maximum supported input voltage for the LTC1735CS#PBF?
The LTC1735CS#PBF has an absolute maximum input voltage rating of 36V, with recommended continuous operation from 4V to 30V. Exceeding 30V may reduce reliability or trigger undervoltage lockout recovery delays. The device includes internal UVLO that disables operation below 3.5V (typical) to protect external MOSFETs during brownout conditions. Always verify external FET voltage ratings match the full 36V transient margin when designing with LTC1735CS#PBF.
Does the LTC1735CS#PBF support remote output voltage sensing?
Yes, the LTC1735CS#PBF supports true remote output voltage sensing via dedicated VOSENSE, SENSE+, and SENSE− pins. This allows the feedback divider to be placed at the load point, compensating for PCB trace resistance and ensuring ±1% regulation accuracy at the actual load - not just at the converter output terminals. Remote sense is essential for high-current applications like CPU core supplies where even 50mΩ trace resistance causes significant voltage drop.
How does Burst Mode™ operation improve light-load efficiency in the LTC1735CS#PBF?
Burst Mode™ operation in the LTC1735CS#PBF disables switching cycles when load current falls below ~10mA, reducing quiescent current to <25µA and maintaining >85% efficiency at 1mA. This is achieved by clamping the ITH voltage at 0.86V and turning off both MOSFETs until output capacitor discharge lowers VOSENSE enough to restart regulation. The result is dramatically lower standby power versus continuous mode - critical for battery-powered notebooks and PDAs using LTC1735CS#PBF.
Can the LTC1735CS#PBF be synchronized to an external clock?
Yes, the LTC1735CS#PBF can be synchronized to an external clock applied to the FCB pin. When driven with a signal >1.3V high and <0.3V low for ≥0.3µs, the internal oscillator locks to frequencies between 90% and 130% of its nominal value (set by COSC). This enables EMI reduction by aligning switching edges with system clocks and eliminates beat frequencies in multi-rail systems - a key advantage confirmed in LTC1735CS#PBF application notes and functional diagrams.
What protection features are integrated into the LTC1735CS#PBF?
The LTC1735CS#PBF integrates foldback current limiting, output overvoltage crowbar (triggered at VOSENSE > 0.86V), latched short-circuit shutdown with defeatable timer, undervoltage lockout (UVLO), and bootstrap capacitor recharge management during dropout. These protections operate independently of external components - for example, the crowbar actively pulls the bottom MOSFET gate (BG) low to clamp VOUT during transients, safeguarding downstream logic powered by LTC1735CS#PBF.
LTC1735CS#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):
- 4V ~ 30V
- Frequency - Switching:
- 300kHz
- Duty Cycle (Max):
- 99.4%
- Synchronous Rectifier:
- Yes
- Clock Sync:
- No
- Serial Interfaces:
- -
- Control Features:
- Enable, Power Good, Soft Start
- Operating Temperature:
- 0°C ~ 85°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 16-SO
LTC1735CS#PBF FAQ
1.How can I place an order for LTC1735CS#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC1735CS#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 LTC1735CS#PBF reliable?
The price and inventory of LTC1735CS#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC1735CS#PBF is usually 5 days.
3.What payment methods are accepted for LTC1735CS#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC1735CS#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC1735CS#PBF?
LTC1735CS#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC1735CS#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 LTC1735CS#PBF?
For technical support, including LTC1735CS#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC1735CS#PBF requirements.
6.How does Aetrix verify that LTC1735CS#PBF is sourced from the original manufacturer or authorized distributors?
All LTC1735CS#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 LTC1735CS#PBF meets industry standards.
7.What is the process for return or replacement of LTC1735CS#PBF?
All LTC1735CS#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC1735CS#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 LTC1735CS#PBF part is unused and in its original packaging.
Return procedure for LTC1735CS#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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