NXP Semiconductors MC68HC705JJ7CDW

Overview

MC68HC705JJ7CDW from Freescale Semiconductor is a 8-bit HCMOS microcontroller featuring 1.5 KB on-chip EPROM, 64 bytes RAM, and integrated analog subsystem including dual voltage comparators, 8-channel 8-bit ADC, and internal temperature sensor. It operates at up to 4 MHz with 5 V supply and supports multiple low-power modes (Stop, Wait, Halt). It targets embedded control in appliance motor interfaces and industrial sensor nodes.

For engineers reviewing the MC68HC705JJ7CDW datasheet, MC68HC705JJ7CDW pinout, MC68HC705JJ7CDW application, or MC68HC705JJ7CDW equivalent, key selection criteria include its 20-pin SOIC-W package, COP watchdog timer, SIOP synchronous serial interface, and PEPROM personality configuration capability - all critical for legacy replacement and cost-sensitive 5 V control designs.

Technical Context

The MC68HC705JJ7CDW implements the M68HC05 CPU core with accumulator-based architecture, 16-bit program counter, and condition code register. Its memory map includes 1.5 KB EPROM (user-programmable OTP), 64 B RAM, and dedicated I/O registers mapped to $00–$3F address space.

It integrates three timing peripherals: a 16-bit programmable timer with input capture/output compare, an 8-bit core timer with real-time interrupt capability, and a COP watchdog with configurable timeout via PEPROM bits. Analog functions are managed through dedicated control/status registers for ADC, comparators, and current source.

Key Specifications

Pinout & Package

MC68HC705JJ7CDW is housed in a 20-pin Small Outline Integrated Circuit – Wide (SOIC-W) package with 0.3 inch body width and 0.050 inch lead pitch. Pin numbering follows standard SOIC convention (pin 1 marked, counterclockwise).

Key Features

Applications

Equivalent & Alternatives

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

Compared with MC68HC705P6CDW, the MC68HC705JJ7CDW adds integrated analog sensing and serial communication at the cost of reduced program memory; versus MC68HC908QT4CDW, it offers proven reliability and simpler toolchain support but lacks FLASH endurance and modern debug features.

Availability

MC68HC705JJ7CDW is available at Aetrix Electronics and suitable for appliance motor control, industrial sensor nodes, legacy automotive subsystems, and small-appliance power supply monitors requiring stable component supply and long-term obsolescence management.

Supply support for MC68HC705JJ7CDW 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

Freescale Semiconductor (now part of NXP Semiconductors) was a leading designer of embedded processors and analog/mixed-signal ICs for automotive, industrial, and consumer markets.

The MC68HC705 family was engineered for cost-sensitive, low-pin-count 8-bit control applications where integration of analog peripherals, low-power operation, and OTP programmability were essential design requirements.

FAQ

What is the maximum operating frequency of the MC68HC705JJ7CDW?

The MC68HC705JJ7CDW supports a maximum system clock frequency of 4 MHz when driven by an external crystal or resonator. This limit is defined by the internal HCMOS timing characteristics and applies across the full commercial temperature range (0°C to +70°C). Operation above this frequency may result in undefined CPU behavior or peripheral malfunction. The MC68HC705JJ7CDW does not support internal PLL multiplication.

Does the MC68HC705JJ7CDW include built-in flash memory or EEPROM?

No, the MC68HC705JJ7CDW uses one-time programmable (OTP) EPROM for program storage - not flash or EEPROM. Once programmed, the EPROM cannot be electrically erased or rewritten. The device includes 64 bytes of volatile RAM for runtime data storage, but no non-volatile data memory. Field updates require replacement of the MC68HC705JJ7CDW unit.

Can the MC68HC705JJ7CDW operate from a 3.3 V supply?

No, the MC68HC705JJ7CDW is specified only for 5.0 V ±10% operation (4.5 V to 5.5 V). Its internal oscillator, analog subsystem, and I/O voltage levels are designed for 5 V logic compatibility. Attempting 3.3 V operation will cause failure of the ADC, comparators, and core timing functions, and is outside the device's absolute maximum ratings.

How is the COP watchdog timer configured on the MC68HC705JJ7CDW?

The COP watchdog timer on the MC68HC705JJ7CDW is enabled or disabled, and its timeout period is set, via configuration bits stored in the Personality EPROM (PEPROM). These bits are programmed once during manufacturing or final test and cannot be altered in-circuit. The MC68HC705JJ7CDW requires a specific write sequence to the COP register during runtime to prevent timeout reset.

What analog input channels are available on the MC68HC705JJ7CDW?

The MC68HC705JJ7CDW provides eight analog input channels (AN0 through AN7), multiplexed onto Port B pins PB0–PB7. These channels feed into an 8-bit successive-approximation ADC with selectable reference sources (internal bandgap or external VREF). Channel selection is controlled via the Analog Multiplex Register (AMUX), and conversions are initiated either automatically or under software control.