ISL6131, ISL6132
7
FN9119.6
February 11, 2014
Applications Usage
Using the ISL6131EVAL1Z and
ISL6132EVAL1Z Platforms
The ISL6131EVAL1Z platform is set up to monitor and report an
undervoltage condition on each of 12V, 5V, 3.3V and 1.2V
supplies to a -20% tolerance.
Each monitored supply has an individual STATUS output and an
AND’ed PGOOD output signal for all four supplies. An OFF LED is
the PGOOD indicator for all four supplies. The ENABLE input
enables or disables the voltage monitoring function. See Figures
10 to 17 for performance and function examples.
The ISL6132EVAL1Z platform is set up to monitor and report
either an undervoltage or an overvoltage condition on 5V and
12V supplies to a ±10% tolerance. There is an OV and a UV
STATUS output for each of the two supplies and individual
AND’ed PGOOD outputs when each voltage is within the
programmed voltage range. An OFF LED indicates compliance to
the voltage range upper and lower limits.
The ENABLE inputs enable or disable the voltage monitoring
functions for each monitor supply.
See Figures 18 to 24 for performance and function examples.
Figures 25 and 26 illustrate the ISL6131EVAL1Z and
ISL6132EVAL1Z platforms respectively in image and schematic.
Using the ISL6131, ISL6132 for Negative
Voltage Monitoring Applications
The ISL6131, ISL6132 can be used for -V monitoring because it
monitors any voltage that is more positive relative to its GND pin.
With correct bias differential, these parts can monitor any
voltage, regardless of polarity or amplitude.
Using the ISL6131 for “Lossless” Sequencing
Applications
The ISL6131 can be used in a “lossless” sequencing application
in which a monitored output voltage determines the start of the
next sequenced turn-on. As shown in Figure 7, VMON_A input
looks at the common V
IN
of several DC-DC converters and
enables DC-DC_A with STATUS _A, once both V
IN
and ENABLE are
satisfied. VMON_B monitors the output of DC-DC_A, and when
the acceptable output voltage is reached, DC-DC_B is enabled
with STATUS_B output. This sequencing pattern continues until
all DC-DC outputs are on, at which time PGOOD signal is
released. A delay of 160ms from VMON > V
VMONVth
to STATUS
high ensures stability at each step prior to subsequent turn-on.
Additional ISL6131s can be employed in parallel to sequence any
number of DC-DC convertors in this fashion.
Using the ISL6131 for System Voltage and
Over-Temperature Monitoring
As a multi-voltage monitoring IC, the ISL6131 can monitor
over-temperature as well as voltage for more complete coverage
of system stability. Using a Negative Temperature Coefficient
(NTC) passive device in place of one of the resistors in a VMON
divider provides over-temperature monitoring either locally or
remotely.
Evaluations of this application configuration have involved the
QT0805T-202J, QT0805Y-502J and QT0805Y-103J NTCs from
Quality Thermistor.
ISL6131 over-temperature monitoring is not as accurate as
specific temperature monitor ICs, but this implementation
provides a cost-efficient solution with 5% tolerances achievable.
See Figures 8 and 9 for over-temperature sensing configuration
and operation results. In this example, the desired maximum
temperature is 100°C. The QT0805Y-103J NTC was placed at the
end of 3 feet of twisted pair wire to emulate a remote sensing
application. According to the Quality Thermistor data sheet, this
NTC device has a +25°C value of 10K and a +100°C value of
0.923K. An accompanying standard value resistor of 3.83K was
chosen for the divider so that at 100°C, VMON ~0.633V with the
bias voltage at 3.3V.
The resulting falling VMON trip point with the configuration
shown is ~0.634V, with ~0.642V for rising, which equates to
~95°C for under-temperature and ~97°C for over-temperature,
respectively. Choosing the standard resistor value above and
below R1 allows for small adjustments in the temperature trip
point.
FIGURE 7. ISL6131 “LOSSLESS” SEQUENCING CONFIGURATION
DC-DC_A
VIN
VOUT
EN
VIN
VIN
VOUT
VOUT
EN
EN
DC-DC_B
DC-DC_C
VMON_A
VMON_D
VMON_C
VMON_B
ABC
STATUS
PGOOD
GND
VDD
ENABLE
ISL6131
