pca9546abs NXP Semiconductors, pca9546abs Datasheet - Page 7

• Manufacturer Part Number: pca9546abs
• Description: 4-channel I2c Switch With Reset
• Manufacturer: NXP Semiconductors

Philips Semiconductors
PCA9546A_4
Product data sheet
6.3 RESET input
6.4 Power-on reset
6.5 Voltage translation
The RESET input is an active LOW signal which may be used to recover from a bus fault
condition. By asserting this signal LOW for a minimum of t
its registers and I
must be connected to V
When power is applied to V
a reset condition until V
and the PCA9546A registers and I
states (all zeroes) causing all the channels to be deselected. Thereafter, V
lowered below 0.2 V to reset the device.
The pass gate transistors of the PCA9546A are constructed such that the V
be used to limit the maximum voltage that will be passed from one I
Figure 7
was generated using the data specified in
sheet). In order for the PCA9546A to act as a voltage translator, the V
be equal to, or lower than the lowest bus voltage. For example, if the main bus was
running at 5 V, and the downstream buses were 3.3 V and 2.7 V, then V
equal to or below 2.7 V to effectively clamp the downstream bus voltages. Looking at
Figure
3.5 V or lower, so the PCA9546A supply voltage could be set to 3.3 V. Pull-up resistors
can then be used to bring the bus voltages to their appropriate levels (see
Fig 7. Pass gate voltage versus supply voltage
(1) maximum
(2) typical
(3) minimum
7, we see that V
shows the voltage characteristics of the pass gate transistors (note that the graph
2
C-bus state machine and will deselect all channels. The RESET input
V
o(sw)
(V)
Rev. 04 — 29 August 2006
o(sw)(max)
DD
5.0
4.0
3.0
2.0
1.0
DD
2.0
has reached V
through a pull-up resistor.
DD
, an internal Power-On Reset (POR) holds the PCA9546A in
2.5
will be at 2.7 V when the PCA9546A supply voltage is
2
C-bus state machine are initialized to their default
3.0
POR
3.5
Section 10 “Static characteristics”
. At this point, the reset condition is released
4.0
(1)
(2)
(3)
4.5
4-channel I
002aaa964
5.0
V
w(rst)L
DD
© Koninklijke Philips Electronics N.V. 2006. All rights reserved.
(V)
5.5
, the PCA9546A will reset
2
C-bus switch with reset
PCA9546A
2
C-bus to another.
o(sw)
o(sw)
DD
voltage should
Figure
DD
should be
of this data
must be
voltage can
14).
7 of 25