X40030_13 Datasheet, PDF (7/23 Pages) Intersil Corporation – Triple Voltage Monitor with Integrated CPU Supervisor

X40030, X40031, X40034, X40035
Principles of Operation
Power-on Reset
Applying power to the X40030, X40031, X40034, X40035
activates a Power-on Reset Circuit that pulls the
RESET/RESET pins active. This signal provides several
benefits.
• It prevents the system microprocessor from starting to
operate with insufficient voltage.
• It prevents the processor from operating prior to
stabilization of the oscillator.
• It allows time for an FPGA to download its configuration
prior to initialization of the circuit.
• It prevents communication to the EEPROM, greatly reducing
the likelihood of data corruption on power-up.
When V_CC exceeds the device V_TRIP1 threshold value for
t_PURST (selectable), the circuit releases the RESET (X40031,
X40035) and RESET (X40030, X40034) pin allowing the
system to begin operation.
X40030, X40034
V_CC
SYSTEM
RESET
RESET
MR
MANUAL
RESET
FIGURE 1. CONNECTING A MANUAL RESET PUSH-BUTTON
Manual Reset
By connecting a push-button directly from MR to ground, the
designer adds manual system reset capability. The MR pin is
LOW while the push-button is closed and RESET/RESET
pin remains HIGH/LOW until the push-button is released and
for t_PURST thereafter.
Low Voltage V_CC (V1 Monitoring)
During operation, the X40030, X40031, X40034, X40035
monitors the V_CC level and asserts RESET/RESET if the
supply voltage falls below a preset minimum V_TRIP1. The
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_TRIP1 for
t_PURST.
Low Voltage V2 Monitoring
The X40030 also monitors a second voltage level and
asserts V2FAIL if the voltage falls below a preset minimum
V_TRIP2. The V2FAIL signal is either ORed with RESET to
prevent the microprocessor from operating in a power fail or
brownout condition or used to interrupt the microprocessor
with notification of an impending power failure.
For the X40030 and X40031 the V2FAIL signal remains
active until the V2MON drops below 1V (V2MON falling). It
also remains active until V2MON returns and exceeds
V_TRIP2.This voltage sense circuitry monitors the power
supply connected to V2MON pin. If V_CC = 0, V2MON can still
be monitored.
For the X40034 and X40035, the V2FAIL signal remains
active until V_CC drops below 1V and remains active until
V2MON returns and exceeds V_TRIP2.This sense circuitry is
powered by V_CC. If V_CC = 0, V2MON cannot be monitored.
Low Voltage V3 Monitoring
The X40030, X40031, X40034, X40035 also monitors a third
voltage level and asserts V3FAIL if the voltage falls below a
preset minimum V_TRIP3. The V3FAIL signal is either ORed
with RESET to prevent the microprocessor from operating in
a power fail or brownout condition or used to interrupt the
microprocessor with notification of an impending power
failure. The V3FAIL signal remains active until the V3MON
drops below 1V (V3MON falling). It also remains active until
V3MON returns and exceeds V_TRIP3.
This voltage sense circuitry monitors the power supply
connected to V3MON pin. If V_CC = 0, V3MON can still be
monitored.
Early Low V_CC Detection (LOWLINE)
This CMOS output goes LOW earlier than RESET/RESET
whenever V_CC falls below the V_TRIP1 voltage and returns
high when V_CC exceeds the V_TRIP1 voltage. There is no
power-up delay circuitry (t_PURST) on this pin.
V_CC
6V TO 10V
X40031-A
5V
V_CC
RESET
1M
3.3V V2MON ^V2FAIL
390k
V3MON
(1.7V) _V3FAIL
SYSTEM
RESET
POWER
FAIL
INTERRUPT
UNREG.
SUPPLY
5V
REG
3.0V
REG
1.8V
REG
V_CC
X40031-B
V_CC
RESET
V2MON
V2FAIL
V3MON
V3FAIL
SYSTEM
RESET
NOTICE: NO EXTERNAL COMPONENTS REQUIRED TO MONITOR
THREE VOLTAGES.
FIGURE 2. TWO USES OF MULTIPLE VOLTAGE MONITORING
7
FN8114.2
August 25, 2008