Figure 7-2. Noise vs Conversion Time

7.5 Programming

7.5.1 I2C Serial Interface

The INA236 operates only as a target on both the SMBus and I2C interfaces. Connections to the bus are

made through the open-drain SDA and SCL lines. The SDA and SCL pins feature integrated spike suppression

filters and Schmitt triggers to minimize the effects of input spikes and bus noise. Although the device integrates

spike suppression into the digital I/O lines, proper layout techniques help minimize the amount of coupling into

the communication lines. This noise introduction could occur from capacitive coupling signal edges between

the two communication lines themselves or from other switching noise sources present in the system. Routing

traces in parallel with ground in between layers on a printed circuit board (PCB) typically reduces the effects of

coupling between the communication lines. Shielded communication lines reduce the possibility of unintended

noise coupling into the digital I/O lines that could be incorrectly interpreted as start or stop commands.

The INA236 supports the transmission protocol for fast mode up to 400 kHz and high-speed mode up to 2.94

MHz. All data bytes are transmitted most significant byte first and follow the SMBus 3.0 transfer protocol.

To communicate with the INA236, the controller must first address targets through a target address byte. The

target address byte consists of seven address bits and a direction bit that indicates whether the action is to be a

read or write operation.

The INA236 uses a single address pin, A0. Table 7-1 shows possible configurations for A0 and the

corresponding address for both the A and B versions of the device. The INA236 samples the state of the

A0 pin on every bus communication. The pin state for A0 must be established before any activity on the interface

occurs. When connecting the SDA pin to A0 to set the device address, make sure to add an additional hold time

of 100 ns on the MSB of the I2C address to ensure correct device addressing. The A and B device options,

each with four unique addresses, allows users to connect up to eight devices in a system without I2C address

conflicts.

Table 7-1. Address Pins and Target Addresses

A0

INA236A DEVICE OPTION

INA236B DEVICE OPTION

GND

1000000

1001000

VS

1000001

1001001

SDA

1000010

1001010

SCL

1000011

1001011

INA236

SBOSA81C – MAY 2021 – REVISED DECEMBER 2022

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