Microchip Technology AT93C66B-SSHM-B

Overview

AT93C66B-SSHM-B from Microchip Technology is a 4-Kbit three-wire serial EEPROM organized as 512 × 8 or 256 × 16, operating from 1.7V to 5.5V with industrial temperature range (−40°C to +85°C), 2 MHz max clock rate at 5V, and self-timed write cycle ≤5 ms. It serves as nonvolatile configuration storage in microcontroller-based embedded systems requiring low-voltage operation and space-constrained PCB layouts.

For engineers reviewing the AT93C66B-SSHM-B datasheet, AT93C66B-SSHM-B pinout, AT93C66B-SSHM-B application, or AT93C66B-SSHM-B equivalent, key selection considerations include voltage compatibility (1.7–5.5V), ORG-pin-selectable memory organization, three-wire interface timing constraints, and industrial-grade reliability (1M write cycles, 100-year data retention).

Technical Context

The AT93C66B-SSHM-B implements a synchronous three-wire serial interface (CS/SK/DI/DO) with chip-select–gated communication and rising-edge–synchronized data latching on SK. Its internal organization is dynamically selected via the ORG pin: tied to VCC for 256 × 16 mode, to GND for 512 × 8 mode, or left floating (with internal ~10 MΩ pull-up) for default x16 configuration.

It supports seven command types (READ, EWEN, EWDS, ERASE, WRITE, WRAL, ERAL), all initiated by a rising CS edge followed by start bit and opcode. Write and erase operations are self-timed (t_WP ≤5 ms), and DO pin provides Ready/Busy status when CS is reasserted after command initiation-enabling host polling without fixed delay loops.

Key Specifications

Pinout & Package

AT93C66B-SSHM-B is supplied in an 8-lead SOIC package (3.9 mm × 4.9 mm body, 1.27 mm pitch). Pin 1 is marked with a beveled corner or dot; the package is RoHS-compliant, lead-free, and halide-free.

Key Features

Applications

Equivalent & Alternatives

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

Compared with M95M02-DFMN6TP and 25AA040A-I/P, the AT93C66B-SSHM-B uniquely combines three-wire simplicity, hardware-selectable memory mapping, and guaranteed 1.7V operation - making it optimal for resource-constrained, low-pin-count MCU designs where voltage flexibility and layout efficiency are critical.

Availability

AT93C66B-SSHM-B is available at Aetrix Electronics and suitable for industrial sensor calibration, consumer appliance configuration, and automotive body control modules requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.

Supply support for AT93C66B-SSHM-B 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

Microchip Technology is a global semiconductor company specializing in microcontrollers, analog devices, and nonvolatile memory solutions, with a focus on embedded control and connectivity.

The AT93C66B belongs to Microchip's legacy serial EEPROM product line, designed specifically for cost-sensitive, space-constrained embedded systems needing reliable, low-voltage, three-wire nonvolatile storage without SPI/I²C overhead.

FAQ

What is the memory organization of AT93C66B-SSHM-B, and how is it configured?

The AT93C66B-SSHM-B offers dual memory organizations: 512 × 8 or 256 × 16 bits. Configuration is controlled by the ORG pin - tied to VCC for x16 mode, to GND for x8 mode, or left floating (defaulting to x16 via internal pull-up). This hardware-selectable mapping eliminates software address translation and simplifies firmware development for either byte- or word-oriented data structures. The AT93C66B-SSHM-B datasheet confirms this behavior in Section 2.6 and Table 5-2.

Does AT93C66B-SSHM-B support true 1.7V operation, and what are the timing implications?

Yes, AT93C66B-SSHM-B is fully specified for 1.7V to 5.5V operation. At 1.7V, AC characteristics adjust: maximum SK clock frequency drops to 250 kHz, t_SKH/t_SKL minimum increases to 1000 ns, and t_WP remains ≤5 ms. These deratings ensure reliable charge-pump operation and data integrity across the full voltage range. All DC and AC specs at 1.7V are validated per DS20006260A-page 8–9.

How does the AT93C66B-SSHM-B indicate write completion, and is polling required?

The AT93C66B-SSHM-B uses its DO pin to signal Ready/Busy status: after initiating a WRITE or ERASE command, if CS is brought high again (after ≥t_CS), DO outputs logic 0 during busy and logic 1 when complete. This enables efficient polling without fixed delays. The AT93C66B-SSHM-B does not support interrupt-driven completion - host must monitor DO while CS is high, as detailed in Figures 5-4 through 5-7 and Section 2.4.

Is AT93C66B-SSHM-B pin-compatible with AT93C56B-SSHM-B, and what are the key differences?

Yes, AT93C66B-SSHM-B and AT93C56B-SSHM-B share identical pinout, package (8-lead SOIC), and interface protocol. The primary difference is memory size: AT93C66B-SSHM-B provides 4-Kbit (512 × 8 / 256 × 16), while AT93C56B-SSHM-B is 2-Kbit (256 × 8 / 128 × 16). Addressing differs - AT93C66B-SSHM-B uses 9-bit addresses (A8–A0) in x8 mode versus 8-bit (A7–A0) for AT93C56B-SSHM-B. Both support identical commands and voltage ranges.

What packaging and compliance certifications apply to AT93C66B-SSHM-B?

AT93C66B-SSHM-B is packaged in an 8-lead SOIC (SN) with 3.90 mm body width, RoHS-compliant, lead-free, and halide-free construction. It meets JEDEC standards for moisture sensitivity level (MSL) 1 and is qualified for industrial temperature operation (−40°C to +85°C). The "-SSHM-B" suffix denotes SOIC package, industrial grade, and tape-and-reel packaging - confirmed in Microchip's Packaging Information section (DS20006260A-page 17).