PAC1921 Current Power Sensor - Microchip

PAC1921 Current and Power Measurement ICs

PAC1921 is a high-side current/power sensor with 2-wire bus and configurable analog output that can present power, current or voltage. The PAC1921 is designed for power measurement and diagnostic systems that cannot allow for latency when performing high-speed power management. Measurements are accumulated in large lossless registers, allowing for integration periods of 500 μs to 2.9 s. The measurement is averaged and presented on the analog output with a full scale range of 3 V, 2 V, 1.5 V, or 1.0 V.

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PAC1921 Features

  • Configurable measurement type output: power, current or bus voltage
  • Configurable voltage output (3 V, 2 V, 1.5 V, 1 V)
  • 100 mV full-scale current sense voltage range
  • Second-order delta-sigma ADC with 11-bit or 14-bit resolution
  • 1% power measurement accuracy
  • +/-0.4% current measurement accuracy (Max.)
  • 0.9 ms - 2,900 ms effective sampling interval
  • Auto-zero offset
  • Auto sleep state: automatically shifts to low-power state (3.5 μA)
  • VDD = 3.3 V nominal (operational range 3.0 V to 5.5 V)
  • Bus range: 0 V to 32 V
  • No input filters required
  • Interface: SMBus/I2CTM

PAC1921 Target Applications

  • Diagnostic Equipment
  • Servers
  • Power Supplies
  • Industrial and Power Management Systems
  • Notebook and Desktop Computers

PAC1921 Block Diagram

pac1921-block-diagram.PNG

PAC1921 Pin Descriptions

Symbol Function Type
VDD Positive Power Supply Voltage Power
SENSE+ VBUS/VSENSE+ input AIO40
SENSE- VSENSE- input AIO40
OUT Output Voltage Measurement AIO5
GND Ground Power
ADDR_SEL Select SMBus/I2CTM Address AIO2
RESERVED Reserved for future use. Connect to VDD for SMBus functionality DI (5 V)
READ/INT Controls power states DI
SM_DATA SM_DATA: SMBus/I2CTM Data - requires pull-up resistor DIOD
SM_CLK SM_CLK: SMBus/I2CTM Clock - requires pull-up resistor DI (5 V)
EP Not internally connected, but recommend grounding N/A
Pin Type Description
Power This pin is used to power to the device.
AIO40 Analog Input/Output - this pin is used as an I/O for analog signals. Maximum voltage is 40 V.
AIO2 Analog Input/Output - this pin is used as an I/O for analog signals. Maximum voltage is 2 V.
DI Digital Input - this pin is used for digital inputs.
DIOD Digital Input/Output Open-Drain - this pin is used for digital I/O and is open-drain.
PAC1921 - A World First in High-Side Current/Power Sensors

PAC1921 Application Example

The figure below shows a system diagram using the PAC1921 in SMBus mode. The OUT pin supplies data for systems that cannot tolerate the latencies inherent in embedded communications buses. MCU-based systems, such as PIC® Microcontrollers (MCUs) equipped with ADC inputs can sample the value presented on the OUT pin for immediate use in thermal or power control algorithms. Output values are also available in a digital format via the SMBus interface. The PAC1921 contains a high-side precision current-sensing circuit and a precision bus voltage measurement circuit. The current-sensing circuit contains a differential amplifier that continuously measures the voltage (VSENSE) developed across an external sense resistor (RSENSE) to represent the high-side supply current. The full-scale range of VSENSE is from 0 mV to 100 mV. For power, the current and voltage data is multiplied and accumulated, scaled with two digital gain parameters, then applied to the OUT pin through a 10-bit DAC and a gain output buffer for the output Full-Scale-Range (FSR).

pac1921-application-example.PNG
 
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