 2003 Microchip Technology Inc.

DS21160F-page 1

24LC21A

Features

• Single supply with operation down to 2.5V

• Completely implements DDC1™/DDC2™

interface for monitor identification, including

recovery to DDC1

• Pin and function compatible with 24LC21

• Low-power CMOS technology

- 1 mA typical active current

-10

µA standby current typical at 5.5V

• 100 kHz (2.5V) and 400 kHz (5V) compatibility

• Self-timed write cycle (including auto-erase)

• Page write buffer for up to eight bytes

•

1,000,000 erase/write cycles ensured

• Data retention > 200 years

• ESD Protection > 4000V

• 8-pin PDIP and SOIC package

• Available for extended temperature ranges

Description

The Microchip Technology Inc. 24LC21A is a 128 x 8-bit

dual-mode Electrically Erasable PROM. This device is

designed for use in applications requiring storage and

serial transmission of configuration and control informa-

tion. Two modes of operation have been implemented:

Transmit-only mode and Bidirectional mode. Upon

power-up, the device will be in the Transmit-only mode,

sending a serial bit stream of the memory array from 00h

to 7Fh, clocked by the VCLK pin. A valid high-to-low

transition on the SCL pin will cause the device to enter

the transition mode, and look for a valid control byte on

master, it will switch into Bidirectional mode, with byte

selectable read/write capability of the memory array

using SCL. If no control byte is received, the device will

revert to the Transmit-only mode after it receives 128

consecutive VCLK pulses while the SCL pin is idle. The

24LC21A is available in a standard 8-pin PDIP and

SOIC package in both commercial and industrial

temperature ranges.

Package Types

Block Diagram

Pin Function Table

- Commercial (C):

0°C

to

+70°C

- Industrial (I):

-40°C to

+85°C

Name

Function

Ground

SDA

Serial Address/Data I/O

SCL

Serial Clock (Bidirectional mode)

VCLK

Serial Clock (Transmit-only mode)

+2.5V to 5.5V Power Supply

NC

No Connection

PDIP

SOIC

NC

NC

NC

1

2

3

4

8

7

6

5

Vcc

VCLK

SCL

SDA

NC

NC

NC

Vss

1

2

3

4

8

7

6

5

Vcc

VCLK

SCL

SDA

I/O

Control

Logic

HV Generator

EEPROM

Array

Page Latches

YDEC

XDEC

Sense AMP

R/W Control

Memory

Control

Logic

SDA

SCL

VCLK

DDC is a trademark of the Video Electronics Standards

Association.