14/19

REV1A

Application Information (Continued)

Inputs and Input Selection

The XR18910 includes 8 differential inputs and a 8:1

wire serial interface. The XR18910 is designed to accept 8

differential inputs.

■

■

If fewer than 4 differential inputs are required, tie the unused

inputs to GND.

■

■

If single ended inputs are required, tie the unused inputs to 1.5V.

The input common mode range of the XR18910 is typically

0.6V to 2.4V when running from a 3.3V supply.

The

XR18910 offers a very wide gain range. In most cases, the

output voltage swing will be the limiting factor.

When the XR18910 is powered-up, the default input

selected is Channel 1.

0x10, 0x12, 0x14, 0x15, 0x18, 0x1A, 0x1C, or 0x1E. Refer

to the Register List in Table 1.

Example: The example below illustrates how to select

Channel 4.

Step 1

0

Master sends start condition

S

Step 2

7 6 5 4 3 2 1 0

Master sends XR18910 address with write bit

0

1

1

0

1

1

1

0

6

7

W

7-bit XR18910 Address = 0x67

Step 3

9

XR18910 sends acknowledge

A

Step 4

7 6 5 4 3 2 1 0

Master sends address of register to access

0

0

0

1

0

1

0

1

Select_Input 4 register address

= 0x15

Step 5

9

XR18910 sends acknowledge

A

Step 6

0

Master sends stop condition

P

NOTES:

White Block = host to XR18910, Orange Block = XR18910 to host, Grey Block =

Notes.

Gain Selection

The XR18910 offers 8 selectable fixed gains ranging from

2V/V to 760V/V. When the XR18910 is powered-up, the

default gain is 2V/V.

followed by another byte of data to select the gain. Refer

to the Register List in Table 1 and the Gain Register list in

Table 3.

Example: The example below illustrates how to select a

gain of 150V/V.

To start communication with the XR18910, repeat steps 1-3 as

shown in the Inputs and Input Selection section on page 14.

Step 4

7 6 5 4 3 2 1 0

Master sends address of register to access

0

0

0

0

0

1

1

0

Gain Select register address =

0x06

Step 5

9

XR18910 sends acknowledge

A

Since the Gain Select register was accessed, the XR18910

is expecting another byte of data from the master to complete

the command. Refer to the “Byte of Parameter” column in

the Register List (Table 1). D0 thru D2 are used to select

the gain. Refer to the Gain Register list in Table 3, 150V/V

is D2 = 1, D1 = 0, and D0 = 0. This translates to a hex code

of 0x04, since a full byte of data (8-bits) will be sent.

Step 6

7 6 5 4 3 2 1 0

Master sends gain register data to select G=150

0

0

0

0

0

1

0

0

Gain of 150V/V = 0x04

Step 7

9

XR18910 sends acknowledge

A

Step 8

0

Master sends stop condition

P

NOTES:

White Block = host to XR18910, Orange Block = XR18910 to host, Grey Block =

Notes.

XR

18910