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Texas Instruments LM87CIMT/NOPB
- Part No.:
- LM87CIMT/NOPB
- Manufacturer:
- Texas Instruments
- Category:
- Thermal Management
- Package:
- 24-TSSOP (0.173", 4.40mm Width)
- Datasheet:
-
LM87CIMT/NOPB.pdf
- Description:
- IC MONITOR SYS HARDWARE 24TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:1,531
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Product details
Overview
LM87CIMT/NOPB from Texas Instruments is a highly integrated hardware monitor IC for server, workstation, and PC motherboard thermal and power management. It performs 8-channel voltage monitoring (±2% error), dual remote diode temperature sensing (±4 °C max), on-chip temperature measurement (±3 °C), fan speed counting (2 channels), and closed-loop fan control via 8-bit DAC (0–2.5 V output). It operates from 2.8–3.8 V and interfaces via SMBus/I²C.
For engineers reviewing the LM87CIMT/NOPB datasheet, LM87CIMT/NOPB pinout, LM87CIMT/NOPB application, or LM87CIMT/NOPB equivalent, key selection considerations include its 24-pin TSSOP package, programmable VID/IRQ inputs, chassis intrusion detection, watchdog-triggered INT# and THERM# interrupts, and support for Pentium-class processor voltage identification and thermal throttling.
Technical Context
The LM87CIMT/NOPB integrates a slow-speed ΣΔ ADC for stable 8-bit voltage and temperature conversion in noisy environments, with dedicated analog front-end scaling resistors for +12 V, +5 V, +3.3 V, +2.5 V, Vccp1, and Vccp2 inputs. Its dual-purpose FAN1/FAN2 pins function as either Schmitt-trigger tachometer inputs (0–V+ range) or 0–2.5 V analog inputs, supporting fan RPM measurement down to ~1100 RPM at full-scale count 153.
It implements two independent interrupt outputs: INT# (fully maskable, multi-source), and THERM# (dedicated to temperature limit violations only). The device uses an internal asynchronous clock for ADC and fan counters, while SMBus/I²C communication relies solely on external SMBCLK/SMBData timing - compliant with tTIMEOUT = 25–35 ms bus reset and 2.5 μs minimum clock period.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Supply Voltage | 2.8–3.8 V - Enables direct connection to +3.3 V system rail with minimal external regulation. |
| Voltage Monitoring Error | ±2% (max) - Ensures accurate detection of out-of-spec supply rails (e.g., +12 V, +5 V, Vccp) for reliable system protection. |
| Internal Temp Error | ±3 °C (−40 to +125 °C) - Supports precise CPU/motherboard junction temperature tracking without external calibration. |
| Remote Temp Error | ±4 °C (max) - Validated for 2N3904 or Pentium diode sensors, enabling accurate remote die temperature monitoring. |
| Fan Input Range | 0–V+ with V+/2 threshold - Accommodates standard open-collector tachometer outputs across full supply range. |
| DAC Output Range | 0–2.5 V - Directly drives common PWM fan controllers or linear fan drivers without level-shifting. |
| SMBus/I²C Compatibility | Full protocol compliance with timeout reset (25–35 ms) - Ensures robust communication in multi-device bus systems. |
Pinout & Package
LM87CIMT/NOPB is housed in a 24-pin TSSOP (PW0024A) package with 0.65 mm pitch, optimized for high-density motherboard layouts and thermal performance (θJA = 95 °C/W).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| ADD/NTEST_OUT | Address select / NAND test output | Configures SMBus address LSBs (00/01/10); enables board-level connectivity testing when driven externally. |
| THERM# | Open-drain thermal interrupt | Asserts low on temperature limit violation only; internally pulled up to 100 kΩ - connects directly to CPU thermal throttle input. |
| SMBData | Bidirectional serial data | Open-drain I/O compatible with SMBus/I²C; supports multi-master arbitration and alert response protocol. |
| SMBCLK | Serial clock input | Asynchronous to internal ADC/fan clocks; defines timing for all register reads/writes per SMBus spec. |
| FAN1/AIN1−, FAN2/AIN2 | Programmable tachometer/analog input | Configurable via Channel Mode Register: Schmitt-trigger mode for fan pulses or 0–2.5 V analog sensing. |
| CI | Chassis intrusion latch input/output | Accepts active-high intrusion signal; also provides 20 ms min pulse via CI Clear Register (46h) for alarm signaling. |
| GND | Analog/digital ground reference | Common return for all analog inputs, DAC output, and internal circuitry - requires low-noise analog plane routing. |
| V+ | +2.8–3.8 V power supply | Bypassed with 10 μF + 0.1 μF capacitors; powers entire IC including ADC, DAC, and digital logic. |
| INT#/ALERT# | Maskable multi-source interrupt | Active-low open-drain output; configurable to assert on any monitored event (voltage, temp, fan, VID, CI) except THERM#-only triggers. |
| DACOut/NTEST_IN | DAC output / NAND test input | 0–2.5 V 8-bit DAC output; forced high at power-up enters NAND Tree Test mode for PCB continuity verification. |
| RESET# | Open-drain master reset | 5 mA driver, active-low, 20 ms min pulse; serves as both system reset source and power-on reset input. |
| D1−, D1+, D2−, D2+ | Remote diode sense terminals | Four dedicated pins for two independent external temperature diodes (e.g., CPU/GPU die sensors). |
| +12Vin, +5Vin, +2.5Vin, Vccp1, Vccp2 | Scalable voltage inputs | Internally resistor-divided for direct monitoring of standard PC power rails without external components. |
| VID0–VID4/IRQ0–IRQ4 | Dual-function digital inputs | Read Pentium/PRO/PII VID codes for core voltage identification or serve as general-purpose interrupt request lines. |
Key Features
| Feature | Design Value |
|---|---|
| 8-channel voltage monitoring with scaling resistors | Eliminates need for external dividers on +12 V, +5 V, +3.3 V, +2.5 V, Vccp1, Vccp2 - reduces BOM count and layout area. |
| Dual remote diode temperature sensing | Supports simultaneous CPU and GPU die temperature monitoring using standard 2N3904 or integrated diodes - enables per-component thermal management. |
| On-chip ΣΔ ADC architecture | Provides noise-immune 8-bit conversion of analog inputs in electrically noisy PC environments - avoids false alarms during high-current transients. |
| Programmable fan tachometer inputs | Enables RPM measurement across wide speed range (1100–8800 RPM) with selectable divisors - adapts to diverse cooling solutions without firmware changes. |
| Dedicated THERM# interrupt output | Hardware-isolated thermal alert line allows immediate CPU throttling or shutdown without software polling - critical for safety-critical thermal events. |
Applications
| Server Thermal Management | Workstation Power Integrity |
|---|---|
Use Scenario: Real-time monitoring of CPU, memory, and VRM temperatures alongside +12 V, +5 V, and Vccp supplies in 1U/2U rack servers. IC Role / Device Role / Timing Role: Central hardware monitor providing synchronized voltage, temperature, and fan telemetry to BMC/IPMI controller via SMBus. Use Value: Enables predictive fan speed control and early warning of thermal runaway or supply droop before system instability occurs. | Use Scenario: Continuous validation of multi-rail power delivery (Vccp1/Vccp2, +3.3 V, +2.5 V) and GPU diode temperature in high-end CAD/CAM workstations. IC Role / Device Role / Timing Role: Analog acquisition engine feeding real-time health data to host OS or embedded microcontroller for dynamic power budgeting. Use Value: Prevents undervoltage-induced computation errors and thermal throttling by triggering corrective action within 280 ms monitoring cycle time. |
| PC Motherboard Health Monitoring | Networking Equipment Environmental Control |
Use Scenario: Integration into ATX motherboard designs to monitor core voltages, chassis temperature, and case fan speeds during boot and runtime. IC Role / Device Role / Timing Role: System-level sensor hub interfacing with BIOS/UEFI firmware to report hardware status and trigger SMI-based thermal responses. Use Value: Provides hardware-enforced watchdog limits that persist even if OS hangs - ensures safe shutdown on overtemperature or fan failure. | Use Scenario: Monitoring power supply stability and ambient/processor temperature in carrier-grade Ethernet switches and routers. IC Role / Device Role / Timing Role: Standalone environmental supervisor managing fan profiles and issuing SNMP-trap-capable alerts via SMBus-connected microcontroller. Use Value: Maintains optimal operating temperature under variable load conditions while meeting NEBS Level 3 thermal reliability requirements. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar hardware monitoring applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LM92CIMM/NOPB | Single-channel remote diode sensor, no voltage monitoring or fan control; 12-bit temperature resolution (0.0625 °C) | Used where only high-accuracy local/remote temperature logging is required - lacks power/fan subsystem integration | Select when precision thermal profiling is primary need and voltage/fan functions are handled elsewhere. |
| ADM1027ARUZ | 12-bit ADC, 3 remote diode channels, integrated PWM fan controller (not DAC), Intel SMBus Alert-only interface | Targeted at Intel platform-specific implementations requiring Alert Response Protocol and tighter fan control granularity | Choose for Intel-centric designs needing Alert Response and higher-resolution thermal/voltage monitoring than LM87CIMT/NOPB offers. |
Compared with LM92CIMM/NOPB and ADM1027ARUZ, the LM87CIMT/NOPB uniquely balances 8-voltage-channel monitoring, dual remote diode sensing, and DAC-based fan control in a single 24-pin TSSOP - making it optimal for cost-sensitive, space-constrained PC/server motherboards requiring full-system health supervision without external support ICs.
Availability
LM87CIMT/NOPB is available at Aetrix Electronics and suitable for server thermal management, workstation power integrity, and PC motherboard health monitoring requiring stable component supply and long-term industrial availability.
Supply support for LM87CIMT/NOPB 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
Texas Instruments is a global semiconductor leader delivering analog, embedded processing, and connectivity solutions for industrial, automotive, and computing applications.
The LM87CIMT/NOPB belongs to TI's hardware monitoring IC product line, designed specifically for real-time voltage, temperature, and fan supervision in x86-based computing platforms - emphasizing SMBus compatibility, noise immunity, and integration density.
FAQ
What is the SMBus address configuration method for LM87CIMT/NOPB?
The LM87CIMT/NOPB SMBus address is fixed as 01011XY, where XY bits are set by the ADD pin state at power-up: grounded → 10, tied to V+ → 01, floating → 00. This allows up to three LM87CIMT/NOPB devices on the same bus without address conflict. The ADD pin must be connected through a 5 kΩ series resistor to preserve NAND Tree test functionality.
Does LM87CIMT/NOPB support both SMBus and I²C protocols?
Yes, LM87CIMT/NOPB fully supports both SMBus 1.1 and standard I²C protocols, including clock stretching, alert response, and timeout reset (25–35 ms). Its open-drain SMBData/SMBCLK pins meet voltage and timing specs for both buses, enabling interoperability with host controllers designed for either interface.
How does LM87CIMT/NOPB handle fan speed measurement and control?
LM87CIMT/NOPB measures fan speed using two Schmitt-trigger inputs (FAN1/FAN2) that count tachometer pulses with an 8-bit counter; nominal speeds (1100–8800 RPM) are set via programmable divisors. Fan control is implemented via its 8-bit DAC (0–2.5 V output), which directly interfaces with common voltage-controlled fan drivers or PWM generator circuits.
What is the purpose of the CI pin on LM87CIMT/NOPB?
The CI (Chassis Intrusion) pin on LM87CIMT/NOPB serves dual roles: as an input, it latches an active-high signal from a case-open switch; as an output, it can generate a 20 ms minimum low pulse via Bit 7 of the CI Clear Register (46h) to signal intrusion events to the system or log security breaches.
Can LM87CIMT/NOPB monitor negative supply voltages like −12 V or −5 V?
LM87CIMT/NOPB does not directly monitor negative voltages, but −12 V or −5 V rails can be measured using an external resistor divider applied to the +AIN1 or +AIN2 inputs (0–2.5 V full scale), converting the negative voltage into a positive range acceptable to the ADC - requiring careful offset and scaling design per application.
LM87CIMT/NOPB Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- -
- Package/Case:
- 24-TSSOP (0.173", 4.40mm Width)
- Packaging:
- Tube
- Product Status:
- Obsolete
- Function:
- Hardware Monitor
- Sensor Type:
- Internal and External
- Sensing Temperature:
- -40°C ~ 125°C
- Accuracy:
- ±3°C Local(Typ), ±4°C Remote(Max)
- Topology:
- ADC (Sigma Delta), Comparator, Fan Speed Counter, Register Bank
- Output Type:
- 2-Wire Serial, I2C/SMBUS
- Output Alarm:
- No
- Output Fan:
- Yes
- Voltage - Supply:
- 2.8V ~ 3.8V
- Operating Temperature:
- -40°C ~ 125°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 24-TSSOP
LM87CIMT/NOPB FAQ
1.How can I place an order for LM87CIMT/NOPB through Aetrix?
Please submit a Request for Quotation (RFQ) for LM87CIMT/NOPB 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 LM87CIMT/NOPB reliable?
The price and inventory of LM87CIMT/NOPB are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LM87CIMT/NOPB is usually 5 days.
3.What payment methods are accepted for LM87CIMT/NOPB?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LM87CIMT/NOPB transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LM87CIMT/NOPB?
LM87CIMT/NOPB orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM87CIMT/NOPB 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 LM87CIMT/NOPB?
For technical support, including LM87CIMT/NOPB datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM87CIMT/NOPB requirements.
6.How does Aetrix verify that LM87CIMT/NOPB is sourced from the original manufacturer or authorized distributors?
All LM87CIMT/NOPB 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 LM87CIMT/NOPB meets industry standards.
7.What is the process for return or replacement of LM87CIMT/NOPB?
All LM87CIMT/NOPB units undergo pre-shipment inspection (PSI). If there is an issue with LM87CIMT/NOPB, 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 LM87CIMT/NOPB part is unused and in its original packaging.
Return procedure for LM87CIMT/NOPB:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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