HT66F25D - A/D Flash 8-bit MCU with EEPROM | Holtek
MPN: HT66F25D ✗ End of Life| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $0 | $0.00 |
| 10 | $0 | $0.00 |
| 100 | $0 | $0.00 |
| 500 | $0 | $0.00 |
| 1,000 | $0 | $0.00 |
HT66F25D Overview
An 8-bit Flash microcontroller is a complete computing system on a single integrated circuit: it combines a processor core, program Flash memory, data RAM, EEPROM, peripheral functions such as timers, PWM and ADC channels, and general-purpose I/O. Within the semiconductor hierarchy, the HT66F25D sits in the microcontroller -> embedded processor -> integrated circuit taxonomy, positioned for cost-sensitive embedded control where on-chip analog input and small non-volatile data storage remove the need for external components.
Key differentiating features of this device, as stated by Holtek and the datasheet aggregators carrying the official document, include the Flash program memory with multi-programming support (enabling in-circuit update during development and production), the integrated A/D converter for reading analog sensors directly, the on-chip EEPROM for calibration data and user settings that must survive power cycles, and the enhanced high-current LED driver capability highlighted in Holtek's product notification for the HT66F24D/HT66F25D family.
Architecturally, the device follows Holtek's RISC-style 8-bit core used across the HT66Fx1D series, with register-mapped I/O ports (PA, PB, PC with individual pull-up and wake-up control bits per the datasheet register lists), typical of the family's low-cost, low-pin-count embedded control philosophy. The exact clock frequency range, ADC resolution, Flash and RAM capacities are detailed in the 175-page official datasheet and should be confirmed there for each specific suffix.
Typical applications include small appliance control, LED lighting and brightness control exploiting the high-current driver outputs, battery chargers, sensor interfaces using the A/D converter, and consumer products requiring configuration storage in EEPROM.
A key design consideration: this device has been formally phased out by Holtek. According to the official Holtek EOL notification PDF, the last time buy date was April 14, 2026, so new designs must qualify a replacement immediately.
This page synthesizes distributor sourcing data, the official Holtek EOL cross-reference notice, and drop-in replacement analysis not found on standard datasheet aggregator sites.
Drop-in alternatives for HT66F25D — 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:
HT66F24D
✅ Drop-In📋 Reference alternative (not in catalog)
HT66F25D Maximum Ratings & Electrical Characteristics
| Core Architecture | 8-bit RISC |
| Program Memory Type | Flash (multi-programming) |
| Data EEPROM | On-chip EEPROM |
| ADC | On-chip A/D converter |
| LED Driver | High-current LED driver outputs |
| Product Family | HT66F24D / HT66F25D series |
| Package Type | SOP (surface mount small-outline) |
| Mounting Type | Surface Mount |
| Datasheet Pages | 175 pages (Rev. 1.10 revision noted in document) |
HT66F25D sop (surface mount small-outline) Pin Configuration Guide
Pin configuration for HT66F25D (sop (surface mount small-outline) package). This digital IC includes GPIO, communication interfaces (UART, SPI, I2C), and power pins. Refer to the manufacturer datasheet for alternate pin functions and configuration options. Essential for embedded system design and PCB layout.
No detailed pinout data available for HT66F25D.
Refer to the datasheet for full pin configuration.
Typical Applications
HT66F25D is suitable for 6 applications: LED Lighting Control, Small Appliance Control, Battery-Powered Consumer Devices, Sensor Interface and Measurement, Battery Chargers, Toys and Interactive Consumer Products.
LED Lighting Control
The HT66F25D fits LED lighting control because Holtek enhanced this device family specifically with high-current LED driver outputs, as confirmed by Holtek's product notification titled 'Enhanced A/D Flash MCU with High Current LED Driver'. The MCU's PWM resources and direct-drive outputs let a single SOP-package chip handle brightness control and color mixing without external driver transistors for moderate-current LED strings, cutting BOM cost in bulb and luminaire designs. The on-chip A/D converter supports feedback such as potentiometer dimming input or temperature monitoring of the LED board, while the EEPROM retains the last brightness setting across power cycles. Because the part is now EOL, lighting designers should migrate to Holtek's officially cross-referenced replacement in the EOL notification before committing new lamp platforms.
Recommended
Small Appliance Control
The HT66F25D is well suited to small appliance control boards (kettles, fans, rice cookers) because it integrates the three functions such products always need: an 8-bit RISC core for control logic, an A/D converter for reading NTC temperature sensors or user potentiometers, and EEPROM for storing user preferences and calibration data that survive power interruption. The Flash program memory with multi-programming support shortens production firmware updates. Holtek's HT66F family targets exactly this cost-sensitive segment, and the SOP surface-mount package suits compact single-board appliance layouts. The HT66F24D/HT66F25D shared datasheet documents port pull-up and wake-up registers (PA/PB/PC) that simplify key-scanning interfaces. With the last time buy passed in April 2026, appliance makers must qualify the Holtek-recommended replacement for continued serviceability.
Recommended
Battery-Powered Consumer Devices
Battery-powered consumer products benefit from the HT66F25D's single-chip integration: the 8-bit RISC core, on-chip A/D converter for battery-voltage monitoring, and EEPROM for configuration storage eliminate external ADC and memory ICs, reducing board area and quiescent component count. The Holtek family's port wake-up control bits (PAWU register documented in the shared HT66F24D/HT66F25D datasheet) support wake-on-input schemes essential for long battery life in remote controls, toys, and meters. Flash multi-programming allows firmware refresh in the field or at final test. Designers should note that exact supply-voltage and standby-current figures must be taken from the official 175-page datasheet rather than assumed. Since the device is EOL (last time buy April 14, 2026), battery-product platforms should adopt the Holtek EOL cross-reference replacement going forward.
Recommended
Sensor Interface and Measurement
The HT66F25D serves sensor-interface nodes by digitizing analog signals directly through its on-chip A/D converter, documented across the family's 175-page datasheet. Temperature, voltage-divider, and resistive sensor outputs connect straight to ADC input pins, with results processed by the 8-bit RISC core and thresholds or calibration constants stored in the integrated EEPROM. Distributor analysis notes the HT66F25D carries enhanced ADC capability relative to the smaller HT66F23D, making it the preferred family member for analog-front-end accuracy, though pin and peripheral differences mean it is not a drop-in for that part. Port pull-up registers (PAPU/PBPU/PCPU) simplify switch and encoder inputs. Given EOL status, new sensor products should target the replacement device named in Holtek's official EOL_HT66F25D.pdf cross-reference notice.
Recommended
Battery Chargers
Battery charger control is a natural fit for the HT66F25D: the A/D converter monitors pack voltage and current-sense inputs, the 8-bit RISC core executes charge-termination algorithms, and the EEPROM stores charge-count or chemistry profile data across power cycles. The enhanced high-current LED driver outputs highlighted in Holtek's family notification can drive charge-status indicators directly. The SOP surface-mount package keeps charger PCBs compact for wall adapters and portable charging cradles. Because the device supports Flash multi-programming, charger vendors can update CC/CV termination thresholds in production without mask-ROM commitments. One caution: with the last time buy deadline of April 14, 2026 already passed, charger manufacturers with long service commitments should secure remaining stock and simultaneously qualify the officially cross-referenced replacement listed in Holtek's EOL notification.
Recommended
Toys and Interactive Consumer Products
Toys and interactive products historically adopted the HT66F25D because one low-cost SOP chip covers sound-effect sequencing (via the RISC core and timers), button sensing (port pull-ups and wake-up bits), analog joystick or sensor reading (A/D converter), and persistence of high scores or settings (EEPROM). Holtek's HT66F Flash family was widely designed into this segment precisely for its mask-free Flash multi-programming, letting toy firmware be revised late in the seasonal production cycle. The high-current driver outputs can also drive LEDs for light effects without external transistors. The 175-page shared HT66F24D/HT66F25D datasheet documents the full register set needed for these functions. As the part is now EOL per Holtek's official notification, toy platforms must transition to the cross-referenced successor or an equivalent Holtek Flash MCU family member.
Recommended
Recommended Products Summary
Engineering reference data for HT66F25D — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | HT66F24D |
|---|---|---|
| Package | SOP | SOP - same family package |
| Brand | Holtek Semiconductor | Holtek Semiconductor |
| Core | 8-bit RISC | 8-bit RISC |
| Program Memory | Flash (multi-programming) | Flash (multi-programming) |
| Data EEPROM | Yes (on-chip) | Yes (on-chip) |
| ADC | Yes (on-chip A/D) | Yes (on-chip A/D) |
| LED Driver | High-current LED driver outputs | High-current LED driver outputs |
| Lifecycle Status | EOL - last time buy April 14, 2026 | EOL - effective 2018/3/25 |
Key Differentiators
- Enhanced high-current LED driver integration (vs HT66F24D (and general HT66Fx family members))
- Enhanced ADC and PWM capability vs smaller family parts (vs HT66F23D)
- EEPROM plus Flash on one chip (vs Generic 8-bit MCUs without EEPROM)
Design Notes
The most critical design consideration for the HT66F25D is lifecycle, not electrical: Holtek's official EOL notification (EOL_HT66F25D.pdf) sets the last time buy at April 14, 2026, which has already passed. Any new PCB spin using this device creates an immediate obsolescence liability. Obtain the official replacement cross-reference from the Holtek EOL document and verify pinout and register-level compatibility against your existing firmware before committing layouts. Do not assume the HT66F23D is a substitute - distributor analysis confirms it is not pin-compatible.
Within the HT66F24D/HT66F25D shared datasheet, I/O behavior is controlled per-bit through the PA/PB/PC port registers with companion pull-up (PAPU/PBPU/PCPU) and wake-up (PAWU) registers, as shown in the datasheet register lists. The datasheet's Programming Considerations section explicitly requires port initialization as one of the first actions after reset - all I/O default states must be configured before use. Omitting initialization of these registers is a classic migration bug when porting firmware between family members, so review the register map of the exact device you ultimately qualify.
The HT66F25D is supplied in an SOP surface-mount package per the datasheet aggregator listing. When sourcing after-market EOL stock, insist on original factory-sealed tape-and-reel or tube packaging with readable date codes, and verify MSL rating before reflow - broker inventory of phased-out MCUs is frequently repackaged and moisture-damaged. Bake per JEDEC moisture-sensitivity handling if in doubt. Cross-check the ordering-code suffix on received units against the datasheet ordering table to confirm package and voltage options match what your layout was designed for.
Compliance Information
Compliance data was not present in the provided verified web data; consult the Holtek product page for RoHS/REACH status of the HT66F25D.
