PCA9306_08 Datasheet, PDF (7/16 Pages) Texas Instruments – DUAL BIDIRECTIONAL I2C BUS AND SMBus VOLTAGE-LEVEL TRANSLATOR

PCA9306
www.ti.com....................................................................................................................................................... SCPS113I – OCTOBER 2004 – REVISED JULY 2008
APPLICATION INFORMATION
General Applications of I²C
In I²C applications, the bus capacitance limit of 400 pF restricts the number of devices and bus length. Using the
PCA9306 enables the system designer to isolate two halves of a bus; thus, more I²C devices or longer trace
length can be accommodated.
The PCA9306 also can be used to run two buses, one at 400-kHz operating frequency and the other at 100-kHz
operating frequency. If the two buses are operating at different frequencies, the 100-kHz bus must be isolated
when the 400-kHz operation of the other bus is required. If the master is running at 400 kHz, the maximum
system operating frequency may be less than 400 kHz because of the delays added by the repeater.
As with the standard I²C system, pullup resistors are required to provide the logic high levels on the translator's
bus. The PCA9306 has a standard open-collector configuration of the I²C bus. The size of these pullup resistors
depends on the system, but each side of the repeater must have a pullup resistor. The device is designed to
work with standard-mode and fast-mode I²C devices, in addition to SMBus devices. Standard-mode I²C devices
only specify 3 mA in a generic I²C system where standard-mode devices and multiple masters are possible.
Under certain conditions, high termination currents can be used.
V_DPU = 3.3 V
200 kΩ
V_REF1 = 1.8 V
PCA9306
EN ₈
2
V_REF1
7
V_REF2
V_CC
SCL
R_PU
R_PU
3 ^SCL1
SCL2 ₆
SW
2
I C Bus
Master
SDA
4 ^SDA1
SDA2 ₅
SW
GND
GND
1
R_PU
R_PU
V_CC
SCL
2
I C Bus
Device
SDA
GND
Figure 2. Typical Application Circuit (Switch Always Enabled)
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