CAT1161 Catalyst Semiconductor, CAT1161 Datasheet - Page 5

• Manufacturer Part Number: CAT1161
• Description: Supervisory Circuits with I2C Serial CMOS EEPROM/ Precision Reset Controller and Watchdog Timer
• Manufacturer: Catalyst Semiconductor

PIN DESCRIPTIONS
WP:
If the pin is tied to V
becomes Write Protected (READ only). When the pin
is tied to GND or left floating normal read/write
operations are allowed to the device.
RESET/RESET
These are open drain pins and can be used as reset
trigger inputs. By forcing a reset condition on the pins
the device will initiate and maintain a reset condition.
The RESET pin must be connected through a pull-
down resistor, and the RESET pin must be connected
through a pull-up resistor.
SDA:
The bidirectional serial data/address pin is used to
transfer all data into and out of the device. The SDA
pin is an open drain output and can be wire-ORed
with other open drain or open collector outputs.
If there is no transition on the SDA for more than 1.6
seconds, the watchdog timer times out.
SCL:
Serial clock input.
DEVICE OPERATION
Reset Controller Description
The CAT1161/2 precision RESET controller ensures
correct system operation during brownout and power
up/down conditions. It is configured with open drain
RESET outputs. During power-up, the RESET outputs
Figure 1. RESET Output Timing
RESET
RESET
V
WRITE PROTECT
SERIAL DATA ADDRESS
SERIAL CLOCK
RESET
RESET
RESET: RESET I/O
RESET
CC
V
RVALID
V
TH
CC
the entire memory array
t
PURST
t
GLITCH
remain active until V
continue 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
will be valid so long as V
The RESET pins are I/Os; therefore, the CAT1161/2 can act
as a signal conditioning circuit for an externally applied
manual reset. The inputs are edge triggered; that is, the
RESET input in the CAT1161/2 will initiate a reset timeout
after detecting a low to high transition and the RESET input
will initiate a reset timeout after detecting a high to low
transition.
Watchdog Timer
The Watchdog Timer provides an independent protection for
microcontrollers. During a system failure, the CAT1161will
respond with a reset signal after a time-out interval of 1.6
seconds for a lack of activity. The CAT1161 is designed with
the Watchdog Timer feature on the SDA input. If the
microcontroller does not toggle the SDA input pin within 1.6
seconds, the Watchdog Timer times out. This will generate
a reset condition on reset outputs. The Watchdog Timer is
cleared by any transition on SDA.
As long as the reset signal is asserted, the Watchdog Timer
will not count and will stay cleared.
The CAT1162 does not have a Watchdog.
5
t
RPD
TH
. After the t
CC
CC
falls below V
reaches the V
CC
t
PURST
is >1.0V (V
PURST
TH
. The RESET outputs
TH
timeout interval, the
RVALID
threshold and will
t
RPD
).
Doc No. 3002, Rev. D
CAT1161/2
PURST
)