Data Sheet

2010-2021 Microchip Technology Inc. and its subsidiaries DS20001191U-page 7
24AA128/24LC128/24FC128
2.0 PIN DESCRIPTIONS
The descriptions of the pins are listed in Table 2-1.
TABLE 2-1: PIN FUNCTION TABLE
2.1 A0, A1, A2 Chip Address Inputs
The A0, A1 and A2 inputs are used by the 24XX128 for
multiple device operations. The levels on these inputs
are compared with the corresponding bits in the client
address. The chip is selected if the compare is true.
Up to eight devices (two for the MSOP package) may
be connected to the same bus by using different Chip
Select bit combinations. These inputs must be
connected to either VCC or VSS.
In most applications, the chip address inputs A0, A1
and A2 are hardwired to logic 0 or logic 1. For
applications in which these pins are controlled by a
microcontroller or other programmable device, the chip
address pins must be driven to logic 0 or logic 1
before normal device operation can proceed.
2.2 Serial Data (SDA)
This is a bidirectional pin used to transfer addresses
and data into and out of the device. It is an open-drain
terminal. Therefore, the SDA bus requires a pull-up
resistor to VCC (typical 10 k for 100 kHz, 2k for
400 kHz and 1 MHz).
For normal data transfer, SDA is allowed to change
only during SCL low. Changes during SCL high are
reserved for indicating the Start and Stop conditions.
2.3 Serial Clock (SCL)
This input is used to synchronize the data transfer to
and from the device.
2.4 Write-Protect (WP)
This pin must be connected to either VSS or VCC. If tied
to VSS, write operations are enabled. If tied to VCC,
write operations are inhibited but read operations are
not affected.
Name DFN
(1)
MSOP PDIP SOIC SOIJ TDFN
(1)
TSSOP Function
A0 1111 11User Configurable Chip Select
A1 2222 22User Configurable Chip Select
A2 33333 33User Configurable Chip Select
VSS 44444 44Ground
SDA 55555 55Serial Address/Data I/O
SCL 66666 66Serial Clock
WP 77777 77Write-Protect Input
VCC 88888 88Power Supply
Note 1: The exposed pad on the DFN/TDFN package can be connected to VSS or left floating.
Note: For the MSOP package only, pins A0 and
A1 are not connected.