Datasheet

10-Port Constant-Current LED Drivers and I/O
Expanders with PWM Intensity Control
Serial Interface
The MAX6966/MAX6967 communicate through an SPI-
compatible 4-wire serial interface. The interface has
three inputs: clock (SCLK), chip select (CS), and data
in (DIN), and one output, data out (DOUT). CS must be
low to clock data into or out of the device, and DIN
must be stable when sampled on the rising edge of
SCLK. DOUT is stable on the rising edge of SCLK.
Note that the SPI protocol expects DOUT to be high
impedance when the MAX6966/MAX6967 are not being
accessed; DOUT on the MAX6966/MAX6967 is never
high impedance. Go to www.maxim-ic.com/an1879 for
ways to convert the MAX6966/MAX6967 to tri-state,
if required.
SCLK and DIN can be used to transmit data to other
peripherals. The MAX6966/MAX6967 ignore all activity
on SCLK and DIN except when CS is low.
Control and Operation Using the 4-Wire
Interface
Controlling the MAX6966/MAX6967 requires sending a
16-bit word. The first byte, D15 through D8, is the com-
mand, and the second byte, D7 through D0, is the data
byte (Table 11).
Connecting Multiple MAX6966/MAX6967s
to the 4-Wire Bus
Multiple MAX6966/MAX6967s can be interfaced to a
common SPI bus by connecting DIN inputs together,
connecting SCLK inputs together, and providing an
individual CS per MAX6966/MAX6967 device (Figure
8). This connection works regardless of the configura-
tion of DOUT/OSC, but does not allow the MAX6966/
MAX6967s to be read.
D15
D14 D13 D12 D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1
D0
R/W
MSB
ADDRESS
LSB MSB
DATA
LSB
Table 11. Serial-Data Format
DIN
SCLK
CS3
DIN
SCLK
CS2
DIN
SCLK
MOSI
SCLK
CS1
CS3
CS2
CS1
MAX6966
MAX6967
MAX6966
MAX6967
MAX6966
MAX6967
µC
Figure 8. MAX6966/MAX6967 Multiple CS Connection
MAX6966/MAX6967
Maxim Integrated
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