JS202011SCQN datasheet(31/45 Pages) MICROCHIP

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Hardware Description

 2017 Microchip Technology Inc.

DS50002673A-page 31

J30 may be used to provide external power in place of the +5V USB power derived from

VBUS if the USB is not connected. J30 is labeled 5V, but external voltages applied to

the pin labeled 5V may be anywhere from 5.5V to 2.7V. This may be needed if the

external I2C signals are used with no USB connection

J25 sets the I2C/SMBus address to 20h when the shunt is in place. Removing the shunt

on J25 changes the address to 22h. Replacing R22 allows selection of other addresses

(see the PAC1934 Data Sheet).

The shunt on J23 pulls the SLOW pin to ground, so the device is operating at the pro-

grammed sample rate. Removing this shunt selects an 8 Hz sample rate for low power

operation. The PAC1934 has a unique feature in that the status of this pin is tracked in

a register bit. This allows the GUI to change the displayed sample rate to 8 Hz when

the SLOW pin goes high. This is useful in real applications as well, when the user goes

to a SLOW sample rate and wants to capture the energy usage before and after the

SLOW pin transition. Requirements like this can also benefit from the features

described for the SLOW register settings, where the device can automatically be

refreshed by a SLOW pin transition.

4.9

DIRECT EXTERNAL I2C CONNECTION

The ADM00805 can be used with direct I2C control from a PC running Windows®,

Linux® or other digital controller. VDD_IO may need a different voltage for external I2C

use than the default settings for USB control. This is easily implemented by moving

SW1 from the ON/5V position used for USB control to the OFF/EXT position used for

external I2C control. Connect the external SCA and SCL signals is then required, along

with the power (VIO) and ground used for these I2C signals, to J27. Generally, the user

will not be able to use the PAC193x Demo Application with direct I2C connection.

For Windows® 10 systems, the user can embed sense resistors in series with the

power rails to be monitored/measured, interface to the ADM00805 with direct I2C con-

nections and use the Windows® 10 driver to interface the energy metering functions

with the OS.

4.10 JUMPER CONNECTIONS - DEFAULT CONFIGURATION AND OTHER

INFORMATION TABULATED

Table 4-1 shows the default configuration for the shunts on the board to achieve the

functionality described in the Section 1.1 “Introduction”. Using this table with the

schematic will give a good understanding of the default configuration. In the DEMO

mode and SYSTEM/SHUNT mode columns of Table 4-1, a dash (—) means that no

jumper is installed or that there is no information needed in this cell. Numbers 12 and

23 mean that the jumper is installed either between the pins 1 and 2 (12) or between

the pins 2 and 3 (23).

TABLE 4-1:

DEFAULT SHUNT CONNECTIONS

Jumper

no.

DEMO mode

SYSTEM/SHUNT mode

Special connection

Options/Info

—

External source

Channel 1 +input, GND,

channel 1 –input

—

External source

Channel 2 +input, GND,

channel 2 –input

—

External source

Channel 3 +input, GND,

channel 3 –input

—

External source

Channel 4 +input, GND,

channel 4 –input

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