pca9306 datasheet

14
PCA9306
SCPS113M –OCTOBER 2004–REVISED APRIL 2019 www.ti.com
Product Folder Links: PCA9306
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Overview (continued)
8.1.8 Current Limiting Resistance on V
REF2
The resistor is used to limit the current between V
REF2
and V
REF1
(denoted as R
CC
) and helps to establish the
reference voltage on the enable pin. The 200k resistor can be changed to a lower value; however, the bias
current proportionally increases as the resistor decreases.
I
bias
= (V
CC2
- V
en
)/R
CC
: V
en
= V
REF1
+ V
th
where
• V
th
is approximately 0.6V (5)
Keep in mind R
CC
should not be sized low enough that I
CC
exceeds the absolute maximum continuous channel
current specified in section 6.1 which is described in Equation 6.
R
CC
(min) ≥ (V
CC2
- V
en
)/0.128 : V
en
= V
REF1
+ V
th
where
• V
th
is approximately 0.6V (6)
8.2 Functional Block Diagram
Figure 15. Block Diagram of PCA9306
8.3 Feature Description
8.3.1 Enable (EN) Pin
The PCA9306 device is a double-pole, single-throw switch in which the gate of the transistors is controlled by the
voltage on the EN pin. In Figure 16, the PCA9306 device is always enabled when power is applied to V
REF2
. In
Figure 17, the device is enabled when a control signal from a processor is in a logic-high state.
8.3.2 Voltage Translation
The primary feature of the PCA9306 device is translating voltage from an I
2
C bus referenced to V
REF1
up to an
I
2
C bus referenced to V
DPU
, to which V
REF2
is connected through a 200-kΩ pullup resistor. Translation on a
standard, open-drain I
2
C bus is achieved by simply connecting pullup resistors from SCL1 and SDA1 to V
REF1
and connecting pullup resistors from SCL2 and SDA2 to V
DPU
. Information on sizing the pullup resistors can be
found in the Sizing Pullup Resistors section.