24LC21A
2
1K 2.5V Dual Mode I C Serial EEPROM
FEATURES
PACKAGE TYPES
PDIP
• Single supply with operation down to 2.5V
• Completely implements DDC1 /DDC2
interface for monitor identification, including recov-
ery to DDC1
NC
NC
1
2
8
7
VCC
VCLK
• Pin and function compatible with 24LC21
• Low power CMOS technology
- 1 mA typical active current
NC
3
4
6
5
SCL
SDA
VSS
- 10 µA standby current typical at 5.5V
2
• 2-wire serial interface bus, I C compatible
SOIC
• 100 kHz (2.5V) and 400 kHz (5V) compatibility
• Self-timed write cycle (including auto-erase)
• Page-write buffer for up to eight bytes
•
10,000,000 erase/write cycles guaranteed
1
8
NC
VCC
• Data retention > 200 years
• ESD Protection > 4000V
• 8-pin PDIP and SOIC package
• Available for extended temperature ranges
2
3
4
7
6
5
NC
NC
VCLK
SCL
SDA
- Commercial (C):
- Industrial (I):
0°C to +70°C
-40°C to +85°C
VSS
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
information. Two modes of operation have been imple-
mented: 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 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
BLOCK DIAGRAM
HV GENERATOR
I/O
CONTROL
LOGIC
MEMORY
CONTROL
LOGIC
EEPROM
ARRAY
XDEC
PAGE LATCHES
2
byte on the I C bus. If it detects a valid control byte from
SDA
SCL
the master, it will switch into Bi-directional 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.
YDEC
VCLK
SENSE AMP
R/W CONTROL
VCC
VSS
DDC is a trademark of the Video Electronics Standards Association.
I2C is a trademark of Philips Corporation.
1996 Microchip Technology Inc.
Preliminary
DS21160B-page 1
This document was created with FrameMaker 4 0 4