PCA9646 Datasheet, PDF (1/22 Pages) NXP Semiconductors – Buffered 4-channel 2-wire bus switch

PCA9646
Buffered 4-channel 2-wire bus switch
Rev. 1 — 1 March 2011
Product data sheet
1. General description
The PCA9646 is a monolithic CMOS integrated circuit for 2-wire bus buffering and
switching in applications including I²C-bus, SMBus, PMBus, and other systems based on
similar principles.
Each of the four outputs may be independently enabled in any combination as determined
by the contents of the programmable control register. Each I/O is impedance isolated from
all others, thus allowing a total of five branches of 2-wire bus with the maximum specified
load (e.g., 5  400 pF for Fm+ I²C-bus at 1 MHz, or 5  4 nF at lower frequencies)
(Ref. 1). More than one PCA9646 may be used in series, providing a substantial fan-out
capability.
As per the PCA9525 and PCA9605 simple bus buffers, the PCA9646 includes a
unidirectional buffer for the clock signal, and a bidirectional buffer for the data signal. The
direction of the clock signal may also be set by the contents of the programmable control
register. Clock stretching and timing must always be under control of the master device.
The PCA9646 has excellent application to 2-wire bus address expansion and increasing
of maximum load capacitance. Very large LED displays are a perfect example.
2. Features and benefits
 Drop-in pin compatible with PCA9546A, etc.
 Each I/O is impedance isolated from all others allowing maximum capacitance on all
branches
 30 mA static sink capability on all ports
 Works with I²C-bus (Standard-mode, Fast-mode, and Fast-mode Plus (Fm+)),
SMBus (standard and high power mode), and PMBus
 Fast switching times allow operation in excess of 1 MHz
 Allows driving of large loads (e.g., 5  4 nF)
 Hysteresis on I/O increases noise immunity
 Operating voltages from 2.7 V to 5.5 V
 Uncomplicated characteristics suitable for quick implementation in most common
2-wire bus applications
3. Applications
 Large arrays of I²C-bus components, e.g., LED displays
 Power management systems
 Game consoles, computers, RAID systems