pca9545ad NXP Semiconductors, pca9545ad Datasheet - Page 9

• Manufacturer Part Number: pca9545ad
• Description: 4-channel I2c Switch With Interrupt Logic And Reset
• Manufacturer: NXP Semiconductors

NXP Semiconductors
PCA9545A_45B_45C_6
Product data sheet
6.4 Power-on reset
6.5 Voltage translation
When power is applied to V
PCA9545A/45B/45C in a reset condition until V
reset condition is released and the PCA9545A/45B/45C registers and I
machine are initialized to their default states (all zeroes) causing all the channels to be
deselected. Thereafter, V
The pass gate transistors of the PCA9545A/45B/45C are constructed such that the V
voltage can be used to limit the maximum voltage that will be passed from one I
another.
Figure 9
was generated using the data specified in
sheet). In order for the PCA9545A/45B/45C to act as a voltage translator, the V
voltage should 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
should be equal to or below 2.7 V to effectively clamp the downstream bus voltages.
Looking at
supply voltage is 3.5 V or lower, so the PCA9545A/45B/45C 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
More Information can be found in Application Note AN262: PCA954X family of I
multiplexers and switches .
Fig 9. Pass gate voltage versus supply voltage
(1) maximum
(2) typical
(3) minimum
shows the voltage characteristics of the pass gate transistors (note that the graph
Figure
Figure
9, we see that V
16).
V
o(sw)
(V)
Rev. 06 — 19 March 2007
5.0
4.0
3.0
2.0
1.0
DD
2.0
DD
must be lowered below 0.2 V to reset the device.
, an internal Power-On Reset (POR) holds the
2.5
4-channel I
o(sw)(max)
3.0
3.5
Section 10 “Static characteristics”
2
will be at 2.7 V when the PCA9545A/45B/45C
C-bus switch with interrupt logic and reset
4.0
DD
PCA9545A/45B/45C
(1)
(2)
(3)
has reached V
4.5
002aaa964
5.0
V
DD
(V)
5.5
POR
. At this point, the
2
© NXP B.V. 2007. All rights reserved.
C-bus state
of this data
2
o(sw)
2
C/SMBus
C-bus to
o(sw)
9 of 28
DD