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Analog Devices Inc. LTC1735CF#PBF
- Part No.:
- LTC1735CF#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 20-TSSOP (0.173", 4.40mm Width)
- Datasheet:
-
LTC1735CF#PBF.pdf
- Description:
- IC REG CTRLR BUCK 20TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:4,799
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Product details
Overview
LTC1735CF#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 with ±1% accuracy, supports 4V–30V input, and achieves up to 99.4% duty cycle for ultra-low dropout. Used in notebook DC-DC power stages requiring high efficiency at light loads via Burst Mode™.
For engineers reviewing the LTC1735CF#PBF datasheet, LTC1735CF#PBF pinout, LTC1735CF#PBF application, or LTC1735CF#PBF equivalent, key selection criteria include programmable frequency via COSC capacitor, OPTI-LOOP™ compensation for wide output capacitance/ESR tolerance, forced continuous mode control (FCB pin), remote voltage sensing, and latched short-circuit shutdown with defeat option.
Technical Context
The LTC1735CF#PBF implements a constant-frequency, current-mode control architecture with dual N-channel gate drivers (TG, BG), precision 0.8V reference, and transconductance error amplifier (gm = 1.3 mmho). Its ITH pin controls peak inductor current, while VOSENSE enables closed-loop feedback with ±1% output voltage accuracy over temperature and line/load conditions.
Burst Mode™ operation-enabled by FCB > 0.8V-reduces quiescent current to <25µA in shutdown and maintains high efficiency below ~100mA load. Synchronization capability (up to 500kHz) and forced continuous mode (FCB = GND) provide noise-sensitive and secondary-winding regulation support, respectively.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Voltage Range | 0.8V to 6V - set externally via resistive divider on VOSENSE; compatible with microprocessor core supplies. |
| Input Voltage Range | 4V to 30V (36V abs max) - supports wide industrial and computing input rails including 5V, 12V, and 24V systems. |
| Reference Accuracy | ±1% over temp - ensures stable output under thermal stress without calibration. |
| Oscillator Frequency | 265–335 kHz (COSC = 43pF) - user-programmable via external capacitor; synchronizable up to 500kHz. |
| Max Duty Cycle | 99.4% - enables ultra-low dropout operation (e.g., 5V→4.95V at high load) without external boost. |
| Shutdown IQ | <25 µA - enables micropower hold states in battery-backed or portable systems. |
| Current Sense Threshold | 60–85 mV - sets peak inductor current limit; foldback activated when VOUT drops below 70% nominal. |
Pinout & Package
Package: 20-Lead Plastic TSSOP (F package), 0.65mm pitch, exposed pad for thermal enhancement. Pin count and layout match LTC1735F family; not pin-compatible with 16-lead SSOP/SO variants.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VOSENSE | Feedback Input | Receives divided output voltage; servo loop maintains 0.8V at this node for precise regulation. |
| SENSE+, SENSE− | Current Sense Differential Inputs | Measure voltage across RSENSE to regulate peak inductor current; built-in offset enables accurate low-value sense resistors. |
| FCB | Forced Continuous / Sync Input | Ground = forced continuous mode; INTVCC = Burst Mode™; external clock = synchronization + cycle-skipping. |
| RUN/SS | Run Control / Soft-Start | Capacitor-based soft-start timing (~1.25s/µF); <1.5V disables all functions including INTVCC. |
| PGOOD | Power-Good Output | Open-drain signal asserted low when VOSENSE deviates >±7.5% from 0.8V reference - only on F-package variants. |
| TG, BG | Top/Bottom Gate Drivers | Drive external N-MOSFETs; TG swings from SW to INTVCC+SW; BG swings from PGND to INTVCC. |
| INTVCC | Internal 5.2V Regulator Output | Powers internal logic and gate drivers; can be bypassed by EXTVCC ≥4.7V for higher efficiency. |
Key Features
| Feature | Design Value |
|---|---|
| OPTI-LOOP™ Compensation | Minimizes required output capacitance and relaxes ESR constraints - simplifies design across diverse ceramic/tantalum/POSCAP selections. |
| Burst Mode™ Operation | Reduces no-load IQ to <25µA while maintaining regulated output - critical for always-on subsystems in portable electronics. |
| Programmable Foldback Current Limit | Automatically reduces peak current when VOUT falls below 70% nominal - protects against sustained overload without external circuitry. |
| Remote Output Voltage Sense | Compensates for PCB trace IR drop - maintains ±1% regulation at load point, not at IC pins. |
| Latched Short-Circuit Shutdown | Disables switching after timeout determined by RUN/SS capacitor CSS - prevents thermal runaway during hard shorts. |
Applications
| High-Efficiency Notebook Core Supply | Industrial DC Power Distribution |
|---|---|
Use Scenario: 1.6V/9A CPU core rail in ultraportable laptop with 5V–24V adapter input. IC Role / Device Role / Timing Role: Primary synchronous buck controller managing dynamic load steps and low-power idle states. Use Value: Burst Mode™ sustains >85% efficiency at 10mA load; OPTI-LOOP™ accommodates low-ESR POSCAP output capacitors. |
Use Scenario: Distributed 3.3V supply in factory automation PLC with 24V bus input and variable load. IC Role / Device Role / Timing Role: Fixed-frequency current-mode controller delivering stable output despite wide ambient temperature swing (−40°C to 85°C). Use Value: ±1% reference accuracy and remote sensing maintain regulation at remote I/O modules; EXTVCC support enables self-powered gate drive. |
| Wireless Modem Baseband Power | Cellular Handset PMIC Sub-Stage |
Use Scenario: 2.5V/3A RF baseband processor supply in LTE modem with bursty traffic patterns. IC Role / Device Role / Timing Role: High-transient-response buck controller synchronized to system clock via FCB pin. Use Value: Synchronization eliminates beat frequencies; forced continuous mode prevents RF interference during transmit bursts. |
Use Scenario: Secondary 1.2V/2A core supply derived from main 3.3V rail in multi-rail smartphone PMIC architecture. IC Role / Device Role / Timing Role: Secondary synchronous buck controller using primary rail's EXTVCC for gate drive and efficiency. Use Value: EXTVCC switchover reduces power loss vs. internal LDO; PGOOD enables safe sequencing with application processor. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar synchronous buck controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC1735IF#PBF | Same pinout, identical electrical specs, but rated for −40°C to 85°C industrial temp range (vs. 0°C to 85°C for LTC1735CF#PBF). | Required for extended-temperature deployments (e.g., outdoor telecom, automotive under-hood). | Select LTC1735IF#PBF when operating ambient exceeds 0°C minimum or when AEC-Q200 qualification is needed. |
| MP2315DJ-LF-Z | Integrated power stage (no external MOSFETs), lower max VIN (24V), no Burst Mode™, no PGOOD, no EXTVCC support. | Suitable for cost-sensitive, space-constrained designs where 5A max output and fixed 500kHz operation suffice. | Choose MP2315 when board area and BOM count are prioritized over efficiency flexibility and robust protection features. |
Compared with LTC1735CF#PBF, LTC1735IF#PBF offers identical functionality with extended temperature rating, while MP2315DJ-LF-Z trades external power stage control and advanced low-load efficiency for integration and simplicity - making it appropriate only for less demanding, thermally benign applications.
Availability
LTC1735CF#PBF is available at Aetrix Electronics and suitable for notebook computing, industrial DC distribution, and wireless modem power management requiring stable component supply, long-term lifecycle support, and guaranteed parametric performance.
Supply support for LTC1735CF#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 product support, documentation, and manufacturing continuity for the LTC portfolio.
The LTC1735CF#PBF belongs to Linear's high-efficiency synchronous buck controller family, designed specifically for microprocessor core and system rail regulation in portable and industrial equipment where efficiency, transient response, and protection integrity are critical.
FAQ
What is the maximum input voltage rating for the LTC1735CF#PBF?
The LTC1735CF#PBF has an absolute maximum input voltage (VIN) rating of 36V. Continuous operation is specified from 4V to 30V. Exceeding 36V risks permanent damage to internal circuitry, especially the SW, BOOST, and TG pins, which share the same voltage stress path. Always observe derating guidelines in high-reliability designs.
Does the LTC1735CF#PBF include a power-good output?
Yes, the LTC1735CF#PBF includes an open-drain PGOOD output that asserts low when the VOSENSE voltage deviates more than ±7.5% from the 0.8V reference. This feature is exclusive to the 20-lead TSSOP (F) package variants - including LTC1735CF#PBF and LTC1735IF#PBF - and is absent in 16-lead SO/SSOP versions.
How is the switching frequency programmed on the LTC1735CF#PBF?
The LTC1735CF#PBF uses an external capacitor (COSC) connected from the COSC pin to ground to set its free-running oscillator frequency between 265 kHz and 335 kHz (for 43pF). Frequency scales inversely with COSC value; Figure 2 in the datasheet provides the exact pF-to-kHz mapping. The FCB pin also accepts external clock signals for synchronization up to 500kHz.
What protection features does the LTC1735CF#PBF provide against output overvoltage?
The LTC1735CF#PBF includes an output overvoltage crowbar protection circuit that triggers when VOSENSE exceeds 0.84V–0.88V (±5 mV tolerance). Upon detection, the top MOSFET (TG) is immediately disabled and the bottom MOSFET (BG) is forced on to clamp the output, preventing damage to downstream loads. Recovery is automatic once the fault condition clears.
Can the LTC1735CF#PBF operate with only the internal INTVCC regulator, or is EXTVCC required?
The LTC1735CF#PBF operates fully with only the internal INTVCC regulator - a 5.2V LDO powered from VIN. EXTVCC is optional: when driven above 4.7V, it disables the internal LDO and directly powers INTVCC, improving efficiency by eliminating LDO dropout loss. EXTVCC must not exceed 7V and must remain ≤ VIN.
LTC1735CF#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 20-TSSOP (0.173", 4.40mm 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:
- 20-TSSOP
LTC1735CF#PBF FAQ
1.How can I place an order for LTC1735CF#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC1735CF#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 LTC1735CF#PBF reliable?
The price and inventory of LTC1735CF#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC1735CF#PBF is usually 5 days.
3.What payment methods are accepted for LTC1735CF#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC1735CF#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC1735CF#PBF?
LTC1735CF#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC1735CF#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 LTC1735CF#PBF?
For technical support, including LTC1735CF#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC1735CF#PBF requirements.
6.How does Aetrix verify that LTC1735CF#PBF is sourced from the original manufacturer or authorized distributors?
All LTC1735CF#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 LTC1735CF#PBF meets industry standards.
7.What is the process for return or replacement of LTC1735CF#PBF?
All LTC1735CF#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC1735CF#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 LTC1735CF#PBF part is unused and in its original packaging.
Return procedure for LTC1735CF#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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