CAT1025 CATALYST [Catalyst Semiconductor], CAT1025 Datasheet - Page 7

• Manufacturer Part Number: CAT1025
• Description: Supervisory Circuits with I2C Serial 2k-bit CMOS EEPROM and Manual Reset
• Manufacturer: CATALYST [Catalyst Semiconductor]

DEVICE OPERATION
Reset Controller Description
The CAT1024/25 precision RESET controllers ensure
correct system operation during brownout and power
up/down conditions. They are configured with open
drain RESET outputs.
During power-up, the RESET outputs remain active
until V
driving the outputs for approximately 200ms (t
after reaching V
device will cease to drive the reset outputs. At this point
the reset outputs will be pulled up or down by their
respective pull up/down resistors.
During power-down, the RESET outputs will be active
when V
valid so long as V
designed to ignore the fast negative going V
pulses (glitches).
Reset output timing is shown in Figure 1.
Manual Reset Operation
The RESET pin can operate as reset output and manual
reset input. The input is edge triggered; that is, the
RESET input will initiate a reset timeout after detecting
a high to low transition.
When RESET I/O is driven to the active state, the 200
msec timer will begin to time the reset interval. If external
reset is shorter than 200 ms, Reset outputs will remain
active at least 200 ms.
CAT1024/25 also have a separate manual reset input.
Driving the MR input low by connecting a pushbutton
(normally open) from MR pin to GND will generate a
reset condition. The input has a internal pull up resistor.
Reset remains asserted while MR is low and for the
Reset Timeout period after MR input has gone high.
Glitches shorter than 100 ns on MR input will not
generate a reset pulse. No external debouncing circuits
are required. Manual reset operation using MR input is
shown in Figure 2.
Hardware Data Protection
The CAT1024/25 family has been designed to solve
many of the data corruption issues that have long been
associated with serial EEPROMs. Data corruption occurs
when incorrect data is stored in a memory location which
is assumed to hold correct data.
Whenever the device is in a Reset condition, the
embedded EEPROM is disabled for all operations,
CC
CC
reaches the V
falls below V
TH
. After the t
CC
is >1.0V (V
TH
TH
. The RESET output will be
threshold and will continue
PURST
RVALID
timeout interval, the
). The device is
CC
transient
PURST
)
7
including write operations. If the Reset output(s) are
active, in progress communications to the EEPROM are
aborted and no new communications are allowed. In this
condition an internal write cycle to the memory can not be
started, but an in progress internal non-volatile memory
write cycle can not be aborted. An internal write cycle
initiated before the Reset condition can be successfully
finished if there is enough time (5ms) before VCC reaches
the minimum value of 2V.
In addition, the CAT1025 includes a Write Protection Input
which when tied to V
to the device.
CC
will disable any write operations
CAT1024, CAT1025
Doc No. 3008, Rev. M