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Analog Devices Inc. LTC1735IS#PBF
- Part No.:
- LTC1735IS#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 16-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
LTC1735IS#PBF.pdf
- Description:
- IC REG CTRLR BUCK 16SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:101
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Product details
Overview
LTC1735IS#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 with ±1% output voltage accuracy, 4V–30V input range, and Burst Mode™ for high efficiency at light loads. Used in notebook DC-DC power rails requiring precise low-voltage regulation.
For engineers reviewing the LTC1735IS#PBF datasheet, LTC1735IS#PBF pinout, LTC1735IS#PBF application, or LTC1735IS#PBF equivalent, key selection criteria include its OPTI-LOOP™ compensation for wide-output-capacitance stability, forced continuous mode via FCB pin, programmable soft-start, and dual N-MOSFET synchronous drive capability.
Technical Context
The LTC1735IS#PBF implements a constant-frequency, current-mode control architecture with an error amplifier (EA) output at ITH pin controlling peak inductor current via a transconductance gm of 1.3 mmho. Its internal 0.8V reference feeds VOSENSE with ±1% accuracy over temperature and line/load conditions.
Burst Mode™ operation-enabled when FCB > 0.8V-clamps ITH at 0.86V and disables switching below ~0.5V, reducing quiescent current to <25µA in shutdown. Synchronization up to 500kHz is achieved by applying an external clock to FCB, disabling Burst Mode while maintaining constant-frequency discontinuous conduction.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Voltage Range | 0.8V to 6V - supports core logic, DDR, and ASIC supply rails with precision feedback via external resistor divider. |
| Input Voltage Range | 4V to 30V (36V abs max) - enables direct use from 5V, 12V, or 24V industrial/PCB bus inputs. |
| Output Voltage Accuracy | ±1% over temp & load - ensures microprocessor VDD compliance without margining overhead. |
| Switching Frequency | 265–335 kHz (COSC = 47pF) - balances MOSFET switching loss vs. inductor size; synchronizable up to 500kHz. |
| Shutdown Quiescent Current | <25 µA - minimizes battery drain in portable systems during sleep states. |
| Current Sense Threshold | 60–85 mV - sets peak inductor current limit via RSENSE; foldback activates below 70% VOUT. |
| Duty Cycle Max | 98–99.4% - supports ultra-low dropout operation down to VIN – VOUT ≈ 100mV at full load. |
Pinout & Package
Package: 16-lead narrow plastic SSOP (GN), 110°C/W θJA, RoHS-compliant, lead-free (Pb-free) finish.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| COSC | Oscillator timing capacitor node | External capacitor sets operating frequency; 47pF yields ~300kHz free-run. |
| RUN/SS | Soft-start ramp & shutdown control | Capacitor sets startup time (~1.25s/µF); <1.5V forces shutdown; >4.1V triggers latchoff on undervoltage. |
| ITH | Error amplifier output / current limit control | Voltage (0–2.4V) sets peak inductor current; clamped at 0.86V in Burst Mode. |
| FCB | Forced continuous/sync input | Ground = forced continuous; INTVCC = Burst Mode; external clock = sync + cycle-skipping. |
| VOSENSE | Feedback voltage input | Receives divided output voltage; referenced to 0.8V internal bandgap with ±1% tolerance. |
| SENSE+, SENSE− | Current sense differential inputs | Measure voltage across RSENSE; built-in offset enables accurate 60–85mV threshold setting. |
| TG, BG | Top/bottom gate drivers | Drive external N-MOSFETs; TG swings from SW to INTVCC+SW; BG swings from PGND to INTVCC. |
| VIN, SW, PGND, BOOST, INTVCC, EXTVCC | Power domain connections | VIN supplies main rail; SW connects to inductor/diode; BOOST powers floating TG driver; INTVCC = 5.2V LDO output. |
Key Features
| Feature | Design Value |
|---|---|
| OPTI-LOOP™ compensation | Allows stable loop response across wide COUT/ESR ranges (e.g., 10µF ceramic + 100µF polymer), eliminating need for custom compensation per output cap. |
| Burst Mode™ operation | Reduces no-load IQ to <25µA and maintains >80% efficiency at 1mA load, critical for battery-backed systems. |
| Forced continuous mode control | FCB pin disables Burst Mode to eliminate low-frequency ripple and EMI, enabling clean supply for RF/analog circuits. |
| Internal foldback current limiting | Automatically reduces peak current to ~25% of max when VOUT drops below 70%, protecting MOSFETs during short-circuit events. |
| Remote output voltage sensing | VOSENSE accepts Kelvin connection to load, rejecting PCB trace IR drop and ensuring ±1% regulation at point-of-load. |
Applications
| Portable Computing Power Rails | Industrial DC Distribution |
|---|---|
Use Scenario: Regulating 1.6V/9A CPU core voltage in ultraportable notebooks with 5–24V adapter input. IC Role / Device Role / Timing Role: Primary synchronous buck controller managing top/bottom N-MOSFETs, ITH-based current-mode loop, and Burst Mode for idle efficiency. Use Value: Delivers 99% duty cycle dropout and ±1% VOUT accuracy under dynamic load steps, meeting Intel VR12.5 specifications without external DAC. |
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 synchronous controller with FCB-synchronized operation to avoid beat frequencies with PLC clock domains. Use Value: Enables 300kHz synchronized switching and forced continuous mode to suppress audible noise and meet CISPR-22 Class B conducted emissions. |
| Wireless Baseband Power | Test Equipment DC Supplies |
Use Scenario: Supplying 1.2V/3A FPGA I/O bank in LTE small cell radio with thermal constraints. IC Role / Device Role / Timing Role: Current-mode buck controller using OPTI-LOOP™ to stabilize output with low-ESR ceramic caps only. Use Value: Achieves <10mVpp ripple in Burst Mode and <20mVpp in continuous mode, preventing digital jitter in high-speed SerDes links. |
Use Scenario: Programmable 5V/2A bench supply with remote sense and soft-start sequencing for DUT biasing. IC Role / Device Role / Timing Role: Controller with RUN/SS-programmable soft-start and EXTVCC-powered INTVCC for clean turn-on and low-noise output. Use Value: Supports <1ms soft-start ramp via CSS capacitor and 5.2V INTVCC rail decoupled with 1µF + 4.7µF, eliminating turn-on overshoot. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar synchronous buck controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| MP2451DT-LF-Z | Integrated 2A MOSFETs; fixed 500kHz fSW; no Burst Mode; 4.5–28V VIN | Suitable for lower-current (<2A), space-constrained designs where external FETs are undesirable | Select MP2451DT-LF-Z only if integrated power stage suffices and Burst Mode efficiency is not required. |
| TPS54332DR | Integrated 3.5A MOSFETs; adjustable 200–1200kHz fSW; Eco-mode™ instead of Burst Mode; 3.5–28V VIN | Preferred for mid-power (≤3.5A) applications needing higher switching frequency and smaller magnetics | Choose TPS54332DR when board area is limited and Eco-mode's light-load efficiency meets system requirements. |
Compared with MP2451DT-LF-Z and TPS54332DR, the LTC1735IS#PBF provides superior light-load efficiency via Burst Mode™, external FET flexibility for >9A designs, and OPTI-LOOP™ stability across diverse output capacitors-making it optimal for high-reliability, high-current, thermally constrained applications.
Availability
LTC1735IS#PBF is available at Aetrix Electronics and suitable for notebook computing power rails, industrial DC distribution systems, and wireless baseband supply applications requiring stable component supply and long-term lifecycle support.
Supply support for LTC1735IS#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 and manufacturing continuity for legacy Linear power products.
The LTC1735IS#PBF belongs to Linear's high-efficiency synchronous buck controller family, designed specifically for demanding portable and industrial DC-DC conversion where precision, efficiency across load range, and robust protection are mandatory.
FAQ
What is the maximum output current supported by the LTC1735IS#PBF?
The LTC1735IS#PBF itself does not deliver current-it controls external N-channel MOSFETs. With appropriate FET selection (e.g., FDS6680A), the LTC1735IS#PBF enables up to 9A output, as validated in the typical application circuit (Figure 1) using RSENSE = 0.005Ω and 2µH inductor. Peak current is set by the 60–85mV sense threshold and inductor value.
Does the LTC1735IS#PBF include an internal voltage reference?
Yes, the LTC1735IS#PBF integrates a precision 0.8V bandgap reference with ±1% accuracy over temperature and line/load conditions. This reference is used internally for the VOSENSE feedback comparator and is accessible only through the feedback loop-not as a standalone output.
How does Burst Mode™ operation improve light-load efficiency in the LTC1735IS#PBF?
Burst Mode™ in the LTC1735IS#PBF disables switching when ITH falls below ~0.5V, allowing the output capacitor to supply load current until voltage droop raises ITH above the 60mV hysteresis threshold. This reduces average input current to <25µA in shutdown and maintains >80% efficiency at 1mA load-critical for battery-powered systems.
Can the LTC1735IS#PBF be synchronized to an external clock?
Yes-the FCB pin accepts an external clock signal (1.3VPP min, 0.3µs pulse width) to synchronize the internal oscillator between 90% and 130% of its nominal frequency set by COSC. When synchronized, Burst Mode™ is disabled, and constant-frequency discontinuous operation is maintained across the full load range.
What package type is used for the LTC1735IS#PBF?
The LTC1735IS#PBF uses a 16-lead narrow plastic SSOP (GN) package, marked "1735I", with 110°C/W junction-to-ambient thermal resistance. It is RoHS-compliant and features a lead-free (Pb-free) finish, as indicated by the "#PBF" suffix in the orderable part number.
LTC1735IS#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:
- -40°C ~ 85°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 16-SO
LTC1735IS#PBF FAQ
1.How can I place an order for LTC1735IS#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC1735IS#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 LTC1735IS#PBF reliable?
The price and inventory of LTC1735IS#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC1735IS#PBF is usually 5 days.
3.What payment methods are accepted for LTC1735IS#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC1735IS#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC1735IS#PBF?
LTC1735IS#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC1735IS#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 LTC1735IS#PBF?
For technical support, including LTC1735IS#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC1735IS#PBF requirements.
6.How does Aetrix verify that LTC1735IS#PBF is sourced from the original manufacturer or authorized distributors?
All LTC1735IS#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 LTC1735IS#PBF meets industry standards.
7.What is the process for return or replacement of LTC1735IS#PBF?
All LTC1735IS#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC1735IS#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 LTC1735IS#PBF part is unused and in its original packaging.
Return procedure for LTC1735IS#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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