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Maxim > Design Support > Technical Documents > Application Notes > Digital Potentiometers > APP 4021
Maxim > Design Support > Technical Documents > Application Notes > Display Drivers > APP 4021
Maxim > Design Support > Technical Documents > Application Notes > Power-Supply Circuits > APP 4021
Keywords: MAX6956, MAX6957, MAX7300, MAX7301, MAX6946, constant-current LED drivers,
transition detection, driving RGB LEDs, push-pull output ports, 28 LED drive ports, max6956
programming, driving white LEDs
APPLICATION NOTE 4021
MAX6956 Programming Guide
By: Walter Chen, Principle Member of the Technical Staff, Applications
Mar 22, 2007
Abstract: This instructional guide provides detailed information on programming the MAX6956 LED
display driver and I/O expander. Programming tips for similar devices (the MAX6957, MAX7300, and
MAX7301) are also discussed.
Overview
The MAX6956 LED driver and I/O expander can provide and
maintain desired constant-current levels on all of its 20 or 28
(depending on the package type) LED drive ports without the use
of external current-limiting resistors. Sixteen constant-current levels
(from 1.5mA to 24mA) can be applied to all ports simultaneously or
selected differently for each individual port. The MAX6956 not only
controls LED intensity levels, but also its port-matching accuracy
makes their hues more consistent. In addition to being a constant-
current LED driver, the MAX6956 allows individual ports to be used
as input ports with transition-detection capability, or as push-pull output ports with a sinking current of
10mA and sourcing current of 4.5mA.
The MAX6957 is similar to the MAX6956, but it has an SPI™- instead of an I²C-compatible interface.
The MAX7300 is a general-purpose I/O (GPIO) port expander that is similar to the MAX6956, except
that it does not have the constant-current LED-drive capability. The MAX7301 is a GPIO port expander
similar to the MAX7300, but it has an SPI- instead of an I²C-compatible interface.
Figure 1 shows a simple application example that uses the MAX6956 to drive ten white and RGB LEDs
without requiring current-limiting resistors.
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