ISL28022_15 Datasheet, PDF (13/32 Pages) Intersil Corporation – Precision Digital Power Monitor

ISL28022
Functional Description
Overview
The ISL28022 is a digital power monitor (DPM) device that is
capable of measuring bidirectional currents while monitoring the
bus voltage.
The DPM requires an external shunt resistor to enable current
measurements. The shunt resistor translates the bus current to a
voltage. The DPM measures the voltage across the shunt
resistors and reports the measured value out digitally via an I²C
interface. A register within the DPM is reserved to store the value
of the shunt resistor. The stored current sense resistor value
allows the DPM to output the current value to an external digital
device.
The ISL28022 measures bus voltage and current sequentially.
The device has a power measurement functionality that
multiplies current and voltage measured values. The power
calculation is stored in a unique register. The power
measurement allows the user to monitor power to or from the
load in addition to current and voltage.
The ISL28022 can monitor supplies from 0V to 60V while
operating on a chip supply ranging from 3V to 5.5V.
The ISL28022 ADC sample rate can be configured to an internal
oscillator (500kHz) or a user can provide a synchronized clock.
Detailed Description
The ISL28022 consists of a two channel analog front end
multiplexer, a 16-bit sigma delta ADC and digital signal
processing/serial communication circuitry.
The main block within the device is a 3rd order Sigma Delta ADC.
The input signal bandwidth is 1kHz, wide enough for power
monitoring applications. The main block includes an internal
1.2V bandgap voltage reference that is used to drive the ADC.
The analog front end multiplexer selects the input to the ADC.
The selection to the input of the ADC is either a single-ended
V_BUS measurement or a fully differential measurement across a
shunt resistor.
The digital block contains controllable registers, I²C serial
communication circuitry and a state machine. The state machine
controls the behavior of the ADC acquisition, whether the acquisition
is triggered or continuous. A more detailed description of the state
machine states can be found in “MODE: Operating Mode” on
page 15.
Pin Descriptions
A1
A1 is the address select pin. A1 is one of two I²C/SMBus slave
address select pins that are multilogic programmable for a total
of 16 different address combinations.
There are four selectable levels for A1, VCC, GND, SCL/SMBCLK,
and SDA/SMBDAT. See Table 22 for more details in setting the
slave address of the device.
A0
A0 is the address select pin. A0 is one of two I²C/SMBus slave
address select pins that are multilogic programmable for a total
of 16 different address combinations.
There are four selectable levels for A0, VCC, GND, SCL/SMBCLK,
and SDA/SMBDAT. See Table 22 for more details in setting the
slave address of the device.
EXT_CLK/INT
EXT_CLK/INT is the External/Interrupt clock pin. EXT_CLK/INT is
a bidirectional pin. The pin provides a connection to the system
clock. The system clock is connected to the ADC. The
acquisitions rate of the ADC can be varied through the
EXT_CLK/INT pin. The pin functionality is set through a control
register bit.
When the EXT_CLK/INT pin is configured as an output, the pin
functionality becomes an interrupt flag to connecting devices.
EXT_CLK/INT pin as an output requires a pull-up resistor to a
power supply, up to 20V, for proper operation. The internal
threshold detectors (OV_sh/UV_sh/OV_b/UV_b) signal level relative to
the measured value determines the state of the INT pin.
SDA/SMBDAT
SDA/SMBDAT is the serial data input/output pin. SDA/SMBDAT
is a bidirectional pin used to transfer data to and from the device.
The pin is an open-drain output and may be wired with other
open-drain/collector outputs. The open-drain output requires a
pull-up resistor for proper functionality. The pull-up resistor
should be connected to VCC of the device.
SCL/SMBCLK
SCL/SMBCLK is the serial clock input pin. The SCL/SMBCLK
input is responsible for clocking in all data to and from the
device.
VCC
VCC is the positive supply voltage pin. VCC is an analog power
pin. VCC supplies power to the device.
GND
GND is the ground pin. All voltages internal to the chip are
referenced to ground. GND should be tied to 0V for single supply
applications. For dual supply applications, the pin should be
connected to the most negative voltage in the application.
VBUS
VBUS is the power bus voltage input pin. The pin should be
connected to the desired power supply bus to be monitored.
VINP
VINP is the shunt voltage monitor positive input pin. The pin
connects to the most positive voltage of the current shunt
resistor.
VINM
VINM is the shunt voltage monitor negative input pin. The pin
connects to the most negative voltage of the current shunt
resistor.
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FN8386.7
October 2, 2015