ISL28022 Datasheet, PDF (25/28 Pages) Intersil Corporation – Precision Digital Power Monitor

ISL28022
The regulation node of the circuit, shown in Figure 38 is at V_OUT.
The ISL97516 has feedback circuitry that removes the current
sense resistor, RSH, from impacting the regulation voltage. The
current sense resistor is calculated using Equation 11.
Equation 11 shows the formula used to calculate R_shunt.
The ISL28022 interrupt pin is connected to the Enable pin of the
regulator. The ISL28022 has OV/UV alerts for both the Bus and
Shunt channels. A fault condition from either channel powers
down the voltage regulator.
V_high
VOUT
VLOAD
Reg
VINP
VINM
VBUS
VOUT
ISL28022 DPM
VCC
ADC
16-Bit
GND
SCL
3VÆ5.5V
SHUNT
REG
OPTOCOUPLERS
SDA
V_low
OPTOCOUPLER
ECLK/INT
REG
MAP
A0
A1
MCU
GPIO
FIGURE 39. FLOATING SUPPLY DESIGN IDEA
Floating Supply DPM (> 60V or < 0V
Operation)
The ISL28022 is operational when the potential of the measured
circuitry is greater than the potential at the ground pin. In most
application the ground pin potential equals 0V. A zero potential
ground reference limits the operating range of the ISL28022 to
0V to 60V. This application illustrates the connectivity of the DPM
to measure and operate at potentials greater than 60V or less
than 0V.
Assume an application that measures a -48V supply. The ground
reference voltage of the system, V_low, equals -48V. V_high
equals 0V for the example. The power supply voltage to the
system is -48V. The load supply voltage is set by the voltage
regulator, Vload Reg. The regulator can be either a shunt or a
linear regulator.
The voltage levels for I²C communication lines are determined by
V_low and the ISL28022 shunt regulator. A low voltage equals
the V_low potential. A high level equals the summation of V_low
and the Shunt Regulator voltage. For a -48V system with a 3.3V
shunt regulator, a low voltage equals -48V and a high voltage
level equals -44.7V. The voltage from the I²C communication
pins can not be directly connected to a ground referenced
micro-controller. The optocouplers are used to translate the
voltage level from the -48V referenced system to the ground
referenced micro-controller system.
The ISL28022 measures voltage between two nodes. For the
shunt input, the ISL28022 measures the voltage between VINP
and VINM nodes. For the Bus input, the ISL28022 measures the
difference between V_bus and GND nodes. The V_bus voltage for a
floating system is calculate using Equation 12.
( ) V _bus V _low + Vbus _LSB⋅Vbus _Reg
(EQ. 12)
V_LOW is the ground reference voltage of the system. In this
instance, the value is -48V. Vbus_LSB is the step size of the V_bus
measurement. This equals 4mV. Vbus_Reg is the integer value of
the V_bus measurement reported by the ISL28022.
25
FN8386.1
April 26, 2013