NXP Semiconductors MC9RS08KB12CWJ

Overview

MC9RS08KB12CWJ from NXP Semiconductors (formerly Freescale) is an 8-bit RS08 core microcontroller in a 24-pin QFN package, delivering up to 20 MHz CPU operation across 1.8–5.5 V and –40 °C to 85 °C, with 12 KB flash, 254-byte RAM, and integrated ADC, ACMP, TPM, IIC, SCI, and real-time clock - deployed in industrial sensor nodes and low-power control modules.

For engineers reviewing the MC9RS08KB12CWJ datasheet, MC9RS08KB12CWJ pinout, MC9RS08KB12CWJ application, or MC9RS08KB12CWJ equivalent, key selection criteria include its 24-pin QFN thermal performance (θJA = 113 °C/W), single-wire background debug interface, 10-bit 12-channel ADC with temperature sensor, and support for stop-mode wakeup via RTI/KBI/ADC/ACMP/SCI/LVD.

Technical Context

The MC9RS08KB12CWJ implements an RS08 CPU core - a subset of the HC08 instruction set augmented with BGND - using a single global interrupt vector and no nested interrupts. Its internal clock source (ICS) employs a frequency-locked loop (FLL) with precision-trimmed internal reference (0.2% resolution, ±2% deviation over voltage/temperature), enabling bus frequencies up to 10 MHz.

System protection includes COP reset with dedicated 1 kHz low-power oscillator, low-voltage detection (LVD) with reset/interrupt, illegal opcode/address detection, and flash-block protection. Power management supports Wait mode (clocks active, full regulation) and Stop mode (clocks halted, regulator in standby), with wakeup sources including RTI, KBI, ADC, ACMP, SCI, and LVD.

Key Specifications

Pinout & Package

MC9RS08KB12CWJ is housed in a 24-pin QFN package (case 1982-01, 4 × 4 mm, 0.5 mm pitch) with exposed thermal pad. Pin 1 indicator located at top-left corner; package complies with JEDEC MO-220, RoHS-compliant, copper-wire bonded per QFN Addendum Rev. 0 (98ASA00602D).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar 8-bit microcontroller applications.

Compared with MC9RS08KA2CFUE and MC9S08QG8CDTE, the MC9RS08KB12CWJ delivers balanced integration - 12 KB flash, 254-byte RAM, 10-bit ADC with temp sensor, ACMP, and single-wire debug - making it optimal for compact, sensor-rich embedded control where peripheral completeness and debug simplicity are critical.

Availability

MC9RS08KB12CWJ is available at Aetrix Electronics and suitable for industrial sensor nodes, smart thermostat controllers, and programmable logic controller I/O modules requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.

Supply support for MC9RS08KB12CWJ 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

NXP Semiconductors is a global semiconductor leader focused on secure connectivity solutions for automotive, industrial, IoT, mobile, and communication infrastructure markets.

The MC9RS08KB12CWJ belongs to NXP's RS08 microcontroller family, designed specifically for cost-sensitive, ultra-low-power embedded control applications demanding high integration, small footprint, and simplified development - especially where analog sensing and robust debug are essential.

FAQ

What is the maximum operating frequency of the MC9RS08KB12CWJ?

The MC9RS08KB12CWJ supports up to 20 MHz CPU operation across its full 1.8–5.5 V supply range and –40 °C to 85 °C temperature range. Its internal clock source (ICS) uses a frequency-locked loop (FLL) to generate a bus frequency up to 10 MHz, which is the effective limit for peripheral timing and instruction execution speed in most configurations. The device also supports external crystal or ceramic resonator inputs from 31.25 kHz to 39.0625 kHz or 1–16 MHz.

Does the MC9RS08KB12CWJ include an analog-to-digital converter (ADC)?

Yes, the MC9RS08KB12CWJ integrates a 12-channel, 10-bit successive-approximation ADC with 2.5 μs conversion time, automatic compare function, internal bandgap reference channel, and a built-in 1.7 mV/°C temperature sensor. It operates in Run, Wait, and Stop modes, enabling low-power periodic sensing. The ADC supports hardware triggering and flexible input multiplexing across multiple port pins (ADP0–ADP11), making it suitable for direct sensor interfacing without external signal conditioning.

What debug interface does the MC9RS08KB12CWJ support?

The MC9RS08KB12CWJ features a single-wire background debug (BKGD) interface on PTA4, enabling full in-circuit debugging including breakpoint setting, memory inspection, and register access using only one dedicated pin. This eliminates the need for multi-pin debug headers or external emulators. The interface is compatible with standard Freescale/NXP BDM tools and supports real-time program flow control during development and field firmware updates.

What power-saving modes are available on the MC9RS08KB12CWJ?

The MC9RS08KB12CWJ offers three power-saving modes: Run (full operation), Wait (CPU halted, system clocks active, full voltage regulation), and Stop (CPU and clocks halted, voltage regulator in standby). In Stop mode, typical current consumption is 0.39 μA at 1.8 V and 25 °C. Wakeup is supported from RTI, KBI, ADC, ACMP, SCI, and LVD events - allowing responsive low-power operation ideal for battery-powered sensor applications.

Is the MC9RS08KB12CWJ pin-compatible with other RS08 family members?

No, the MC9RS08KB12CWJ is not pin-compatible with other RS08 variants such as MC9RS08KA2 or MC9RS08LA8 due to differing pin counts (24-pin QFN vs. 6-pin DFN or 24-pin QFN with distinct pin assignments) and incompatible peripheral mappings. While the MC9RS08KB12 series shares the same 24-pin QFN package footprint with MC9RS08KB8 and MC9RS08KB4, their pin functions differ in flash/RAM configuration and optional features. Always verify pin assignment tables and electrical characteristics before substitution.