TS4956
Typical application schematic
5/51
2.1
I2C interface
The TS4956 uses a serial bus, which conforms to the IC protocol (the TS4956 must be
powered when it is connected to IC bus), to control the chip’s functions via two wires: Clock
and Data.
The Clock line and the Data line are bidirectional (open-collector) with an external chip pull-
up resistor (typically 10 k
). The maximum clock frequency in fast-mode specified by the IC
standard is 400kHz, and this frequency is supported by the TS4956. In this application, the
TS4956 is always the slave device and the controlling MCU is the master device.
The I2CVCC pin determines the power supply of the TS4956’s I2C interface. The voltage
connected to this pin must be equal or less than the TS4956 power supply voltage VCC. The
minimum value of the I2CVCC voltage is 2.7V.
When the I2CVCC pin is connected to an I2C voltage, the TS4956 is ready to communicate
via the I2C bus.
When the I2CVCC pin is connected to the ground, the TS4956 is in total standby mode, with
an ultra low standby current on the order of a few nanoamperes. In this condition the
TS4956 cannot receive I2C command from the I2C bus.
In both cases, pins SDA and SCL must respect logic HI or logic LOW thresholds (not
floating) presented in
Table 3 on page 2, in order for the circuit to function properly.
Table on page 5 summarizes the pin descriptions for the IC bus interface.
2.1.1
IC operation description
The host MCU can write into the TS4946 control register to control the TS4956 and read
from the control register to get the current configuration of the TS4956. The TS4956 is
addressed by a single byte consisting of a 7-bit slave address and an R/W bit. The TS4956
control register address is $5Dh.
Table 6.
The first byte after the START message for addressing the device
In order to write data into the TS4956 control register, after the “start” message the MCU
must send the following data:
●
send byte with the IC 7-bit slave address and with the R/W bit set low
●
send the data (control register setting)
All bytes are sent with MSB bit first. The transfer of written data ends with a “stop” message.
When transmitting several data, the data can be written with no need to repeat the “start”
message and addressing byte with the slave address.
Table 5.
IC bus interface: pin descriptions
Pin
Functional description
SDA
This is the serial data pin
SCL
This is the clock input pin
I2CVCC
I2C interface power supply
A6
A5
A4
A3
A2
A1
A0
Rw
101
1
0
1
X