MC68HC908QT4CP - 8MHz 8-bit HC08 MCU 4KB FLASH 8-PDIP | NXP
MPN: MC68HC908QT4CP ✗ End of Life| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $4.95 | $4.95 |
| 10 | $4.46 | $44.60 |
| 100 | $3.96 | $396.00 |
| 500 | $3.55 | $1,775.00 |
| 1,000 | $3.15 | $3,150.00 |
MC68HC908QT4CP Overview
An 8-bit microcontroller (MCU) is a single-chip computer that integrates a CPU, memory, and peripherals onto one silicon die. The HC08 family is a low-cost, high-performance extension of the M68HC05 line, implementing a Complex Instruction Set Computer (CISC) with a Von Neumann memory map (a single shared address space for program and data, simplifying pointer-based access). MCUs like the MC68HC908QT4CP occupy the bottom tier of embedded computing - below 32-bit microcontrollers and microprocessors, but above discrete logic - and are used where deterministic I/O control, low power, and small footprint are more important than raw throughput.
Key features of the MC68HC908QT4CP include 4KB (4K x 8) of on-chip FLASH for program storage, 128 x 8 bytes of RAM, an internal ADC for sensor interface, a PWM channel for motor or LED control, and a Low-Voltage Detection (LVD) plus Power-On Reset (POR) for robust supply supervision. The 5 general-purpose I/O pins are software-configurable for pull-up, direction, and interrupt-on-edge. The CPU08 core provides 16-bit index register, 16-bit stack pointer, and BCD arithmetic instructions that simplify decimal handling in metering and panel applications.
The part operates from a 3V supply (typical 3.0V to 5.5V range per the family datasheet), supports in-circuit programming through the monitor ROM, and uses a FLASH page-erase architecture that allows at least 1000 program/erase cycles. The 8-pin PDIP package is the most user-friendly variant for breadboarding and through-hole hobbyist designs, while a surface-mount SO-8 variant exists in the same family.
Typical applications for the MC68HC908QT4CP include low-cost consumer appliances, IR remote-control transmitters, simple motor/LED controllers, white-goods user interfaces, and battery-powered sensor nodes where the small 8-pin footprint and on-chip ADC reduce BOM cost. According to the NXP MC68HC908QY4 family datasheet, the QT/QY sub-family targets cost-sensitive applications that need ADC, PWM, and FLASH in 8- or 16-pin packages.
When using this MCU, ensure the supply decoupling is adequate (typically 100nF plus 10uF bulk at VDD/VSS) and that the analog supply (AVDD/AVSS, where present on larger-pin-count siblings) is properly filtered if the ADC is used. FLASH write/erase operations require the supply to remain above the LVD threshold, and the monitor mode entry sequence (PTB3/PTB4 handshake on larger siblings, or PTA0 on this 8-pin device) must be respected when using in-system programming.
This page synthesizes distributor pricing, drop-in same-family alternatives (MC68HC908QT2CP, MC68HC908QT1CP), and practical design notes that go beyond the manufacturer datasheet alone.
Drop-in alternatives for MC68HC908QT4CP — 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 MC68HC908QT4CP (same form factor and footprint) — differing in Mounting Type, Program Memory Size, RAM Size.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
MC68HC908QT4CPE
✅ Drop-In📋 Reference alternative (not in catalog)
MC68HC908QT2CP
✅ Drop-In✓ In Stock
$1.78 / Unit
View Datasheet →MC68HC908QT1CP
✅ Drop-In📋 Reference alternative (not in catalog)
MC68HC908QY4CP
✅ Drop-In📋 Reference alternative (not in catalog)
MC9S08SH4CP
✅ Drop-In📋 Reference alternative (not in catalog)
MC68HC908QT4CP Maximum Ratings & Electrical Characteristics
| Core Processor | HC08 |
| Core Size | 8-Bit |
| Maximum Clock Speed | 8 MHz |
| Program Memory Size | 4 KB (4K x 8) FLASH |
| RAM Size | 128 x 8 bytes |
| EEPROM Size | None |
| Number of I/O Pins | 5 |
| On-chip Peripherals | LVD, POR, PWM, ADC |
| Connectivity | Single-wire monitor / ICP |
| Architecture | Von Neumann (CISC) |
| Package | 8-PDIP (DIP-8) |
| Mounting Type | Through-Hole |
| FLASH Endurance | >=1000 program/erase cycles (family spec) |
| Part Status | Obsolete (per distributor listing) |
MC68HC908QT4CP Pin Configuration
| Pin 1 | PTA0/IRQ — Port A bit 0; also monitor-mode entry request (IRQ) |
| Pin 2 | PTA1 — Port A bit 1; GPIO / ADC channel |
| Pin 3 | PTA2 — Port A bit 2; GPIO / ADC channel |
| Pin 4 | PTA3 — Port A bit 3; GPIO / ADC channel |
| Pin 5 | PTA4 — Port A bit 4; GPIO / ADC channel |
| Pin 6 | PTA5 — Port A bit 5; GPIO / PWM output / ADC channel |
| Pin 7 | VSS — Ground reference |
| Pin 8 | VDD — Positive supply (3.0V to 5.5V family-typical) |
Typical Applications
MC68HC908QT4CP is suitable for 6 applications: IR Remote Control Transmitter, Battery-Powered Sensor Node, White-Goods User Interface, LED Dimmer / PWM Controller, Simple Fan or Pump Controller, Educational / Hobby 8-bit Platform.
IR Remote Control Transmitter
The MC68HC908QT4CP is well suited to low-cost IR remote control transmitters where its 8-pin PDIP footprint, 5 GPIO, on-chip PWM, and HC08 core provide all required peripherals. The 8MHz CPU08 core runs a carrier-generation interrupt service routine that drives the PWM output at typically 38 kHz with sub-carrier duty cycle, while the small 4KB FLASH budget is sufficient for protocol state machines (RC5, NEC, SIRC). The on-chip LVD prevents under-voltage transmission glitches when battery droops below 2.7V.
Recommended
Battery-Powered Sensor Node
In a battery-powered sensor node, the MC68HC908QT4CP's 5 GPIO with wake-on-edge, on-chip ADC for sensor reading, and HC08 STOP/WAIT low-power modes minimize quiescent current. The 128-byte RAM is enough to buffer a single sensor sample plus protocol header, and the 4KB FLASH holds a tiny MAC layer plus application code. With the LVD configured for brown-out, the MCU safely supervises a 3V coin cell through end-of-life.
Recommended
White-Goods User Interface
The MC68HC908QT4CP's PWM drives a buzzer or LED backlight, while its 5 GPIO scan a small keypad matrix or capacitive touch pad in a washing machine or microwave user interface. The 8-pin PDIP form factor is through-hole friendly for low-volume white-goods modules, and the HC08 core's BCD arithmetic simplifies timer-display handling. The 4KB FLASH comfortably holds menu and beep-pattern libraries.
Recommended
LED Dimmer / PWM Controller
For single-channel LED dimming or motor-speed control, the MC68HC908QT4CP provides a hardware PWM channel that can drive a logic-level MOSFET gate directly, freeing the CPU for user-input handling. The HC08 core updates duty cycle from a potentiometer read through the on-chip ADC, and the 8MHz clock gives 8-bit PWM resolution at 31 kHz - above the audible band. The 5 GPIO handle the potentiometer, mode button, status LED, and MOSFET drive.
Recommended
Simple Fan or Pump Controller
In a low-cost 12V DC fan or small pump controller, the MC68HC908QT4CP reads an NTC thermistor through its ADC and adjusts PWM drive to maintain a temperature setpoint. The 4KB FLASH holds a simple PID loop, and the LVD protects the firmware from corrupted state during cold-crank voltage drops. The 8-pin PDIP is well suited to through-hole assembly for compact appliance modules.
Recommended
Educational / Hobby 8-bit Platform
The MC68HC908QT4CP is widely used in university embedded-systems courses and hobbyist projects because of its breadboard-friendly 8-pin PDIP, classic HC08 architecture that teaches CISC concepts, and free development tools (CodeWarrior HC08, P&E Multilink). The 4KB FLASH and 128 B RAM are tight but realistic constraints that teach memory-conscious firmware design. The 5 GPIO drive LEDs, buttons, and a serial UART bit-banged through PTA0/PTA1.
Recommended
Recommended Products Summary
Engineering reference data for MC68HC908QT4CP — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | MC68HC908QT4CPE | MC68HC908QT2CP | MC68HC908QT1CP | MC68HC908QY4CP | MC9S08SH4CP |
|---|---|---|---|---|---|---|
| Brand | NXP Semiconductors | NXP Semiconductors | NXP Semiconductors | NXP Semiconductors | NXP Semiconductors | NXP Semiconductors |
| Package | 8-PDIP (DIP-8) | 8-PDIP (DIP-8) - same | 8-PDIP (DIP-8) - same | 8-PDIP (DIP-8) - same | 16-PDIP (DIP-16) | 8-PDIP (DIP-8) - same |
| Core | HC08 (CPU08) | HC08 (CPU08) | HC08 (CPU08) | HC08 (CPU08) | HC08 (CPU08) | S08 (forward-migration) |
| Clock Speed | 8 MHz | 8 MHz | 8 MHz | 8 MHz | 8 MHz | 20 MHz (S08) |
| FLASH Program Memory | 4 KB | 4 KB | 2 KB | 1 KB | 4 KB | 4 KB |
| RAM Size | 128 B | 128 B | 128 B | 128 B | 128 B | 256 B |
| GPIO Pins | 5 | 5 | 5 | 5 | 13 | 5 |
| Lifecycle Status | Obsolete | Obsolete | Obsolete | Obsolete | Obsolete | Active (recommended migration) |
Key Differentiators
- Largest FLASH in 8-pin PDIP HC08 line (vs MC68HC908QT1CP)
- Through-hole PDIP form factor (vs MC9S08SH4CP)
- Native 5 GPIO with on-chip ADC and PWM (vs MC68HC908QY4CP)
- On-chip FLASH with in-circuit programming (vs Older OTP MCUs)
Design Notes
Estimated: at 8MHz bus clock and 5V supply, the HC08 core draws approximately 5 to 10 mA active and <10 uA in STOP mode. Decouple VDD/VSS with a 100nF ceramic capacitor placed within 5 mm of the pins, plus a 10 uF bulk capacitor on the supply rail. The LVD threshold should be set above the minimum operating voltage (3.0V family-typical) so that firmware cannot write to FLASH under-voltage and corrupt the program image.
The PTA0/IRQ pin doubles as the monitor-mode entry request line. If your application pulls PTA0 high at power-up, the MCU will enter monitor mode instead of running user code. Use a weak pull-up on PTA0 or leave it undriven at reset, or include a 100 ms delay before driving PTA0 to allow user code to start and clear the monitor flag.
For the 8-pin PDIP footprint, use a standard 0.300 inch / 7.62 mm row spacing and 2.54 mm / 0.100 inch pin pitch. Place the decoupling capacitor between VDD (pin 8) and VSS (pin 7) with the shortest possible trace length. For ADC accuracy, route analog inputs PTA1-PTA5 away from the PWM output (PTA5) and keep a ground pour under the analog traces.
When using the on-chip ADC, run an acquisition cycle of at least 16 ADC clocks and avoid switching the PTA5 PWM output during ADC sampling. Internal channel-to-channel crosstalk is typically <1 LSB but can rise if digital outputs toggle simultaneously. Average 4 to 16 samples in firmware for sensor-reading noise reduction below the 10-bit raw resolution.
At 8MHz and 5V the HC08 core dissipates well under 100 mW, so no heatsink is required. Industrial-temperature variants (e.g. MC68HC908QT4CPE) operate from -40C to +85C junction. In sealed enclosures, derate ambient temperature by 10C to account for self-heating from nearby power components.
Compliance Information
Part is marked obsolete by NXP; full compliance certificates may not be available for older 8-PDIP lots. Lead-free and RoHS status not explicitly stated in provided data - mark unknown.
