24LC21
1K 2.5V Dual Mode I
2
C
™
Serial EEPROM
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
µ
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
- Commercial (C):
0˚C to +70˚C
- Industrial (I):
-40˚C to +85˚C
PACKAGE TYPES
PDIP
NC
NC
NC
V
SS
1
2
3
4
24LC21
8
7
6
5
V
CC
VCLK
SCL
SDA
SOIC
1
2
3
4
24LC21
8
7
5
5
NC
NC
NC
V
SS
V
CC
VCLK
SCL
SDA
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.
BLOCK DIAGRAM
VCLK
HV GENERATOR
I/O
CONTROL
LOGIC
MEMORY
CONTROL
LOGIC
XDEC
EEPROM
ARRAY
PAGE LATCHES
SDA
SCL
YDEC
V
CC
V
SS
SENSE AMP
R/W CONTROL
DDC is a trademark of the Video Electronics StandarDs Association.
I
2
C is a trademark of Philips Corporation.
©
1996 Microchip Technology Inc.
DS21095F-page 1
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