24LC21A
1K 2.5V Dual Mode I2C™ Serial EEPROM
Features
Package Types
• Single supply with operation down to 2.5V
PDIP
NC
NC
1
8
7
Vcc
• Completely implements DDC1™/DDC2™
interface for monitor identification, including
recovery to DDC1
2
3
4
VCLK
• Pin and function compatible with 24LC21
• Low-power CMOS technology
NC
6
5
SCL
SDA
- 1 mA typical active current
VSS
- 10 µA standby current typical at 5.5V
• 2-wire serial interface bus, I2C™ 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
SOIC
1
2
3
4
8
7
6
5
NC
Vcc
NC
NC
VCLK
•
1,000,000 erase/write cycles ensured
• Data retention > 200 years
SCL
SDA
• ESD Protection > 4000V
• 8-pin PDIP and SOIC package
• Available for extended temperature ranges
Vss
- Commercial (C):
- Industrial (I):
0°C to +70°C
-40°C to +85°C
Block Diagram
Description
HV Generator
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 I2C 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 both commercial and industrial
temperature ranges.
I/O
Control
Logic
Memory
Control
Logic
EEPROM
Array
XDEC
Page Latches
SCL
SDA
YDEC
VCLK
Sense AMP
R/W Control
VCC
VSS
Pin Function Table
Name
Function
VSS
SDA
SCL
VCLK
VCC
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.
NC
2
I C is a trademark of Philips Corporation.
2003 Microchip Technology Inc.
DS21160F-page 1