DS2502

2 of 22

ORDERING INFORMATION

Standard

Lead-Free

Description

DS2502

DS2502+

TO-92 Package

DS2502/T&R

DS2502+T&R

TO-92 Package, 2k Tape & Reel

DS2502R/T&R

DS2502R+T&R

3-pin SOT-23 Package, 3k Tape & Reel

DS2502P

DS2502P+

6-pin TSOC Package

DS2502P/T&R

DS2502P+T&R

TSOC Package, 4k Tape & Reel

DS2502S

DS2502S+

8-pin SO Package

DS2502S/T&R

DS2502S+T&R

SO Package, 2.5k Tape & Reel

DS2502X1

Flip Chip, 10k Tape & Reel

+ Indicates lead-free compliance.

DESCRIPTION

The DS2502 1 kbit Add-Only Memory identifies and stores relevant information about the product to

which it is associated. This lot- or product-specific information can be accessed with minimal interface-

for example, a single port pin of a microcontroller. The DS2502 consists of a factory-lasered registration

number that includes a unique 48-bit serial number, an 8-bit CRC, and an 8-bit Family Code (09h) plus 1

kbit of EPROM which is user-programmable. The power to program and read the DS2502 is derived

Data is transferred serially via the 1-Wire protocol which requires only a single data lead and a ground

return. The entire device can be programmed and then write-protected if desired. Alternatively, the part

may be programmed multiple times with new data being appended to, but not overwriting, existing data

with each subsequent programming of the device. Note: Individual bits can be changed only from a

logical 1 to a logical 0, never from a logical 0 to a logical 1. A provision is also included for indicating

that a certain page or pages of data are no longer valid and have been replaced with new or updated data

that is now residing at an alternate page address. This page address redirection allows software to patch

data and enhance the flexibility of the device as a stand-alone database. The 48-bit serial number that is

factory-lasered into each DS2502 provides a guaranteed unique identity which allows for absolute

traceability. The familiar TO-92 or SOIC or TSOC packages provide a compact enclosure that allows

standard assembly equipment to handle the device easily for attachment to printed circuit boards or

wiring. Typical applications include storage of calibration constants, maintenance records, asset tracking,

product revision status, and access codes.

OVERVIEW

The block diagram in Figure 1 shows the relationships between the major control and memory sections of

the DS2502. The DS2502 has three main data components: 1) 64-bit lasered ROM, 2) 1024-bit EPROM,

and 3) EPROM Status Bytes. The device derives its power for read operations entirely from the 1-Wire

communication line by storing energy on an internal capacitor during periods of time when the signal line

is high and continues to operate off of this “parasite” power source during the low times of the 1-Wire

line until it returns high to replenish the parasite (capacitor) supply. During programming, 1-Wire

communication occurs at normal voltage levels and then is pulsed momentarily to the programming

voltage to cause the selected EPROM bits to be programmed. The 1-Wire line must be able to provide 12

volts and 10 milliamperes to adequately program the EPROM portions of the part. Whenever

programming voltages are present on the 1-Wire line a special high voltage detect circuit within the

DS2502 generates an internal logic signal to indicate this condition. The hierarchical structure of the 1-

Wire protocol is shown in Figure 2. The bus master must first provide one of the six ROM Function

Commands, 1) Read ROM, 2) Match ROM, 3) Search ROM, 4) Skip ROM. These commands operate on

the 64-bit lasered ROM portion of each device and can singulate a specific device if many are present on