LM63CIMA - Remote Diode Temp Sensor & Fan Control | TI SOIC-8
MPN: LM63CIMA ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $3.2 | $3.20 |
| 10 | $2.86 | $28.60 |
| 100 | $2.42 | $242.00 |
| 500 | $1.95 | $975.00 |
| 1,000 | $1.62 | $1,620.00 |
| 3,000 | $1.31 | $3,930.00 |
LM63CIMA Overview
A remote diode digital temperature sensor is a class of thermal-management IC that converts the temperature-dependent Vbe of a small-signal transistor into a digital reading via an on-chip ADC. In the broader power-management hierarchy these ICs sit alongside fan drivers, hot-swap controllers, and hardware monitors, enabling closed-loop thermal regulation in systems where overheating degrades reliability. Unlike thermistors or thermocouples, remote-diode sensors provide noise-immune digital output and factory-trimmed calibration, which simplifies firmware development on the chip.
Key features include ±1°C local accuracy and ±3°C remote accuracy (typical), factory-calibrated series-resistance correction, a 10-bit-plus-sign remote-diode temperature ADC with 0.25°C LSB resolution, a TACH input for closed-loop fan-speed feedback, and a PWM output whose duty-cycle to support both low-frequency and high-frequency fans. The device also integrates a digital over-temperature alarm with ALERT pin interrupt, an SMBus ALERT-response address, and an offset register for system-level error trimming. The 8-pin SOIC (DIMA) package and SMBus interface allow direct drop-in upgrade of legacy LM63 designs.
Architecturally, the LM63 uses a delta-Vbe sensing front-end, an integrating ADC with chopper-stabilized offset cancellation, and a state machine that handles SMBus transactions and PWM pulse-width calculation in hardware. The remote channel supports series-resistance cancellation up to a few hundred ohms of trace resistance, allowing flexible PCB routing between the IC and the sense diode. An on-chip digital filter suppresses spurious readings caused by PWM edge noise.
Typical applications include processor and chipset thermal monitoring in desktop and server motherboards, graphics-card GPU thermal management, embedded-system fan-speed control, set-top-boxed and projector lamp-cooling control, and industrial chassis-temperature regulation. Designers can create boards based on TI's LM63 EVM reference schematic, which shows the recommended 2N3904 diode-connection topology, bypass-cap placement, and PWM low-pass network.
When designing with this device, place the 0.1 µF VDD bypass capacitor within a few millimeters of the supply pin and use a 10 kΩ NTC bypass resistor at the D+/D- pins when the diode is omitted. Program the PWM output frequency to match the fan's tachometer gearing, and use the ALERT instruction to drive an interrupt for hot-swap events.
Drop-in alternatives for LM63CIMA — same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
Variants in this series
Same-series models that are drop-in compatible with LM63CIMA (same form factor and footprint) — differing in Package, Function, Remote Diode Accuracy, Fan Control Output, Interface.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
LM63CIMAX/NOPB
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Contact for price
View Datasheet →LM63CIMAX
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$2.18 / Unit
View Datasheet →LM63CIMA/NOPB
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$2.05 / Unit
View Datasheet →EMC1412-1-AIA-LLC-TR
✅ Drop-In📋 Reference alternative (not in catalog)
LM63CIMA Maximum Ratings & Electrical Characteristics
| Function | Fan Control, Temp Monitor |
| Sensor Type | Internal and External (remote diode) |
| Remote Diode Accuracy | ±3 °C (typical) |
| Local Temperature Accuracy | ±1 °C (typical) |
| Sensing Temperature Range | 0 °C to 125 °C |
| Output Type | 2-Wire SMBus (digital, signed 10-bit) |
| Supply Voltage (VDD) | 3.0 V to 3.6 V |
| Resolution | 8/10-bit + Sign (0.25 °C LSB) |
| Interface | SMBus / I2C-compatible |
| Fan Control Output | PWM, open-drain |
| Tachometer Input | Yes |
| ALERT Interrupt Pin | Yes (SMBus ALERT supported) |
| Remote Diode Compensation | Series-resistance cancellation (factory-trimmed) |
| Operating Temperature Range | 0 °C to 85 °C (junction/ambient for grade) |
| Package | 8-SOIC (DIMA) |
| Mounting Type | Surface Mount |
| MSL Level | 1 (per JEDEC J-STD-020) |
| Lead-Free / RoHS | Lead-free available (LM63CIMA/NOPB variant); standard LM63CIMA is SnPb |
| JESD-609 Code | e0 (SnPb finish on LM63CIMA; e3 on /NOPB) |
LM63CIMA Pin Configuration
| Pin 1 | GND — Ground reference |
| Pin 2 | D+ — Remote-diode anode (to CPU/GPU thermal diode or 2N3904 collector) |
| Pin 3 | D- — Remote-diode cathode (to thermal diode base/emitter) |
| Pin 4 | VDD — Positive supply, 3.0 V to 3.6 V |
| Pin 5 | ALERT — SMBus ALERT interrupt output (active low, open-drain) |
| Pin 6 | TACH — Fan tachometer input |
| Pin 7 | PWM — PWM fan-control output (open-drain) |
| Pin 8 | SDA/SCL — SMBus data and clock (2-wire interface) |
Typical Applications
LM63CIMA is suitable for 6 applications: Server / Desktop CPU Thermal Monitoring, GPU Thermal Management on Graphics Cards, Embedded System Fan-Speed Control, Set-Top Box / Projector Lamp Cooling, Industrial Chassis Thermal Regulation, ASIC / Processor Thermal-Diode Sensing.
Server / Desktop CPU Thermal Monitoring
The LM63CIMA's ±1 °C local and ±3 °C remote accuracy makes it a strong fit for CPU thermal monitoring on server and desktop boards. The remote channel senses the on-die thermal diode of an Intel or AMD processor directly, while the local channel monitors the VRM heatsink. The 3.0–3.6 V supply matches the standby rail of typical ATX designs, and the signed 10-bit SMBus output (0.25 °C LSB) drives ACPI thermal-zone firmware without additional scaling. Compared with thermistor solutions, the LM63CIMA removes calibration overhead and noise pickup, and the integrated PWM output regulates cooling in closed loop with the TACH input. Designers should place the LM63 within 50 mm of the CPU socket and route the D+/D- differential traces through an IDC to suppress PWM-induced noise. Reference: TI LM63 datasheet SNIS082 and the EVB schematic.
Recommended
GPU Thermal Management on Graphics Cards
On graphics cards, the LM63CIMA drives GPU thermal placement (the GPU's integrated thermal diode is the remote sensor) while a separate local channel monitors VRM or memory-junction temperature. The LM63's 0.25 °C resolution allows GPU boost algorithms to throttle clock rates before reaching critical thermal limits, and the PWM output controls a small axial or blower fan with closed-loop feedback via TACH. The 8-SOIC footprint fits easily next to the GPU socket, and the SMBus interface is shared with the GPU's existing management bus. For multi-GPU boards, multiple LM63 ICs can be addressed on the same bus using the LM63's ALERT-response address. According to TI, the LM63 family is widely adopted in industry reference designs for both AMD and NVIDIA platforms.
Recommended
Embedded System Fan-Speed Control
The LM63CIMA is well-suited for embedded-system fan-speed control in fan-control platforms where a single IC must monitor one or two thermal zones and drive a 4-wire PWM fan. The remote channel senses an external 2N3904 (or MMBT3904 SMD) diode placed near the hot-spot, the TACH input reads fan RPM, and the PWM output drives the fan's speed-control input directly through a small gate resistor. The ALERT pin can wake the host MCU on over-temperature, enabling low-power sleep modes where the fan is off until the ALERT fires. With 3.0–3.6 V supply and <1 mA quiescent current, the LM63 is also ideal for battery-powered embedded enclosures using meshed battery topologies. Reference: TI LM63 datasheet, section on PWM programming.
Recommended
Set-Top Box / Projector Lamp Cooling
In set-top boxes, projectors, and AV receivers, the LM63CIMA provides lamp thermal monitoring and chassis-fan regulation. The remote diode is bonded to the lamp heatsink or to a critical ASIC, and the local sensor monitors intake air. The PWM output drives a low-noise fan that ramps up gradually as temperature rises, avoiding acoustic spikes during movie playback. The SMBus interface allows the main SoC to log thermal telemetry for warranty diagnostics, and the ALERT pin enables graceful power-off before lamp damage. The 8-SOIC package fits in tight chassis geometries, and the 3.3 V supply rails from the main PMY are straightforward to design. Designers should use the /NOPB variant for RoHS-compliant consumer products shipping to the EU.
Recommended
Industrial Chassis Thermal Regulation
For industrial chassis, the LM63CIMA drives fan trays and monitors inlet/outlet air in an industrial environment. The 0–125 °C sensing range covers most industrial operating envelopes, and the 8-SOIC package mounts on the chassis backplane near the fans. The TACH input validates fan health and triggers a system fault when RPM is out of spec, while the ALERT pin can drive an e-stop or system-shutdown signal. The SMBus interface ties into the backplane management controller (BMC) for remote telemetry. Compared with discrete thermistor + op-amp solutions, the LM63CIMA eliminates calibration drift and provides a digital output that survives long cable runs. Reference: TI LM63 datasheet for backplane thermal-management reference schematic.
Recommended
ASIC / Processor Thermal-Diode Sensing
The LM63CIMA is designed to read the on-die thermal diode of CPUs, GPUs, FPGAs, and ASICs. The remote channel accepts any diode-connected small-signal transistor (2N3904, MMBT3904, or processor substrate diode), and TI's factory-trimmed series-resistance cancellation compensates for trace resistance up to a few hundred ohms, which is essential when the diode is several centimeters away on the PCB. The signed 10-bit SMBus output (0.25 °C LSB) feeds the host's thermal-management firmware, and the ALERT pin can interrupt the host on critical thermal events. For multi-ASIC designs, multiple LM63 ICs can share a single SMBus bus using individual addresses. The 8-SOIC footprint fits next to processor sockets in compact designs.
Recommended
Recommended Products Summary
Engineering reference data for LM63CIMA — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | LM63CIMAX/NOPB | LM63CIMAX | LM63CIMA/NOPB | EMC1412-1-AIA-LLC-TR | MAX31790ATI+ |
|---|---|---|---|---|---|---|
| Package | 8-SOIC (DIMA) | 8-SOIC (DIMA) - same | 8-SOIC (DIMA) - same | 8-SOIC (DIMA) - same | 8-SOIC - same | 8-TQFN-EP - different |
| Brand | Texas Instruments | Texas Instruments | Texas Instruments | Texas Instruments | Microchip Technology | Analog Devices |
| Function | Remote-diode temp sensor + PWM fan control | Remote-diode temp sensor + PWM fan control | Remote-diode temp sensor + PWM fan control | Remote-diode temp sensor + PWM fan control | Remote-diode temp sensor | Multi-channel fan controller + temp sensor |
| Remote Accuracy | ±3 °C (typ) | ±3 °C (typ) | ±3 °C (typ) | ±3 °C (typ) | ±1 °C (typ) | ±2 °C (typ) |
| Supply Voltage | 3.0 V to 3.6 V | 3.0 V to 3.6 V | 3.0 V to 3.6 V | 3.0 V to 3.6 V | 3.0 V to 3.6 V | 3.0 V to 3.6 V |
| Interface | SMBus (2-wire) | SMBus (2-wire) | SMBus (2-wire) | SMBus (2-wire) | SMBus / I2C | I2C |
| PWM Output | Yes (open-drain) | Yes (open-drain) | Yes (open-drain) | Yes (open-drain) | No | Yes |
| TACH Input | Yes | Yes | Yes | Yes | No | Yes |
| RoHS / Lead-Free | SnPb finish (e0); /NOPB variant is RoHS (e3) | Lead-free (e3), RoHS | SnPb (e0) | Lead-free (e3), RoHS | Lead-free, RoHS | Lead-free, RoHS |
Key Differentiators
- Integrated PWM + TACH closed-loop fan control on the same die (vs EMC1412-1-AIA-LLC-TR (Microchip))
- Factory-trimmed series-resistance cancellation (vs Generic thermistor solutions)
- Wide 0 °C to 125 °C sensing range with 0.25 °C resolution (vs MAX31790ATI+ (Analog Devices))
- Mature, widely-adopted TI thermal-management platform (vs Cross-brand alternatives)
Design Notes
Route the D+ and D- traces as a tightly coupled differential pair from the LM63CIMA pins to the remote-diode transistor (typically a 2N3904 or processor-substrate thermal diode). Keep trace length under 50 mm, surround the pair with ground copper, and place a 10 kΩ resistor between D+ and D- close to the IC for noise filtering. Place the 0.1 µF VDD bypass capacitor within 5 mm of pin 4 (VDD).
Do not connect the LM63CIMA's PWM output directly to a fan motor — the open-drain stage cannot source enough current. Drive an external N-MOSFET low-side switch or a dedicated driver such as the LM63's companion fan-driver stage. Also, do not omit the series resistance on the D+/D- lines if the diode is far from the IC; use TI's series-resistance-cancellation register to compensate. According to TI's datasheet, omitting these bypass components degrades accuracy by several °C.
Estimated: at 25 °C ambient and a typical 1 mA active supply current, the LM63CIMA dissipates roughly 3.3 mW (3.3 V × 1 mA), which yields a junction-temperature rise of <1 °C in the 8-SOIC package. Thermal management is therefore not a concern for the IC itself, but the LM63's own self-heating can affect the local-channel reading if the IC is mounted near a hot component; mount the LM63 away from VRMs, MOSFETs, and other heat sources for best local-channel accuracy.
The SMBus SDA/SCL lines are open-drain and require external pull-up resistors (typically 4.7 kΩ to 10 kΩ to VDD). Place pull-ups close to the LM63CIMA's pin 8. The TACH input should be AC-coupled (or filtered) if the fan's tach signal is noisy; TI's reference design uses a 100 kΩ pull-up and a 1 nF cap to ground. The ALERT pin should also be pulled up externally since it is open-drain.
Compliance Information
Standard LM63CIMA uses SnPb finish (JESD-609 code e0), so it is NOT RoHS-compliant; choose LM63CIMA/NOPB or LM63CIMAX/NOPB for RoHS-compliant lead-free production. REACH compliance per TI product page. Not AEC-Q100 qualified — for automotive thermal management, contact TI for the LM63-Q1 automotive grade. Conflict-minerals statement per TI's CMRT.
