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Analog Devices Inc. LTC1840CGN#PBF
- Part No.:
- LTC1840CGN#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- Motor Drivers, Controllers
- Package:
- 16-SSOP (0.154", 3.90mm Width)
- Datasheet:
-
LTC1840CGN#PBF.pdf
- Description:
- IC MOTOR DRVR 2.7V-5.75V 16SSOP
- Quantity:
- Payment:
- Shipping:
Inventory:105
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Product details
Overview
LTC1840CGN#PBF from Analog Devices (acquired Linear Technology) is a dual fan controller IC with two 8-bit current-output DACs, two programmable tachometer interfaces, and four GPIO pins. It operates from a single 2.7V–5.75V supply, delivers guaranteed monotonic 100µA full-scale DAC output, supports I²C/SMBus communication, and targets thermal management in servers and desktop computers.
For engineers reviewing the LTC1840CGN#PBF datasheet, LTC1840CGN#PBF pinout, LTC1840CGN#PBF application, or LTC1840CGN#PBF equivalent, key selection criteria include its 16-pin SSOP package, 2-wire interface watchdog timer, BLAST pin-triggered DAC override, tachometer frequency division (25kHz/12.5kHz/6.25kHz/3.125kHz), and fault register reporting for TACH overflow and GPIO state changes.
Technical Context
The LTC1840CGN#PBF integrates an internal 50kHz oscillator divided by 2/4/8/16 to generate tachometer clock inputs, enabling precise fan speed measurement across two independent channels. Its DACs sink 0–100µA with ±0.9 LSB DNL and ±4 LSB INL, maintaining compliance down to 1.1V output voltage while interfacing directly with external switching regulator feedback nodes.
GPIO pins operate as CMOS digital inputs or open-drain pull-down outputs (10mA sink capability), configurable via serial interface registers; BLAST pin provides hardware-level DAC override and enables/disables the serial access watchdog timer (≈90s timeout). Fault detection includes TACH counter overflow (255 max), GPIO state-change events, and UVLO-induced shutdown.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Supply Voltage | 2.7V to 5.75V - supports direct connection to common logic rails without level-shifting. |
| DAC Resolution & Output | 8-bit, 0–100µA sinking - enables precise analog control of external DC/DC converter feedback voltage. |
| Tachometer Input Range | Programmable 3.125kHz–25kHz counting window - accommodates standard 2-pulse-per-revolution fan tach signals. |
| I²C/SMBus Compatibility | 0–100kHz operation, 1V logic threshold - interoperable with standard microcontroller I²C peripherals. |
| Operating Temperature | 0°C to 70°C (Commercial grade) - validated for server/desktop ambient environments. |
| Package | 16-lead SSOP (GN), 0.150" width - surface-mount compatible with standard PCB assembly processes. |
| GPIO Sink Current | 10mA at 0.7V drop - sufficient to drive indicator LEDs with external series resistors. |
Pinout & Package
Package: 16-lead plastic SSOP (GN), 0.150" body width, JEDEC MS-013AC compliant.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| SCL | Serial Clock Input | Asynchronous master-controlled clock line; 1V threshold enables robust noise immunity on shared bus. |
| SDA | Serial Data Bidirectional | Open-drain I²C data line; requires external pull-up; handles address, command, and data transfer. |
| A1, A0 | Three-State Address Inputs | Each pin accepts VCC, GND, or NC to configure one of nine unique I²C slave addresses (111xxxxx format). |
| FAULT | Fault Indicator Output | Open-drain active-low signal asserting on TACH overflow, GPIO fault, BLAST event, or UVLO condition. |
| GPIO1–GPIO4 | Configurable I/O Terminals | Default to non-faulting CMOS inputs at power-up; programmable as blink-capable pull-down outputs. |
| IDACOUTA/B | Current DAC Outputs | High-impedance 0–100µA sinking outputs; maintain regulation down to 1.1V and up to VCC+0.75V. |
| TACHA/TACHB | Fan Tachometer Inputs | Rising-edge sensitive digital inputs; count intervals between pulses and store result in accessible registers. |
| BLAST | Blast/Timer Control Input | 1V threshold pin forcing immediate DAC full-scale output and enabling serial watchdog timer when high. |
| VCC, GND | Power Supply | Decoupling requires 10µF tantalum + 0.1µF ceramic per datasheet layout guidance. |
Key Features
| Feature | Design Value |
|---|---|
| Guaranteed Monotonic DACs | ±0.9 LSB DNL ensures no code-to-code speed reversals during closed-loop fan velocity control. |
| Programmable Tachometer Clock | Four selectable frequencies (25/12.5/6.25/3.125kHz) allow optimization for fan RPM range and resolution trade-offs. |
| Serial Interface Watchdog Timer | ~90s timeout triggers BLAST and FAULT if no I²C activity - prevents unresponsive thermal control in system hangs. |
| Known Power-Up State | All registers initialize to documented defaults (e.g., GPIOs as inputs, TACH FLTEN disabled, DIV=16), eliminating startup uncertainty. |
| Hardware Blast Function | Single-pin assertion forces both DACs to 100µA instantly - enables emergency fan ramp-up independent of firmware. |
Applications
| Server Rack Thermal Management | Desktop PC Fan Control |
|---|---|
Use Scenario: Real-time monitoring and adjustment of multiple chassis fans in 1U/2U rack-mounted servers under variable CPU/GPU load. IC Role / Device Role / Timing Role: Dual tachometer inputs track two independent fan speeds; DAC outputs regulate switching controllers powering each fan bank. Use Value: Enables closed-loop velocity control with fault detection on stalled fans, reducing acoustic noise and improving thermal reliability without host CPU intervention. |
Use Scenario: Adaptive cooling of CPU, GPU, and chipset in consumer desktop motherboards with BIOS or EC-managed thermal policy. IC Role / Device Role / Timing Role: Acts as dedicated fan controller interfacing with motherboard SMBus; GPIOs drive status LEDs or report chassis intrusion. Use Value: Offloads thermal management from main processor, supports low-power S3/S4 states, and provides deterministic response to overtemperature events. |
| Industrial Power Supply Cooling | Network Equipment Fan Supervision |
Use Scenario: Thermal regulation of forced-air-cooled AC/DC and DC/DC power modules in telecom or industrial enclosures. IC Role / Device Role / Timing Role: Monitors fan health via tachometer counters and adjusts drive current to maintain setpoint airflow despite dust accumulation or bearing wear. Use Value: Prevents thermal runaway by detecting fan stall before PSU overtemperature shutdown, extending system uptime and service intervals. |
Use Scenario: Redundant fan supervision in modular switches/routers where multiple fans serve separate airflow zones. IC Role / Device Role / Timing Role: Aggregates tachometer data from up to four fans (via wired-OR on TACHA/TACHB) and reports faults to system management controller. Use Value: Enables hot-swap-aware fan replacement alerts and coordinated speed balancing across zones using GPIO signaling. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar fan controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC1695CMS8#PBF | Single-channel fan controller in 8-pin MSOP; lacks second tach input, GPIOs, and BLAST function; integrates linear regulator. | Targeted at space-constrained single-fan systems; no support for dual-fan closed-loop or hardware blast override. | Select when board area is critical and only one fan requires regulation with integrated 0.75Ω PMOS driver. |
| ADM1032ARMZ-REEL | Temperature + fan speed monitor (no DAC outputs); uses PWM fan control instead of current DAC; 10-bit ADC for temp sensing. | Requires external PWM fan drivers; provides temperature-based speed lookup tables but no analog DAC interface to regulators. | Select when thermal monitoring dominates requirements and fan control is handled by discrete PWM generators or MCU GPIOs. |
Compared with LTC1840CGN#PBF, LTC1695CMS8#PBF reduces integration for size-constrained designs but sacrifices dual-fan coordination and hardware safety features, while ADM1032ARMZ-REEL shifts control architecture from analog DAC-based regulation to digital PWM, requiring redesign of fan drive circuitry and losing the BLAST fail-safe mechanism.
Availability
LTC1840CGN#PBF is available at Aetrix Electronics and suitable for server thermal management, desktop PC cooling systems, and industrial power supply fan control requiring stable component supply and long-term industrial lifecycle support.
Supply support for LTC1840CGN#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 its precision analog and power management product lines with full technical documentation and long-term support commitments.
The LTC1840CGN#PBF belongs to Linear's legacy thermal management IC family, designed specifically for closed-loop fan speed control in computing and communications infrastructure where reliability, fault reporting, and hardware-level safety overrides are critical.
FAQ
What is the operating temperature range of the LTC1840CGN#PBF?
The LTC1840CGN#PBF is rated for commercial-grade operation from 0°C to 70°C. This range is validated across all electrical specifications including DAC accuracy, tachometer timing, and GPIO performance. The device features thermal shutdown protection and is intended for use in controlled-environment applications such as desktop PCs and enterprise servers where ambient temperatures remain within this envelope.
How does the BLAST pin function on the LTC1840CGN#PBF?
The BLAST pin on the LTC1840CGN#PBF has dual functionality: it forces both IDACOUTA and IDACOUTB to full-scale 100µA output upon power-up if held high, and it gates the serial interface watchdog timer. When asserted, it also sets the BLAST bit in the fault register. The pin has a fixed ~1V logic threshold independent of VCC, allowing reliable triggering even with varying supply conditions. A write to the fault register clears the BLAST flag.
Can the LTC1840CGN#PBF control fans with different tachometer pulse rates?
Yes, the LTC1840CGN#PBF supports four programmable tachometer counting frequencies - 25kHz, 12.5kHz, 6.25kHz, and 3.125kHz - selected via DIV1/DIV0 bits in the STATUS register. This allows adaptation to fans producing 2, 3, or 4 pulses per revolution across RPM ranges from ~300 RPM to ~7500 RPM. The tach counters store values up to 255 and auto-load 0xFF on overflow for immediate stalled-fan detection.
What GPIO configurations are supported by the LTC1840CGN#PBF?
The LTC1840CGN#PBF supports four GPIO pins (GPIO1–GPIO4) that default to CMOS digital inputs at power-up. They can be reconfigured via the GPIO Setup register as open-drain pull-down outputs capable of sinking 10mA, with optional 1.5Hz blinking enabled per pin. Each GPIO can also be set to generate a latched fault on logic-state change, cleared only by software write to the fault register or disabling FLTEN.
Is the LTC1840CGN#PBF pin-compatible with other Linear fan controllers?
No, the LTC1840CGN#PBF is not pin-compatible with other Linear fan controllers such as the LTC1695 or LTC1771. Its 16-pin SSOP layout, dual DAC outputs, dedicated TACHA/TACHB inputs, and BLAST pin assignment are unique to this device. Migration requires PCB layout revision and firmware adaptation due to differences in register map, interface behavior, and functional scope.
LTC1840CGN#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 16-SSOP (0.154", 3.90mm Width)
- Packaging:
- Tube
- Product Status:
- Active
- Motor Type - Stepper:
- -
- Motor Type - AC, DC:
- Brushed DC
- Function:
- Controller - Speed
- Output Configuration:
- Pre-Driver - High Side (2)
- Interface:
- I2C, SMBus
- Technology:
- PMOS
- Step Resolution:
- -
- Applications:
- Fan Controller
- Current - Output:
- -
- Voltage - Supply:
- 2.7V ~ 5.75V
- Voltage - Load:
- -
- Operating Temperature:
- 0°C ~ 70°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 16-SSOP
LTC1840CGN#PBF FAQ
1.How can I place an order for LTC1840CGN#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC1840CGN#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 LTC1840CGN#PBF reliable?
The price and inventory of LTC1840CGN#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC1840CGN#PBF is usually 5 days.
3.What payment methods are accepted for LTC1840CGN#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC1840CGN#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC1840CGN#PBF?
LTC1840CGN#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC1840CGN#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 LTC1840CGN#PBF?
For technical support, including LTC1840CGN#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC1840CGN#PBF requirements.
6.How does Aetrix verify that LTC1840CGN#PBF is sourced from the original manufacturer or authorized distributors?
All LTC1840CGN#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 LTC1840CGN#PBF meets industry standards.
7.What is the process for return or replacement of LTC1840CGN#PBF?
All LTC1840CGN#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC1840CGN#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 LTC1840CGN#PBF part is unused and in its original packaging.
Return procedure for LTC1840CGN#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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