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Texas Instruments LM90CIMMX
- Part No.:
- LM90CIMMX
- Manufacturer:
- Texas Instruments
- Category:
- Analog and Digital Output
- Package:
- 8-TSSOP, 8-MSOP (0.118", 3.00mm Width)
- Datasheet:
-
LM90CIMMX.pdf
- Description:
- SENSOR DIGITAL 0C-85C 8VSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:2,207
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Product details
Overview
LM90CIMMX from Texas Instruments is a dual-sensing ±3°C accurate digital temperature sensor with local die and remote diode junction measurement capability, 11-bit remote/8-bit local resolution, SMBus 2.0 interface, and dedicated T_CRIT_A shutdown output - used for real-time thermal monitoring in CPU/GPU thermal management subsystems.
For engineers reviewing the LM90CIMMX datasheet, LM90CIMMX pinout, LM90CIMMX application, or LM90CIMMX equivalent, key selection considerations include remote diode accuracy across 0°C–125°C ambient, open-drain ALERT/T_CRIT_A timing behavior, SMBus timeout compliance, and offset register compensation for non-ideal diodes (e.g., Pentium III 1.008 ideality factor).
Technical Context
The LM90CIMMX implements a delta-VBE-based sensing architecture with separate 10-bit-plus-sign ADC paths for local and remote channels, supporting simultaneous conversion of both temperatures in ~31.25 ms per cycle. Its SMBus 2.0 slave interface operates at 10–100 kHz with TIMEOUT reset support and ARA alert response protocol compliance.
It features dual independent digital comparators (HIGH/LOW/T_CRIT) for local and remote readings, hysteresis-controlled T_CRIT_A output with TH-register programmability, and diode fault detection that loads RTHB/RTLB with +127°C or −128°C codes on open/short conditions - all managed via 7-bit fixed slave address 1001100b.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Remote Temp Accuracy | ±3.0°C max (TA=30–50°C, TD=60–100°C), factory-trimmed for 1.008 diode ideality - enables direct use with mobile Pentium III thermal diodes without calibration. |
| Local Temp Accuracy | ±4.0°C max (TA=25–125°C), excludes self-heating effects - requires thermal layout consideration for high-power PCB zones. |
| Resolution | Remote: 0.125°C (11-bit left-justified); Local: 1°C (8-bit) - supports fine-grained fan control thresholds and coarse system-level alerts. |
| Supply Range | 3.0 V to 3.6 V - compatible with standard 3.3 V logic rails; power-on reset triggers at 1.8–2.4 V threshold. |
| Quiescent Current | 0.8 mA typ at 16 Hz conversion rate - enables low-overhead integration into always-on thermal supervision circuits. |
| SMBus Timing | tTIMEOUT = 25–35 ms low pulse resets state machine - prevents bus lockup during communication faults. |
| Operating Temp | 0°C to +125°C ambient - validated for laptop/desktop/server motherboard environments near VRMs and CPUs. |
Pinout & Package
LM90CIMMX uses an 8-pin VSSOP (DGK) package with 0.65 mm pitch and exposed thermal pad - optimized for compact thermal sensor placement near heat sources.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VDD (Pin 1) | Positive supply input | Accepts 3.0–3.6 V; internal POR circuit activates below 2.4 V - must be decoupled with ≥0.1 µF ceramic near pin. |
| D+ (Pin 2) | Diode current source | Drives 110–315 µA into remote diode anode; sensitive to >50 mV forward bias - requires short trace routing. |
| D− (Pin 3) | Diode return sink | Completes remote diode current path; D− voltage ≤0.7 V ensures valid measurement - connects directly to cathode. |
| T_CRIT_A (Pin 4) | Critical temp alarm output | Open-drain, active-low; asserts when any temp exceeds T_CRIT register value - drives hardware shutdown logic without software intervention. |
| GND (Pin 5) | Power ground | Reference for all analog/digital blocks; must tie to low-impedance system ground plane to minimize noise coupling. |
| ALERT (Pin 6) | Configurable interrupt/alert | Open-drain SMBus-compliant output; supports comparator/interrupt/ARA modes - requires external pull-up (≤82 kΩ @ 3.0 V). |
| SMBData (Pin 7) | SMBus bidirectional data | Open-drain I/O; complies with SMBus 2.0 voltage thresholds (VIH ≥2.1 V, VIL ≤0.8 V) - shares bus with other slaves. |
| SMBCLK (Pin 8) | SMBus clock input | Asynchronous input only; no clock stretching supported - master controls timing; hysteresis ≥400 mV rejects noise. |
Key Features
| Feature | Design Value |
|---|---|
| Offset register compensation | RTOLB/RTOHB registers adjust remote reading for diode non-ideality (e.g., 1.008 vs. 1.000) - eliminates software correction in host firmware. |
| Diode fault detection | Auto-detects open-circuit (loads RTHB=+127°C) or short-circuit (loads RTHB=−128°C) - provides unambiguous hardware fault signaling without polling. |
| T_CRIT_A hysteresis control | TH register sets hysteresis width (T_CRIT − TH) - prevents chatter during thermal transients near critical shutdown threshold. |
| Three ALERT operating modes | Configurable as standalone comparator, interrupt flag, or SMBus ARA responder - adapts to host controller architecture without external logic. |
| Power-on defaults | Preloaded LHS/RHS=+70°C, LCS/RCS=+85°C, conversion rate=16 Hz - enables immediate thermal supervision after power-up, no initialization required. |
Applications
| Laptop CPU Thermal Management | Server Blade Fan Control |
|---|---|
Use Scenario: Real-time monitoring of mobile processor die temperature and discrete GPU thermal diode in thin-profile notebooks. IC Role / Device Role / Timing Role: Dual-channel temperature sensor providing local (LM90CIMMX die) and remote (CPU diode) readings every 31.25 ms - feeds closed-loop fan speed algorithm. Use Value: ±3°C remote accuracy at 60–100°C junction range ensures reliable throttling before thermal violation; T_CRIT_A directly triggers VRM shutdown. | Use Scenario: Distributed thermal supervision across multi-socket server blades with hot-swap capability and redundant fans. IC Role / Device Role / Timing Role: SMBus slave device reporting local board ambient and remote ASIC junction temps to baseboard management controller (BMC). Use Value: ARA-compatible ALERT allows BMC to identify LM90CIMMX among dozens of sensors on shared bus; open-drain outputs tolerate mixed-voltage domains. |
| Workstation GPU Diode Monitoring | Industrial Embedded Controller |
Use Scenario: High-precision thermal feedback for air-cooled workstation GPUs using discrete NPN transistor junctions as remote sensors. IC Role / Device Role / Timing Role: Remote diode interface with programmable offset register - compensates for 2N3904 transistor non-ideality mismatch versus Pentium III reference. Use Value: Offset register eliminates need for per-unit calibration; 0.125°C resolution enables sub-degree fan ramping granularity. | Use Scenario: Long-life thermal watchdog in fanless industrial PCs where silent operation and reliability are mandatory. IC Role / Device Role / Timing Role: Always-on local temperature monitor with shutdown-capable T_CRIT_A output - operates continuously at 0.8 mA quiescent current. Use Value: Power-on default T_CRIT=+85°C provides immediate overtemperature protection; shutdown mode draws only 315 µA for battery-backed operation. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar dual-channel digital temperature sensor applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LM86CIMM | Pin- and register-compatible; identical SMBus interface and pinout; same ±3°C remote accuracy but lacks diode fault detection circuitry. | No automatic open/short diode reporting - requires host firmware polling of status bits to infer faults. | Select LM86CIMM only if diode fault detection is unnecessary and legacy design reuse is prioritized. |
| MAX6657ESA+ | Same 8-pin SO package; SMBus-compatible; ±4°C remote accuracy (wider tolerance); no T_CRIT_A output - ALERT only. | Requires external logic or host MCU to implement critical shutdown - no hardware-level T_CRIT assertion. | Choose MAX6657ESA+ when cost sensitivity outweighs need for autonomous shutdown capability. |
Compared with LM86CIMM and MAX6657ESA+, the LM90CIMMX uniquely delivers integrated diode fault detection, dedicated T_CRIT_A hardware shutdown output, and factory-trimmed 1.008 ideality compensation - reducing firmware complexity and improving system-level thermal safety integrity.
Availability
LM90CIMMX is available at Aetrix Electronics and suitable for laptop thermal management, server blade monitoring, and industrial embedded controller applications requiring stable component supply and long-term lifecycle support.
Supply support for LM90CIMMX 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 specializing in analog, embedded processing, and connectivity technologies with broad industrial, automotive, and computing product portfolios.
The LM90CIMMX belongs to TI's precision analog temperature sensor family, designed specifically for high-accuracy, dual-point thermal monitoring in compute-intensive platforms where junction-level thermal control directly impacts performance and reliability.
FAQ
What is the remote diode temperature accuracy specification for LM90CIMMX under typical CPU operating conditions?
The LM90CIMMX achieves ±3.0°C maximum remote diode temperature accuracy when ambient temperature (TA) is between +30°C and +50°C and remote diode junction temperature (TD) is between +60°C and +100°C - matching typical mobile CPU thermal diode operating ranges. This specification is factory-trimmed for the 1.008 non-ideality factor of the Pentium III thermal diode, and the offset register allows extension to other diodes. The LM90CIMMX datasheet confirms this accuracy applies without software calibration.
Does LM90CIMMX support true hardware-based critical temperature shutdown independent of host software?
Yes, LM90CIMMX provides autonomous hardware shutdown via the T_CRIT_A pin - an open-drain, active-low output that asserts when either local or remote temperature exceeds its respective T_CRIT register value. Unlike the ALERT output, T_CRIT_A remains asserted until temperature falls below (T_CRIT − TH), where TH is set by the hysteresis register. This enables direct connection to VRM enable pins or power sequencer inputs without MCU involvement - a core safety feature confirmed in the LM90CIMMX functional description.
How does LM90CIMMX handle remote diode connection faults such as open-circuit or short-circuit conditions?
The LM90CIMMX integrates dedicated diode fault detection: an open-circuit on D+ loads the remote temperature high byte (RTHB) with +127°C and sets the OPEN bit (D2) in the status register; a short to ground or D− loads RTHB with −128°C. Neither condition activates T_CRIT_A, but both trigger ALERT if corresponding limit registers are configured. This behavior is explicitly documented in the LM90CIMMX datasheet's "DIODE FAULT DETECTION" section and distinguishes it from legacy sensors that report 0°C on shorts.
Can LM90CIMMX operate on a shared SMBus with other devices without bus contention or false alerts?
Yes, LM90CIMMX fully supports SMBus 2.0 ARA (Alert Response Address) protocol: when multiple devices assert ALERT simultaneously, the master sends ARA (0001100b), and each alerting device transmits its unique 7-bit address while releasing ALERT - preventing bus lockup. The LM90CIMMX disables its ALERT output after successful ARA transmission by setting the ALERT mask bit, ensuring deterministic multi-device arbitration. This is verified in the "ALERT Output as an SMBus ALERT" section of the LM90CIMMX datasheet.
What are the power supply requirements and quiescent current characteristics of LM90CIMMX?
LM90CIMMX operates from 3.0 V to 3.6 V DC with a power-on reset threshold of 1.8–2.4 V. Its quiescent current is 0.8 mA typical at 16 Hz conversion rate (31.25 ms cycle), rising to 1.7 mA maximum; in shutdown mode, current drops to 315 µA. These values are measured per the LM90CIMMX electrical characteristics table and reflect actual silicon behavior - not typical estimates - enabling accurate power budgeting for always-on thermal monitoring circuits.
LM90CIMMX Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- -
- Package/Case:
- 8-TSSOP, 8-MSOP (0.118", 3.00mm Width)
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Obsolete
- Sensor Type:
- Digital, Local/Remote
- Sensing Temperature - Local:
- 0°C ~ 85°C
- Sensing Temperature - Remote:
- 0°C ~ 85°C
- Output Type:
- SMBus
- Voltage - Supply:
- 3V ~ 3.6V
- Resolution:
- 7 b (Local), 10 b (Remote)
- Features:
- One-Shot, Output Switch, Programmable Limit, Shutdown Mode, Standby Mode
- Accuracy - Highest (Lowest):
- ±4°C
- Test Condition:
- 25°C ~ 125°C
- Operating Temperature:
- 0°C ~ 125°C
- Mounting Type:
- Surface Mount
- Grade:
- -
- Qualification:
- -
- Supplier Device Package:
- 8-VSSOP
LM90CIMMX FAQ
1.How can I place an order for LM90CIMMX through Aetrix?
Please submit a Request for Quotation (RFQ) for LM90CIMMX 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 LM90CIMMX reliable?
The price and inventory of LM90CIMMX are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LM90CIMMX is usually 5 days.
3.What payment methods are accepted for LM90CIMMX?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LM90CIMMX transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LM90CIMMX?
LM90CIMMX orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM90CIMMX 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 LM90CIMMX?
For technical support, including LM90CIMMX datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM90CIMMX requirements.
6.How does Aetrix verify that LM90CIMMX is sourced from the original manufacturer or authorized distributors?
All LM90CIMMX 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 LM90CIMMX meets industry standards.
7.What is the process for return or replacement of LM90CIMMX?
All LM90CIMMX units undergo pre-shipment inspection (PSI). If there is an issue with LM90CIMMX, 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 LM90CIMMX part is unused and in its original packaging.
Return procedure for LM90CIMMX:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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