Intensity Control

and Interdigit Blanking

The MAX7219/MAX7221 allow display brightness to be

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 vari-

able to allow brightness adjustment from the front

panel. Its minimum value should be 9.53

Ω, which typi-

cally sets the segment current at 40mA. Display bright-

ness 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

intensity register format. The minimum interdigit blank-

ing time is set to 1/32 of a cycle.

Serially Interfaced, 8-Digit LED Display Drivers

8

_______________________________________________________________________________________

Table 5. Code B Font

Table 6. No-Decode Mode Data Bits and

Corresponding Segment Lines

0

0

X

0

0

0

1

1

1

1

1

1

D7*

REGISTER DATA

0

7-SEGMENT

CHARACTER

D3

D6–D4

D1

D2

DP*

D0

B

A

D

C

F

E

G

1

0

X

0

0

1

1

0

ON SEGMENTS = 1

0

1

0

0

0

2

0

X

1

0

0

1

1

1

0

0

1

1

3

0

X

1

0

1

1

1

1

1

0

0

1

4

0

X

0

1

0

1

0

0

1

1

0

1

5

0

X

0

1

1

0

1

1

1

1

0

1

6

0

X

1

1

0

0

1

1

1

1

1

1

7

0

X

1

1

1

1

1

0

1

0

0

0

8

1

X

0

0

0

1

1

1

1

1

1

1

9

1

X

0

0

1

1

1

1

1

1

0

1

—

1

X

1

0

0

0

0

0

0

0

0

1

E

1

X

1

0

1

0

1

1

0

1

1

1

H

1

X

0

1

0

1

0

0

1

1

1

1

L

1

X

0

1

1

0

0

1

0

1

1

0

P

1

X

1

1

0

1

1

0

0

1

1

1

blank

1

X

1

1

1

0

0

0

0

0

0

0

*The decimal point is set by bit D7 = 1

F

E

A

G

D

C

B

STANDARD 7-SEGMENT LED

DP

A

Corresponding

Segment Line

D6

DP

C

D4

B

D5

E

D2

D

G

REGISTER DATA

D0

F

D1

D3

D7