X40620 Datasheet, PDF (2/17 Pages) Xicor Inc. – Dual Voltage CPU Supervisor with 64K Serial EEPROM

X40620
PACKAGE/PINOUTS
V_SS
WP
SDA
RESET
8L TSSOP
1
8
2
7
3
6
4
5
V_CC
V2MON
SCL
V2FAIL
PIN NAMES
V_SS
SDA
V_CC
SCL
WP
V2MON
RESET
V2FAIL
Ground
Serial Data
Power
Serial Clock
Write Protect
Voltage monitor input
Low Voltage Detect Output
V2 Voltage Fail Output
PIN DESCRIPTIONS
Serial Clock (SCL)
The SCL input is used to clock all data into and out of
the device.
Serial Data (SDA)
SDA is a bidirectional pin used to transfer data into
and out of the device. It is an open drain output and
may be wire-ORed with other open drain or open col-
lector outputs. An open drain requires the use of a
pull-up resistor.
Write Protect (WP)
The WP pin should be tied HIGH at all time. (This WP
pin is reserved for internal factory testing only).
Reset Output (RESET)
RESET is an active LOW, open drain output which
goes active whenever V_CC falls below the minimum
Vtrip sense level. It will remain active until V_CC rises
above the minimum Vtrip sense level for 150ms.
RESET goes active if the Watchdog Timer is enabled
and there is no start bit before the end of the select-
able Watchdog time-out period. A serial start bit will
reset the Watchdog Timer. RESET also goes active on
power up at 1V and remains active for 150ms after the
power supply stabilizes.
V2 Voltage Fail Output (V2FAIL)
V2FAIL is an active LOW, open drain output which
goes active whenever V2MON falls below the mini-
mum V2trip sense level. It will remain active until
V2MON rises above the minimum V2MON sense level.
DEVICE OPERATION
Power On Reset
Application of power to the X40620 activates a Power
On Reset Circuit. This circuit goes active at 1V and
pulls the RESET pin active. This signal prevents the
system microprocessor from starting to operate with
insufficient voltage or prior to stabilization of the oscil-
lator. When V_CC exceeds the device V_TRIP value for
200ms (nominal) the circuit releases RESET allowing
the processor to begin executing code.
Low Voltage V_CC (V1) Monitoring
During operation, the X40620 monitors the V_CC level
and asserts RESET if supply voltage falls below a pre-
set minimum V_TRIP. The RESET signal prevents the
microprocessor from operating in a power fail or
brownout condition. The RESET signal remains active
until the voltage drops below 1V. It also remains active
until V_CC returns and exceeds V_TRIP for 200ms.
When the internal low voltage detect circuitry senses
that V_CC is low, the following happens:
– The RESET pin goes active.
– Communication to the device is interrupted and any
command is aborted. If a serial nonvolatile store is in
progress when power fails, the circuitry does not
stop the nonvolatile store operation, but attempts to
complete the operation.
The low V_CC threshold is typically set to 3.1V for a 2.5
to 3.7V operating range.
LOW VOLTAGE V2 MONITORING
The X40620 also monitors a second voltage level and
asserts V2FAIL if the voltage falls below a preset mini-
mum V2_TRIP. The V2FAIL signal is either ORed with
RESET to prevent the microprocessor from operating
in a power fail or brownout condition or used to inter-
rupt the microprocessor with notification of an impend-
ing power failure. The V2FAIL signal remains active
until the V_CC drops below 1V. It also remains active
until V2MON returns and exceeds V2_TRIP by 0.2V
Characteristics subject to change without notice. 2 of 17