X5648 INTERSIL [Intersil Corporation], X5648 Datasheet - Page 3

• Manufacturer Part Number: X5648
• Description: CPU Supervisor with 64Kbit SPI EEPROM
• Manufacturer: INTERSIL [Intersil Corporation]

PRINCIPLES OF OPERATION
Power-on Reset
Application of power to the X5648/X5649 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
value for 200ms (nominal) the circuit releases
RESET/RESET, allowing the processor to begin exe-
cuting code.
Low Voltage Monitoring
During operation, the X5648/X5649 monitors the V
level and asserts RESET/RESET if supply voltage
falls
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
V
The X5648/X5649 has a standard V
(V
operating and storage conditions. However, in applica-
tions where the standard V
for
X5648/X5649 threshold may be adjusted.
Setting the V
This procedure sets the V
value. For example, if the current V
the new V
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
threshold to the Vcc pin and tie the CS pin and the WP
pin HIGH. RESET/RESET and SO pins are left uncon-
nected. Then apply the programming voltage V
both SCK and SI and pulse CS LOW then HIGH.
Remove V
CC
CC
TRIP
returns and exceeds V
Threshold Reset Procedure
higher
) voltage. This value will not change over normal
below
TRIP
P
and the sequence is complete.
precision
TRIP
is 4.6V, this procedure directly makes
a
TRIP
Voltage
preset
voltage, apply the desired V
CC
in
3
TRIP
TRIP
exceeds the device V
TRIP
minimum
the
for 200ms.
is not exactly right, or
to a higher voltage
V
TRIP
TRIP
CC
V
is 4.4V and
TRIP
value,
threshold
.
X5648, X5649
P
TRIP
TRIP
The
the
CC
to
Figure 1. Set V
Resetting the V
This procedure sets the V
level. For example, if the current V
V
1.7V. This procedure must be used to set the voltage
to a lower value.
To reset the V
and 5.5V to the V
and the SCK pin HIGH. RESET/RESET and SO pins
are left unconnected. Then apply the programming volt-
age V
HIGH. Remove V
Figure 2. Reset V
TRIP
P
is reset, the new V
SCK
SCK
SI
to the SI pin ONLY and pulse CS LOW then
CS
SI
CS
V
V
V
V
TRIP
P
CC
P
P
TRIP
TRIP
P
CC
TRIP
voltage, apply a voltage between 2.7
and the sequence is complete.
Voltage
Voltage
pin. Tie the CS pin, the WP pin,
Voltage
TRIP
TRIP
is something less than
to a “native” voltage
TRIP
is 4.4V and the
March 17, 2005
FN8136.0