Serially Interfaced, 8-Digit LED Display Drivers
______________________________________________________________Pin Description
PIN
1
2, 3, 5–8,
10, 11
4, 9
NAME
DIN
DIG 0–DIG 7
GND
LOAD
(MAX7219)
CS
(MAX7221)
CLK
FUNCTION
Serial-Data Input. Data is loaded into the internal 16-bit shift register on CLK’s rising edge.
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.
Ground (both GND pins must be connected)
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.
Connect to V
DD
through a resistor (R
SET
) to set the peak segment current (Refer to
Selecting
R
SET
Resistor
section).
Positive Supply Voltage. Connect to +5V.
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.
MAX7219/MAX7221
12
13
14–17,
20–23
18
19
24
SEG A–SEG G,
DP
ISET
V+
DOUT
_________________________________________________________Functional Diagram
SEG A–SEG G, DP
SEGMENT DRIVERS
DIG 0–DIG 7
DIGIT DRIVERS
8
8
V+
CODE B
ROM WITH
BYPASS
R
SET
SEGMENT
CURRENT
REFERENCE
8
8x8
DUAL-PORT
SRAM
8
8
ADDRESS
REGISTER
DECODER
4
DIN
CLK
( ) MAX7221 ONLY
D0 D1 D2 D3 D4 D5 D6 D7 D8 D9 D10 D11 D12 D13 D14 D15
DOUT
SHUTDOWN REGISTER
MODE REGISTER
INTENSITY REGISTER
SCAN-LIMIT REGISTER
DISPLAY-TEST REGISTER
MULTIPLEX
SCAN
CIRCUITRY
INTENSITY
PULSE-
WIDTH
MODULATOR
LOAD (CS)
(LSB)
(MSB)
_______________________________________________________________________________________
5
MAXIM [ MAXIM INTEGRATED PRODUCTS ]
