SC18IS602B_1008 Datasheet, PDF (11/25 Pages) NXP Semiconductors – I2C-bus to SPI bridge

NXP Semiconductors
SC18IS602B
I²C-bus to SPI bridge
pulled LOW by an external device, the weak pull-up turns off, and only the very weak
pull-up remains on. In order to pull the pin LOW under these conditions, the external
device has to sink enough current to overpower the weak pull-up and pull the pin below its
input threshold voltage.
The third pull-up is referred to as the ‘strong’ pull-up. This pull-up is used to speed up
LOW-to-HIGH transitions on a quasi-bidirectional pin when the port latch changes from a
logic 0 to a logic 1. When this occurs, the strong pull-up turns on for two CPU clocks
quickly pulling the pin HIGH.
The quasi-bidirectional pin configuration is shown in Figure 15.
Although the SC18IS602B is a 3 V device, most of the pins are 5 V tolerant. If 5 V is
applied to a pin configured in quasi-bidirectional mode, there will be a current flowing from
the pin to V_DD causing extra power consumption. Therefore, applying 5 V to pins
configured in quasi-bidirectional mode is discouraged.
A quasi-bidirectional pin has a Schmitt-triggered input that also has a glitch suppression
circuit.
2 SYSTEM
CLOCK
CYCLES
V_DD
P
P very P
strong
weak
weak
pin latch data
V_SS
input data
Fig 15. Quasi-bidirectional output configuration
GPIO pin
glitch rejection
002aac548
7.1.11.2 Open-drain output configuration
The open-drain output configuration turns off all pull-ups and only drives the pull-down
transistor of the pin when the port latch contains a logic 0. To be used as a logic output, a
pin configured in this manner must have an external pull-up, typically a resistor tied to
V_DD. The pull-down for this mode is the same as for the quasi-bidirectional mode.
The open-drain pin configuration is shown in Figure 16.
An open-drain pin has a Schmitt-triggered input that also has a glitch suppression circuit.
SC18IS602B
Product data sheet
All information provided in this document is subject to legal disclaimers.
Rev. 5 — 3 August 2010
© NXP B.V. 2010. All rights reserved.
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