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Analog Devices Inc. LTC1709EG-85#TRPBF
- Part No.:
- LTC1709EG-85#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 36-SSOP (0.209", 5.30mm Width)
- Datasheet:
-
LTC1709EG-85#TRPBF.pdf
- Description:
- IC REG CTRLR BUCK 36SSOP
- Quantity:
- Payment:
- Shipping:
Inventory:2,577
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Product details
Overview
LTC1709EG-85 from Analog Devices (formerly Linear Technology) is a 2-phase, 5-bit VID-programmable, current-mode synchronous step-down switching regulator controller driving two external N-channel MOSFET stages. It operates at fixed frequencies from 150kHz to 300kHz, delivers ±1% output voltage accuracy across 1.05V–1.825V (VRM 8.5), supports true remote differential sensing, and integrates OPTI-LOOP compensation for wide ESR capacitor compatibility - deployed in high-current server CPU core power supplies.
For engineers reviewing the LTC1709EG-85 datasheet, LTC1709EG-85 pinout, LTC1709EG-85 application, or LTC1709EG-85 equivalent, key selection criteria include its dual-phase antiphase operation reducing input RMS ripple, programmable forced-PWM/Burst/Cycle-Skip modes, integrated overvoltage soft-latch protection, and 36-lead narrow SSOP package with verified thermal performance up to 85°C ambient.
Technical Context
The LTC1709EG-85 implements a constant-frequency, current-mode control architecture with two independent 180° out-of-phase output channels. Each channel uses peak-current sensing via dedicated SENSE+/- inputs, ITH-controlled threshold modulation, and separate top/bottom gate drivers (TG1/TG2, BG1/BG2) with 90ns max transition times and 180ns minimum on-time.
Its PLL-based frequency control accepts DC voltage (0–2.4V) on PLLFLTR to tune oscillator output from 120kHz to 360kHz, while PLLIN enables external synchronization. The FCB pin selects among three operational modes: forced continuous PWM (FCB < 0.8V), Burst Mode (0.8V < FCB < VINTVCC–2V), or constant-frequency discontinuous mode (FCB = INTVCC).
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Voltage Range | 1.05V to 1.825V via 5-bit VID code (VRM 8.5 compliant); enables dynamic CPU core voltage scaling. |
| Switching Frequency | Programmable 150kHz–300kHz (typical 220kHz); higher frequencies reduce inductor size but increase switching losses. |
| Input Voltage Range | 4V to 36V VIN; supports wide-range industrial and server DC distribution rails. |
| Current Sense Threshold | 75mV (typical) per channel; sets peak inductor current with ±12.5mV tolerance over temperature. |
| Output Voltage Accuracy | ±1% over line/load/temperature; ensures stable CPU core regulation under transient load steps. |
| Thermal Performance | θJA = 85°C/W; junction temperature limited to 125°C; validated for 0°C to 70°C operating range (full spec assured –40°C to 85°C). |
| Remote Sensing | Differential amplifier (ADA = 1.005V/V, CMRR = 55dB) on VOS+/VOS–/VDIFFOUT pins; compensates for PCB trace IR drop in >40A applications. |
Pinout & Package
Package: 36-lead narrow SSOP (G package), 0.209" body width, exposed pad not present, RoHS-compliant.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| RUN/SS (Pin 1) | Soft-start timing & short-circuit latch control | Capacitor-connected node enabling controlled current ramp-up; discharges during output fault to trigger shutdown after programmable timeout. |
| SENSE1+/SENSE1– (Pins 2,3) SENSE2+/SENSE2– (Pins 14,13) | Differential current sense inputs per phase | Measure voltage drop across external RSENSE resistors; enable precise per-phase current limiting and inherent current sharing. |
| EAIN (Pin 4) | Error amplifier feedback input | Compares regulated output voltage (via VDIFFOUT divider) against 0.800V internal reference; determines ITH voltage and thus peak current setpoint. |
| TG1/TG2 (Pins 35,24) BG1/BG2 (Pins 31,27) | Top/bottom N-MOSFET gate drivers | Drive external power switches with 3A peak sink/source capability; TG outputs swing referenced to SW nodes via BOOST capacitors. |
| PGOOD (Pin 23) | Open-drain power-good indicator | Asserts low when output deviates >±7.5% from nominal; provides system-level power sequencing and fault signaling. |
Key Features
| Feature | Design Value |
|---|---|
| 2-phase antiphase operation | Reduces input capacitor RMS ripple by ~70%, cutting required CIN rating and lowering EMI noise coupling into shared supply rails. |
| OPTI-LOOP compensation | Enables stable loop response across 10µF–1000µF output capacitors with ESR from 1mΩ to 50mΩ - eliminates need for custom compensation networks. |
| True remote differential sensing | VOS+/VOS– inputs feed a precision op-amp (CMRR 55dB) generating VDIFFOUT; maintains ±1% regulation despite >100mV PCB trace drop at 40A loads. |
| Three selectable operating modes | Burst Mode (high efficiency at light load), Cycle-Skip (low-noise constant frequency), Forced PWM (fast transient response); selected via single FCB pin voltage level. |
| Integrated overvoltage soft-latch | OV comparator triggers immediate top-FET turn-off and bottom-FET turn-on upon +7.5% VOUT excursion; prevents nuisance trips via 60mV hysteresis. |
Applications
| Server CPU Core Power | High-Density Memory Arrays |
|---|---|
Use Scenario: Delivering tightly regulated 1.2V/40A to dual-socket Xeon processors in 1U rack servers with strict thermal envelope limits. IC Role / Device Role / Timing Role: Primary 2-phase VRM controller managing parallel power stages, synchronizing gate drive timing, and executing VID voltage transitions within 10µs. Use Value: Antiphase operation cuts input capacitor count by 50% versus single-phase designs; ±1% accuracy ensures CPU stability under 10A/µs load transients. |
Use Scenario: Powering DDR4/DDR5 memory modules in AI accelerator cards where board space is constrained and EMI must meet Class B limits. IC Role / Device Role / Timing Role: Dual-output synchronous buck controller supplying matched 1.1V rails with current sharing enforced by per-phase current-mode control. Use Value: Burst Mode extends system standby time; differential sensing maintains voltage at memory VDDQ pins despite 80mV interconnect loss across PCIe carrier board. |
| Industrial DC Power Distribution | Telecom Base Station RF Power Amplifiers |
Use Scenario: Converting 24VDC plant bus to 1.8V/30A for FPGA-based real-time control systems operating continuously at 70°C ambient. IC Role / Device Role / Timing Role: High-reliability step-down controller with overvoltage soft-latch and thermal derating support for unattended operation. Use Value: EXTVCC pin allows powering INTVCC from regulated 5V rail, reducing self-heating; 125°C junction limit enables full output current at elevated temperatures. |
Use Scenario: Providing dynamically scaled bias voltage to GaN RF power amplifiers in 5G macro base stations requiring fast VID updates during TDD slot transitions. IC Role / Device Role / Timing Role: VID-programmable controller responding to baseband processor commands to adjust VDD_PA between 28V and 32V in <50µs. Use Value: 5-bit VID interface matches VRM 8.5 standard; PLLIN synchronization aligns switching edges with system clock to suppress beat-frequency interference in adjacent RF bands. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar dual-phase synchronous buck controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| ISL6522CRZ-T | Fixed 300kHz frequency only; no PLLIN sync input; requires external bootstrap diodes; no VID interface. | Suitable for cost-sensitive industrial SMPS where dynamic voltage scaling is unnecessary. | Choose ISL6522CRZ-T only if VID programming and external sync are not required; verify thermal design for same 40A load. |
| MP2940AGQKT-Z | Supports VRM 9.1/10.x VID codes; includes digital telemetry (SMBus); higher integration (integrated MOSFET drivers with 5A peak). | Targeted at modern client/server platforms needing PMBus communication and telemetry reporting. | Choose MP2940AGQKT-Z when digital monitoring, fault logging, or VRM 10.x compliance are mandatory; note different pinout and layout requirements. |
Compared with ISL6522CRZ-T and MP2940AGQKT-Z, the LTC1709EG-85 uniquely balances analog precision (±1% VOUT), flexible frequency tuning (120–360kHz), and robust analog VID decoding without requiring digital infrastructure - making it optimal for legacy VRM 8.5 deployments where reliability and thermal margin outweigh telemetry needs.
Availability
LTC1709EG-85 is available at Aetrix Electronics and suitable for server motherboard design, high-density memory power delivery, and industrial DC distribution systems requiring stable component supply with long-term lifecycle assurance.
Supply support for LTC1709EG-85 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, manufacturing continuity, and qualification for all Linear power management ICs.
The LTC1709EG-85 belongs to Linear's high-current PolyPhase® controller family, engineered specifically for CPU/GPU core voltage regulation in enterprise computing platforms demanding tight accuracy, fast transient response, and multi-rail coordination.
FAQ
What is the maximum supported input voltage for the LTC1709EG-85?
The LTC1709EG-85 specifies an absolute maximum input supply voltage (VIN) of 36V, with recommended operating range from 4V to 36V. Exceeding 36V risks permanent damage to internal circuitry including the RUN/SS, EAIN, and SENSE pins. For reliable 28V operation - common in server backplanes - external MOSFET voltage ratings must be independently verified per Figure 1 design.
How does the LTC1709EG-85 achieve current sharing between its two phases?
The LTC1709EG-85 achieves inherent current sharing through identical current-mode control architecture per phase: each channel uses matched internal current comparators referenced to the same ITH voltage, synchronized clock edges, and independent SENSE+/- inputs. No external current-sharing resistors or balun transformers are needed - sharing accuracy remains within ±5% across load and temperature when using matched external components.
Can the LTC1709EG-85 operate without an external crystal or oscillator?
Yes - the LTC1709EG-85 contains a fully integrated, PLL-based oscillator with no external crystal required. Frequency is set either by applying a DC voltage (0–2.4V) to PLLFLTR or by injecting a clean square wave into PLLIN for external synchronization. Leaving PLLIN open defaults the oscillator to minimum frequency (~120kHz), confirmed in the Electrical Characteristics table.
What is the purpose of the VDIFFOUT, VOS+, and VOS– pins on the LTC1709EG-85?
These pins implement a precision differential amplifier for true remote output voltage sensing: VOS+ and VOS– connect directly to the load's positive and negative output terminals, VDIFFOUT delivers the amplified difference to the EAIN feedback network. This compensates for IR drops across PCB traces and connectors - critical for maintaining ±1% regulation at 40A where even 50mΩ resistance causes 2V drop.
Does the LTC1709EG-85 support both ceramic and electrolytic output capacitors?
Yes - the OPTI-LOOP compensation architecture in the LTC1709EG-85 is explicitly designed to stabilize the control loop across a wide range of output capacitor types and ESR values (1mΩ to 50mΩ), including low-ESR ceramics (e.g., 100µF X5R) and bulk aluminum polymer electrolytics (e.g., 1000µF). No external compensation components are required regardless of capacitor choice.
LTC1709EG-85#TRPBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 36-SSOP (0.209", 5.30mm Width)
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Output Type:
- Transistor Driver
- Function:
- Step-Down
- Output Configuration:
- Positive
- Topology:
- Buck
- Number of Outputs:
- 2
- Output Phases:
- 2
- Voltage - Supply (Vcc/Vdd):
- 4V ~ 36V
- Frequency - Switching:
- 140kHz ~ 310kHz
- Duty Cycle (Max):
- 99.5%
- 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:
- 36-SSOP
LTC1709EG-85#TRPBF FAQ
1.How can I place an order for LTC1709EG-85#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC1709EG-85#TRPBF 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 LTC1709EG-85#TRPBF reliable?
The price and inventory of LTC1709EG-85#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC1709EG-85#TRPBF is usually 5 days.
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LTC1709EG-85#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC1709EG-85#TRPBF 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 LTC1709EG-85#TRPBF?
For technical support, including LTC1709EG-85#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC1709EG-85#TRPBF requirements.
6.How does Aetrix verify that LTC1709EG-85#TRPBF is sourced from the original manufacturer or authorized distributors?
All LTC1709EG-85#TRPBF 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 LTC1709EG-85#TRPBF meets industry standards.
7.What is the process for return or replacement of LTC1709EG-85#TRPBF?
All LTC1709EG-85#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC1709EG-85#TRPBF, 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 LTC1709EG-85#TRPBF part is unused and in its original packaging.
Return procedure for LTC1709EG-85#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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