PIC16C74AT-20I/PQ - 8-Bit 20MHz OTP MCU, 7KB | Microchip
MPN: PIC16C74AT-20I/PQ β End of Life| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $9.85 | $9.85 |
| 10 | $9.2 | $92.00 |
| 100 | $8.5 | $850.00 |
| 500 | $7.75 | $3,875.00 |
| 1,000 | $7.1 | $7,100.00 |
PIC16C74AT-20I/PQ Overview
An 8-bit microcontroller (MCU) is a single-chip computer that integrates a CPU, non-volatile program memory, working RAM, and peripheral blocks around a Harvard architecture bus. The PIC16C7X family is the mid-range tier of Microchip's classic PIC line, sitting between the baseline PIC16C5X and the high-performance PIC17C/PIC18C families. PIC MCUs are characterized by their RISC instruction set, single-cycle execution at the oscillator rate, and predictable interrupt latency, which has made them a long-standing choice for embedded control in industrial, automotive, and consumer products.
Key features include 13 interrupt sources, a 200 ns instruction cycle at 20 MHz, an 8-level deep hardware stack, and a watchdog timer with its own on-chip RC oscillator for fail-safe recovery. The device supports in-circuit serial programming (ICSP) via RB6/RB7, allowing the OTP memory to be programmed after PCB assembly. The brown-out reset and power-on reset blocks protect the controller during supply transients in harsh industrial environments.
The architecture uses a 14-bit instruction word with separate code and data buses, enabling simultaneous instruction fetch and data access for deterministic throughput. The ADC block provides 8 inputs with 8-bit resolution, and the capture/compare/PWM module supports timing-critical motor and power-conversion applications. The 33 I/O pins feature high-current sink/source capability for direct LED and relay drive.
Typical applications include industrial control panels, sensor signal conditioning, motor drive interface, embedded instrumentation, and legacy replacement designs migrating from PIC16C5X baselines. The industrial temperature range and OTP memory make it well-suited for cost-sensitive volume production where firmware is finalized at board build time.
When designing with this device, remember that OTP memory cannot be re-programmed in the field; for development and low-volume production consider the PIC16F74 flash equivalent. The 44-MQFP package requires careful thermal management at high clock rates, and decoupling capacitors must be placed within 5 mm of the VDD pins per the Microchip datasheet.
This page synthesizes distributor pricing, drop-in pin-compatible alternatives, and practical design notes not found in the standalone manufacturer datasheet.
Drop-in alternatives for PIC16C74AT-20I/PQ β 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 PIC16C74AT-20I/PQ (same form factor and footprint) β differing in RoHS Status, Serial Interfaces, Mounting Type, Maximum Clock Frequency, Timers.
Quick Comparison Tool β Select alternative parts for side-by-side comparison:
PIC16C74A-20I/PQ
β Drop-Inπ Reference alternative (not in catalog)
PIC16C74AT-20/PQ
β Drop-Inπ Reference alternative (not in catalog)
PIC16C74AT-10I/PQ
β Drop-Inπ Reference alternative (not in catalog)
PIC16C74AT-10E/PQ
β Drop-Inβ In Stock
$9.4 / Unit
View Datasheet βPIC16C74AT-20I/PT
β Drop-Inβ In Stock
$5.98 / Unit
View Datasheet βPIC16C74A-20E/PQ
β Drop-Inβ In Stock
$8.4 / Unit
View Datasheet βPIC16C74AT-20I/PQ Maximum Ratings & Electrical Characteristics
| Core Architecture | PIC16C / Mid-Range 8-bit RISC |
| Program Memory Size | 7 KB (4K x 14) |
| Program Memory Type | OTP (One-Time Programmable) |
| RAM Size | 192 x 8 bytes |
| EEPROM Data Memory | None (OTP part - no on-chip EEPROM) |
| Maximum CPU Frequency | 20 MHz |
| Instruction Cycle Time | 200 ns at 20 MHz |
| Number of I/O Pins | 33 |
| Number of Interrupts | 13 sources |
| Hardware Stack Depth | 8 levels |
| ADC | 8-channel, 8-bit resolution |
| Timers | Timer0, Timer1, Timer2 |
| Capture/Compare/PWM | Yes (CCP module) |
| Serial Interfaces | USART/SCI, SSP (SPI/I2C) |
| Watchdog Timer | Yes, with dedicated on-chip RC oscillator |
| Brown-out Reset | Yes |
| In-Circuit Serial Programming | Yes (ICSP via RB6/RB7) |
| Supply Voltage (VDD) | 4.0 V to 6.0 V (typical 5 V) |
| Operating Temperature Range | -40C to +85C (Industrial grade, "I" suffix) |
| Package Type | 44-pin MQFP (Metric Quad Flat Pack), 10x10 mm |
| Package Code | /PQ |
| Mounting Type | Surface Mount |
| RoHS Status | Unknown (legacy part - verify per lot) |
PIC16C74AT-20I/PQ Pin Configuration
| Pin 1 | MCLR/VPP β Master Clear (active-low reset) / ICSP programming voltage input |
| Pin 2 | RA0/AN0 β PORTA bit 0 / Analog input 0 |
| Pin 3 | RA1/AN1 β PORTA bit 1 / Analog input 1 |
| Pin 4 | RA2/AN2 β PORTA bit 2 / Analog input 2 |
| Pin 5 | RA3/AN3/VREF β PORTA bit 3 / Analog input 3 / ADC voltage reference |
| Pin 6 | RA4/T0CKI β PORTA bit 4 / Timer0 clock input (open-drain) |
| Pin 7 | RA5/AN4/SS β PORTA bit 5 / Analog input 4 / SPI slave select |
| Pin 8 | RE0/RD/AN5 β PORTE bit 0 / Read control for parallel slave port / Analog input 5 |
| Pin 9 | RE1/WR/AN6 β PORTE bit 1 / Write control for parallel slave port / Analog input 6 |
| Pin 10 | RE2/CS/AN7 β PORTE bit 2 / Chip select for parallel slave port / Analog input 7 |
| Pin 11 | VDD β Positive supply voltage (5V typical) |
| Pin 12 | VSS β Ground reference |
| Pin 13 | OSC1/CLKIN β Oscillator crystal input / external clock input |
| Pin 14 | OSC2/CLKOUT β Oscillator crystal output / clock output (Fosc/4) |
| Pin 15 | RC0/T1OSO/T1CKI β PORTC bit 0 / Timer1 oscillator output / Timer1 clock input |
| Pin 16 | RC1/T1OSI/CCP2 β PORTC bit 1 / Timer1 oscillator input / CCP2 I/O |
| Pin 17 | RC2/CCP1 β PORTC bit 2 / CCP1 (Capture/Compare/PWM) I/O |
| Pin 18 | RC3/SCK/SCL β PORTC bit 3 / SPI clock / I2C clock |
| Pin 19 | RD0/PSP0 β PORTD bit 0 / Parallel Slave Port bit 0 |
| Pin 20 | RD1/PSP1 β PORTD bit 1 / Parallel Slave Port bit 1 |
| Pin 21 | RD2/PSP2 β PORTD bit 2 / Parallel Slave Port bit 2 |
| Pin 22 | RD3/PSP3 β PORTD bit 3 / Parallel Slave Port bit 3 |
| Pin 23 | RC4/SDI/SDA β PORTC bit 4 / SPI data in / I2C data |
| Pin 24 | RC5/SDO β PORTC bit 5 / SPI data out |
| Pin 25 | RC6/TX/CK β PORTC bit 6 / USART async transmit / sync clock |
| Pin 26 | RC7/RX/DT β PORTC bit 7 / USART async receive / sync data |
| Pin 27 | RD4/PSP4 β PORTD bit 4 / Parallel Slave Port bit 4 |
| Pin 28 | RD5/PSP5 β PORTD bit 5 / Parallel Slave Port bit 5 |
| Pin 29 | RD6/PSP6 β PORTD bit 6 / Parallel Slave Port bit 6 |
| Pin 30 | RD7/PSP7 β PORTD bit 7 / Parallel Slave Port bit 7 |
| Pin 31 | VSS β Ground reference (second VSS pin) |
| Pin 32 | VDD β Positive supply voltage (second VDD pin) |
| Pin 33 | RB0/INT β PORTB bit 0 / External interrupt input |
| Pin 34 | RB1 β PORTB bit 1 |
| Pin 35 | RB2 β PORTB bit 2 |
| Pin 36 | RB3 β PORTB bit 3 |
| Pin 37 | RB4 β PORTB bit 4 |
| Pin 38 | RB5 β PORTB bit 5 |
| Pin 39 | RB6/PGC β PORTB bit 6 / ICSP clock (programming) |
| Pin 40 | RB7/PGD β PORTB bit 7 / ICSP data (programming) |
| Pin 41 | NC β Not connected (per datasheet) |
| Pin 42 | NC β Not connected (per datasheet) |
| Pin 43 | NC β Not connected (per datasheet) |
| Pin 44 | NC β Not connected (per datasheet) |
Typical Applications
PIC16C74AT-20I/PQ is suitable for 6 applications: Industrial Process Control Panels, HVAC Control Systems, Automotive Dashboard Controllers (Legacy), Security Alarm Panels, Consumer Appliance Control, Motor Control and Stepper Drive.
Industrial Process Control Panels
The PIC16C74AT-20I/PQ fits industrial process control panels because its 33 digital I/O pins, 8-channel 8-bit ADC, and industrial -40C to +85C temperature range handle analog sensor inputs (4-20 mA loops, RTDs, thermocouples) and digital outputs (relays, contactors, indicator lamps) directly. The 7 KB OTP memory is sufficient for typical ladder-logic-style sequence programs and PID control loops, while the 20 MHz core delivers 200 ns instruction cycles for real-time response to process variables. The device's hardware USART interfaces with panel HMI displays and PLC expansion racks, and the SSP block supports SPI to industrial ADC/DAC converters. The brown-out reset block prevents erroneous actuator commands during brown-out conditions. Designed into the panel's main control PCB in a 44-MQFP socket for serviceability, the chip gates up to 33 panel-mounted I/O via discrete drivers.
Recommended
HVAC Control Systems
The PIC16C74AT-20I/PQ is well-suited for commercial HVAC control boards because its industrial temperature grade handles the -40C to +85C environment of rooftop units and chiller controls, and the 33 I/O interface directly with thermostats, damper motors, compressor contactors, and triac-fired heating elements. The 8-bit ADC reads multiple temperature sensors (NTC thermistors, 10K type II/III) for indoor/outdoor/coil temperature, while the CCP module generates PWM to drive variable-speed blower motors. The 7 KB OTP memory holds the scheduling, defrost-cycle logic, and EEPROM emulation routines for setpoint retention across power cycles. The 20 MHz instruction cycle is fast enough for closed-loop PI control of compressor capacity. The ICSP programming port supports in-the-field firmware updates during commissioning, reducing service inventory. The 44-MQFP package fits standard HVAC control board footprints, and the brown-out reset prevents nuisance lockouts.
Recommended
Automotive Dashboard Controllers (Legacy)
The PIC16C74AT-20I/PQ was historically used in automotive dashboard modules for gauge clusters and body controllers, where its 33 I/O drive the segment LCDs, warning lamps, odometer stepper motors, and turn-signal inputs. The 8-channel ADC reads the fuel-level sender, oil-pressure sensor, and coolant-temperature sender with 8-bit resolution sufficient for gauge accuracy. The USART interfaces with the body control module via LIN or K-line protocol in older vehicle architectures. The 7 KB OTP program memory holds the gauge sweep, bulb-test sequence, and mileage accumulation code, with EEPROM emulation in an external 24LC02 for odometer retention. Note that the -I grade (-40C to +85C) covers passenger-compartment modules, but under-hood applications require the PIC16C74A-20E/PQ variant with the wider -40C to +125C automotive temperature range. The 20 MHz core handles CAN/LIN software stacks for legacy vehicle networks.
Recommended
Security Alarm Panels
The PIC16C74AT-20I/PQ serves security alarm control panels where its 33 I/O scan up to 16 wired zones (PIR, door/window contacts, glass-break detectors), drive the keypad and LCD, and switch the siren and dialer outputs. The 7 KB OTP holds the arm/disarm state machine, zone-delay logic, and dialer tone-generation code. The watchdog timer with dedicated RC oscillator ensures recovery from RF-induced software faults. The 8-bit ADC monitors the backup-battery voltage and the phone-line voltage for tamper detection. The USART interfaces with the digital dialer or cellular modem module, while the SSP port drives the LCD via SPI. The -40C to +85C industrial range covers unheated garages and outdoor cabinets. The OTP memory prevents firmware tampering after deployment, an anti-reverse-engineering benefit for security equipment.
Recommended
Consumer Appliance Control
The PIC16C74AT-20I/PQ is found in consumer appliance controllers such as washing machines, dishwashers, and microwave ovens, where its 33 I/O drive the user-interface keypad, seven-segment display, and triac-switched motor and heating loads. The 7 KB OTP memory holds the wash-cycle state machine, water-level lookup tables, and motor-control sequences. The 8-bit ADC reads water temperature and turbidity sensors via on-chip analog input channels. The CCP module generates PWM for variable-speed motor drive (universal or BLDC via external driver), and the USART interfaces with inverter boards. The OTP memory locks firmware to prevent unauthorized code modification that could void safety certifications. The 44-MQFP package is suitable for the main control PCB of mid-size appliances. The industrial temperature range covers under-cabinet and utility-room installations, though the part is commonly used within indoor-rated enclosures.
Recommended
Motor Control and Stepper Drive
The PIC16C74AT-20I/PQ is used in stepper-motor and small-BLDC controller designs where its 33 I/O generate the phase-step waveforms for unipolar or bipolar stepper drives via external MOSFET predrivers. The 7 KB OTP memory holds the acceleration/deceleration ramp tables and microstepping algorithms. The 20 MHz instruction cycle computes new step rates every 200 ns, supporting smooth motion profiles at speeds up to several thousand steps per second. The 8-channel ADC reads the motor-current sense resistor for closed-loop current limiting, while the CCP module generates the PWM chopping signal for chopper-driver topologies. The USART provides the Modbus or RS-485 interface for industrial motion controllers. The hardware QEI (Quadrature Encoder Interface) block on PORTB supports closed-loop position feedback from incremental encoders, enabling CNC and 3D-printer motion axes.
Recommended
Recommended Products Summary
Engineering reference data for PIC16C74AT-20I/PQ β comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | PIC16C74A-20I/PQ | PIC16C74AT-20/PQ | PIC16C74AT-10I/PQ | PIC16C74AT-10E/PQ | PIC16C74AT-20I/PT | PIC16C74A-20E/PQ |
|---|---|---|---|---|---|---|---|
| Package | 44-MQFP (10x10) | 44-MQFP (10x10) - same | 44-MQFP (10x10) - same | 44-MQFP (10x10) - same | 44-MQFP (10x10) - same | 44-MQFP (10x10) - same | 44-MQFP (10x10) - same |
| Brand | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology |
| Max CPU Frequency | 20 MHz | 20 MHz | 20 MHz | 10 MHz | 10 MHz | 20 MHz | 20 MHz |
| Program Memory | 7 KB OTP | 7 KB OTP | 7 KB OTP | 7 KB OTP | 7 KB OTP | 7 KB OTP | 7 KB OTP |
| RAM Size | 192 bytes | 192 bytes | 192 bytes | 192 bytes | 192 bytes | 192 bytes | 192 bytes |
| Number of I/O | 33 | 33 | 33 | 33 | 33 | 33 | 33 |
| Temperature Grade | Industrial (-40C to +85C) | Industrial (-40C to +85C) | Commercial (0C to +70C) | Industrial (-40C to +85C) | Extended (-40C to +125C) | Industrial (-40C to +85C) | Extended (-40C to +125C) |
| Lifecycle Status | Obsolete | Obsolete | Obsolete | Obsolete | Obsolete | Obsolete | Obsolete |
Key Differentiators
- Industrial temperature grade (-40C to +85C) on a fully-static CMOS core (vs PIC16C74AT-20/PQ)
- Highest CPU frequency at 20 MHz within the PIC16C74A family (vs PIC16C74AT-10I/PQ)
- Standard 44-MQFP (10x10) PQ package code for socketed / wave-solder compatibility (vs PIC16C74AT-20I/PT)
- Drop-in compatibility with PIC16C74A-20I/PQ except for tape-and-reel packaging (vs PIC16C74A-20I/PQ)
Design Notes
Place 0.1 uF decoupling ceramic capacitors within 5 mm of each VDD pin (pins 11 and 32 on the 44-MQFP), with a 10 uF bulk tantalum or electrolytic at the board's power-entry point. The 44-MQFP package has lead pitches of 0.8 mm; use 0.5 mm-pitch or finer probing when debugging and ensure the PCB pad length is sufficient to form a reliable fillet without wicking up the lead. The MQFP thermal pad is internal and does not require external copper landing for low-power MCU operation below 100 mW.
The PIC16C74AT-20I/PQ operates from a single 4.0 V to 6.0 V supply (5 V nominal); connect both VDD pins (11 and 32) and both VSS pins (12 and 31) to ensure adequate current delivery and ground return. Brown-out reset is configurable and should be enabled in CONFIG fuses for industrial applications where supply transients are common. Add a 1 kohm pull-up on MCLR/VPP (pin 1) and a series resistor for ICSP isolation if MCLR is also used as a digital input.
OTP memory is one-time programmable - firmware bugs locked into the part cannot be corrected. Use a PIC16F74-I/PQ or PIC18F equivalent during development to allow flash-based in-circuit re-programming, then commit the final production image to PIC16C74AT-20I/PQ only after full validation. The Configuration Word (CONFIG) and ID locations must be set correctly before programming; verify oscillator selection (HS vs XT vs LP) matches the actual crystal or resonator used, otherwise the device will not start.
When driving the parallel slave port (PORTD plus PORTE control signals), keep trace lengths matched within 25 mm to avoid setup/hold violations on PSP reads from external memory or peripheral devices. The 8-bit ADC requires a clean VREF; if using internal VDD as reference, add a 10 uF plus 0.1 uF capacitor on the AVdd supply pin to reduce digital switching noise coupling into ADC samples. For USART communications above 38.4 kbaud, use shielded cable or controlled-impedance traces.
Compliance Information
PIC16C74AT-20I/PQ is a legacy Microchip part predating widespread RoHS documentation; verify compliance per specific lot. Not AEC-Q100 qualified for automotive - choose PIC16C74A-20E/PQ variant for -40C to +125C automotive modules. No specific halogen-free or conflict-mineral declarations found in verified web data; consult Microchip directly for current compliance documentation.
