1996 Microchip Technology Inc. DS21095F-page 1

FEATURES

• Single supply with operation down to 2.5V
• Completely implements DDC1



/DDC2



inter-
face for monitor identification
• Low power CMOS technology
- 1 mA active current typical
- 10

m

A standby current typical at 5.5V
• 2-wire serial interface bus, I

2

C



compatible
• Self-timed write cycle (including auto-erase)
• Page-write buffer for up to 8 bytes
• 100 kHz (2.5V) and 400 kHz (5V) compatibility
• Factory programming (QTP) available
• 1,000,000 erase/write cycles guaranteed
• Data retention > 200 years
• 8-pin PDIP and SOIC package
• Available for extended temperature ranges

DESCRIPTION

The Microchip Technology Inc. 24LC21 is a 128 x 8 bit
Electrically Erasable PROM. This device is designed for
use in applications requiring storage and serial trans-
mission of configuration and control information. Two
modes of operation have been implemented: Transmit
Only Mode and Bi-Directional Mode. Upon power-up,
the device will be in the Transmit Only Mode, sending a
serial bit stream of the entire memory array contents,
clocked by the VCLK pin. A valid high to low transition
on the SCL pin will cause the device to enter the
Bi-Directional Mode, with byte selectable read/write
capability of the memory array. The 24LC21 is available
in a standard 8-pin PDIP and SOIC package in both
commercial and industrial temperature ranges.
- Commercial (C): 0˚C to +70˚C
- Industrial (I): -40˚C to +85˚C

PACKAGE TYPES
BLOCK DIAGRAM
24LC21
NC
NC
NC
VSS
1
2
3
4
8
7
6
5
VCC
VCLK
SCL
SDA
24LC21
NC
NC
NC
VSS
1
2
3
4
8
7
5
5
VCC
VCLK
SCL
SDA
PDIP
SOIC
HV GENERATOR
EEPROM
ARRAY
PAGE LATCHES
YDEC
XDEC
SENSE AMP
R/W CONTROL
MEMORY
CONTROL
LOGIC
I/O
CONTROL
LOGIC
VCLK
SDA SCL
VCC
VSS

24LC21

1K 2.5V Dual Mode I

2

C



Serial EEPROM

DDC is a trademark of the Video Electronics StandarDs Association.
I

2

C is a trademark of Philips Corporation.

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