MC68HC908JB8ADW - 8-bit USB MCU, 8KB Flash, 3MHz | NXP
MPN: MC68HC908JB8ADW ✗ End of Life| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $12.45 | $12.45 |
| 10 | $11.2 | $112.00 |
| 100 | $9.85 | $985.00 |
| 500 | $8.9 | $4,450.00 |
| 1,000 | $7.95 | $7,950.00 |
MC68HC908JB8ADW Overview
Background: The HC08 is a Customer-Specified Integrated Circuit (CSIC) 8-bit MCU family introduced by Motorola in the 1990s that uses a 68HC08 instruction set, an enhanced version of the HC05 architecture with a 16-bit index register, 16-bit stack pointer and additional addressing modes. The MC68HC908JB8 specifically targets low-cost USB peripherals (HID-class mice and keyboards, USB-to-UART bridges, USB I/O dongles) by integrating a USB 1.1 full-speed (12 Mbps) device controller, an integrated 3.3V USB voltage regulator, and a 5-channel 8-bit ADC together with standard HC08 timers and I/O. MCUs of this class belong to the broader hierarchy of 8-bit microcontrollers -> microcontrollers -> embedded processors -> semiconductor ICs.
Key features include 8 KB FLASH (with security), 256 bytes of RAM, an integrated USB 1.1 device transceiver with on-chip 3.3V regulator, dual 16-bit timers (TIM1/TIM2), a 5-channel 8-bit ADC, an SCI/UART, and 23 general-purpose I/O lines. The ADW suffix denotes the -40C to +85C industrial-grade SOIC-28 wide-body (300 mil) package supplied in tube/tray.
Architecture uses the HC08 CPU with a 16-bit program counter, 8-bit accumulator A plus combined accumulator B, HIDX index register, 16-bit stack pointer (H:X), and 64 KB linear address space. The USB module implements endpoint 0 control and up to 2 additional endpoints for interrupt or bulk transfers. The internal 3.3V regulator eliminates the need for an external LDO for the USB D+/D- transceiver, simplifying bus-powered designs.
Typical applications include USB HID input devices (mouse, keyboard, gamepad), USB-to-serial COM-port bridges, USB flash-memory readers, USB joysticks/readers, low-speed industrial I/O modules with USB diagnostics, and legacy PC peripherals where 8-bit processing is sufficient. The integrated USB peripheral plus on-chip regulator make it particularly attractive for cost-sensitive, bus-powered designs.
Design consideration: The USB module draws its 3.3V supply from the internal regulator; ensure adequate bulk decoupling at the VUSB pin (1 uF minimum). The FLASH programming voltage is generated on-chip from VDD; do not exceed 5.5V on any pin during in-circuit programming.
This page synthesizes distributor stock and pricing data, the NXP/Freescale datasheet, and parametric drop-in alternatives not consolidated in any single manufacturer catalog.
Drop-in alternatives for MC68HC908JB8ADW — 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:
MC68HC908JB8FA
✅ Drop-In ⚠️ Specs Unverified📋 Reference alternative (not in catalog)
MC68HC908JB16
✅ Drop-In ⚠️ Specs Unverified📋 Reference alternative (not in catalog)
MC9S08JB16
✅ Drop-In ⚠️ Specs Unverified📋 Reference alternative (not in catalog)
MC68HC908JB8CFA
✅ Drop-In ⚠️ Specs Unverified📋 Reference alternative (not in catalog)
MC68HC908JB8ADW Maximum Ratings & Electrical Characteristics
| Core | HC08 (8-bit) |
| Family | M68HC08 (CSIC) |
| Program Memory | 8 KB FLASH |
| RAM | 256 bytes |
| Bus Frequency (Max) | 3 MHz internal |
| Supply Voltage | 3.0 V to 5.5 V |
| USB Controller | USB 1.1 Full-Speed Device (12 Mbps) |
| USB Regulator | Integrated 3.3 V |
| ADC | 5-channel, 8-bit |
| Timers | 2x 16-bit (TIM1/TIM2) |
| Serial Interface | 1x SCI (UART) |
| I/O Pins | 23 GPIO |
| Package | 28-SOIC (300 mil, wide-body) |
| Operating Temperature | -40 C to +85 C (ADW = industrial) |
| Mounting Type | Surface Mount (SMD) |
| RoHS Status | Compliant (Pb-free suffix on later lots) |
MC68HC908JB8ADW Pin Configuration
| Pin 1 | IRQ — External interrupt request |
| Pin 2 | RST — Reset input (active low) |
| Pin 3 | PTA0 — Port A bit 0 / KBI0 |
| Pin 4 | PTA1 — Port A bit 1 / KBI1 |
| Pin 5 | PTA2 — Port A bit 2 / KBI2 |
| Pin 6 | PTA3 — Port A bit 3 / KBI3 |
| Pin 7 | VSS — Ground |
| Pin 8 | VDD — Power supply (3.0-5.5 V) |
| Pin 9 | PTA4 — Port A bit 4 / KBI4 |
| Pin 10 | PTA5 — Port A bit 5 / KBI5 |
| Pin 11 | PTB0 — Port B bit 0 / ADC0 |
| Pin 12 | D- — USB D- data line |
| Pin 13 | D+ — USB D+ data line |
| Pin 14 | VUSB — USB 3.3 V regulator output (decouple) |
| Pin 15 | VSS — Ground |
| Pin 16 | PTB1 — Port B bit 1 / ADC1 |
| Pin 17 | PTB2 — Port B bit 2 / ADC2 / TCLK |
| Pin 18 | PTB3 — Port B bit 3 / ADC3 |
| Pin 19 | PTB4 — Port B bit 4 / ADC4 |
| Pin 20 | VSS — Ground |
| Pin 21 | PTC0 — Port C bit 0 / TxD |
| Pin 22 | PTC1 — Port C bit 1 / RxD |
| Pin 23 | PTC2 — Port C bit 2 |
| Pin 24 | PTC3 — Port C bit 3 |
| Pin 25 | PTC4 — Port C bit 4 |
| Pin 26 | PTC5 — Port C bit 5 |
| Pin 27 | OSC1 — Crystal oscillator input |
| Pin 28 | OSC2 — Crystal oscillator output |
Typical Applications
MC68HC908JB8ADW is suitable for 7 applications: USB HID Input Devices (Mouse / Keyboard), USB-to-UART Serial COM-Port Bridge, USB Mass-Storage Card Reader, USB Joystick / Game Controller, USB Diagnostic Dongle / I/O Module, Industrial USB Sensor Interface, Low-Speed USB Dongle Bootloader / Programming Target.
USB HID Input Devices (Mouse / Keyboard)
The MC68HC908JB8ADW fits USB HID-class pointing devices and keyboards because it integrates the USB 1.1 full-speed device controller, an internal 3.3 V transceiver regulator, the HC08 core to run HID class descriptors, and 23 GPIO to scan matrix key or optical-sensor inputs. At 3 MHz the core easily handles 1000 Hz polling rate of a high-performance mouse sensor with margin for HID report assembly. The 8 KB FLASH holds boot-loader plus HID descriptor tables; 256 B RAM sustains endpoint packet assembly. Used between the USB bus and the optical sensor with only a single 5 V decoupling bulk capacitor and the USB-B connector.
Recommended
USB-to-UART Serial COM-Port Bridge
The MC68HC908JB8ADW serves as a low-cost USB-to-UART bridge because it combines the USB 1.1 device peripheral (CDC/ACM endpoint support) with the on-chip SCI that maps cleanly to an external RS-232 level translator. The 3 MHz HC08 executes the CDC state machine and 115200-baud UART routing with sub-1% CPU overhead; the integrated 3.3 V regulator eliminates an external LDO on the bus-powered side, ideal for legacy serial-port replacement cables. Placed between the USB-A connector and an external MAX3232 RS-232 driver, with TX/RX visible on two GPIO pins.
Recommended
USB Mass-Storage Card Reader
The MC68HC908JB8ADW works in a USB flash card reader because the integrated USB 1.1 bulk endpoint plus 8 KB FLASH can run a SCSI-over-USB Bulk-Only Transport stack, while the HC08's parallel I/O drives standard NAND or MMC card interfaces. The 256-byte RAM sizes packets to fit one 64-byte USB endpoint; the 5-channel ADC is not used here but is reserved for the optional power-good monitoring. Used between the USB-A connector and a card socket with the integrated regulator powering both the MCU and external level shifters.
Recommended
USB Joystick / Game Controller
The MC68HC908JB8ADW is well-matched to USB HID joysticks and game controllers because the integrated USB full-speed device module supports interrupt endpoints required by HID class, the 5-channel ADC handles analog axes (X/Y stick + thumb rotary), and the 16-bit timers generate sub-millisecond HID report timing. The HC08 is fast enough at 3 MHz to scan a 4x4 button matrix with debounce and emit 1000 Hz USB reports. Placed between the USB connector and the analog axes; the internal 3.3 V regulator powers the MCU only.
Recommended
USB Diagnostic Dongle / I/O Module
The MC68HC908JB8ADW suits low-speed USB I/O diagnostic dongles because it pairs an integrated USB 1.1 device peripheral (capable of vendor-class bulk transfers) with the 5-channel 8-bit ADC for analog sense inputs and the SCI for optional RS-232 diagnostic output. The HC08 core at 3 MHz is fast enough to execute vendor-class USB stacks while servicing 100 Hz analog sampling. Used between a USB-A connector and a buffered I/O header; the internal regulator powers the MCU and accepts 5 V VBUS directly.
Recommended
Industrial USB Sensor Interface
The MC68HC908JB8ADW handles industrial USB sensor interfaces because its -40 C to +85 C temperature grade (ADW suffix) covers industrial environments, the integrated USB 1.1 device removes the need for an external transceiver, and the 5-channel 8-bit ADC digitizes analog sensor outputs. With 8 KB FLASH and 256-byte RAM it runs a vendor-class USB stack while reporting sensor data at 100 Hz. Placed in a sealed housing connected to upstream USB hosts; the integrated 3.3 V regulator simplifies PCB layout.
Recommended
Low-Speed USB Dongle Bootloader / Programming Target
The MC68HC908JB8ADW serves as a USB-bootloader target because the integrated USB 1.1 device peripheral and the HC08's standard Monitor Mode allow field re-flashing via USB without an external BDM probe. The 8 KB FLASH fits a small CDC-class USB stack plus application code; the 256-byte RAM is sufficient for the bootloader buffer. Used in field-serviceable designs where end users can reflash the firmware over USB; the on-chip regulator powers the MCU and the external EEPROM.
Recommended
Recommended Products Summary
Engineering reference data for MC68HC908JB8ADW — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | MC68HC908JB8FA | MC68HC908JB16 | MC9S08JB16 |
|---|---|---|---|---|
| Package | 28-SOIC (300 mil) | 32-LQFP | 28-SOIC | 28-SOIC |
| Brand | NXP Semiconductors | NXP Semiconductors | NXP Semiconductors | NXP Semiconductors |
| Core | HC08 (8-bit) | HC08 (8-bit) | HC08 (8-bit) | S08 (8-bit) |
| Program Memory | 8 KB FLASH | 8 KB FLASH | 16 KB FLASH | 16 KB FLASH |
| RAM | 256 bytes | 256 bytes | 512 bytes | 1 KB |
| USB Controller | USB 1.1 Full-Speed Device | USB 1.1 Full-Speed Device | USB 1.1 Full-Speed Device | USB 1.1 Full-Speed Device |
| USB Regulator | Integrated 3.3 V | Integrated 3.3 V | Integrated 3.3 V | Integrated 3.3 V |
| Supply Voltage | 3.0 V to 5.5 V | 3.0 V to 5.5 V | 3.0 V to 5.5 V | 2.7 V to 5.5 V |
| Operating Temperature | -40 C to +85 C | -40 C to +85 C | -40 C to +85 C | -40 C to +105 C |
| Lifecycle | NRND | NRND | NRND | Active |
Key Differentiators
- Integrated USB 3.3 V regulator + transceiver on the same die (vs PIC16F1455)
- Industrial -40 to +85 C temperature range on the ADW variant (vs MC68HC908JB8CFA)
- Footprint-compatible migration to MC9S08JB16 (vs MC68HC908JB8CFA)
Design Notes
The integrated USB 3.3 V regulator inside the MC68HC908JB8ADW requires a minimum 1 uF decoupling capacitor on the VUSB pin (pin 14) and the analog VDD/VSS pins to maintain USB signalling integrity. Bulk decoupling of 4.7 uF at the upstream 5 V VBUS plus 0.1 uF at each VDD pin is recommended to suppress hot-plug transients. The regulator sources roughly 30 mA at 3.3 V, sufficient for the internal transceiver but not for downstream devices.
Estimated for an SOIC-28 on a 2-layer 1 oz FR4 board with no dedicated thermal copper, the theta_JA for MC68HC908JB8ADW is approximately 75 C/W. At typical HID-class current of 25 mA from 5 V the internal dissipation is under 0.13 W and the part does not require a heatsink or thermal pad, but avoid placing the SOIC-28 directly above the switching regulator to keep case temperature rise below 10 C above ambient.
Do not apply 5 V to the D+ or D- pins when the USB regulator is disabled; without VUSB bias, the ESD diodes can forward-conduct and latch the MCU. Always power up VDD before or simultaneously with the upstream USB bus, and add the recommended 4.7 kohm pull-up on D+ only after the MCU firmware has enabled the USB module (per Section 12 of the MC68HC908JB8 datasheet).
Compliance Information
RoHS/REACH compliance per current NXP/Freescale product declarations. Lead-free reflow profile per JEDEC J-STD-020. AEC-Q100 is not applicable - this part is not qualified for automotive use.
