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Texas Instruments LM99CIMM
- Part No.:
- LM99CIMM
- Manufacturer:
- Texas Instruments
- Category:
- Analog and Digital Output
- Package:
- 8-TSSOP, 8-MSOP (0.118", 3.00mm Width)
- Datasheet:
-
LM99CIMM.pdf
- Description:
- SENSOR DIGITAL 0C-85C 8VSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:1,337
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Product details
Overview
LM99CIMM from Texas Instruments is an 11-bit remote diode temperature sensor IC with SMBus 2.0 interface, measuring both local die temperature (±3.0°C max error from 0°C to 85°C) and remote diode junction temperature (±1.0°C max error at TD = 120–140°C, TA = 30–50°C), delivering 0.125°C resolution for remote sensing and supporting GPU/CPU thermal shutdown via T_CRIT_A output in an 8-pin VSSOP package.
For engineers reviewing the LM99CIMM datasheet, LM99CIMM pinout, LM99CIMM application, or LM99CIMM equivalent, this page delivers verified technical context, exact pin functions, real-world thermal management use cases, and two confirmed alternative parts - all grounded in TI's SNIS129D specification and official VSSOP-8 implementation data.
Technical Context
The LM99CIMM implements a delta-VBE-based remote diode sensing architecture with a 10-bit plus sign ΔΣ ADC, digitally compensating for non-ideal diode behavior using programmable offset registers (RTOLB/RTOHB). Its dual-sensing capability operates on two distinct data formats: 8-bit two's complement for local temperature (1°C LSB), and 11-bit left-justified word for remote temperature (0.125°C LSB, shifted by +16°C).
It features dual open-drain alarm outputs - ALERT (SMBus 2.0-compliant, configurable as comparator/interrupt/ARA alert) and T_CRIT_A (dedicated critical-temperature shutdown signal with hysteresis) - both driven by independent digital comparators against user-programmable HIGH/LOW/T_CRIT limit registers for local and remote channels.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Remote Temp Accuracy | ±1.0°C max (TA = 30–50°C, TD = 120–140°C): enables precise GPU junction monitoring without calibration overhead. |
| Local Temp Accuracy | ±3.0°C max (TA = 0–85°C): sufficient for board-level ambient or IC die temperature tracking. |
| Remote Resolution | 0.125°C (11-bit format): supports fine-grained thermal throttling decisions in high-performance graphics subsystems. |
| Supply Voltage | 3.0 V to 3.6 V: compatible with standard 3.3V system rails; includes POR threshold at 1.8–2.4 V. |
| Quiescent Current | 0.8 mA typ (16 Hz conversion rate): low power draw suitable for always-on thermal supervision in embedded systems. |
| SMBus Compatibility | Fully compliant with SMBus 2.0: supports ARA protocol, timeout reset, and standard clock/data timing (10–100 kHz). |
| Conversion Time | 31.25 ms per full cycle (local + remote): deterministic update interval for predictable interrupt latency. |
Pinout & Package
LM99CIMM is housed in an 8-pin VSSOP (Very Small Outline Package) with 0.65 mm lead pitch, optimized for compact thermal sensor placement near GPUs or CPUs. Thermal resistance θJA = 210°C/W on 2 oz copper PCB.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VDD (Pin 1) | Positive supply input | Requires 0.1 µF + 100 pF bypass capacitors close to pin; bulk 10 µF nearby - critical for noise immunity during remote diode measurement. |
| D+ (Pin 2) | Diode current source | Drives base-collector junction of remote transistor (e.g., 2N3904); must be paired with 2.2 nF capacitor to D− for noise filtering. |
| D− (Pin 3) | Diode return current sink | Connects to emitter of remote diode-connected transistor; forms RC filter with D+ to suppress EMI-induced measurement errors. |
| T_CRIT_A (Pin 4) | Critical temperature alarm output | Open-drain, active-low; asserts when any sensed temperature exceeds its T_CRIT register - directly drives power supply shutdown logic. |
| GND (Pin 5) | Power supply ground | Common reference for all analog and digital circuitry; must be low-impedance connection to minimize self-heating artifacts. |
| ALERT (Pin 6) | Configurable system alert output | Open-drain, SMBus 2.0-compliant; supports three modes: comparator (auto-clear), interrupt (mask-controlled), or ARA alert (bus-wide resolution). |
| SMBData (Pin 7) | SMBus bidirectional data line | Open-drain I/O; requires external pull-up; handles command, address, and data transfer per SMBus 2.0 timing specs (tHD;DAT, tSU;DAT, etc.). |
| SMBCLK (Pin 8) | SMBus clock input | Input-only, no clock stretching; accepts 10–100 kHz clock; defines timing for all SMBus transactions including ARA response. |
Key Features
| Feature | Design Value |
|---|---|
| Remote diode offset compensation | Two 8-bit offset registers (RTOLB/RTOHB) correct for transistor non-ideality - eliminates need for external calibration across multiple thermal diodes. |
| True T_CRIT hardware comparator | Dedicated T_CRIT_A output with built-in hysteresis (programmable via TH register) ensures glitch-free shutdown signaling without software polling. |
| Three-mode ALERT functionality | Single pin supports comparator (auto-reset), interrupt (mask-gated), and SMBus ARA protocols - reduces system-level GPIO count and firmware complexity. |
| Shifted remote temperature reporting | Reports remote diode temperature as TLM99 = TDIODE − 16°C - simplifies host-side math and aligns with industry-standard GPU thermal diode conventions. |
| Diode fault detection | Monitors D+ for short-to-VDD or floating conditions and flags OPEN bit in Status Register - prevents false thermal alarms due to broken sensor connections. |
Applications
| Graphics Processor Thermal Management | Computer Processor Thermal Management |
|---|---|
|
Use Scenario: Real-time monitoring of GPU die temperature using integrated thermal diode on discrete graphics cards. IC Role / Device Role / Timing Role: Remote diode sensor interfacing with GPU's internal PNP transistor; performs 31.25 ms periodic conversions synchronized to SMBus clock. Use Value: Enables dynamic fan speed control and hard thermal shutdown at 126°C junction (via +110°C register setting), preventing silicon damage under sustained load. |
Use Scenario: Monitoring CPU package temperature in desktop/laptop motherboards where thermal diodes are embedded in processor packages. IC Role / Device Role / Timing Role: Local temperature sensor for motherboard ambient + remote sensor for CPU diode; dual-channel alerts feed BIOS thermal policy engine. Use Value: Delivers ±1.0°C accuracy at high junction temperatures (120–140°C), allowing tighter thermal margins and higher sustained boost clocks. |
| Electronic Test Equipment | Office Electronics |
|
Use Scenario: Temperature stabilization and over-temperature protection in automated test equipment (ATE) chassis housing multiple high-power instruments. IC Role / Device Role / Timing Role: System-level thermal supervisor; reads local ambient and remote heatsink diodes to trigger forced-air cooling or graceful instrument shutdown. Use Value: Uses ALERT output in interrupt mode to minimize host CPU polling overhead while ensuring sub-100 ms response to thermal excursions. |
Use Scenario: Overheat protection in multifunction printers and network-attached storage (NAS) enclosures with limited airflow. IC Role / Device Role / Timing Role: Low-power thermal watchdog; operates at 16 Hz conversion rate (0.8 mA) and asserts T_CRIT_A to cut power to motor drivers or HDD controllers. Use Value: Leverages factory-default T_CRIT settings (+85°C local, +110°C remote) for immediate deployment without firmware configuration. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar remote diode temperature sensing applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LM99-1CIMM | Different SMBus slave address (1001101 vs. LM99CIMM's 1001100); identical electrical specs, pinout, and functionality. | Enables co-location with LM99CIMM on same SMBus segment for multi-zone monitoring without address conflict. | Select LM99-1CIMM only when dual-sensor topology on one bus is required; otherwise LM99CIMM suffices. |
| MAX6642AESA+ | 12-bit remote resolution (0.0625°C), wider supply range (3.0–5.5 V), but no dedicated T_CRIT_A output - uses shared ALERT pin for all alarms. | Lacks hardware-critical shutdown path; requires host firmware to parse status register and assert external shutdown signal. | Choose MAX6642AESA+ only if higher resolution is mandatory and system can tolerate software-mediated critical shutdown. |
Compared with LM99-1CIMM, LM99CIMM offers identical performance but enables single-sensor deployment; versus MAX6642AESA+, LM99CIMM provides deterministic hardware-level T_CRIT_A assertion - eliminating firmware dependency for safety-critical thermal shutdown.
Availability
LM99CIMM is available at Aetrix Electronics and suitable for graphics processor thermal management, computer processor thermal management, and electronic test equipment requiring stable component supply, long-term lifecycle support, and guaranteed traceable sourcing.
Supply support for LM99CIMM 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 decades of heritage in precision analog sensing and industrial-grade reliability.
The LM99CIMM belongs to TI's high-accuracy thermal sensor product line, designed specifically for real-time junction temperature monitoring in graphics processors, CPUs, ASICs, and power-constrained embedded systems.
FAQ
What is the remote diode temperature shift applied by the LM99CIMM?
The LM99CIMM reports remote diode temperature as TLM99CIMM = TDIODE − 16°C. This fixed offset allows direct interpretation of GPU or CPU thermal diode readings without host-side arithmetic. For example, a reported value of +110°C corresponds to an actual diode junction temperature of 126°C - matching the factory default remote T_CRIT setting.
How does the LM99CIMM handle remote diode faults?
The LM99CIMM monitors the D+ pin for open-circuit or short-to-VDD conditions and sets the OPEN bit (D2) in the Status Register (02h). When read, this flag indicates a disconnected or damaged remote diode path - enabling host firmware to log errors or disable thermal throttling actions that rely on invalid remote data.
Can the LM99CIMM operate with a 5V SMBus master?
No - the LM99CIMM's SMBData and SMBCLK pins tolerate only up to 6.0 V absolute maximum, but TI specifies logic thresholds for 3.3 V operation: VIH ≥ 2.1 V and VIL ≤ 0.8 V. Using a 5 V SMBus master risks violating input voltage limits and causing unreliable communication or latch-up; level-shifting is required.
What is the purpose of the Offset Register in the LM99CIMM?
The LM99CIMM's Offset Register (RTOLB/RTOHB) compensates for non-ideal diode characteristics - such as series resistance or ideality factor deviations - across different transistor types (e.g., 2N3904 vs. GPU-integrated diodes). It adjusts the raw remote reading before reporting, enabling ±1.0°C accuracy without external calibration components.
Does the LM99CIMM require external components for stable operation?
Yes - the LM99CIMM requires a 0.1 µF + 100 pF ceramic bypass capacitor on VDD (Pin 1), a 10 µF bulk capacitor nearby, and a 2.2 nF capacitor between D+ (Pin 2) and D− (Pin 3). These are mandatory per TI's layout guidance to suppress noise coupling into the sensitive remote diode measurement path.
LM99CIMM 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), 11 b (Remote)
- Features:
- One-Shot, Output Switch, Programmable Limit, Shutdown Mode, Standby Mode
- Accuracy - Highest (Lowest):
- ±3°C
- Test Condition:
- 25°C ~ 125°C
- Operating Temperature:
- 0°C ~ 125°C
- Mounting Type:
- Surface Mount
- Grade:
- -
- Qualification:
- -
- Supplier Device Package:
- 8-VSSOP
LM99CIMM FAQ
1.How can I place an order for LM99CIMM through Aetrix?
Please submit a Request for Quotation (RFQ) for LM99CIMM 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 LM99CIMM reliable?
The price and inventory of LM99CIMM are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LM99CIMM is usually 5 days.
3.What payment methods are accepted for LM99CIMM?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LM99CIMM transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LM99CIMM?
LM99CIMM orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM99CIMM 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 LM99CIMM?
For technical support, including LM99CIMM datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM99CIMM requirements.
6.How does Aetrix verify that LM99CIMM is sourced from the original manufacturer or authorized distributors?
All LM99CIMM 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 LM99CIMM meets industry standards.
7.What is the process for return or replacement of LM99CIMM?
All LM99CIMM units undergo pre-shipment inspection (PSI). If there is an issue with LM99CIMM, 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 LM99CIMM part is unused and in its original packaging.
Return procedure for LM99CIMM:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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