ATMEGA48-20PJ - 8-Bit AVR MCU, 20MHz, 4KB Flash | Microchip
MPN: ATMEGA48-20PJ ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $2.1 | $2.10 |
| 10 | $1.86 | $18.60 |
| 100 | $1.52 | $152.00 |
| 500 | $1.34 | $670.00 |
| 1,000 | $1.18 | $1,180.00 |
ATMEGA48-20PJ Overview
A microcontroller (MCU) is a single integrated circuit that combines a processor core, program memory, data memory, and peripherals such as timers, ADCs, and communication interfaces. The ATmega48 belongs to the AVR family of 8-bit MCUs, which sits within the broader hierarchy of microcontrollers under the semiconductor and embedded processor taxonomy. AVR MCUs are widely used in embedded systems because they combine low power with a simple, easy-to-program architecture supported by AVR GCC toolchains and Arduino-compatible ecosystems such as MiniCore.
Key features include 23 general-purpose I/O lines, 32 general-purpose working registers, three flexible timer/counters with compare modes, an 8-channel 10-bit ADC, and a two-wire serial interface (TWI/I2C) plus SPI and USART serial ports. The device operates from 1.8V to 5.5V and includes DebugWIRE on-chip debug for low-cost debugging over the RESET pin. A watchdog timer, internal calibrated RC oscillator, and picoPower sleep modes round out the low-power feature set.
Architecturally, the ATmega48 uses a Harvard-structure AVR core with single-cycle instruction execution, self-programming Flash for in-system updates, and 256 bytes of on-chip EEPROM for non-volatile parameter storage. The 4KB Flash accommodates compact firmware typical of sensor nodes, motor control loops, and simple human-machine interfaces.
Typical applications include industrial control boards, battery-powered sensor nodes, appliance controls, and hobby/education platforms where DIP mounting supports socketed, replaceable designs. The 28-PDIP package is especially valuable for prototyping and legacy repair.
Design consideration: program the clock fuse bits carefully; switching from the internal 8 MHz RC oscillator to an external 20 MHz crystal requires setting CKSEL/SUT fuses, and an incorrect setting can brick the device until a high-voltage programmer is used.
This page synthesizes distributor pricing, drop-in alternatives, pinout data, and practical design notes not found in the manufacturer datasheet.
Drop-in alternatives for ATMEGA48-20PJ — 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 ATMEGA48-20PJ (same form factor and footprint) — differing in EEPROM, SRAM, ADC, Operating Temperature, Serial Interfaces.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
ATMEGA48-20PI
✅ Drop-In✓ In Stock
$0.98 / Unit
View Datasheet →ATMEGA48A-PU
✅ Drop-In ⚠️ 参数待验证✓ In Stock
$0.78 / Unit
View Datasheet →ATMEGA48PA-PU
✅ Drop-In ⚠️ 参数待验证✓ In Stock
$2.05 / Unit
View Datasheet →ATMEGA88-20PJ
✅ Drop-In ⚠️ 参数待验证📋 Reference alternative (not in catalog)
ATMEGA168-20PJ
✅ Drop-In ⚠️ 参数待验证📋 Reference alternative (not in catalog)
ATMEGA328P-PU
✅ Drop-In✓ In Stock
Contact for price
View Datasheet →ATMEGA48-20PJ Maximum Ratings & Electrical Characteristics
| Core Architecture | 8-bit AVR RISC |
| Maximum Clock Frequency | 20 MHz |
| Flash Program Memory | 4 KB (2K x 16) |
| SRAM | 512 B |
| EEPROM | 256 B |
| Throughput | Up to 20 MIPS at 20 MHz |
| Operating Voltage Range | 1.8 V to 5.5 V |
| GPIO Count | 23 |
| ADC Resolution | 10-bit, 8-channel |
| Timer/Counters | 3 |
| Serial Interfaces | USART, SPI, TWI (I2C) |
| Instructions | 131, most single-cycle |
| Debug Interface | DebugWIRE on-chip debug |
| Package | 28-PDIP |
| Mounting Type | Through Hole |
ATMEGA48-20PJ Pin Configuration
| Pin 1 | RESET/PC6 — Reset input or GPIO PC6 |
| Pin 2 | PD0/RXD — Port D bit 0 / USART receive |
| Pin 3 | PD1/TXD — Port D bit 1 / USART transmit |
| Pin 4 | PD2/INT0 — Port D bit 2 / External interrupt 0 |
| Pin 5 | PD3/INT1/OC2B — Port D bit 3 / External interrupt 1 / Timer2 output compare B |
| Pin 6 | PD4/T0/XCK — Port D bit 4 / Timer0 external clock / USART external clock |
| Pin 7 | VCC — Digital supply voltage |
| Pin 8 | GND — Ground |
| Pin 9 | PB6/XTAL1/TOSC1 — Port B bit 6 / Crystal oscillator input |
| Pin 10 | PB7/XTAL2/TOSC2 — Port B bit 7 / Crystal oscillator output |
| Pin 11 | PD5/T1/OC0B — Port D bit 5 / Timer1 external clock / Timer0 output compare B |
| Pin 12 | PD6/AIN0/OC0A — Port D bit 6 / Analog comparator positive input / Timer0 output compare A |
| Pin 13 | PD7/AIN1 — Port D bit 7 / Analog comparator negative input |
| Pin 14 | PB0/ICP1/CLKO — Port B bit 0 / Timer1 input capture / Clock output |
| Pin 15 | PB1/OC1A — Port B bit 1 / Timer1 output compare A (PWM) |
| Pin 16 | PB2/SS/OC1B — Port B bit 2 / SPI slave select / Timer1 output compare B (PWM) |
| Pin 17 | PB3/MOSI/OC2A — Port B bit 3 / SPI master output / Timer2 output compare A (PWM) |
| Pin 18 | PB4/MISO — Port B bit 4 / SPI master input |
| Pin 19 | PB5/SCK — Port B bit 5 / SPI serial clock |
| Pin 20 | AVCC — ADC supply voltage |
| Pin 21 | AREF — ADC analog reference |
| Pin 22 | GND — Ground |
| Pin 23 | PC0/ADC0 — Port C bit 0 / ADC channel 0 |
| Pin 24 | PC1/ADC1 — Port C bit 1 / ADC channel 1 |
| Pin 25 | PC2/ADC2 — Port C bit 2 / ADC channel 2 |
| Pin 26 | PC3/ADC3 — Port C bit 3 / ADC channel 3 |
| Pin 27 | PC4/ADC4/SDA — Port C bit 4 / ADC channel 4 / TWI data |
| Pin 28 | PC5/ADC5/SCL — Port C bit 5 / ADC channel 5 / TWI clock |
Typical Applications
ATMEGA48-20PJ is suitable for 6 applications: Industrial Control and Automation, Battery-Powered Sensor Nodes, Appliance and White-Goods Control, Education and Hobby Prototyping, Motor and Actuator Control, Legacy Repair and Obsolescence Management.
Industrial Control and Automation
The ATMEGA48-20PJ fits industrial control nodes because its 23 GPIO lines, three timer/counters, and 10-bit ADC cover relay driving, button debouncing, and analog sensor acquisition in one 5V-tolerant 28-PDIP device. Single-cycle RISC execution at 20 MHz handles deterministic control loops such as PID regulation at several kHz update rates. The socketed DIP format simplifies field firmware replacement in legacy industrial boards, and DebugWIRE lowers commissioning cost. For RS-485 fieldbus nodes, pair the USART with an external transceiver and use the CRC-capable serial framing typical of Modbus RTU implementations.
Recommended
Battery-Powered Sensor Nodes
With a 1.8V to 5.5V supply range and AVR power-down sleep modes, the ATMEGA48-20PJ is well suited to battery-powered sensor nodes operating from two or three cells. The internal 8 MHz calibrated RC oscillator removes crystal cost for low-accuracy timing, while the watchdog timer provides periodic wake-up from power-down for duty-cycled sampling. The 8-channel 10-bit ADC digitizes analog sensor outputs directly, and 256 bytes of EEPROM stores calibration coefficients across battery swaps. Trade-off: 512B SRAM limits buffering, so firmware should stream readings over TWI or USART rather than batching large arrays.
Recommended
Appliance and White-Goods Control
Appliance control boards benefit from the ATMEGA48-20PJ's combination of cost, robustness, and through-hole assembly. The 20 MHz performance is ample for user-interface scanning, NTC temperature measurement via the 10-bit ADC, and PWM output from the 8-bit timer/counters for fan or heater control. The watchdog timer adds failsafe recovery for mains-powered products, and the self-programming Flash enables field firmware updates from a bootloader. Because 4KB constrains complex menus and multi-language strings, design teams typically keep UI assets in external EEPROM or upgrade pin-compatible to the ATMEGA168-20PJ or ATMEGA328P-PU when feature creep occurs.
Recommended
Education and Hobby Prototyping
The ATMEGA48-20PJ is a staple of electronics education and hobby prototyping because the 28-PDIP package is breadboard-friendly and socketed, tolerating repeated insertion, and the device is programmable with inexpensive tools such as USBasp or an Arduino acting as ISP. The MiniCore Arduino hardware package explicitly supports the ATmega48, providing Arduino IDE workflows. Students learn fuse programming, DebugWIRE debugging, and SPI/TWI protocols directly. The 4KB Flash enforces lean, well-structured C code, which is pedagogically useful; for larger sketches, the same-footprint ATMEGA328P-PU swaps in without any wiring change.
Recommended
Motor and Actuator Control
The ATMEGA48-20PJ supports small motor and actuator control through its three timer/counters, which generate hardware PWM on multiple channels without CPU intervention. At 20 MHz, an 8-bit PWM resolution supports carrier frequencies of roughly 78 kHz, fast enough for silent fan or brushed-DC control. The 10-bit ADC reads back current-sense shunts and potentiometer feedback, and the input-capture feature of the 16-bit timer measures tachometer pulses. GPIO drives MOSFET gate drivers; the 23 I/O lines cover rotary encoders, limit switches, and indicator LEDs in compact embedded motion products.
Recommended
Legacy Repair and Obsolescence Management
The socketed 28-PDIP ATMEGA48-20PJ is frequently specified in legacy equipment for which the MCU can be replaced in minutes without soldering. For obsolescence management, the entire Microchip megaAVR DIP family (ATmega48, 88, 168, 328) shares the same pinout, allowing capacity-constrained buyers to substitute larger-memory variants as drop-ins. The ATMEGA48A-PU and ATMEGA48PA-PU serve as actively promoted refresh devices with the same 4KB functionality. When replacing, always read and reprogram the fuse bytes (clock source, BOD level, SPIEN) to match the original board configuration before inserting the new device.
Recommended
Recommended Products Summary
Engineering reference data for ATMEGA48-20PJ — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | ATMEGA48-20PI | ATMEGA48A-PU | ATMEGA88-20PJ | ATMEGA168-20PJ | ATMEGA328P-PU |
|---|---|---|---|---|---|---|
| Package | 28-PDIP | 28-PDIP - same | 28-PDIP - same | 28-PDIP - same | 28-PDIP - same | 28-PDIP - same |
| Brand | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology |
| Flash Memory | 4 KB | 4 KB | 4 KB | 8 KB | 16 KB | 32 KB |
| SRAM | 512 B | 512 B | 512 B | 1 KB | 1 KB | 2 KB |
| EEPROM | 256 B | 256 B | 256 B | 512 B | 512 B | 1 KB |
| Max Clock Frequency | 20 MHz | 20 MHz | 20 MHz | 20 MHz | 20 MHz | 20 MHz |
| Operating Voltage | 1.8 V to 5.5 V | 1.8 V to 5.5 V | 1.8 V to 5.5 V | 1.8 V to 5.5 V | 1.8 V to 5.5 V | 1.8 V to 5.5 V |
| Low-Power Optimization | Standard ATmega48 | Standard ATmega48 | Improved ('A' refresh) | Standard ATmega88 | Standard ATmega168 | picoPower core |
Key Differentiators
- Minimum memory size in the megaAVR 28-pin DIP family (vs ATMEGA88-20PJ)
- Massive pin-compatible memory headroom for future-proofing (vs ATMEGA328P-PU)
- Active low-power refresh path exists (vs ATMEGA48A-PU)
Design Notes
Fuse programming is the single most common failure mode with the ATmega48 family. When switching from the internal 8 MHz RC oscillator to an external 20 MHz crystal, the CKSEL and SUT fuse bits must be set correctly; selecting a clock source that is absent (for example, external clock on a crystal-only board) leaves the device without a clock and unrecoverable except by high-voltage parallel programming. Always verify fuse settings with a readback before disconnecting the programmer, and keep the SPIEN fuse programmed to retain ISP access.
Connect AVCC (pin 20) to VCC through a low-pass filter (for example, a 10 uH inductor or ferrite bead plus 100 nF capacitor) even when VCC and AVCC share the same rail, per the ATmega48 datasheet power supply guidance. AVCC must stay within 0.3V of VCC at all times. Place 100 nF decoupling capacitors directly at VCC and AVCC pins. Estimated: with no BOD enabled, brown-out during Flash self-programming can corrupt EEPROM; enabling brown-out detection at 2.7V or 4.3V (per supply) is recommended for products that write EEPROM at runtime.
For a 20 MHz crystal on XTAL1/XTAL2 (pins 9/10), use a parallel-resonant AT-cut crystal with two load capacitors of typically 12-22 pF chosen to match the crystal CL specification; keep traces shorter than 10 mm and guard them from fast PWM switching lines such as PB1-PB3. Keep the AREF (pin 21) trace short with a 100 nF capacitor to ground when using the internal reference, and never connect a source directly to AREF while the internal reference is enabled.
Although the DIP package is through-hole, keep the 100 nF decoupling capacitors within 5 mm of pins 7, 8, and 20 on the underside of the board. Route ADC inputs (PC0-PC5) away from PWM outputs and crystal traces, and consider a ground pour on the component side tied to pins 8 and 22 to reduce analog noise. If your board may later upgrade to an ATmega328P-PU, keep the RESET pull-up (10 kohm) and ISP header in place, since the pinout is identical and no rework is needed.
Compliance Information
The 'PJ' Pb-free DIP suffix designation on Atmel/Microchip legacy part numbering indicates a lead-free assembly option, but explicit RoHS/REACH declarations were not present in the provided web data. Consult the Microchip product page for current compliance certificates.
