X5168_06 Datasheet, PDF (5/20 Pages) Intersil Corporation – CPU Supervisor with 16Kbit SPI EEPROM

X5168, X5169
Principles of Operation
Power-on Reset
Application of power to the X5168, X5169 activates a power-
on reset circuit. This circuit goes active at about 1V and pulls
the RESET/RESET pin active. This signal prevents the
system microprocessor from starting to operate with
insufficient voltage or prior to stabilization of the oscillator.
When V_CC exceeds the device V_TRIP value for 200ms
(nominal) the circuit releases RESET/RESET, allowing the
processor to begin executing code.
Low Voltage Monitoring
During operation, the X5168, X5169 monitors the V_CC level
and asserts RESET/RESET if supply voltage falls below a
preset minimum V_TRIP. The RESET/RESET signal prevents
the microprocessor from operating in a power fail or
brownout condition. The RESET/RESET signal remains
active until the voltage drops below 1V. It also remains active
until V_CC returns and exceeds V_TRIP for 200ms.
V_CC Threshold Reset Procedure
The X5168, X5169 has a standard V_CC threshold (V_TRIP)
voltage. This value will not change over normal operating
and storage conditions. However, in applications where the
standard V_TRIP is not exactly right, or for higher precision in
the V_TRIP value, the X5168, X5169 threshold may be
adjusted.
Setting the V_TRIP Voltage
This procedure sets the V_TRIP to a higher voltage value. For
example, if the current V_TRIP is 4.4V and the new V_TRIP is
4.6V, this procedure directly makes the change. If the new
setting is lower than the current setting, then it is necessary
to reset the trip point before setting the new value.
To set the new V_TRIP voltage, apply the desired V_TRIP
threshold to the V_CC pin and tie the CS pin and the WP pin
HIGH. RESET/RESET and SO pins are left unconnected.
Then apply the programming voltage V_P to both SCK and SI
and pulse CS LOW then HIGH. Remove V_P and the
sequence is complete.
Resetting the V_TRIP Voltage
This procedure sets the V_TRIP to a “native” voltage level. For
example, if the current V_TRIP is 4.4V and the V_TRIP is reset,
the new V_TRIP is something less than 1.7V. This procedure
must be used to set the voltage to a lower value.
To reset the V_TRIP voltage, apply a voltage between 2.7 and
5.5V to the V_CC pin. Tie the CS pin, the WP pin, and the SCK
pin HIGH. RESET/RESET and SO pins are left unconnected.
Then apply the programming voltage V_P to the SI pin ONLY
and pulse CS LOW then HIGH. Remove V_P and the
sequence is complete.
CS
SCK ^VCC
V_P
SI
FIGURE 2. RESET V_TRIP VOLTAGE
CS
V_P
SCK
V_P
SI
FIGURE 1. SET V_TRIP VOLTAGE
5
FN8130.2
June 15, 2006