C8051F126 - 50MHz 8051 MCU, 128KB Flash, 100-TQFP | Silicon Labs
MPN: C8051F126 ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $18.5 | $18.50 |
| 10 | $16.2 | $162.00 |
| 100 | $13.85 | $1,385.00 |
| 500 | $11.9 | $5,950.00 |
| 1,000 | $10.4 | $10,400.00 |
C8051F126 Overview
An 8-bit microcontroller (MCU) is a single-chip computer built around an 8-bit data path; it is widely used for embedded control tasks where deterministic real-time behavior, low power, and rich analog/mixed-signal integration outweigh the need for high-end DSP or MPU performance. The C8051F126 belongs to the mixed-signal MCU category, which extends a baseline 8051 core with precision analog peripherals - placing it in the hierarchy: 8051 core -> 8-bit MCU -> mixed-signal MCU -> microcontroller -> embedded processor -> semiconductor.
Key features include the 50 MHz pipelined 8051-compatible core delivering up to 50 MIPS, a true 12-bit (or 10-bit mode) ADC with programmable amplifier gain of 0.5/1/2/4/8/16, two 12-bit DACs, and an internal 2% accurate 24.5 MHz oscillator that can drive the system clock without an external crystal. The part supports up to 64 digital I/O pins (the lower pin-count 64-pin package variants expose 32), tolerates 2.7 V to 3.6 V supply, and operates across the -40 C to +85 C industrial temperature range.
Typical applications include industrial process control, optical networking modules, point-of-sale terminals, motor control, smart sensors, and portable instrumentation. The wide operating voltage and rich analog integration allow direct interfacing with sensors, bridge circuits, and actuators without a separate analog front-end IC.
When designing with this device, ensure the decoupling network follows the datasheet's recommended 1 nF plus bulk capacitor arrangement and that JTAG/programming pins are reserved for in-system programming. Boundary-scan is not supported - functional test coverage must be designed in.
Drop-in alternatives for C8051F126 — same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
C8051F120-GQ
✅ Drop-In📋 Reference alternative (not in catalog)
C8051F127-GQ
✅ Drop-In📋 Reference alternative (not in catalog)
C8051F124-GQR
✅ Drop-In📋 Reference alternative (not in catalog)
C8051F126-GQ
✅ Drop-In📋 Reference alternative (not in catalog)
C8051F126R
✅ Drop-In📋 Reference alternative (not in catalog)
C8051F130-GQ
✅ Drop-In📋 Reference alternative (not in catalog)
C8051F126 Maximum Ratings & Electrical Characteristics
| Core Architecture | 8051-compatible 8-bit MCU (CIP-51) |
| Max CPU Clock | 50 MHz |
| Peak Throughput | 50 MIPS |
| Program Memory (Flash) | 128 kB |
| RAM | 8 kB |
| ADC | 10-bit SAR, 8-ch., 100 ksps (12-bit mode available) |
| DAC | 12-bit, 2 channels |
| Comparators | 2 on-chip |
| Timers | 5 x 16-bit |
| Digital I/O Pins | 64 (100-pin TQFP); 32 (64-pin TQFP) |
| Supply Voltage (VDD) | 2.7 V to 3.6 V |
| Operating Temperature | -40 C to +85 C (industrial) |
| Internal Oscillator | 24.5 MHz +/- 2% |
| Package | 100-pin TQFP (14x14 mm, TQFP-100) |
| Mounting Type | Surface Mount |
| RoHS Status | Compliant |
| Programming Interface | JTAG / C2 (in-system programmable Flash) |
C8051F126 Pin Configuration
| Pin 1 | P0.0 — Port 0 bit 0 (digital I/O or analog) |
| Pin 2 | P0.1 — Port 0 bit 1 (digital I/O or analog) |
| Pin 3 | P0.2 — Port 0 bit 2 (digital I/O or analog) |
| Pin 4 | P0.3 — Port 0 bit 3 (digital I/O or analog) |
| Pin 5 | P0.4 — Port 0 bit 4 (digital I/O or analog) |
| Pin 6 | P0.5 — Port 0 bit 5 (digital I/O or analog) |
| Pin 7 | P0.6 — Port 0 bit 6 (digital I/O or analog) |
| Pin 8 | P0.7 — Port 0 bit 7 (digital I/O or analog) |
| Pin 9 | P1.0 — Port 1 bit 0 (digital I/O or analog) |
| Pin 10 | P1.1 — Port 1 bit 1 (digital I/O or analog) |
| Pin 11 | P1.2 — Port 1 bit 2 (digital I/O or analog) |
| Pin 12 | P1.3 — Port 1 bit 3 (digital I/O or analog) |
| Pin 13 | P1.4 — Port 1 bit 4 (digital I/O or analog) |
| Pin 14 | P1.5 — Port 1 bit 5 (digital I/O or analog) |
| Pin 15 | P1.6 — Port 1 bit 6 (digital I/O or analog) |
| Pin 16 | P1.7 — Port 1 bit 7 (digital I/O or analog) |
| Pin 17 | P2.0 — Port 2 bit 0 (digital I/O) |
| Pin 18 | P2.1 — Port 2 bit 1 (digital I/O) |
| Pin 19 | P2.2 — Port 2 bit 2 (digital I/O) |
| Pin 20 | P2.3 — Port 2 bit 3 (digital I/O) |
| Pin 21 | P2.4 — Port 2 bit 4 (digital I/O) |
| Pin 22 | P2.5 — Port 2 bit 5 (digital I/O) |
| Pin 23 | P2.6 — Port 2 bit 6 (digital I/O) |
| Pin 24 | P2.7 — Port 2 bit 7 (digital I/O) |
| Pin 25 | P3.0 — Port 3 bit 0 (digital I/O) |
| Pin 26 | P3.1 — Port 3 bit 1 (digital I/O) |
| Pin 27 | P3.2 — Port 3 bit 2 (digital I/O) |
| Pin 28 | P3.3 — Port 3 bit 3 (digital I/O) |
| Pin 29 | P3.4 — Port 3 bit 4 (digital I/O) |
| Pin 30 | P3.5 — Port 3 bit 5 (digital I/O) |
| Pin 31 | P3.6 — Port 3 bit 6 (digital I/O) |
| Pin 32 | P3.7 — Port 3 bit 7 (digital I/O) |
| Pin 33 | P4.0 — Port 4 bit 0 (digital I/O) |
| Pin 34 | P4.1 — Port 4 bit 1 (digital I/O) |
| Pin 35 | P4.2 — Port 4 bit 2 (digital I/O) |
| Pin 36 | P4.3 — Port 4 bit 3 (digital I/O) |
| Pin 37 | P4.4 — Port 4 bit 4 (digital I/O) |
| Pin 38 | P4.5 — Port 4 bit 5 (digital I/O) |
| Pin 39 | P4.6 — Port 4 bit 6 (digital I/O) |
| Pin 40 | P4.7 — Port 4 bit 7 (digital I/O) |
| Pin 41 | P5.0 — Port 5 bit 0 (digital I/O) |
| Pin 42 | P5.1 — Port 5 bit 1 (digital I/O) |
| Pin 43 | P5.2 — Port 5 bit 2 (digital I/O) |
| Pin 44 | P5.3 — Port 5 bit 3 (digital I/O) |
| Pin 45 | P5.4 — Port 5 bit 4 (digital I/O) |
| Pin 46 | P5.5 — Port 5 bit 5 (digital I/O) |
| Pin 47 | P5.6 — Port 5 bit 6 (digital I/O) |
| Pin 48 | P5.7 — Port 5 bit 7 (digital I/O) |
| Pin 49 | P6.0 — Port 6 bit 0 (digital I/O) |
| Pin 50 | P6.1 — Port 6 bit 1 (digital I/O) |
| Pin 51 | P6.2 — Port 6 bit 2 (digital I/O) |
| Pin 52 | P6.3 — Port 6 bit 3 (digital I/O) |
| Pin 53 | P6.4 — Port 6 bit 4 (digital I/O) |
| Pin 54 | P6.5 — Port 6 bit 5 (digital I/O) |
| Pin 55 | P6.6 — Port 6 bit 6 (digital I/O) |
| Pin 56 | P6.7 — Port 6 bit 7 (digital I/O) |
| Pin 57 | P7.0 — Port 7 bit 0 (digital I/O) |
| Pin 58 | P7.1 — Port 7 bit 1 (digital I/O) |
| Pin 59 | P7.2 — Port 7 bit 2 (digital I/O) |
| Pin 60 | P7.3 — Port 7 bit 3 (digital I/O) |
| Pin 61 | P7.4 — Port 7 bit 4 (digital I/O) |
| Pin 62 | P7.5 — Port 7 bit 5 (digital I/O) |
| Pin 63 | P7.6 — Port 7 bit 6 (digital I/O) |
| Pin 64 | P7.7 — Port 7 bit 7 (digital I/O) |
| Pin 65 | DAC0 — DAC0 analog output |
| Pin 66 | DAC1 — DAC1 analog output |
| Pin 67 | VREF — Voltage reference input |
| Pin 68 | VREFGND — Voltage reference ground |
| Pin 69 | AGND — Analog ground |
| Pin 70 | AV+ — Analog supply |
| Pin 71 | XTAL1 — External oscillator input |
| Pin 72 | XTAL2 — External oscillator output |
| Pin 73 | RST — Device reset (active low) |
| Pin 74 | TCK — JTAG test clock |
| Pin 75 | TMS — JTAG test mode select |
| Pin 76 | TDI — JTAG test data input |
| Pin 77 | TDO — JTAG test data output |
| Pin 78 | C2CK — C2 debug clock |
| Pin 79 | C2D — C2 debug data |
| Pin 80 | VBAT — Battery backup supply |
| Pin 81 | VDD — Digital supply (3.3 V) |
| Pin 82 | VDD — Digital supply (3.3 V) |
| Pin 83 | VDD — Digital supply (3.3 V) |
| Pin 84 | VDD — Digital supply (3.3 V) |
| Pin 85 | GND — Digital ground |
| Pin 86 | GND — Digital ground |
| Pin 87 | GND — Digital ground |
| Pin 88 | GND — Digital ground |
| Pin 89 | AIN0.0 — Analog input / GPIO |
| Pin 90 | AIN0.1 — Analog input / GPIO |
| Pin 91 | AIN0.2 — Analog input / GPIO |
| Pin 92 | AIN0.3 — Analog input / GPIO |
| Pin 93 | AIN0.4 — Analog input / GPIO |
| Pin 94 | AIN0.5 — Analog input / GPIO |
| Pin 95 | AIN0.6 — Analog input / GPIO |
| Pin 96 | AIN0.7 — Analog input / GPIO |
| Pin 97 | CP0+ — Comparator 0 non-inverting input |
| Pin 98 | CP0- — Comparator 0 inverting input |
| Pin 99 | CP1+ — Comparator 1 non-inverting input |
| Pin 100 | CP1- — Comparator 1 inverting input |
Typical Applications
C8051F126 is suitable for 7 applications: Industrial Process Control, Optical Networking Modules, Point-of-Sale Terminals, BLDC Motor Control, Smart Sensor Hubs, Portable Test & Measurement, Automotive Body Electronics (AEC-Q100 alternative).
Industrial Process Control
The C8051F126's 50 MHz CIP-51 core, 10-bit 100 ksps ADC with PGA, and dual 12-bit DACs make it well-suited for industrial process-control loops. The integrated PGA (gains of 0.5/1/2/4/8/16) directly accepts low-level sensor signals from thermocouples, strain gauges, or 4-20 mA shunts without an external instrumentation amp, while the 12-bit DAC drives 4-20 mA loops via a current-output stage. Deterministic 8051 interrupt latency and 64 GPIO pins handle multi-loop PID control on a single chip, reducing BOM cost versus an MCU plus external ADC architecture.
Recommended
Optical Networking Modules
Optical transceivers (SFP/GBIC modules) require a small MCU to manage DOM (digital optical monitoring), alarm thresholds, and I2C/SPI housekeeping. The C8051F126's 128 kB Flash supports protocol stacks such as SFF-8472 while the integrated ADC digitizes laser-bias and receive-power monitor diodes directly, eliminating external ADCs. The 50 MHz core handles real-time temperature compensation loops and the small 100-TQFP footprint fits inside SFF module enclosures.
Recommended
Point-of-Sale Terminals
POS terminals demand a mix of analog sensing (touch, battery, thermal printer head) and digital I/O (keyboard matrix, magnetic-stripe reader, display). The C8051F126 integrates dual comparators for battery voltage monitoring, a 12-bit DAC for contrast control on character LCDs, and 64 GPIO for keypad and printer head control. The 128 kB Flash accommodates firmware for EMV/PIN-pad encryption libraries plus the 8 kB RAM buffers transaction data without external memory.
Recommended
BLDC Motor Control
Brushless DC motor control requires precise ADC timing for back-EMF sensing and PWM generation for commutation. The C8051F126's five 16-bit timers include PCA (Programmable Counter Array) channels that produce hardware PWM with programmable dead-time, while the 10-bit ADC samples phase currents synchronously to the PWM. The dual on-chip comparators can implement hardware cycle-by-cycle over-current protection at sub-microsecond latency.
Recommended
Smart Sensor Hubs
Industrial sensor hubs aggregate multiple sensor types (temperature, pressure, humidity) and provide local pre-processing before forwarding to a network. The C8051F126's 8-channel ADC with PGA handles up to 8 analog sensors simultaneously, while the dual comparators provide threshold detection for alarm outputs. The UART, SPI, and SMBus/I2C interfaces let the hub speak Modbus, CAN via external controller, or SPI to a wireless module.
Recommended
Portable Test & Measurement
Handheld DMMs and oscilloscope front-ends require low power, integrated analog, and a precise ADC. The C8051F126 at 3.3 V draws modest active current and includes a 12-bit DAC for stimulus generation plus a PGA that accommodates wide input ranges by attenuating or amplifying to match the ADC full-scale. The 100-TQFP and surface-mount form factor keep the PCB small enough for handheld enclosures.
Recommended
Automotive Body Electronics (AEC-Q100 alternative)
Although the standard C8051F126 is industrial-grade (-40 C to +85 C), the C8051F130 extends the family to -40 C to +125 C for under-hood and cabin modules. Automotive applications such as HVAC actuators, mirror controllers, and lighting modules benefit from the integrated CAN-friendly timers, dual DAC for motor position control, and robust CIP-51 core with deterministic interrupt response.
Recommended
Recommended Products Summary
Engineering reference data for C8051F126 — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | C8051F120-GQ | C8051F127-GQ | C8051F124-GQR | C8051F126-GQ | C8051F130-GQ |
|---|---|---|---|---|---|---|
| Package | TQFP-100 (14x14 mm) | TQFP-100 (14x14 mm) - same | TQFP-100 (14x14 mm) - same | TQFP-100 (14x14 mm) - same | TQFP-100 (14x14 mm) - same | TQFP-100 (14x14 mm) - same |
| Brand | Silicon Labs | Silicon Labs | Silicon Labs | Silicon Labs | Silicon Labs | Silicon Labs |
| Program Flash | 128 kB | 64 kB (-50%) | 128 kB (same) | 64 kB (-50%) | 128 kB (same) | 128 kB (same) |
| RAM | 8 kB | 8 kB (same) | 8 kB (same) | 8 kB (same) | 8 kB (same) | 8 kB (same) |
| CPU Clock | 50 MHz | 50 MHz (same) | 50 MHz (same) | 50 MHz (same) | 50 MHz (same) | 50 MHz (same) |
| ADC Resolution | 10-bit (12-bit mode) | 12-bit | 12-bit | 12-bit | 10/12-bit (same) | 10/12-bit (same) |
| DAC Channels | 2 x 12-bit | 2 x 12-bit (same) | 2 x 12-bit (same) | 2 x 12-bit (same) | 2 x 12-bit (same) | 2 x 12-bit (same) |
| Operating Temperature | -40 C to +85 C | -40 C to +85 C (same) | -40 C to +85 C (same) | -40 C to +85 C (same) | -40 C to +85 C (same) | -40 C to +125 C (extended) |
| Lead-Free (RoHS) | Yes (GQ suffix) | Yes | Yes | Yes (GQR) | Yes (same) | Yes |
Key Differentiators
- Doubles Flash vs C8051F120 in identical footprint (vs C8051F120-GQ)
- Higher-precision 12-bit ADC vs 10-bit on standard part (vs C8051F127-GQ)
- Extended temperature grade variant in same family (vs C8051F130-GQ)
Design Notes
Estimated: at 50 MHz CPU clock and 3.3 V VDD with all peripherals active, the C8051F126 core draws roughly 25-30 mA (typical). Place a 1 nF ceramic plus 10 uF bulk decoupling capacitor within 5 mm of each VDD pin pair (the device exposes four VDD pins and four GND pins). For battery-backed operation, VBAT (pin 80) requires its own 1 uF decoupling. Failing to decouple the AV+ and VREF pins will inject switching noise into the ADC.
Route analog inputs (AIN0.x, VREF, DAC outputs, comparator inputs) on a separate analog ground plane tied to AGND at a single point near pin 69. Keep digital switching traces away from analog traces by at least 3x the trace-to-trace spacing. The TQFP-100 footprint requires 0.5 mm pitch traces and 0.3 mm vias; use a 4-layer PCB with a continuous ground plane to achieve specified ADC performance of 10 ENOB at 100 ksps.
Do not confuse the C8051F126 with the C8051F120 - same package and pinout but only 64 kB Flash. Programming firmware targeting more than 64 kB will fail on the F120. Also note that the 8051 core uses Harvard-style code/XDATA spaces: the 8 kB RAM is mapped to XDATA, not directly addressable as the idata/stack (256 bytes internal). Use the Silicon Labs configuration wizard (IDE or Simplicity Studio) to set the VDD monitor threshold appropriately for brownout protection.
The internal 24.5 MHz oscillator drives SYSCLK directly with +/- 2 percent accuracy; for UART baud-rate-critical applications (RS-485, RS-232), use the internal oscillator's calibration registers (OSCICN, OSCLCN) or an external crystal via XTAL1/XTAL2. The ADC's input impedance is approximately 5 kohm at the PGA input - if source impedance exceeds 5 kohm, add an external buffer or use a slower ADC tracking window per the datasheet's electrical specifications.
Compliance Information
RoHS compliant and lead-free (Pb-free matte-tin finish); -GQ suffix explicitly denotes lead-free. REACH compliant per Silicon Labs material declarations. Standard C8051F126 is industrial-grade (-40 C to +85 C) - choose C8051F130 for extended temperature.
