AT28HC256-70SU from Microchip Tech, in a SOIC-28-300mil. Pinout and pin descriptions extracted from the manufacturer datasheet (extract_pins, cross-checked by a second model); symbol, footprint, and 3D from KiCad-official CAD.

Pinout

Pin	Name	Type	Function
1	A14	input	Address input A14.
2	A12	input	Address input A12.
3	A7	input	Address input A7.
4	A6	input	Address input A6.
5	A5	input	Address input A5.
6	A4	input	Address input A4.
7	A3	input	Address input A3.
8	A2	input	Address input A2.
9	A1	input	Address input A1.
10	A0	input	Address input A0.
11	I/O0	bidirectional	Data input/output bit 0.
12	I/O1	bidirectional	Data input/output bit 1.
13	I/O2	bidirectional	Data input/output bit 2.
14	GND	power_in	Ground.
15	I/O3	bidirectional	Data input/output bit 3.
16	I/O4	bidirectional	Data input/output bit 4.
17	I/O5	bidirectional	Data input/output bit 5.
18	I/O6	bidirectional	Data input/output bit 6.
19	I/O7	bidirectional	Data input/output bit 7; used for DATA Polling to detect end of write.
20	CE	input	Chip Enable input; deselecting the device puts it in standby.
21	A10	input	Address input A10.
22	OE	input	Output Enable input.
23	A11	input	Address input A11.
24	A9	input	Address input A9.
25	A8	input	Address input A8.
26	A13	input	Address input A13.
27	WE	input	Write Enable input.
28	VCC	power_in	Device power supply, single 5V ± 10%.

Key specifications

Parameter	Value
Manufacturer	Microchip Tech
Package	SOIC-28-300mil
Category	Embedded Processors & Controllers
Pins	28

Electrical characteristics

Limits as printed in the datasheet (page.json metadata.characteristics carries them as data).

Parameter	Symbol	Min	Typ	Max	Unit	Conditions	Page
VCC Standby Current TTL (AT28HC256-70)	ISB1			60	mA	CE = 2.0V to VCC	7
Input Load Current	ILI			10	μA	VIN = 0V to VCC + 1V	7
Output Leakage Current	ILO			10	μA	VI/O = 0V to VCC	7
VCC Active Current	ICC			80	mA	f = 5 MHz; IOUT = 0 mA	7
Input Low Voltage	VIL			0.8	V		7
Input High Voltage	VIH	2			V		7
Output Low Voltage	VOL			0.45	V	IOL = 6.0 mA	7
Output High Voltage	VOH	2.4			V	IOH = -4 mA	7
Address to Output Delay	tACC			70	ns	AT28HC256-70	11
CE to Output Delay	tCE			70	ns	AT28HC256-70	11
OE to Output Delay	tOE	0		35	ns	AT28HC256-70	11
CE or OE to Output Float	tDF	0		35	ns	AT28HC256-70	11
Output Hold from OE, CE or Address	tOH	0			ns	AT28HC256-70	11
Address, OE Setup Time	tAS, tOES	0			ns		13
Address Hold Time	tAH	50			ns		13
Chip Select Setup Time	tCS	0			ns		13
Chip Select Hold Time	tCH	0			ns		13
Write Pulse Width (WE or CE)	tWP	100			ns		13
Data Setup Time	tDS	50			ns		13
Data, OE Hold Time	tDH, tOEH	0			ns		13
Write Cycle Time	tWC			10	ms	AT28HC256 (standard option)	14
Byte Load Cycle Time	tBLC			150	µs		14
Write Pulse Width High	tWPH	50			ns		14
Data Polling Data Hold Time	tDH	0			ns	Data Polling	18
Data Polling OE Hold Time	tOEH	0			ns	Data Polling	18
Data Polling Write Recovery Time	tWR	0			ns	Data Polling	18
Toggle Bit Data Hold Time	tDH	10			ns	Toggle Bit	19
Toggle Bit OE Hold Time	tOEH	10			ns	Toggle Bit	19
Toggle Bit OE High Pulse	tOEHP	150			ns	Toggle Bit	19
Toggle Bit Write Recovery Time	tWR	0			ns	Toggle Bit	19
Input Capacitance	CIN		4	6	pF	VIN = 0V; f = 1 MHz, TA = 25°C	8
Output Capacitance	COUT		8	12	pF	VOUT = 0V; f = 1 MHz, TA = 25°C	8
Temperature under bias		-55		125	°C		7
Storage temperature		-65		150	°C		7
All input voltages (including NC pins) with respect to ground		-0.6		6.25	V		7
All output voltages with respect to ground		-0.6			V	Upper limit VCC + 0.6V	7
Voltage on OE and A9 with respect to ground		-0.6		13.5	V		7
VCC Power Supply	VCC	4.5	5	5.5	V	5V ± 10%	30
Operating Temperature (Case), Industrial		-40		85	°C	AT28HC256-70	7

Materials and finish

As the datasheet states them (page.json metadata.appearance; the 3D model's colours follow it).

Part	Material	Colour / plating	Datasheet says	Page
contacts		tin	U = -40°C to +85°C Industrial Temperature Grade, 100% Matte Sn Terminal Finish AT28 HC 256 ( )- 90 JU-T	30

CAD (KiCad official)

Symbol: AT28HC256-70SU
Footprint: Package_SO:SOIC-28W_7.5x17.9mm_P1.27mm
3D model: SOIC-28-300mil (KiCad packages3D, STEP)
3D model files: at28hc256-70su-etched.step / at28hc256-70su-etched.glb carry the MPN laser-etched on the die in a toggleable Adom.LaserEtch group (Fusion-ready); at28hc256-70su.step / at28hc256-70su.glb are the bare package body.

Provenance

Data extracted from the manufacturer datasheet, not a distributor listing:

Datasheet: Microchip Tech datasheet (34 pp, sha256 9fbfb62b758b1eb8, retrieved 2026-10-30, tier: manufacturer)
Extractor: parts-factory 2.0.0 / extract_pins 0.3, primary claude-sonnet-5-5 (text), consensus claude-sonnet-5-5 (agreed), guards: pin_guards 0.1: passed. Pins are checked against the footprint pad set and their cited datasheet pages before publish.
CAD: KiCad official libraries (CC-BY-SA 4.0).

Datasheet PDF

AT28HC256-70SU

Verified AT28HC256-70SU

Verification log 1 record

3D Model

Symbol & Footprint

Schematic Symbol

PCB Footprint

Datasheet

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