Datasheet

INA226
www.ti.com SBOS547 –JUNE 2011
Data transfer is then initiated and eight bits of data are sent, followed by an Acknowledge bit. During data
transfer, SDA must remain stable while SCL is high. Any change in SDA while SCL is high is interpreted as a
start or stop condition.
Once all data have been transferred, the master generates a stop condition, indicated by pulling SDA from low to
high while SCL is high. The INA226 includes a 28ms timeout on its interface to prevent locking up the bus.
Serial Bus Address
To communicate with the INA226, the master must first address slave devices via a slave address byte. The
slave 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 INA226 has two address pins, A0 and A1. Table 7 describes the pin logic levels for each of the 16 possible
addresses. The state of pins A0 and A1 is sampled on every bus communication and should be set before any
activity on the interface occurs.
Table 7. INA226 Address Pins and
Slave Addresses
A1 A0 SLAVE ADDRESS
GND GND 1000000
GND V
S+
1000001
GND SDA 1000010
GND SCL 1000011
V
S+
GND 1000100
V
S+
V
S+
1000101
V
S+
SDA 1000110
V
S+
SCL 1000111
SDA GND 1001000
SDA V
S+
1001001
SDA SDA 1001010
SDA SCL 1001011
SCL GND 1001100
SCL V
S+
1001101
SCL SDA 1001110
SCL SCL 1001111
Serial Interface
The INA226 operates only as a slave device on both the I
2
C bus and the SMBus. Connections to the bus are
made via the open-drain I/O lines SDA and SCL. The SDA and SCL pins feature integrated spike suppression
filters and Schmitt triggers to minimize the effects of input spikes and bus noise. While there is spike suppression
integrated into the digital I/O lines, proper layout should be used to minimize the amount of coupling into the
communication lines. This noise introduction could occur from capacitively 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. Shielding communication lines in general is recommended to reduce to
possibility of unintended noise coupling into the digital I/O lines that could be incorrectly interpreted as start or
stop commands.
The INA226 supports the transmission protocol for Fast (1kHz to 400kHz) and High-speed (1kHz to 3.4MHz)
modes. All data bytes are transmitted most significant byte first.
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