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Analog Devices Inc. LTC1735CS-1#PBF
- Part No.:
- LTC1735CS-1#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 16-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
LTC1735CS-1#PBF.pdf
- Description:
- IC REG CTRLR BUCK 16SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:2,414
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Product details
Overview
LTC1735CS-1 from Analog Devices (formerly Linear Technology) is a synchronous step-down switching regulator controller optimized for CPU core power delivery in mobile computing systems. It delivers 0.8V–7V output with ±1% accuracy, supports 3.5V–30V input, features OPTI-LOOP™ compensation, 99% duty cycle dropout operation, and programmable current limit via external sense resistor.
For engineers reviewing the LTC1735CS-1 datasheet, LTC1735CS-1 pinout, LTC1735CS-1 application, or LTC1735CS-1 equivalent, key selection criteria include Intel Mobile CPU-compliant power-good window (±7.5%), Burst Mode™ efficiency at light load, dual N-MOSFET gate drive capability, and 16-lead SO package compatibility with notebook DC/DC designs requiring dynamic voltage scaling.
Technical Context
The LTC1735CS-1 implements a constant-frequency, current-mode control architecture with an internal transconductance error amplifier (gm = 1.3 mmho) and dual current comparators for peak-current limiting and foldback protection. Its OPTI-LOOP™ compensation minimizes required output capacitance by adapting loop response to wide ESR/capacitance ranges.
It integrates synchronized dual gate drivers (TG/BG) capable of 3A peak current, supports external clock synchronization up to 1.3× nominal frequency (max 500 kHz), and uses a floating bootstrap supply (BOOST) with dropout recovery logic that forces 500 ns off-time every 10 cycles below VIN – VOUT < 100 mV.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Voltage Range | 0.8V to 7V; set by external resistive divider on VOSENSE pin, enabling dynamic VOUT adjustment per SpeedStep® requirements. |
| Input Voltage Range | 3.5V to 30V (absolute max 36V); supports wide-input battery/supply rails including 5V, 12V, and 24V industrial sources. |
| Output Accuracy | ±1% over temperature; ensures stable CPU core voltage within Intel Mobile CPU specification tolerance bands. |
| Power-Good Window | ±7.5% of programmed VOUT; open-drain PGOOD asserts low when VOSENSE deviates beyond this window, meeting Intel timing compliance. |
| Max Duty Cycle | 99.4%; enables ultra-low dropout operation essential for high-current, low-VOUT CPU applications where VIN approaches VOUT. |
| Quiescent Current | 450 µA in normal mode; <25 µA in shutdown; critical for battery life in notebook/palmtop standby states. |
| Oscillator Frequency | 265–335 kHz (COSC = 47 pF); externally programmable up to 500 kHz for EMI/efficiency trade-off tuning. |
Pinout & Package
Package: 16-lead plastic SO (Small Outline) with θJA = 110°C/W; RoHS-compliant, lead-free (PbF) finish per #PBF suffix.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| COSC | Oscillator Timing Input | Connects external capacitor to set switching frequency; determines fOSC via charge-current integration (8.477×10¹¹/COSC). |
| RUN/SS | Soft-Start & Enable Control | Capacitor-to-ground sets soft-start ramp time (~1.25 s/µF); <1.5 V disables controller and initiates latchoff under short-circuit. |
| ITH | Error Amplifier Output | Controls peak inductor current threshold; voltage range 0–2.4 V directly scales current limit via RSENSE. |
| PGOOD | Open-Drain Status & Sync Input | Pulled low when VOSENSE outside ±7.5%; also accepts external sync clock (1.3 VPP min) to lock oscillator frequency. |
| SENSE– / SENSE+ | Differential Current Sense Inputs | Monitor voltage across external RSENSE; built-in offset sets trip point at 60–85 mV for accurate current limiting. |
| VOSENSE | Feedback Voltage Input | Receives divided VOUT; referenced to 0.8 V internal bandgap; enables precise regulation and PGOOD monitoring. |
| TG / BG | Top/Bottom Gate Drivers | Drive external N-MOSFET gates; TG operates floating (SW-referenced), BG referenced to PGND; each rated for 3 A peak. |
| VIN / SW / BOOST / INTVCC / EXTVCC | Power Supply Terminals | VIN powers control logic; SW is switch node; BOOST supplies floating TG driver; INTVCC = 5.2 V LDO output; EXTVCC enables efficient auxiliary supply switchover. |
Key Features
| Feature | Design Value |
|---|---|
| OPTI-LOOP™ Compensation | Minimizes required COUT and relaxes ESR constraints-enables use of low-cost, high-ESR capacitors without sacrificing transient response. |
| Burst Mode™ Operation | Enables >85% efficiency at 10 mA load (vs ~60% in continuous mode); reduces audible noise and quiescent power in idle CPU states. |
| Programmable Foldback Current Limit | Reduces peak inductor current to ~25% of max during short-circuit; limits thermal stress and enables safe fault recovery without external circuitry. |
| Remote Output Voltage Sensing | VOSENSE pin allows Kelvin connection to load, eliminating IR drop errors in high-current PCB traces (>10 A applications). |
| Logic-Controlled Micropower Shutdown | IQ < 25 µA shutdown current; supports instant-on wake-up and extends battery runtime in portable systems. |
| Internal Overvoltage Crowbar | Disables top MOSFET and turns on bottom MOSFET if VOUT exceeds +7.5%, preventing damage to downstream CPU I/O or memory. |
Applications
| Mobile CPU Core Power | Dynamic Voltage Scaling System |
|---|---|
|
Use Scenario: Power delivery to Intel Mobile Pentium® III processor with SpeedStep™ technology during active and throttled states. IC Role / Device Role / Timing Role: Primary synchronous buck controller managing VCORE transitions between 1.35 V and 1.60 V based on workload. Use Value: Meets Intel's ±7.5% PGOOD window and fast transient response (<10 µs settling) required for reliable CPU voltage sequencing. |
Use Scenario: Adaptive voltage regulation in palmtop computers where battery voltage decays from 4.5 V to 3.0 V during discharge. IC Role / Device Role / Timing Role: Step-down controller maintaining stable 1.5 V output while VIN drops, leveraging 99% duty cycle for minimal dropout loss. Use Value: Enables >90% efficiency across full input range without external LDO post-regulation, extending usable battery capacity. |
| Notebook System Power Rail | Wireless Modem Baseband Supply |
|
Use Scenario: Main 3.3 V or 5 V system rail generation in space-constrained notebook motherboards. IC Role / Device Role / Timing Role: High-efficiency synchronous controller driving discrete FDS6680A MOSFETs with integrated gate drivers. Use Value: Eliminates need for external driver ICs; reduces BOM count and layout area while supporting 12 A peak output current. |
Use Scenario: Low-noise, low-quiescent power supply for cellular baseband processors during deep-sleep modes. IC Role / Device Role / Timing Role: Controller operating in Burst Mode™ to maintain 1.2 V output with <25 µA total system standby current. Use Value: Achieves >80% efficiency at 1 mA load-critical for multi-day standby in GSM/UMTS modems. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar synchronous buck controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| TPS51220ARGER | Integrated MOSFETs (no external FETs required); fixed 500 kHz frequency; no Burst Mode™, only diode emulation. | Lower component count but less flexible for high-current (>15 A) or custom efficiency optimization. | Choose for simplified design where 12 A max output suffices and board space is premium; avoid if OPTI-LOOP™ adaptability or ultra-low-IQ is required. |
| ISL6264CRZ | Supports 3-phase interleaving; higher gate drive strength (4 A); requires external op-amp for remote sensing. | Targeted at high-end mobile platforms needing >20 A CPU rails and tighter ripple control. | Choose for multi-phase scalability and enhanced transient immunity; avoid if single-phase 12 A solution and SO-16 footprint are mandatory. |
Compared with LTC1735CS-1, TPS51220ARGER reduces external component count but sacrifices programmable frequency and adaptive compensation, while ISL6264CRZ adds phase flexibility at the cost of increased complexity and larger footprint-neither offers identical OPTI-LOOP™ or Burst Mode™ behavior.
Availability
LTC1735CS-1 is available at Aetrix Electronics and suitable for notebook computing, mobile CPU power delivery, and wireless modem baseband supply requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.
Supply support for LTC1735CS-1 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 legacy Linear parts including the LTC series.
The LTC1735CS-1 belongs to Linear's high-performance power management controller family, designed specifically for demanding CPU core voltage regulation in mobile and embedded systems with dynamic voltage scaling requirements.
FAQ
What is the maximum supported switching frequency for the LTC1735CS-1?
The LTC1735CS-1 supports synchronization up to 500 kHz, with nominal free-running frequency adjustable from 265 kHz to 335 kHz using COSC = 47 pF. Exceeding 500 kHz risks slope compensation instability at high duty cycles; lowering COSC value restores stability if external sync exceeds 1.3× nominal fOSC. The LTC1735CS-1 datasheet specifies 550 kHz as absolute maximum recommended frequency.
How does the LTC1735CS-1 implement power-good monitoring?
The LTC1735CS-1 uses an internal window comparator referenced to the 0.8 V bandgap to monitor VOSENSE. PGOOD asserts low when VOSENSE deviates more than ±7.5% from the target-matching Intel Mobile CPU specifications. This signal is open-drain and requires an external pull-up; it also doubles as a sync input when driven with a 1.3 VPP square wave.
Can the LTC1735CS-1 operate with only ceramic output capacitors?
Yes-the LTC1735CS-1's OPTI-LOOP™ compensation architecture is explicitly designed to stabilize with low-ESR ceramic capacitors alone. Unlike conventional controllers requiring bulk electrolytic + ceramic combinations, the LTC1735CS-1 maintains phase margin across wide ESR ranges, enabling compact, high-reliability ceramic-only output filters.
What is the purpose of the EXTVCC pin on the LTC1735CS-1?
The EXTVCC pin allows an external 4.7–7 V supply (e.g., converter secondary output) to power the INTVCC regulator, bypassing the internal LDO. When EXTVCC > 4.7 V, the internal switch connects it directly to INTVCC, reducing power loss and improving overall efficiency-especially beneficial in multi-rail systems where a clean 5 V rail is already available.
Does the LTC1735CS-1 support forced continuous conduction mode (FCCM)?
Yes-driving the PGOOD pin low (e.g., tying to GND) forces the LTC1735CS-1 into continuous conduction mode regardless of load. This disables Burst Mode™ and ensures constant-frequency operation, useful for noise-sensitive applications. However, efficiency drops significantly below ~200 mA, and reverse current sinking must be carefully managed to avoid input voltage boost.
LTC1735CS-1#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):
- 3.5V ~ 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-1#PBF FAQ
1.How can I place an order for LTC1735CS-1#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC1735CS-1#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-1#PBF reliable?
The price and inventory of LTC1735CS-1#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-1#PBF is usually 5 days.
3.What payment methods are accepted for LTC1735CS-1#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC1735CS-1#PBF transactions.
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4.How is shipping managed for LTC1735CS-1#PBF?
LTC1735CS-1#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC1735CS-1#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-1#PBF?
For technical support, including LTC1735CS-1#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC1735CS-1#PBF requirements.
6.How does Aetrix verify that LTC1735CS-1#PBF is sourced from the original manufacturer or authorized distributors?
All LTC1735CS-1#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-1#PBF meets industry standards.
7.What is the process for return or replacement of LTC1735CS-1#PBF?
All LTC1735CS-1#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC1735CS-1#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-1#PBF part is unused and in its original packaging.
Return procedure for LTC1735CS-1#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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