MAX6957_14 Datasheet, PDF (20/23 Pages) Maxim Integrated Products – 4-Wire-Interfaced, 2.5V to 5.5V, 20-Port and 28-Port LED Display Driver and I/O Expander

MAX6957
4-Wire-Interfaced, 2.5V to 5.5V, 20-Port and
28-Port LED Display Driver and I/O Expander
SPI Routing Considerations
The MAX6957’s SPI interface is guaranteed to operate at
26Mbps on a 2.5V supply, and on a 5V supply typically
operates at 50Mbps. This means that the transmission
line issues should be considered when the interface con-
nections are longer that 100mm, particularly with higher
supply voltages. Ringing manifests itself as communica-
tion issues, often intermittent, typically due to double
clocking due to ringing at the SCLK input. Fit a 1kΩ to
10kΩ parallel termination resistor to either GND or V+ at
the DIN, SCLK, and CS input to damp ringing for moder-
ately long interface runs. Use line impedance matching
terminations when making connections between boards.
PC Board Layout Considerations
Ensure that all the MAX6957 GND connections are
used. A ground plane is not necessary, but may be
useful to reduce supply impedance if the MAX6957
outputs are to be heavily loaded. Keep the track length
from the ISET pin to the R_ISET resistor as short as pos-
sible, and take the GND end of the resistor either to the
ground plane or directly to the GND pins.
Power-Supply Considerations
The MAX6957 operates with power-supply voltages of
2.5V to 5.5V. Bypass the power supply to GND with a
0.047µF capacitor as close to the device as possible.
Add a 1µF capacitor if the MAX6957 is far away from the
board’s input bulk decoupling capacitor.
Chip Information
PROCESS: CMOS
Pin Configurations (continued)
TOP VIEW
ISET 1
GND 2
GND 3
DOUT 4
P8 5
P12 6
P9 7
P13 8
P10 9
P14 10
P11 11
P15 12
P16 13
P17 14
P18 15
P19 16
P20 17
P21 18
MAX6957
SSOP
36 V+
35 CS
34 DIN
33 SCLK
32 P4
31 P31
30 P5
29 P30
28 P6
27 P29
26 P7
25 P28
24 P27
23 P26
22 P25
21 P24
20 P23
19 P22
P8 1
P12 2
P9 3
P13 4
P10 5
P14 6
P11 7
P15 8
P16 9
P17 10
MAX6957
30 P4
29 P31
28 P5
27 P30
26 P6
25 P29
24 P7
23 P28
22 P27
21 P26
TQFN
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