PCA9534 All information provided in this document is subject to legal disclaimers. © NXP Semiconductors N.V. 2017. All rights reserved.
Product data sheet Rev. 4 — 7 November 2017 11 of 27
NXP Semiconductors
PCA9534
8-bit I
2
C-bus and SMBus low power I/O port with interrupt
7. Application design-in information
7.1 Minimizing I
DD
when the I/O us used to control LEDs
When the I/Os are used to control LEDs, they are normally connected to V
DD
through a
resistor as shown in Figure 12
. Since the LED acts as a diode, when the LED is off the
I/O V
I
is about 1.2 V less than V
DD
. The supply current, I
DD
, increases as V
I
becomes
lower than V
DD
.
Designs needing to minimize current consumption, such as battery power applications,
should consider maintaining the IOn pins greater than or equal to V
DD
when the LED is off.
Figure 13
shows a high value resistor in parallel with the LED. Figure 14 shows V
DD
less
than the LED supply voltage by at least 1.2 V. Both of these methods maintain the I/O V
I
at or above V
DD
and prevents additional supply current consumption when the LED is off.
Device address configured as 0100 100X for this example.
IO0, IO1, IO2 configured as outputs.
IO3, IO4, IO5 configured as inputs.
IO6, IO7 are not used and must be configured as outputs.
Fig 12. Typical application
PCA9534
IO0
IO1
SCL
SDA
V
DD
002aac476
SCL
SDA
IO2
IO3
V
DD
V
SS
MASTER
CONTROLLER
V
SS
V
DD
(5 V)
2 kΩ
SUBSYSTEM 1
(e.g., temp. sensor)
INT
SUBSYSTEM 2
(e.g., counter)
RESET
controlled switch
(e.g., CBT device)
A
B
enable
INT
5 V
INT
10 kΩ 10 kΩ
SUBSYSTEM 3
(e.g., alarm system)
ALARM
IO4
IO5
V
DD
A2
A1
A0
IO6
IO7
100 kΩ
(× 3)
10 kΩ10 kΩ
