Datasheet
PCAL6416A All information provided in this document is subject to legal disclaimers. © NXP Semiconductors N.V. 2014. All rights reserved.
Product data sheet Rev. 6 — 9 October 2014 24 of 61
NXP Semiconductors
PCAL6416A
Low-voltage translating 16-bit I
2
C-bus/SMBus I/O expander
9. Application design-in information
9.1 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 18
. 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(P)
. The supply current, I
DD(P)
, increases as V
I
becomes
lower than V
DD(P)
.
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 19
shows a high value resistor in parallel with the LED. Figure 20 shows V
DD(P)
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(P)
and prevents additional supply current consumption when the LED is
off.
Device address configured as 0100 000x for this example.
P0_0 and P0_2 through P1_0 are configured as inputs.
P0_1 and P1_1 through P1_7 are configured as outputs.
(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 18. Typical application
PCAL6416A
P0_0
P0_1
SCL
SDA
V
DD
SCL
SDA
P0_2
P0_3
GND
MASTER
CONTROLLER
GND
V
DD(I2C-bus)
= 1.8 V
controlled
switch
A
B
enable
INT
V
DD(P)
INT
10 kΩ
SUBSYSTEM 1
(e.g., alarm system)
ALARM
(1)
P0_4
P0_5
P0_6
P0_7
10 kΩ10 kΩ
RESETRESET
V
DD(P)
002aaf965
P1_0
P1_1
P1_2
P1_3
P1_4
P1_5
P1_6
P1_7
V
DD(I2C-bus)
V
DD(I2C-bus)
ADDR
KEYPAD
10 kΩ
10 kΩ (×7)