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19-4452; Rev 3; 7/97
Serially Interfaced, 8-Digit LED Display Drivers
_______________General Description
The MAX7219/MAX7221 are compact, serial input/output common-cathode display drivers that interface microprocessors (Ps) to 7-segment numeric LED displays of up to 8 digits, bar-graph displays, or 64 individual LEDs. Included on-chip are a BCD code-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 segment current for all LEDs. The MAX7221 is compatible with SPITM, QSPITM, and MicrowireTM, and has slew-ratelimited segment drivers to reduce EMI. A convenient 3-wire serial interface connects to all common Ps. Individual digits may be addressed and updated without rewriting the entire display. The MAX7219/MAX7221 also allow the user to select codeB decoding or no-decode for each digit. The devices include a 150A low-power shutdown mode, analog and digital brightness control, a scanlimit register that allows the user to display from 1 to 8 digits, and a test mode that forces all LEDs on.
____________________________Features
o 10MHz Serial Interface o Individual LED Segment Control o Decode/No-Decode Digit Selection o 150A Low-Power Shutdown (Data Retained) o Digital and Analog Brightness Control o Display Blanked on Power-Up o Drive Common-Cathode LED Display o Slew-Rate Limited Segment Drivers for Lower EMI (MAX7221) o SPI, QSPI, Microwire Serial Interface (MAX7221) o 24-Pin DIP and SO Packages
MAX7219/MAX7221
______________Ordering Information
PART MAX7219CNG MAX7219CWG MAX7219C/D MAX7219ENG TEMP. RANGE 0C to +70C 0C to +70C 0C to +70C -40C to +85C PIN-PACKAGE 24 Narrow Plastic DIP 24 Wide SO Dice* 24 Narrow Plastic DIP
________________________Applications
Bar-Graph Displays 7-Segment Displays Industrial Controllers Panel Meters LED Matrix Displays
MAX7219EWG -40C to +85C 24 Wide SO MAX7219ERG -40C to +85C 24 Narrow CERDIP Ordering Information continued at end of data sheet. *Dice are specified at TA = +25C.
__________________Pin Configuration
TOP VIEW
DIN 1 DIG 0 2 DIG 4 3 GND 4 DIG 6 5 DIG 2 6 DIG 3 7 DIG 7 8 GND 9 DIG 5 10 DIG 1 11 LOAD (CS) 12 ( ) MAX7221 ONLY 24 DOUT 23 SEG D 22 SEG DP 21 SEG E
________Typical Application Circuit
+5V 19 9.53k 18 ISET V+ DIG 0-DIG 7 8 DIGITS MOSI P I/O SCK 1 12 13 9
MAX7219 MAX7221
20 SEG C 19 V+ 18 ISET 17 SEG G 16 SEG B 15 SEG F 14 SEG A 13 CLK
MAX7219 DIN MAX7221
LOAD (CS) CLK GND GND 4 SEG A-G, SEG DP
8 SEGMENTS
DIP/SO
( ) MAX7221 ONLY
8-DIGIT P DISPLAY
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.
Serially Interfaced, 8-Digit LED Display Drivers MAX7219/MAX7221
ABSOLUTE MAXIMUM RATINGS
Voltage (with respect to GND) V+ ............................................................................-0.3V to 6V DIN, CLK, LOAD, CS ...............................................-0.3V to 6V All Other Pins.............................................-0.3V to (V+ + 0.3V) Current DIG0-DIG7 Sink Current................................................500mA SEGA-G, DP Source Current.........................................100mA Continuous Power Dissipation (TA = +85C) Narrow Plastic DIP ..........................................................0.87W Wide SO ..........................................................................0.76W Narrow CERDIP.................................................................1.1W Operating Temperature Ranges MAX7219C_G/MAX7221C_G ..............................0C to +70C MAX7219E_G/MAX7221E_G ............................-40C to +85C Storage Temperature Range .............................-65C to +160C Lead Temperature (soldering, 10sec) .............................+300C
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
(V+ = 5V 10%, RSET = 9.53k 1%, TA = TMIN to TMAX, unless otherwise noted.) PARAMETER Operating Supply Voltage Shutdown Supply Current Operating Supply Current Display Scan Rate Digit Drive Sink Current Segment Drive Source Current Segment Current Slew Rate (MAX7221 only) Segment Drive Current Matching Digit Drive Leakage (MAX7221 only) Segment Drive Leakage (MAX7221 only) Digit Drive Source Current (MAX7219 only) Segment Drive Sink Current (MAX7219 only) SYMBOL V+ I+ I+ fOSC IDIGIT ISEG ISEG/t ISEG IDIGIT ISEG IDIGIT ISEG Digit off, VDIGIT = V+ Segment off, VSEG = 0V Digit off, VDIGIT = (V+ - 0.3V) Segment off, VSEG = 0.3V -2 5 All digital inputs at V+ or GND, TA = +25C RSET = open circuit All segments and decimal point on, ISEG_ = -40mA 8 digits scanned V+ = 5V, VOUT = 0.65V TA = +25C, V+ = 5V, VOUT = (V+ - 1V) TA = +25C, V+ = 5V, VOUT = (V+ - 1V) 500 320 -30 10 -40 20 3.0 -10 1 -45 50 330 800 1300 CONDITIONS MIN 4.0 TYP MAX 5.5 150 8 mA Hz mA mA mA/s % A A mA mA UNITS V A
2
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Serially Interfaced, 8-Digit LED Display Drivers
ELECTRICAL CHARACTERISTICS (continued)
(V+ = 5V 10%, RSET =9.53k 1%, TA = TMIN to TMAX, unless otherwise noted.) PARAMETER LOGIC INPUTS Input Current DIN, CLK, LOAD, CS Logic High Input Voltage Logic Low Input Voltage Output High Voltage Output Low Voltage Hysteresis Voltage TIMING CHARACTERISTICS CLK Clock Period CLK Pulse Width High CLK Pulse Width Low CS Fall to SCLK Rise Setup Time (MAX7221 only) CLK Rise to CS or LOAD Rise Hold Time DIN Setup Time DIN Hold Time Output Data Propagation Delay Load-Rising Edge to Next Clock Rising Edge (MAX7219 only) Minimum CS or LOAD Pulse High Data-to-Segment Delay tCP tCH tCL tCSS tCSH tDS tDH tDO tLDCK tCSW tDSPD CLOAD = 50pF 50 50 2.25 100 50 50 25 0 25 0 25 ns ns ns ns ns ns ns ns ns ns ms IIH, IIL VIH VIL VOH VOL VI DOUT, ISOURCE = -1mA DOUT, ISINK = 1.6mA DIN, CLK, LOAD, CS 1 V+ - 1 0.4 VIN = 0V or V+ -1 3.5 0.8 1 A V V V V V SYMBOL CONDITIONS MIN TYP MAX UNITS
MAX7219/MAX7221
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Serially Interfaced, 8-Digit LED Display Drivers MAX7219/MAX7221
__________________________________________Typical Operating Characteristics
(V+ = +5V, TA = +25C, unless otherwise noted.)
SCAN FREQUENCY vs. POSITIVE SUPPLY VOLTAGE
MAX7219/21 01
SEGMENT DRIVER OUTPUT CURRENT vs. OUTPUT VOLTAGE
MAX7219/21 02
830 820 810 SCAN FREQUENCY (Hz) 800 790 780 770 760 750 740 730 4.0 4.4 4.8 5.2 5.6
70 60 OUTPUT CURRENT (mA) RSET = 10k 50 40 30 20 10 0 RSET = 20k
RSET = 40k
6.0
0
1
2
3
4
5
POSITIVE SUPPLY VOLTAGE (V)
OUTPUT VOLTAGE (V)
MAX7219 SEGMENT OUTPUT CURRENT
MAX7219/21 03
MAX7221 SEGMENT OUTPUT CURRENT
MAXIMUM INTENSITY = 15/16
MAX7219/21 04
MAXIMUM INTENSITY = 31/32
10mA/div
10mA/div
0
0
5s/div
5s/div
4
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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 internal 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 drivers are high-impedance when turned off. Connect to VDD through a resistor (RSET) to set the peak segment current (Refer to Selecting RSET 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 RSET 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 PULSEWIDTH MODULATOR
LOAD (CS)
(LSB)
(MSB)
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Serially Interfaced, 8-Digit LED Display Drivers MAX7219/MAX7221
CS OR LOAD tCSH tCSS CLK tDH tDS DIN D15 D14 D1 D0 tCL tCH tCP
tCSW
tLDCK
tDO DOUT
Figure 1. Timing Diagram
Table 1. Serial-Data Format (16 Bits)
D15 X D14 X D13 X D12 X D11 D10 D9 D8 D7 MSB D6 D5 D4 MSB DATA D3 D2 D1 D0 LSB ADDRESS
_______________Detailed Description
MAX7219/MAX7221 Differences
The MAX7219 and MAX7221 are identical except for two parameters: the MAX7221 segment drivers are slew-rate limited to reduce electromagnetic interference (EMI), and its serial interface is fully SPI compatible.
Digit and Control Registers
Table 2 lists the 14 addressable digit and control registers. 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).
Serial-Addressing Modes
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 control registers on the rising edge 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).
Shutdown Mode
When the MAX7219 is in shutdown mode, the scan oscillator 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 250s 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.
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Serially Interfaced, 8-Digit LED Display Drivers
Table 2. Register Address Map
ADDRESS REGISTER No-Op Digit 0 Digit 1 Digit 2 Digit 3 Digit 4 Digit 5 Digit 6 Digit 7 Decode Mode Intensity Scan Limit Shutdown Display Test D15- D12 X X X X X X X X X X X X X X D11 0 0 0 0 0 0 0 0 1 1 1 1 1 1 D10 0 0 0 0 1 1 1 1 0 0 0 0 1 1 D9 0 0 1 1 0 0 1 1 0 0 1 1 0 1 D8 0 1 0 1 0 1 0 1 0 1 0 1 0 1 HEX CODE X0 X1 X2 X3 X4 X5 X6 X7 X8 X9 XA XB XC XF
Initial Power-Up
On initial power-up, all control registers are reset, the 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.
MAX7219/MAX7221
Decode-Mode Register
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-register 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. When no-decode is selected, data bits D7-D0 correspond 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.
Table 3. Shutdown Register Format (Address (Hex) = XC)
REGISTER DATA MODE Shutdown Mode Normal Operation ADDRESS CODE (HEX) XC XC D7 X X D6 X X D5 X X D4 X X D3 X X D2 X X D1 X X D0 0 1
Table 4. Decode-Mode Register Examples (Address (Hex) = X9)
DECODE MODE No decode for digits 7-0 Code B decode for digit 0 No decode for digits 7-1 Code B decode for digits 3-0 No decode for digits 7-4 Code B decode for digits 7-0 REGISTER DATA D7 0 0 0 1 D6 0 0 0 1 D5 0 0 0 1 D4 0 0 0 1 D3 0 0 1 1 D2 0 0 1 1 D1 0 0 1 1 D0 0 1 1 1 HEX CODE 00 01 0F FF 7
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Serially Interfaced, 8-Digit LED Display Drivers MAX7219/MAX7221
Table 5. Code B Font
7-SEGMENT CHARACTER 0 1 2 3 4 5 6 7 8 9 -- E H L P blank REGISTER DATA D7* D6-D4 X X X X X X X X X X X X X X X X D3 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 D2 0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 1 D1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 D0 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 DP* A 1 0 1 1 0 1 1 1 1 1 0 1 0 0 1 0 B 1 1 1 1 1 0 0 1 1 1 0 0 1 0 1 0 ON SEGMENTS = 1 C 1 1 0 1 1 1 1 1 1 1 0 0 1 0 0 0 D 1 0 1 1 0 1 1 0 1 1 0 1 0 1 0 0 E 1 0 1 0 0 0 1 0 1 0 0 1 1 1 1 0 F 1 0 0 0 1 1 1 0 1 1 0 1 1 1 1 0 G 0 0 1 1 1 1 1 0 1 1 1 1 1 0 1 0
*The decimal point is set by bit D7 = 1
Table 6. No-Decode Mode Data Bits and Corresponding Segment Lines
A
Intensity Control and Interdigit Blanking
The MAX7219/MAX7221 allow display brightness to be controlled with an external resistor (RSET) 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 9.53, 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 RSET (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.
F G
B
STANDARD 7-SEGMENT LED
E C
D
DP
REGISTER DATA D7 Corresponding Segment Line DP D6 A D5 B D4 C D3 D D2 E D1 F D0 G
8
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Serially Interfaced, 8-Digit LED Display Drivers MAX7219/MAX7221
Table 7. Intensity Register Format (Address (Hex) = XA)
DUTY CYCLE MAX7219 1/32 (min on) 3/32 5/32 7/32 9/32 11/32 13/32 15/32 17/32 19/32 21/32 23/32 25/32 27/32 29/32 31/32 MAX7221 1/16 (min on) 2/16 3/16 4/16 5/16 6/16 7/16 8/16 9/16 10/16 11/16 12/16 13/16 14/16 15/16 15/16 (max on) D7 X X X X X X X X X X X X X X X X D6 X X X X X X X X X X X X X X X X D5 X X X X X X X X X X X X X X X X D4 X X X X X X X X X X X X X X X X D3 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 D2 0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 1 D1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 D0 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 HEX CODE X0 X1 X2 X3 X4 X5 X6 X7 X8 X9 XA XB XC XD XE XF
Table 8. Scan-Limit Register Format (Address (Hex) = XB)
SCAN LIMIT Display digit 0 only* Display digits 0 & 1* Display digits 0 1 2* Display digits 0 1 2 3 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 REGISTER DATA 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 0 0 0 1 1 1 1 D1 0 0 1 1 0 0 1 1 D0 0 1 0 1 0 1 0 1 HEX CODE X0 X1 X2 X3 X4 X5 X6 X7
*See Scan-Limit Register section for application.
Scan-Limit Register
The scan-limit register sets how many digits are displayed, 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 rate is 8f OSC /N, where N is the number of digits
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.
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Serially Interfaced, 8-Digit LED Display Drivers MAX7219/MAX7221
If the scan-limit register is set for three digits or less, individual digit drivers will dissipate excessive amounts of power. Consequently, the value of the RSET resistor must be adjusted according to the number of digits displayed, to limit individual digit driver power dissipation. Table 9 lists the number of digits displayed and the corresponding maximum recommended segment current when the digit drivers are used. fourth chip, sent the desired 16-bit word, followed by three no-op codes (hex XX0X, see Table 2). When 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.
__________Applications Information
Supply Bypassing and Wiring
To minimize power-supply ripple due to the peak digit driver currents, connect a 10F electrolytic and a 0.1F 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 electromagnetic interference. Also, both GND pins must be connected to ground.
Display-Test Register
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 registers (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 register format.
Table 9. Maximum Segment Current for 1-, 2-, or 3-Digit Displays
NUMBER OF DIGITS DISPLAYED 1 2 3 MAXIMUM SEGMENT CURRENT (mA) 10 20 30
Selecting RSET Resistor and Using External Drivers
The current per segment is approximately 100 times the current in ISET. To select RSET, see Table 11. The MAX7219/MAX7221's maximum recommended segment current is 40mA. For segment current levels above these levels, external digit drivers will be needed. In this application, the MAX7219/MAX7221 serve only as controllers for other high-current drivers or transistors. Therefore, to conserve power, use RSET = 47k when using external current sources as segment drivers. 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 common-cathode displays. The 5.6V zener diode has been added in series with the decimal point LED because the decimal point LED forward voltage is typically 4.2V. For all other segments the LED forward voltage is typically 8V. Since external transistors 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 drivers are used to sink current and fewer than four digits are displayed, Table 9 specifies the maximum allowable segment current. RSET must be selected accordingly (Table 11). 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.
Table 10. Display-Test Register Format (Address (Hex) = XF)
MODE Normal Operation Display Test Mode REGISTER DATA D7 X X D6 X X D5 X X D4 X X D3 X X D2 X X D1 X X D0 0 1
Note: The MAX7219/MAX7221 remain in display-test mode (all LEDs on) until the display-test register is reconfigured for normal operation.
No-Op Register
The no-op register is used when cascading MAX7219s or MAX7221s. Connect all devices' LOAD/CS inputs together and connect DOUT to DIN on adjacent 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 information on serial input/output timing.) For example, if four MAX7219s are cascaded, then to write to the
10
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Serially Interfaced, 8-Digit LED Display Drivers MAX7219/MAX7221
Table 11. RSET vs. Segment Current and LED Forward Voltage
ISEG (mA) 40 30 20 10 VLED (V) 1.5 12.2 17.8 29.8 66.7 2.0 11.8 17.1 28.0 63.7 2.5 11.0 15.8 25.9 59.3 3.0 10.6 15.0 24.5 55.4 3.5 9.69 14.0 22.6 51.2 24 Narrow DIP 24 Wide SO 24 CERDIP
Table 12. Package Thermal Resistance Data
PACKAGE THERMAL RESISTANCE (JA) +75C/W +85C/W +60C/W
Maximum Junction Temperature (TJ) = +150C Maximum Ambient Temperature (TA) = +85C
Computing Power Dissipation
The upper limit for power dissipation (PD) for the MAX7219/MAX7221 is determined from the following equation: PD = (V + x 8mA) + (V+ - VLED)(DUTY x ISEG x N) where: V+ = supply voltage DUTY = duty cycle set by intensity register N = number of segments driven (worst case is 8) VLED = LED forward voltage ISEG = segment current set by RSET Dissipation Example: ISEG = 40mA, N = 8, DUTY = 31/32, VLED = 1.8V at 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 ( JA = +60C/W from Table 12), the maximum allowed ambient temperature TA is given by: TJ(MAX) = TA + PD x JA + 150C = TA +1.11W x 60C/W where TA = +83.4C.
Cascading Drivers
The example in Figure 3 drives 16 digits using a 3-wire P 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 second 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 information.
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Serially Interfaced, 8-Digit LED Display Drivers MAX7219/MAX7221
AND2307SLC 5 7 9 6 10 4 2 1N5524B 5.6V 5% 3 ANODE DP ANODE A ANODE F ANODE B ANODE G ANODE C ANODE E ANODE D CATHODE 8 5 7 9 6 10 4 2 3
AND2307SLC ANODE DP ANODE A ANODE F ANODE B ANODE G ANODE C ANODE E ANODE D CATHODE 8
23 21 20 17 16 15 14 22 4 9 1 12 13 SEG D SEG E SEG C SEG G SEG B SEG F SEG A SEG DP 18 GND GND DIG 0 DIG 1 ISFT * 2 11 * 4 7 1 10 2 9 NC1 NC2 COM1 3 IRF540 30k 16 4.7k 5V
MAX7219 MAX7221
V+
19
4.7k
DATA IN LOAD (CS) CLOCK
DIN LOAD (CS) CLK
IN1 MAX394 8 IN2 COM2 NO1 NO2 5
*4.7k PULL-UP REQUIRED FOR MAX7221 ( ) MAX7221 ONLY
-5V
IRF540
Figure 2. MAX7219/MAX7221 Driving 2.3-Inch Displays
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Serially Interfaced, 8-Digit LED Display Drivers MAX7219/MAX7221
8 DATA IN DIN DIG 0 DIG 4 GND DIG 6 DIG 2 DIG 3 DIG 7 GND DIG 5 DIG 1 LOAD (CS) LOAD DATA CLOCK DOUT SEG D SEG DP SEG E SEG C V+ ISET SEG G SEG B SEG F SEG A CLK
8
8 DIN DIG 0 DIG 4 GND 5V DIG 6 DIG 2 DIG 3 9.53k DIG 7 GND DIG 5 DIG 1 DOUT SEG D SEG DP SEG E SEG C V+ ISET SEG G SEG B SEG F SEG A CLK
8
5V
9.53k
MAX7219 MAX7221
LOAD (CS)
MAX7219 MAX7221
( ) MAX7221 ONLY
Figure 3. Cascading MAX7219/MAX7221s to Drive 16 7-Segment LED Digits
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Serially Interfaced, 8-Digit LED Display Drivers MAX7219/MAX7221
_Ordering Information (continued)
PART MAX7221CNG MAX7221CWG MAX7221C/D MAX7221ENG MAX7221EWG MAX7221ERG TEMP. RANGE 0C to +70C 0C to +70C 0C to +70C -40C to +85C -40C to +85C -40C to +85C PIN-PACKAGE 24 Narrow Plastic DIP 24 Wide SO Dice* 24 Narrow Plastic DIP 24 Wide SO 24 Narrow CERDIP
DIG 1 LOAD OR CS CLK SEG A GND DIG 7 DIG 3 DIG 2 DIG 6 GND
___________________Chip Topography
DIG 5
DIG 4
*Dice are specified at TA = +25C.
DIG 0 DIN DOUT SEG D 0.093" (2.36mm)
SEG F SEG DP SEG B ISET SEG C SEG G SEG E 0.080" (2.03mm)
TRANSISTOR COUNT: 5267 SUBSTRATE CONNECTED TO GND
14
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Serially Interfaced, 8-Digit LED Display Drivers
________________________________________________________Package Information
PDIPN.EPS
MAX7219/MAX7221
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15
Serially Interfaced, 8-Digit LED Display Drivers MAX7219/MAX7221
___________________________________________Package Information (continued)
SOICW.EPS
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 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 (c) 1997 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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