Datasheet
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.
36
35
34
33
32
31
30
29
28
27
26
25
24
23
1
2
3
4
5
6
7
8
9
10
11
12
13
14
V+
CS
DIN
SCLK
P4
P31
P26
P5
P30
P6
P29
P7
P28
P27
P17
P16
P15
P11
P14
P10
P13
P9
P12
P8
DOUT
GND
GND
ISET
SSOP
TOP VIEW
MAX6957
22
21
20
19
15
16
17
18 P22
P25
P24
P23
P21
P20
P19
P18
P4
P31
P30
P6
P28
P27
P26
P29
P7
P5
P9
P13
P10
P14
P11
P15
P16
P17
P12
P8
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
40
39
38
37
36
35
34
33
32
31
30
29
28
27
26
25
24
23
22
21
P21
P22
P23
P25
N.C.
P20
P19
P18
N.C.
GND
GND
GND
ISET
V+
CS
DIN
SCLK
N.C.
DOUT
TQFN
MAX6957
P24
www.maximintegrated.com
Maxim Integrated
│
20
MAX6957 4-Wire-Interfaced, 2.5V to 5.5V, 20-Port and
28-Port LED Display Driver and I/O Expander
Pin Congurations (continued)
Chip Information
PROCESS: CMOS