PAC1944 Click

How does it work?

PAC1944 Click as its foundation uses the PAC1944, a four-channel, bidirectional, high-side current-sensing solution with precision voltage measurement capabilities, DSP for power calculation and a power accumulator from Microchip Technology. Its real-time calibration minimizes offset and gain errors. There are four current sense shunt resistors connected to PAC1944’s integrated current sense amplifier. Electricity is brought to shunts via screw terminals where the middle screw connector represents GND used for bus voltage monitoring. Bus voltage, sense resistor voltage, and accumulated proportional power are stored in registers for retrieval by the MCU.

One major feature of the PAC1944 design is a set of digital comparators that allows the user to detect over/under voltage, over/undercurrent, and overpower against user-programmed limits for each channel and generate an alert when the threshold is exceeded. Digital circuitry of the PAC1944 performs power calculations and energy accumulation, which enables energy monitoring with integration periods up to one year or longer. After the Start-Up sequence, the PAC1944 is in the Active state and begins sampling the inputs sequentially. Voltage and current are sampled for all active channels at 1024 samples/second by default, and power is calculated and accumulated.

PAC1944 Click communicates with MCU using the standard I2C 2-Wire interface to read data and configure settings, supporting Fast Mode operation with a clock frequency up to 1MHz and High-Speed Mode up to 3.4MHz. Besides, it also allows the choice of the least significant bit of its I2C slave address by positioning the SMD jumper labeled as ADDR SEL to an appropriate position marked as 0 and 1. The Power-Down pin, labeled as EN and routed to the CS pin of the mikroBUS™ socket, optimizes power consumption and is used for power on/off purposes. All circuits, including the interface pins, are inactive in this state, and the PAC1944 is in the form of minimum power dissipation.

The SLW pin, routed to the RST pin of the mikroBUS™ socket, serves as the conversion rate control. If the SLW pin is asserted, the sample rate is eight samples per second. For sampling rates lower than 1024 samples/second, the PAC1944 is in a Sleep mode for a portion of the conversion cycle, which results in lower power dissipation. No matter the programmed sample rate, this new sample rate will affect the following conversion cycle.

The alert functionality, routed to the INT pin of the mikroBUS™ socket, has multiple purposes; to notify the system that a conversion cycle for all active channels is complete, or to notify the system that the accumulator or accumulator count has overflowed, or that an electrical parameter is outside the programmed limit. Besides the INT pin, the SLW pin can function as another alert feature by attaching a pull-up resistor to it, which is done via onboard SMD jumper labeled as SLW PULL by positioning 10k resistor to an appropriate position marked as DOWN or UP.

This Click board™ can operate with both 3.3V and 5V logic voltage levels selected via the VCC SEL jumper. This way, it is allowed for both 3.3V and 5V capable MCUs to use the I2C communication lines properly. However, the Click board™ comes equipped with a library containing easy-to-use functions and an example code that can be used, as a reference, for further development.

Specifications

Pinout diagram

This table shows how the pinout on PAC1944 Click corresponds to the pinout on the mikroBUS™ socket (the latter shown in the two middle columns).

Notes	Pin					Pin	Notes
	NC	1	AN	PWM	16	NC
Conversion Rate Control	SLW	2	RST	INT	15	INT	Interrupt
Chip Enable	EN	3	CS	RX	14	NC
	NC	4	SCK	TX	13	NC
	NC	5	MISO	SCL	12	SCL	I2C Clock
	NC	6	MOSI	SDA	11	SDA	I2C Data
Power Supply	3.3V	7	3.3V	5V	10	5V	Power Supply
Ground	GND	8	GND	GND	9	GND	Ground

Onboard settings and indicators

PAC1944 Click electrical specifications

Software Support

We provide a library for the PAC1944 Click as well as a demo application (example), developed using MikroElektronika compilers. The demo can run on all the main MikroElektronika development boards.

Package can be downloaded/installed directly from NECTO Studio Package Manager(recommended way), downloaded from our LibStock™ or found on mikroE github account.

Library Description

This library contains API for PAC1944 Click driver.

Key functions:

• void pac1944_cfg_setup ( pac1944_cfg_t *cfg ); – Config Object Initialization function.
• PAC1944_RETVAL pac1944_init ( pac1944_t *ctx, pac1944_cfg_t *cfg ); – Initialization function.
• void pac1944_default_cfg ( pac1944_t *ctx ); – Click Default Configuration function.

Examples description

This demo application shows an example of measuring voltage, current and power in a selected part of the circuit. Note that PAC1944 is a high side power monitor, therefore the desired channel should be connected accordingly.

The demo application is composed of two sections :

void application_task ( void ) {
    float voltage_sens;
    float current_sens;
    float power_sens;
    
    pac1944_refresh_cmd( &pac1944 );
    
    voltage_sens = pac1944_get_calc_measurement( &pac1944, PAC1944_MEAS_SEL_V_SOURCE,
                                                           PAC1944_CH_SEL_CH_1,
                                                           PAC1944_AVG_SEL_ENABLE,
                                                           PAC1944_MEAS_MODE_BIPOLAR_FSR );
    
    current_sens = pac1944_get_calc_measurement( &pac1944, PAC1944_MEAS_SEL_I_SENSE,
                                                           PAC1944_CH_SEL_CH_1,
                                                           PAC1944_AVG_SEL_ENABLE,
                                                           PAC1944_MEAS_MODE_BIPOLAR_FSR );
    
    power_sens = pac1944_get_calc_measurement( &pac1944,   PAC1944_MEAS_SEL_P_SENSE,
                                                           PAC1944_CH_SEL_CH_1,
                                                           PAC1944_AVG_SEL_ENABLE,
                                                           PAC1944_MEAS_MODE_BIPOLAR_FSR );
    
    
    log_printf( &logger, "  Voltage :  %.6f   V rn", voltage_sens );
    log_printf( &logger, "  Current :  %.6f   A rn", current_sens );
    log_printf( &logger, "  Power   :  %.6f   W rn", power_sens );
    log_printf( &logger, "-----------------------------rn" );
    Delay_ms( 2000 );
}

The full application code, and ready to use projects can be installed directly from NECTO Studio Package Manager(recommended way), downloaded from our LibStock™ or found on mikroE github account.

Other mikroE Libraries used in the example:

• MikroSDK.Board
• MikroSDK.Log
• Click.PAC1944

Additional notes and informations

Depending on the development board you are using, you may need USB UART click, USB UART 2 click or RS232 click to connect to your PC, for development systems with no UART to USB interface available on the board. The terminal available in all MikroElektronika compilers, or any other terminal application of your choice, can be used to read the message.

mikroSDK

This Click board™ is supported with mikroSDK – MikroElektronika Software Development Kit. To ensure proper operation of mikroSDK compliant Click board™ demo applications, mikroSDK should be downloaded from the LibStock and installed for the compiler you are using.

For more information about mikroSDK, visit the official page.