24LC21A
1K 2.5V Dual Mode I
2
C
™
Serial EEPROM
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
• 2-Wire Serial Interface Bus, I
2
C™ Compatible
• 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
- Industrial (I):
-40°C to +85°C
• Pb-Free and RoHS Compliant
Package Types
PDIP
NC
NC
NC
V
SS
SOIC
NC
NC
NC
Vss
1
24LC21A
2
3
4
8
7
6
5
Vcc
VCLK
SCL
SDA
1
24LC21A
2
3
4
8
7
6
5
Vcc
VCLK
SCL
SDA
Block Diagram
HV Generator
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
the I
2
C bus. If it detects a valid control byte from the
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 industrial temperature range.
I/O
Control
Logic
Memory
Control
Logic
XDEC
EEPROM
Array
Page Latches
SDA
SCL
YDEC
VCLK
Sense AMP
R/W Control
V
CC
V
SS
Pin Function Table
Name
V
SS
SDA
SCL
VCLK
V
CC
NC
Function
Ground
Serial Address/Data I/O
Serial Clock (Bidirectional mode)
Serial Clock (Transmit-Only mode)
+2.5V to 5.5V Power Supply
No Connection
DDC is a trademark of the Video Electronics Standards
Association.
I
2
C is a trademark of Philips Corporation.
©
2008 Microchip Technology Inc.
DS21160G-page 1
MICROCHIP [ MICROCHIP TECHNOLOGY ]
