Serially Interfaced, 8-Digit LED Display Drivers

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5

______________________________________________________________Pin Description

_________________________________________________________Functional Diagram

NAME

FUNCTION

1

DIN

Serial-Data Input. Data is loaded into the internal 16-bit shift register on CLK’s rising edge.

2, 3, 5–8,

10, 11

DIG 0–DIG 7

Eight-Digit Drive Lines that sink current from the display common cathode. The MAX7219 pulls

the digit outputs to V+ when turned off. The MAX7221’s digit drivers are high-impedance when

turned off.

PIN

4, 9

GND

Ground (both GND pins must be connected)

12

LOAD

(MAX7219)

18

ISET

14–17,

20–23

SEG A–SEG G,

DP

13

CLK

CS

(MAX7221)

24

DOUT

Serial-Data Output. The data into DIN is valid at DOUT 16.5 clock cycles later. This pin is used

to daisy-chain several MAX7219/MAX7221’s and is never high-impedance.

19

V+

Positive Supply Voltage. Connect to +5V.

( ) MAX7221 ONLY

V+

8

8

8

8

4

LOAD (CS)

DIN

DOUT

CLK

(MSB)

(LSB)

D0

SEG A–SEG G, DP

DIG 0–DIG 7

SHUTDOWN REGISTER

MODE REGISTER

INTENSITY REGISTER

SCAN-LIMIT REGISTER

DISPLAY-TEST REGISTER

INTENSITY

PULSE-

WIDTH

MODULATOR

MULTIPLEX

SCAN

CIRCUITRY

ADDRESS

REGISTER

DECODER

8x8

DUAL-PORT

SRAM

8

D1 D2 D3 D4 D5 D6 D7 D8 D9 D10 D11 D12

DIGIT DRIVERS

D13 D14 D15

CODE B

ROM WITH

BYPASS

SEGMENT

CURRENT

REFERENCE

SEGMENT DRIVERS

Load-Data Input. The last 16 bits of serial data are latched on LOAD’s rising edge.

Chip-Select Input. Serial data is loaded into the shift register while CS is low. The last 16 bits of

serial data are latched on CS’s rising edge.

Serial-Clock Input. 10MHz maximum rate. On CLK’s rising edge, data is shifted into the inter-

nal shift register. On CLK’s falling edge, data is clocked out of DOUT. On the MAX7221, the

CLK input is active only while CS is low.

Seven Segment Drives and Decimal Point Drive that source current to the display. On the

MAX7219, when a segment driver is turned off it is pulled to GND. The MAX7221 segment dri-

vers are high-impedance when turned off.