Datasheet

Intensity Control
and Interdigit Blanking
The MAX7219/MAX7221 allow display brightness to be
controlled with an external resistor (R
SET
) connected
between V+ and ISET. The peak current sourced from
the segment drivers is nominally 100 times the current
entering ISET. This resistor can either be fixed or variable
to allow brightness adjustment from the front panel. Its
minimum value should be 9.53kΩ, which typically sets the
segment current at 40mA. Display brightness can also be
controlled digitally by using the intensity register.
Digital control of display brightness is provided by an internal
pulse-width modulator, which is controlled by the lower
nibble of the intensity register. The modulator scales the
average segment current in 16 steps from a maximum of
31/32 down to 1/32 of the peak current set by R
SET
(15/16
to 1/16 on MAX7221). Table 7 lists the intensity register
format. The minimum interdigit blanking time is set to 1/32
of a cycle.
Table 5. Code B Font
Table 6. No-Decode Mode Data Bits and
Corresponding Segment Lines
*The decimal point is set by bit D7 = 1
7-SEGMENT
CHARACTER
REGISTER DATA ON SEGMENTS = 1
D7* D6–D4 D3 D2 D1 D0 DP* A B C D E F G
0 X 0 0 0 0 1 1 1 1 1 1 0
1 X 0 0 0 1 0 1 1 0 0 0 0
2 X 0 0 1 0 1 1 0 1 1 0 1
3 X 0 0 1 1 1 1 1 1 0 0 1
4 X 0 1 0 0 0 1 1 0 0 1 1
5 X 0 1 0 1 1 0 1 1 0 1 1
6 X 0 1 1 0 1 0 1 1 1 1 1
7 X 0 1 1 1 1 1 1 0 0 0 0
8 X 1 0 0 0 1 1 1 1 1 1 1
9 X 1 0 0 1 1 1 1 1 0 1 1
— X 1 0 1 0 0 0 0 0 0 0 1
E X 1 0 1 1 1 0 0 1 1 1 1
H X 1 1 0 0 0 1 1 0 1 1 1
L X 1 1 0 1 0 0 0 1 1 1 0
P X 1 1 1 0 1 1 0 0 1 1 1
blank X 1 1 1 1 0 0 0 0 0 0 0
REGISTER DATA
D7 D6 D5 D4 D3 D2 D1 D0
Corresponding
Segment Line
DP A B C D E F G
F
E
A
G
D
C
B
STANDARD 7-SEGMENT LED
DP
MAX7219/MAX7221 Serially Interfaced, 8-Digit LED Display Drivers
www.maximintegrated.com
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