MAX7219C/D [MAXIM]
Serially Interfaced, 8-Digit LED Display Drivers; 串行接口， 8位LED显示驱动器
| 型号： | MAX7219C/D |
| 厂家： | 
MAXIM INTEGRATED PRODUCTS |
| 描述： | Serially Interfaced, 8-Digit LED Display Drivers |
| 文件： | 总16页 (文件大小：180K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
19-4452; Rev 3; 7/97
S e ria lly In t e rfa c e d , 8 -Dig it LED Dis p la y Drive rs
9/MAX721
_______________Ge n e ra l De s c rip t io n
____________________________Fe a t u re s
♦ 10MHz Serial Interface
The MAX7219/MAX7221 are compact, serial input/out-
p ut c ommon-c a thod e d is p la y d rive rs tha t inte rfa c e
microprocessors (µPs) to 7-segment numeric LED dis-
plays of up to 8 digits, bar-graph displays, or 64 indi-
vid ua l LEDs . Inc lud e d on-c hip a re a BCD c od e -B
decoder, multiplex scan circuitry, segment and digit
drivers, and an 8x8 static RAM that stores each digit.
Only one external resistor is required to set the seg-
ment current for all LEDs. The MAX7221 is compatible
with SPI™, QSPI™, and Microwire™, and has slew-rate-
limited segment drivers to reduce EMI.
♦ Individual LED Segment Control
♦ Decode/No-Decode Digit Selection
♦ 150µA Low-Power Shutdown (Data Retained)
♦ Digital and Analog Brightness Control
♦ Display Blanked on Power-Up
♦ Drive Common-Cathode LED Display
♦ Slew-Rate Limited Segment Drivers
A convenient 3-wire serial interface connects to all
common µPs. Individual digits may be addressed and
up d a te d without re writing the e ntire d is p la y. The
MAX7219/MAX7221 also allow the user to select code-
B decoding or no-decode for each digit.
for Lower EMI (MAX7221)
♦ SPI, QSPI, Microwire Serial Interface (MAX7221)
♦ 24-Pin DIP and SO Packages
The d e vic e s inc lud e a 150µA low-p owe r s hutd own
mode, analog and digital brightness control, a scan-
limit register that allows the user to display from 1 to 8
digits, and a test mode that forces all LEDs on.
______________Ord e rin g In fo rm a t io n
PART
TEMP. RANGE
0°C to +70°C
0°C to +70°C
0°C to +70°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
PIN-PACKAGE
24 Narrow Plastic DIP
24 Wide SO
MAX7219CNG
MAX7219CWG
MAX7219C/D
MAX7219ENG
MAX7219EWG
MAX7219ERG
________________________Ap p lic a t io n s
Bar-Graph Displays
Dice*
24 Narrow Plastic DIP
24 Wide SO
7-Segment Displays
Industrial Controllers
24 Narrow CERDIP
Panel Meters
Ordering Information continued at end of data sheet.
*Dice are specified at T = +25°C.
A
LED Matrix Displays
__________________P in Co n fig u ra t io n
________Typ ic a l Ap p lic a t io n Circ u it
TOP VIEW
DIN
DIG 0
DIG 4
GND
1
2
3
4
5
6
7
8
9
24 DOUT
23 SEG D
22 SEG DP
21 SEG E
20 SEG C
19 V+
+5V
19
9.53k
V+
MAX7219
MAX7221
DIG 6
DIG 2
DIG 3
DIG 7
GND
18
DIG 0–DIG 7
I
SET
8 DIGITS
MAX7219
MAX7221
1
18 ISET
MOSI
DIN
17 SEG G
16 SEG B
15 SEG F
14 SEG A
12
µP
I/O
LOAD (CS)
13
9
SEG A–G,
SEG DP
SCK
CLK
GND
DIG 5 10
DIG 1 11
8 SEGMENTS
GND
4
LOAD (CS) 12
13
CLK
( ) MAX7221 ONLY
8-DIGIT µP DISPLAY
( ) MAX7221 ONLY
DIP/SO
SPI and QSPI are trademarks of Motorola Inc. Microwire is a trademark of National Semiconductor Corp.
________________________________________________________________ Maxim Integrated Products
1
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800.
For small orders, phone 408-737-7600 ext. 3468.
S e ria lly In t e rfa c e d , 8 -Dig it LED Dis p la y Drive rs
ABSOLUTE MAXIMUM RATINGS
Voltage (with respect to GND)
Operating Temperature Ranges
V+ ............................................................................-0.3V to 6V
DIN, CLK, LOAD, CS ...............................................-0.3V to 6V
All Other Pins .............................................-0.3V to (V+ + 0.3V)
Current
MAX7219C_G/MAX7221C_G ..............................0°C to +70°C
MAX7219E_G/MAX7221E_G ............................-40°C to +85°C
Storage Temperature Range .............................-65°C to +160°C
Lead Temperature (soldering, 10sec) .............................+300°C
DIG0–DIG7 Sink Current................................................500mA
SEGA–G, DP Source Current.........................................100mA
Continuous Power Dissipation (T = +85°C)
A
Narrow Plastic DIP ..........................................................0.87W
Wide SO ..........................................................................0.76W
Narrow CERDIP.................................................................1.1W
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
9/MAX721
(V+ = 5V ±10%, R
= 9.53kΩ ±1%, T = T
to T , unless otherwise noted.)
SET
A
MIN
MAX
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
Operating Supply Voltage
Shutdown Supply Current
V+
I+
4.0
5.5
150
8
V
All digital inputs at V+ or GND, T = +25°C
µA
A
R
SET
= open circuit
Operating Supply Current
I+
mA
All segments and decimal point on,
= -40mA
330
800
I
SEG_
Display Scan Rate
f
8 digits scanned
V+ = 5V, V = 0.65V
500
320
-30
1300
Hz
OSC
Digit Drive Sink Current
Segment Drive Source Current
I
mA
mA
DIGIT
OUT
I
T
= +25°C, V+ = 5V, V
= (V+ - 1V)
= +25°C, V+ = 5V, V = (V+ - 1V)
OUT
-40
20
-45
50
SEG
A
OUT
Segment Current Slew Rate
(MAX7221 only)
∆I
/∆t
T
A
10
mA/µs
%
SEG
Segment Drive Current Matching
∆I
SEG
3.0
Digit Drive Leakage
(MAX7221 only)
I
Digit off, V
= V+
-10
1
µA
DIGIT
DIGIT
Segment Drive Leakage
(MAX7221 only)
I
Segment off, V
= 0V
µA
mA
mA
SEG
SEG
Digit Drive Source Current
(MAX7219 only)
I
Digit off, V
= (V+ - 0.3V)
-2
5
DIGIT
DIGIT
Segment Drive Sink Current
(MAX7219 only)
I
Segment off, V
= 0.3V
SEG
SEG
2
_______________________________________________________________________________________
S e ria lly In t e rfa c e d , 8 -Dig it LED Dis p la y Drive rs
9/MAX721
ELECTRICAL CHARACTERISTICS (continued)
(V+ = 5V ±10%, R
=9.53kΩ ±1%, T = T
to T , unless otherwise noted.)
MAX
SET
A
MIN
PARAMETER
LOGIC INPUTS
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
Input Current DIN, CLK,
LOAD, CS
I
, I
V
IN
= 0V or V+
-1
1
µA
IH IL
Logic High Input Voltage
Logic Low Input Voltage
Output High Voltage
Output Low Voltage
V
3.5
V
V
V
V
V
IH
V
IL
0.8
0.4
V
OH
DOUT, I
= -1mA
SOURCE
V+ - 1
V
OL
DOUT, I = 1.6mA
SINK
Hysteresis Voltage
∆V
1
DIN, CLK, LOAD, CS
I
TIMING CHARACTERISTICS
CLK Clock Period
t
100
50
ns
ns
ns
CP
CLK Pulse Width High
CLK Pulse Width Low
t
CH
t
50
CL
CS Fall to SCLK Rise Setup Time
(MAX7221 only)
t
25
0
ns
ns
CSS
CLK Rise to CS or LOAD Rise
Hold Time
t
CSH
DIN Setup Time
t
25
0
ns
ns
ns
DS
DH
DO
DIN Hold Time
t
Output Data Propagation Delay
t
C
= 50pF
25
LOAD
Load-Rising Edge to Next Clock
Rising Edge (MAX7219 only)
t
t
50
50
ns
LDCK
Minimum CS or LOAD Pulse
High
t
ns
CSW
Data-to-Segment Delay
2.25
ms
DSPD
_______________________________________________________________________________________
3
S e ria lly In t e rfa c e d , 8 -Dig it LED Dis p la y Drive rs
__________________________________________Typ ic a l Op e ra t in g Ch a ra c t e ris t ic s
(V+ = +5V, T = +25°C, unless otherwise noted.)
A
SCAN FREQUENCY vs.
POSITIVE SUPPLY VOLTAGE
SEGMENT DRIVER OUTPUT CURRENT
vs. OUTPUT VOLTAGE
830
70
60
50
40
30
20
10
0
820
810
800
790
780
770
760
750
740
730
R
SET
= 10kΩ
R
SET
= 20kΩ
R
SET
= 40kΩ
9/MAX721
4.0
4.4
4.8
5.2
5.6
6.0
0
1
2
3
4
5
POSITIVE SUPPLY VOLTAGE (V)
OUTPUT VOLTAGE (V)
MAX7219
MAX7221
SEGMENT OUTPUT CURRENT
SEGMENT OUTPUT CURRENT
MAXIMUM INTENSITY = 31/32
MAXIMUM INTENSITY = 15/16
10mA/div
10mA/div
0
0
5µs/div
5µs/div
4
_______________________________________________________________________________________
S e ria lly In t e rfa c e d , 8 -Dig it LED Dis p la y Drive rs
9/MAX721
______________________________________________________________P in De s c rip t io n
PIN
NAME
FUNCTION
1
DIN
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.
2, 3, 5–8,
10, 11
DIG 0–DIG 7
GND
4, 9
Ground (both GND pins must be connected)
LOAD
(MAX7219)
Load-Data Input. The last 16 bits of serial data are latched on LOAD’s rising edge.
12
CS
(MAX7221)
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.
13
CLK
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.
14–17,
20–23
SEG A–SEG G,
DP
Connect to V through a resistor (R
) to set the peak segment current (Refer to Selecting
DD
SET
18
19
24
ISET
V+
R
Resistor section).
SET
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.
DOUT
_________________________________________________________Fu n c t io n a l Dia g ra m
DIG 0–DIG 7
SEG A–SEG G, DP
SEGMENT DRIVERS
DIGIT DRIVERS
8
8
SHUTDOWN REGISTER
MODE REGISTER
CODE B
ROM WITH
BYPASS
INTENSITY
PULSE-
V+
INTENSITY REGISTER
SCAN-LIMIT REGISTER
DISPLAY-TEST REGISTER
WIDTH
MODULATOR
R
SET
8
SEGMENT
CURRENT
8x8
REFERENCE
DUAL-PORT
SRAM
MULTIPLEX
SCAN
CIRCUITRY
ADDRESS
REGISTER
DECODER
8
8
LOAD (CS)
4
D0 D1 D2 D3 D4 D5 D6 D7 D8 D9 D10 D11 D12 D13 D14 D15
DIN
DOUT
CLK
(LSB)
(MSB)
( ) MAX7221 ONLY
_______________________________________________________________________________________
5
S e ria lly In t e rfa c e d , 8 -Dig it LED Dis p la y Drive rs
CS
OR LOAD
t
CSW
t
CSH
t
CP
t
t
CL
t
CH
t
CSS
LDCK
CLK
t
DH
t
DS
DIN
D15
D14
D1
D0
t
DO
DOUT
9/MAX721
Figure 1. Timing Diagram
Table 1. Serial-Data Format (16 Bits)
D15
X
D14
X
D13
X
D12
X
D11
D10
D9
D8
D7
D6
D5
D4
DATA
D3
D2
D1
D0
ADDRESS
MSB
LSB
Dig it a n d Co n t ro l Re g is t e rs
_______________De t a ile d De s c rip t io n
Table 2 lists the 14 addressable digit and control regis-
ters. The digit registers are realized with an on-chip,
8x8 dual-port SRAM. They are addressed directly so
that individual digits can be updated and retain data as
long as V+ typically exceeds 2V. The control registers
consist of decode mode, display intensity, scan limit
(number of scanned digits), shutdown, and display test
(all LEDs on).
MAX7 2 1 9 /MAX7 2 2 1 Diffe re n c e s
The MAX7219 and MAX7221 are identical except for
two parameters: the MAX7221 segment drivers are
slew-rate limited to reduce electromagnetic interfer-
ence (EMI), and its serial interface is fully SPI compati-
ble.
S e ria l-Ad d re s s in g Mo d e s
For the MAX7219, serial data at DIN, sent in 16-bit
packets, is shifted into the internal 16-bit shift register
with each rising edge of CLK regardless of the state of
LOAD. For the MAX7221, CS must be low to clock data
in or out. The data is then latched into either the digit or
c ontrol re g is te rs on the ris ing e d g e of LOAD/CS.
LOAD/CS must go high concurrently with or after the
16th rising clock edge, but before the next rising clock
edge or data will be lost. Data at DIN is propagated
through the shift register and appears at DOUT 16.5
clock cycles later. Data is clocked out on the falling
edge of CLK. Data bits are labeled D0–D15 (Table 1).
D8–D11 contain the register address. D0–D7 contain
the data, and D12–D15 are “don’t care” bits. The first
received is D15, the most significant bit (MSB).
S h u t d o w n Mo d e
When the MAX7219 is in shutdown mode, the scan oscil-
lator is halted, all segment current sources are pulled to
ground, and all digit drivers are pulled to V+, thereby
blanking the display. The MAX7221 is identical, except
the drivers are high-impedance. Data in the digit and
control registers remains unaltered. Shutdown can be
used to save power or as an alarm to flash the display by
successively entering and leaving shutdown mode. For
minimum supply current in shutdown mode, logic inputs
should be at ground or V+ (CMOS-logic levels).
Typically, it takes less than 250µs for the MAX7219/
MAX7221 to leave shutdown mode. The display driver
can be programmed while in shutdown mode, and
shutdown mode can be overridden by the display-test
function.
6
_______________________________________________________________________________________
S e ria lly In t e rfa c e d , 8 -Dig it LED Dis p la y Drive rs
9/MAX721
In it ia l P o w e r-Up
On initial power-up, all control registers are reset, the
Table 2. Register Address Map
display is blanked, and the MAX7219/MAX7221 enter
shutdown mode. Program the display driver prior to
display use. Otherwise, it will initially be set to scan one
digit, it will not decode data in the data registers, and
the intensity register will be set to its minimum value.
ADDRESS
HEX
CODE
REGISTER
D15–
D12
D11 D10
D9
D8
No-Op
Digit 0
Digit 1
Digit 2
Digit 3
Digit 4
Digit 5
Digit 6
Digit 7
X
X
X
X
X
X
X
X
X
0
0
0
0
0
0
0
0
1
0
0
0
0
1
1
1
1
0
0
0
1
1
0
0
1
1
0
0
1
0
1
0
1
0
1
0
X0
X1
X2
X3
X4
X5
X6
X7
X8
De c o d e -Mo d e Re g is t e r
The decode-mode register sets BCD code B (0-9, E, H,
L, P, and -) or no-decode operation for each digit. Each
bit in the register corresponds to one digit. A logic high
selects code B decoding while logic low bypasses the
decoder. Examples of the decode mode control-regis-
ter format are shown in Table 4.
When the code B decode mode is used, the decoder
looks only at the lower nibble of the data in the digit
registers (D3–D0), disregarding bits D4–D6. D7, which
sets the decimal point (SEG DP), is independent of the
decoder and is positive logic (D7 = 1 turns the decimal
point on). Table 5 lists the code B font.
Decode
Mode
X
1
0
0
1
X9
Intensity
X
X
X
1
1
1
0
0
1
1
1
0
0
1
0
XA
XB
XC
When no-decode is selected, data bits D7–D0 corre-
spond to the segment lines of the MAX7219/MAX7221.
Table 6 shows the one-to-one pairing of each data bit
to the appropriate segment line.
Scan Limit
Shutdown
Display
Test
X
1
1
1
1
XF
Table 3. Shutdown Register Format (Address (Hex) = XC)
REGISTER DATA
ADDRESS CODE
(HEX)
MODE
D7
X
D6
X
D5
X
D4
X
D3
X
D2
X
D1
X
D0
0
Shutdown
Mode
XC
XC
Normal
Operation
X
X
X
X
X
X
X
1
Table 4. Decode-Mode Register Examples (Address (Hex) = X9)
REGISTER DATA
DECODE MODE
HEX
CODE
D7
D6
D5
D4
D3
D2
D1
D0
No decode for digits 7–0
0
0
0
0
0
0
0
0
00
01
Code B decode for digit 0
No decode for digits 7–1
0
0
0
0
0
0
0
1
Code B decode for digits 3–0
No decode for digits 7–4
0
1
0
1
0
1
0
1
1
1
1
1
1
1
1
1
0F
FF
Code B decode for digits 7–0
_______________________________________________________________________________________
7
S e ria lly In t e rfa c e d , 8 -Dig it LED Dis p la y Drive rs
Table 5. Code B Font
REGISTER DATA
ON SEGMENTS = 1
7-SEGMENT
CHARACTER
D7* D6–D4
D3
D2
D1
D0
DP*
A
B
C
D
E
F
G
0
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
1
0
1
1
0
1
1
1
1
1
0
1
0
0
1
0
1
1
1
1
1
0
0
1
1
1
0
0
1
0
1
0
1
1
0
1
1
1
1
1
1
1
0
0
1
0
0
0
1
0
1
1
0
1
1
0
1
1
0
1
0
1
0
0
1
0
1
0
0
0
1
0
1
0
0
1
1
1
1
0
1
0
0
0
1
1
1
0
1
1
0
1
1
1
1
0
0
0
1
1
1
1
1
0
1
1
1
1
1
0
1
0
1
2
3
4
5
6
7
8
9
9/MAX721
—
E
H
L
P
blank
*The decimal point is set by bit D7 = 1
In t e n s it y Co n t ro l
a n d In t e rd ig it Bla n k in g
The MAX7219/MAX7221 allow display brightness to be
controlled with an external resistor (R ) connected
Table 6. No-Decode Mode Data Bits and
Corresponding Segment Lines
SET
A
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-
a b le to a llow b rig htne s s a d jus tme nt from the front
panel. Its minimum value should be 9.53Ω, which typi-
cally sets the segment current at 40mA. Display bright-
ne s s c a n a ls o b e c ontrolle d d ig ita lly b y us ing the
intensity register.
F
B
G
STANDARD 7-SEGMENT LED
E
C
D
DP
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
REGISTER DATA
D7 D6 D5 D4 D3 D2 D1 D0
Corresponding
Segment Line
by R
(15/16 to 1/16 on MAX7221). Table 7 lists the
SET
DP
A
B
C
D
E
F
G
intensity register format. The minimum interdigit blank-
ing time is set to 1/32 of a cycle.
8
_______________________________________________________________________________________
S e ria lly In t e rfa c e d , 8 -Dig it LED Dis p la y Drive rs
9/MAX721
Table 7. Intensity Register Format (Address (Hex) = XA)
DUTY CYCLE
HEX
CODE
D7
D6
D5
D4
D3
D2
D1
D0
MAX7219
MAX7221
1/32
(min on)
1/16
(min on)
X
X
X
X
0
0
0
0
X0
3/32
5/32
2/16
3/16
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
0
0
0
0
0
0
0
1
1
1
1
1
1
1
0
0
0
1
1
1
1
0
0
0
0
1
1
1
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
0
1
0
1
0
X1
X2
X3
X4
X5
X6
X7
X8
X9
XA
XB
XC
XD
XE
7/32
4/16
9/32
5/16
11/32
13/32
15/32
17/32
19/32
21/32
23/32
25/32
27/32
29/32
6/16
7/16
8/16
9/16
10/16
11/16
12/16
13/16
14/16
15/16
15/16
(max on)
31/32
X
X
X
X
1
1
1
1
XF
Table 8. Scan-Limit Register Format (Address (Hex) = XB)
REGISTER DATA
SCAN LIMIT
HEX
CODE
D7
X
X
X
X
X
X
X
X
D6
X
X
X
X
X
X
X
X
D5
X
X
X
X
X
X
X
X
D4
X
X
X
X
X
X
X
X
D3
X
X
X
X
X
X
X
X
D2
0
D1
0
D0
0
Display digit 0 only*
X0
X1
X2
X3
X4
X5
X6
X7
Display digits 0 & 1*
0
0
1
Display digits 0 1 2*
0
1
0
Display digits 0 1 2 3
0
1
1
Display digits 0 1 2 3 4
Display digits 0 1 2 3 4 5
Display digits 0 1 2 3 4 5 6
Display digits 0 1 2 3 4 5 6 7
1
0
0
1
0
1
1
1
0
1
1
1
*See Scan-Limit Register section for application.
scanned. Since the number of scanned digits affects
the display brightness, the scan-limit register should
not be used to blank portions of the display (such as
leading zero suppression). Table 8 lists the scan-limit
register format.
S c a n -Lim it Re g is t e r
The scan-limit register sets how many digits are dis-
played, from 1 to 8. They are displayed in a multiplexed
manner with a typical display scan rate of 800Hz with 8
digits displayed. If fewer digits are displayed, the scan
ra te is 8f
/N, whe re N is the numb e r of d ig its
OSC
_______________________________________________________________________________________
9
S e ria lly In t e rfa c e d , 8 -Dig it LED Dis p la y Drive rs
If the scan-limit register is set for three digits or less,
individual digit drivers will dissipate excessive amounts
fourth chip, sent the desired 16-bit word, followed by
thre e no-op c ode s (he x XX0X, se e Ta b le 2). Whe n
LOAD/CS goes high, data is latched in all devices. The
first three chips receive no-op commands, and the
fourth receives the intended data.
of power. Consequently, the value of the R
resistor
SET
must be adjusted according to the number of digits dis-
played, to limit individual digit driver power dissipation.
Table 9 lists the number of digits displayed and the
corresponding maximum recommended segment cur-
rent when the digit drivers are used.
__________Ap p lic a t io n s In fo rm a t io n
S u p p ly Byp a s s in g a n d Wirin g
To minimize power-supply ripple due to the peak digit
driver currents, connect a 10µF electrolytic and a 0.1µF
ceramic capacitor between V+ and GND as close to
the device as possible. The MAX7219/MAX7221 should
be placed in close proximity to the LED display, and
connections should be kept as short as possible to
minimize the effects of wiring inductance and electro-
magnetic interference. Also, both GND pins must be
connected to ground.
Dis p la y-Te s t Re g is t e r
The display-test register operates in two modes: normal
and display test. Display-test mode turns all LEDs on
by overriding, but not altering, all controls and digit reg-
isters (including the shutdown register). In display-test
mode, 8 digits are scanned and the duty cycle is 31/32
(15/16 for MAX7221). Table 10 lists the display-test reg-
ister format.
Table 9. Maximum Segment Current for
1-, 2-, or 3-Digit Displays
S e le c t in g R
Us in g Ex t e rn a l Drive rs
The current per segment is approximately 100 times
Re s is t o r a n d
S ET
9/MAX721
MAXIMUM SEGMENT
the current in ISET. To select R
, see Table 11. The
SET
NUMBER OF DIGITS
CURRENT
MAX7219/MAX7221’s maximum recommended seg-
me nt c urre nt is 40mA. For s e g me nt c urre nt le ve ls
above these levels, external digit drivers will be need-
ed. In this application, the MAX7219/MAX7221 serve
only as controllers for other high-current drivers or tran-
DISPLAYED
(mA)
1
2
3
10
20
30
sistors. Therefore, to conserve power, use R
= 47kΩ
SET
when using external current sources as segment dri-
vers.
Table 10. Display-Test Register Format
(Address (Hex) = XF)
The example in Figure 2 uses the MAX7219/MAX7221’s
segment drivers, a MAX394 single-pole double-throw
analog switch, and external transistors to drive 2.3”
AND2307SLC c ommon-c a thode disp la ys. The 5.6V
zener diode has been added in series with the decimal
point LED because the decimal point LED forward volt-
age is typically 4.2V. For all other segments the LED
forward voltage is typically 8V. Since external transis-
tors are used to sink current (DIG 0 and DIG 1 are used
as logic switches), peak segment currents of 45mA are
allowed even though only two digits are displayed. In
applications where the MAX7219/MAX7221’s digit dri-
vers are used to sink current and fewer than four digits
are displayed, Table 9 specifies the maximum allow-
REGISTER DATA
MODE
D7 D6 D5 D4 D3 D2 D1 D0
Normal
Operation
X
X
X
X
X
X
X
X
X
X
X
X
X
X
0
1
Display Test
Mode
Note: The MAX7219/MAX7221 remain in display-test mode
(all LEDs on) until the display-test register is reconfigured
for normal operation.
No -Op Re g is t e r
The no-op register is used when cascading MAX7219s
or MAX7221s. Connect all devices’ LOAD/CS inputs
tog e the r a nd c onne c t DOUT to DIN on a d ja c e nt
devices. DOUT is a CMOS logic-level output that easily
drives DIN of successively cascaded parts. (Refer to
the Serial Addressing Modes section for detailed infor-
mation on serial input/output timing.) For example, if
four MAX7219s a re c a s c a d e d , the n to write to the
able segment current. R
ingly (Table 11).
must be selected accord-
SET
Refer to the Power Dissipation section of the Absolute
Maximum Ratings to calculate acceptable limits for
ambient temperature, segment current, and the LED
forward-voltage drop.
10 ______________________________________________________________________________________
S e ria lly In t e rfa c e d , 8 -Dig it LED Dis p la y Drive rs
9/MAX721
Table 11. R
LED Forward Voltage
vs. Segment Current and
Table 12. Package Thermal Resistance
Data
SET
THERMAL RESISTANCE
PACKAGE
V
(V)
LED
I
(mA)
SEG
(θ
)
JA
1.5
2.0
2.5
3.0
3.5
24 Narrow DIP
24 Wide SO
24 CERDIP
+75°C/W
+85°C/W
+60°C/W
40
12.2
17.8
29.8
66.7
11.8
17.1
28.0
63.7
11.0
15.8
25.9
59.3
10.6
15.0
24.5
55.4
9.69
14.0
22.6
51.2
30
20
10
Maximum Junction Temperature (T ) = +150°C
J
Maximum Ambient Temperature (T ) = +85°C
A
Co m p u t in g P o w e r Dis s ip a t io n
Ca s c a d in g Drive rs
The up p e r limit for p owe r d is s ip a tion (PD) for the
MAX7219/MAX7221 is determined from the following
equation:
The example in Figure 3 drives 16 digits using a 3-wire
µP interface. If the number of digits is not a multiple of
8, set both drivers’ scan limits registers to the same
number so one display will not appear brighter than the
other. For example, if 12 digits are need, use 6 digits
per display with both scan-limit registers set for 6 digits
so that both displays have a 1/6 duty cycle per digit. If
11 digits are needed, set both scan-limit registers for 6
digits and leave one digit driver unconnected. If one
display for 6 digits and the other for 5 digits, the sec-
ond display will appear brighter because its duty cycle
per digit will be 1/5 while the first display’s will be 1/6.
Refer to the No-Op Register section for additional infor-
mation.
PD = (V + x 8mA) + (V+ - V )(DUTY x I
x N)
LED
SEG
where:
V+ = supply voltage
DUTY = duty cycle set by intensity register
N = number of segments driven (worst case is 8)
V
= LED forward voltage
LED
I
= segment current set by R
SEG
SET
Dissipation Example:
= 40mA, N = 8, DUTY = 31/32, V
I
= 1.8V at
LED
SEG
40mA, V+ = 5.25V
PD = 5.25V(8mA) + (5.25V - 1.8V)(31/32 x
40mA x 8) = 1.11W
Thus, for a CERDIP package (θ
= +60°C/W from
JA
Table 12), the maximum allowed ambient temperature
T is given by:
A
T
= T + PD x θ + 150°C = T +1.11W x
J(MAX)
A
JA
A
60°C/W
where T = +83.4°C.
A
______________________________________________________________________________________ 11
S e ria lly In t e rfa c e d , 8 -Dig it LED Dis p la y Drive rs
AND2307SLC
ANODE DP
AND2307SLC
ANODE DP
5
7
9
5
7
9
ANODE A
ANODE F
ANODE B
ANODE G
ANODE A
ANODE F
ANODE B
ANODE G
6
6
10
10
4
2
3
4
2
3
ANODE C
ANODE E
ANODE D
ANODE C
ANODE E
ANODE D
1N5524B
5.6V ±5%
CATHODE
8
CATHODE
8
9/MAX721
23
SEG D
SEG E
21
20
SEG C
SEG G
17
16
5V
SEG B
SEG F
MAX7219
MAX7221
19
18
15
14
22
V+
4.7k
4.7k
SEG A
30k
SEG DP
16
4
9
GND
GND
I
SFT
4
7
NC1
NC2
3
*
2
*
COM1
IRF540
1
10
2
1
12
13
DIG 0
DIG 1
DATA IN
DIN
IN1
IN2
NO1
MAX394
11
8
LOAD (CS)
LOAD (CS)
CLK
COM2
CLOCK
9
NO2
5
IRF540
*4.7kΩ PULL-UP REQUIRED FOR MAX7221
( ) MAX7221 ONLY
-5V
Figure 2. MAX7219/MAX7221 Driving 2.3-Inch Displays
12 ______________________________________________________________________________________
S e ria lly In t e rfa c e d , 8 -Dig it LED Dis p la y Drive rs
9/MAX721
8
8
8
8
DIN
DOUT
SEG D
SEG DP
SEG E
SEG C
V+
DIN
DOUT
SEG D
SEG DP
SEG E
SEG C
V+
DATA IN
DIG 0
DIG 4
GND
DIG 0
DIG 4
GND
5V
5V
DIG 6
DIG 2
DIG 3
DIG 7
GND
DIG 6
DIG 2
DIG 3
DIG 7
GND
ISET
ISET
9.53k
9.53k
SEG G
SEG B
SEG F
SEG A
CLK
SEG G
SEG B
SEG F
SEG A
CLK
DIG 5
DIG 1
LOAD (CS)
DIG 5
DIG 1
LOAD (CS)
MAX7219
MAX7221
MAX7219
MAX7221
LOAD DATA
CLOCK
( ) MAX7221 ONLY
Figure 3. Cascading MAX7219/MAX7221s to Drive 16 7-Segment LED Digits
______________________________________________________________________________________ 13
S e ria lly In t e rfa c e d , 8 -Dig it LED Dis p la y Drive rs
_Ord e rin g In fo rm a t io n (c o n t in u e d )
___________________Ch ip To p o g ra p h y
PART
TEMP. RANGE
0°C to +70°C
0°C to +70°C
0°C to +70°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
PIN-PACKAGE
24 Narrow Plastic DIP
24 Wide SO
MAX7221CNG
MAX7221CWG
MAX7221C/D
MAX7221ENG
MAX7221EWG
MAX7221ERG
GND
GND
DIG 3 DIG 2
DIG 7
DIG 6
Dice*
24 Narrow Plastic DIP
24 Wide SO
DIG 5
DIG 1
DIG 4
DIG 0
24 Narrow CERDIP
*Dice are specified at T = +25°C.
A
LOAD
OR
CS
0.093"
(2.36mm)
DIN
CLK
DOUT
SEG A
SEG F
SEG D
9/MAX721
SEG DP
SEG E
SEG B
SEG G
ISET SEG C
0.080"
(2.03mm)
TRANSISTOR COUNT: 5267
SUBSTRATE CONNECTED TO GND
14 ______________________________________________________________________________________
S e ria lly In t e rfa c e d , 8 -Dig it LED Dis p la y Drive rs
9/MAX721
________________________________________________________P a c k a g e In fo rm a t io n
______________________________________________________________________________________ 15
S e ria lly In t e rfa c e d , 8 -Dig it LED Dis p la y Drive rs
___________________________________________P a c k a g e In fo rm a t io n (c o n t in u e d )
9/MAX721
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
16 ____________________Ma x im In t e g ra t e d P ro d u c t s , 1 2 0 S a n Ga b rie l Drive , S u n n yva le , CA 9 4 0 8 6 4 0 8 -7 3 7 -7 6 0 0
© 1997 Maxim Integrated Products
Printed USA
is a registered trademark of Maxim Integrated Products.
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