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Maxim > Design Support > Technical Documents > Application Notes > Display Drivers > APP 4397
Keywords: dot matrix, rows, columns, ports, 4-wire interface, 3-wire interface, digits, display memory, LED,
digits, planes, global indirect, digit access number, DAN, bit-per-pixel, display, red, green, intensity control
APPLICATION NOTE 4397
MAX6960 Programming Guide for Large LED
Displays
By: Walter Chen, Principle Member of the Technical Staff, Applications
Apr 17, 2009
Abstract:
This application
note details how multiple MAX696x 8 x 8 matrix LED drivers can be arranged and
programmed to support larger LED displays or dot-matrix elements. This family of drivers supports up to 256
daisy-chained ICs to drive, control, and program large-matrix displays. The application note explains the
differences among the various devices and how to utilize them for multiplane, multirow, and multicolumn
usage.
Device Overview
Using no external components, the MAX6960 LED driver drives two single-color, 8 x 8 dot-matrix digits
through its multiplexed 8-row and 16-column ports. A single, open-drain, row port can sink currents from all
16-column ports with a maximum constant sourcing current of 40mA each. These 8-row ports are multiplexed
in time; only one row port is activated for current sinking at a given time. The average current through each
column port is, therefore, 5mA.
The MAX6960 can also drive a single two-color (red, green), 8 x 8 dot-matrix digit. Each dot-matrix element
can be turned on or off individually or have four (including off) intensity levels. The lighting intensity of all digits
can be PWM controlled in 256 steps. Up to 256 MAX6960 devices can be daisy-chained to form a larger
control unit, whose display memory can be addressed by a host controller through a 4-wire serial interface
consisting of DIN, DOUT, CLK, and active-low CS. Another 3-wire interface, consisting of ADDCLK, ADDIN,
and ADDOUT used among all the daisy-chained chips, makes the interconnection self-configured; no
intervention is needed from the host controller.
The other members of this LED driver family are similar to the MAX6960. The MAX6961 is, however, limited to
turning the dot-matrix elements on and off. The MAX6962 can only drive single-color digits. Finally, the
MAX6963 turns the dot-matrix elements on and off and can only drive a single-color digit.
Application Example
Figure 1 shows a simple application using two MAX6960s to drive four single-color digits. The LDM-24288NI
is an 8 x 8 green, dot-matrix LED from Lumex®. Four digits (D1, D2, D3, and D4) are placed from left to right
to form a display of 8-rows and 32 columns. The column current levels are all set to a constant 40mA
because RISET0 and RISET1 of U1 and RISET0 and RISET1 of U2 are all grounded.
The 4-wire interface of U1 and U2 is connected in parallel and not daisy-chained through DIN and DOUT.
Only one chip will be selected for individual chip commands because the unique device addresses are
configured through the 3-wire interface after power-up. Global commands apply to all MAX6960s
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