Datasheet
PCAL9535A All information provided in this document is subject to legal disclaimers. © NXP Semiconductors N.V. 2015. All rights reserved.
Product data sheet Rev. 2 — 23 January 2015 20 of 46
NXP Semiconductors
PCAL9535A
Low-voltage 16-bit I
2
C-bus I/O port with interrupt and Agile I/O
8. Application design-in information
8.1 Minimizing I
DD
when the I/Os are 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 13
. 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 I/O pins greater than or equal to V
DD
when the LED is off.
Figure 14
shows a high value resistor in parallel with the LED. Figure 15 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 000X for this example.
P0_0, P0_2, P0_3 configured as outputs.
P0_1, P0_4, P0_5 configured as inputs.
P0_6, P0_7 and (P1_0 to P1_7) configured as inputs.
(1) External resistors are required for inputs (on P port) that may float. Also, internal pull-up or pull-down may be used to eliminate
the need for external components. If a driver to an input will never let the input float, a resistor is not needed. If an output in the
P port is configured as a push-pull output there is no need for external pull-up resistors. If an output in the P port is configured
as an open-drain output, external pull-up resistors are required.
Fig 13. Typical application
PCAL9535A
P0_0
P0_1
SCL
SDA
V
DD
(3.3 V)
MASTER
CONTROLLER
SCL
SDA
INT
P0_2
V
DD
A1
A0
V
DD
V
SS
INT
10 kΩ
SUB-SYSTEM 1
(1)
(e.g., temp sensor)
P0_3
INT
SUB-SYSTEM 2
(e.g., counter)
RESET
controlled
switch
(e.g., CBT device)
V
DD
A
B
enable
SUB-SYSTEM 3
(1)
(e.g., alarm system)
ALARM
P0_4
P0_5
P0_6
10 DIGIT
NUMERIC
KEYPAD
V
SS
002aah430
10 kΩ10 kΩ 2 kΩ 100 kΩ
(×3)
P0_7
P1_0
P1_1
P1_2
P1_3
P1_4
P1_5
P1_6
P1_7
A2