MCHC705JJ7CPE - 8-bit HC05 MCU, 6KB OTP, 2.1MHz, DIP-20 | NXP
MPN: MCHC705JJ7CPE ✗ End of Life| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $6.42 | $6.42 |
| 10 | $5.78 | $57.80 |
| 100 | $5.14 | $514.00 |
| 500 | $4.62 | $2,310.00 |
| 1,000 | $4.15 | $4,150.00 |
MCHC705JJ7CPE Overview
An 8-bit microcontroller (MCU) is a single-chip computer built around an 8-bit data path, on-chip program memory, RAM, peripherals, and I/O. It belongs to the broader hierarchy: microcontroller -> embedded processor -> semiconductor -> electronic component. The HC05 line from NXP/Freescale is one of the longest-lived 8-bit families, designed for deterministic, low-power control tasks that do not need the throughput of a 16- or 32-bit core. Compared with modern ARM Cortex-M0 parts, HC05 MCUs trade raw performance for simplicity, an easy-to-write instruction set, and a small memory footprint that fits mass-market appliance and consumer applications.
Key features of the MCHC705JJ7CPE include 6KB (6144 bytes) of OTP program memory, 224 bytes of on-chip RAM, 14 general-purpose I/O lines, an internal oscillator that removes the need for an external crystal on many designs, a serial communications interface (SCI) for UART-style asynchronous serial, a 16-bit timer with capture and compare, and a five-channel 8-bit ADC. The on-chip monitor ROM provides in-circuit serial programming for development and field updates. The 'C' temperature grade supports 0C to +70C operation, while the 'E' suffix denotes the -40C to +125C extended grade - a key discriminator when selecting between suffixes in the family.
The device uses the legacy HC05 core with a von Neumann memory map. The OTP memory is one-time programmable, so firmware must be fully verified before production programming; for high-volume runs, the masked-ROM equivalent (MCHC705JJ7MPE or similar) is more economical. The internal oscillator and the absence of an external bus make the device suitable for single-chip-mode applications where the MCU is the only active logic on the board.
Typical applications include white-goods motor drivers, small appliance controllers, simple sensor interfaces, security and alarm panels, remote-control transmitters, and educational/development boards where a through-hole DIP package aids manual soldering and lab rework. Designers should note that OTP memory cannot be re-programmed, so a debug-and-reflash workflow typically uses the windowed or EPROM-emulator sibling (MCHC705JJ7PBE) during development, with the OTP device reserved for production.
When designing with the MCHC705JJ7CPE, ensure adequate decoupling on VDD/VSS (typically 100 nF plus bulk), keep the RESET pin high through a pull-up with optional capacitor for POR, and verify that the chosen I/O lines are 5V-tolerant when interfacing 3.3V peripherals. Trade-off: the 2.1 MHz clock caps instruction throughput but minimizes EMI and power consumption versus faster HC08/HC11 derivatives.
This page synthesizes distributor pricing, OTP-versus-mask trade-offs, and practical design notes not found in the legacy NXP datasheet alone.
Drop-in alternatives for MCHC705JJ7CPE — 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 MCHC705JJ7CPE (same form factor and footprint) — differing in Operating Temperature, Package, Timers.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
MCHC705JJ7PBE
✅ Drop-In📋 Reference alternative (not in catalog)
MCHC705JJ7MPE
✅ Drop-In📋 Reference alternative (not in catalog)
MC68HC705J1A
✅ Drop-In📋 Reference alternative (not in catalog)
MC68HC705C8A
✅ Drop-In📋 Reference alternative (not in catalog)
AT89C2051-24PU
✅ Drop-In📋 Reference alternative (not in catalog)
MCHC705JJ7CPE Maximum Ratings & Electrical Characteristics
| Core | HC05 8-bit |
| Program Memory Size | 6 KB (6K x 8) OTP |
| RAM Size | 224 bytes |
| Maximum Clock Frequency | 2.1 MHz |
| Number of I/O Pins | 14 |
| Package | 20-DIP (0.300", 7.62 mm) |
| Mounting Type | Through-Hole (THT) |
| ADC | 5-channel, 8-bit (per family datasheet) |
| Timers | 1 x 16-bit with capture/compare |
| Serial Interface | SCI (UART) |
| Operating Temperature | 0C to +70C (C grade) |
| Program Memory Type | One-Time Programmable (OTP) |
| On-chip Monitor ROM | Yes (in-circuit serial programming) |
| Internal Oscillator | Yes (typical of HC05 'JJ' family) |
MCHC705JJ7CPE Pin Configuration
| Pin 1 | IRQ — External interrupt request input (active low) |
| Pin 2 | VSS — Ground reference |
| Pin 3 | TCMP — Timer compare output |
| Pin 4 | PA0 — Port A bit 0 (digital I/O) |
| Pin 5 | PA1 — Port A bit 1 (digital I/O) |
| Pin 6 | PA2 — Port A bit 2 (digital I/O) |
| Pin 7 | PA3 — Port A bit 3 (digital I/O) |
| Pin 8 | PA5 — Port A bit 5 (digital I/O / SCI RxD) |
| Pin 9 | PA6 — Port A bit 6 (digital I/O / SCI TxD) |
| Pin 10 | PA7 — Port A bit 7 (digital I/O) |
| Pin 11 | PB0 — Port B bit 0 (digital I/O / ADC) |
| Pin 12 | PB1 — Port B bit 1 (digital I/O / ADC) |
| Pin 13 | PB2 — Port B bit 2 (digital I/O / ADC) |
| Pin 14 | PB3 — Port B bit 3 (digital I/O / ADC) |
| Pin 15 | PB4 — Port B bit 4 (digital I/O / ADC) |
| Pin 16 | VDD — Positive supply (typically +5 V) |
| Pin 17 | OSC1 — External clock input / crystal connection (internal osc also used) |
| Pin 18 | OSC2 — Crystal connection / clock output (internal osc also used) |
| Pin 19 | RESET — Active-low reset input with on-chip pull-up |
| Pin 20 | TEST — Test mode pin (must be tied to VDD for normal operation) |
Typical Applications
MCHC705JJ7CPE is suitable for 6 applications: White Goods Motor Control, Small Appliance Controller, Sensor Interface Hub, Security and Alarm Panel, Remote Control Transmitter / Receiver, Educational and Development Boards.
White Goods Motor Control
The MCHC705JJ7CPE fits white-goods motor control because its HC05 core, 14 I/O lines, and 5-channel 8-bit ADC can read speed sensors and commutator feedback, while the 16-bit timer drives TRIAC or relay switching at line frequency. With 6KB OTP it holds typical appliance-state firmware (wash cycles, sensor debouncing, error latching) without external memory, and the 2.1 MHz clock is fast enough for sub-millisecond control loops but low enough to minimize EMI near mains wiring. Designers place the part in 20-DIP for through-hole reliability in washers and dryers; the on-chip oscillator removes the need for a ceramic resonator, saving BOM cost and board area on cost-engineered consumer appliances.
Recommended
Small Appliance Controller
The MCHC705JJ7CPE serves as the central state machine in coffee makers, rice cookers, blenders, and similar small appliances. Its 6KB OTP comfortably stores menu/state tables, its 224-byte RAM handles sensor averaging buffers, and the SCI/UART block supports debug logging or wireless-module hookup for premium models. The HC05's well-known instruction set simplifies firmware porting from previous Freescale designs, and the 20-DIP package simplifies the manual rework typical in low-volume appliance SKUs. Operating temperature range of 0C to +70C covers the kitchen environment, while the active-low RESET with on-chip POR handles power-on in noisy mains conditions.
Recommended
Sensor Interface Hub
The MCHC705JJ7CPE's 5-channel 8-bit ADC, 14 I/O pins, and HC05 core make it a sensible sensor interface hub for HVAC, security panels, and simple IoT edge nodes. The ADC multiplexes thermistor, humidity, and PIR-style sensor inputs; the 16-bit timer captures pulse-width-modulated sensor outputs; the SCI block uplinks readings to a host MCU or radio module. With only 2.1 MHz clock, the part draws low quiescent current, extending battery life in remote sensor nodes. The 20-DIP through-hole package suits field-serviceable panels where technicians may need to swap the MCU; the on-chip monitor ROM supports in-system firmware updates via the serial monitor.
Recommended
Security and Alarm Panel
The MCHC705JJ7CPE runs the central scan loop in legacy security panels, polling 8-12 wired zones through its 14 I/O lines and driving the keypad, siren, and dialer outputs through buffered lines. Its deterministic HC05 core avoids jitter in zone scan timing - critical for false-alarm prevention - and the 6KB OTP holds zone-mapping tables plus dialer protocol stacks. The on-chip SCI talks to a modem IC for PSTN or GSM backup reporting. The 20-DIP package supports field replacement without specialized soldering tools, and the commercial 0C to +70C temperature grade covers indoor wall-mount installations in residential and light-commercial security markets.
Recommended
Remote Control Transmitter / Receiver
The MCHC705JJ7CPE builds simple RF remote controls and receivers where the 6KB OTP stores key-mapping tables, rolling-code state, and modulation profiles. Its SCI drives a low-cost ASK/FSK transmitter IC, while the 16-bit timer generates carrier frequencies and bit-time precision for IR/RF protocols. With 2.1 MHz clock and aggressive idle modes, the part fits battery-powered transmitters that must last years on a coin cell. The 20-DIP package is friendly to hand-built and educational electronics labs, which is where this legacy HC05 family still sees significant volume. The HC05 toolchain (Motorola/Freescale/NXP assemblers and P&E Micro debug probes) remains available from legacy support channels.
Recommended
Educational and Development Boards
The MCHC705JJ7CPE is widely used in legacy university curricula and Freescale/NXP training kits because of its straightforward HC05 instruction set, 20-DIP through-hole package (easy to socket), and on-chip monitor ROM that supports serial debug without a special bond-out part. Students learn timers, ADC scanning, and SCI communications on this device before moving up to HC08/HCS08 or ARM cores. The 6KB OTP is large enough to host complete lab exercises (LED scanners, keypad readers, PWM motor demos) without external memory. Replacement through-hole socketed variants (MCHC705JJ7PBE) let instructors re-flash boards class after class without chip replacement.
Recommended
Recommended Products Summary
Engineering reference data for MCHC705JJ7CPE — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | MCHC705JJ7PBE | MCHC705JJ7MPE | MC68HC705J1A | MC68HC705C8A | AT89C2051-24PU |
|---|---|---|---|---|---|---|
| Brand | NXP Semiconductors | NXP Semiconductors | NXP Semiconductors | NXP Semiconductors | NXP Semiconductors | Microchip Technology |
| Package | 20-DIP (0.300", 7.62 mm) | 20-DIP windowed - same | 20-DIP - same | 20-DIP - same | 20-DIP / PLCC variants - same | 20-DIP (0.300") - same |
| Core | HC05 8-bit | HC05 8-bit | HC05 8-bit | HC05 8-bit | HC05 8-bit | 8051 8-bit (different ISA) |
| Program Memory | 6 KB OTP | 6 KB windowed EPROM | 6 KB mask ROM | 1.2 KB EPROM | 8 KB EPROM | 2 KB flash |
| RAM | 224 bytes | 224 bytes | 224 bytes | 64 bytes | 304 bytes | 128 bytes |
| Max Clock Frequency | 2.1 MHz | 2.1 MHz | 2.1 MHz | 4 MHz | 4 MHz | 24 MHz |
| I/O Pins | 14 | 14 | 14 | 14 | 20 | 15 |
| Program Memory Type | OTP | UV EPROM (erasable) | Mask ROM (locked) | EPROM | EPROM | Flash (reprogrammable) |
| Production Status (2026) | NRD (Not Recommended for New Designs) | NRD / EOL | NRD | NRD | NRD | Active |
Key Differentiators
- On-chip monitor ROM for serial in-circuit programming (vs AT89C2051-24PU)
- Larger code memory than the MC68HC705J1A cousin (vs MC68HC705J1A)
- Reprogrammable windowed EPROM sibling available (vs MC68HC705C8A)
Design Notes
The MCHC705JJ7CPE operates from a single +5 V supply on VDD (pin 16). Place a 100 nF decoupling capacitor within 5 mm of the VDD pin and a bulk 10 uF capacitor on the supply rail close to the MCU. The HC05 internal POR and the external RESET pull-up (typically 4.7 kohm to VDD with a 0.1 uF cap) handle power-on. Note that at 2.1 MHz the part draws single-digit mA of active current, so decoupling alone is sufficient - no bulk capacitance beyond 10 uF is required.
Because the 20-DIP package is through-hole, place the MCU at the board edge or near a socket for easy replacement during development. Keep the RESET trace short and isolated from high-current traces (relay, TRIAC) to avoid false resets. If you use an external crystal on OSC1/OSC2, route the crystal traces short and symmetric with a ground guard ring; otherwise leave the internal oscillator selected and ground OSC2. The TEST pin must be tied to VDD; floating it can latch the device in test mode.
Common pitfalls with the MCHC705JJ7CPE: (1) OTP memory cannot be re-programmed - validate firmware on the MCHC705JJ7PBE windowed EPROM cousin before committing code; (2) the 'C' suffix denotes 0C to +70C commercial grade, not -40C to +125C - select the 'E' suffix for industrial; (3) the TEST/VPP pin MUST be tied to VDD or the part will not enter user mode; (4) the on-chip monitor ROM uses PA0/PA3 - reclaim these as general I/O only after disabling the monitor in the CONFIG register; (5) do not exceed 5.5 V on VDD or the EPROM/OTP cells can be corrupted during programming.
Compliance Information
RoHS / lead-free status not stated in the verified distributor listings; this part pre-dates strict RoHS enforcement and is commonly shipped as SnPb (leaded) through-hole DIP. NXP/Freescale legacy MCUs follow the manufacturer's compliance matrix in the product datasheet; check there for the exact MCHC705JJ7CPE compliance statement. AEC-Q100 is not applicable to this commercial-grade 8-bit MCU.
