MAX6956AAX/V+T ,2-Wire-Interfaced, 2.5V to 5.5V, 20-Port or 28-Port LED Display Driver and I/O ExpanderELECTRICAL CHARACTERISTICS(Typical Operating Circuit, V+ = 2.5V to 5.5V, T = T to T , unless otherw ..
MAX6956AAX+ ,2-Wire-Interfaced, 2.5V to 5.5V, 20-Port or 28-Port LED Display Driver and I/O ExpanderMAX695619-2414; Rev 4; 6/102-Wire-Interfaced, 2.5V to 5.5V, 20-Port or28-Port LED Display Driver an ..
MAX6956ATL ,2-Wire-Interfaced, 2.5V to 5.5V, 20-Port or 28-Port LED Display Driver and I/O ExpanderFeatures2The MAX6956 compact, serial-interfaced LED display 400kbps I C-Compatible Serial Interfac ..
MAX6956ATL ,2-Wire-Interfaced, 2.5V to 5.5V, 20-Port or 28-Port LED Display Driver and I/O ExpanderApplicationsISET 1 28 V+Set-Top Boxes Bar Graph DisplaysGND 2 27 AD1Panel Meters Industrial Control ..
MAX6957AAI+ ,4-Wire-Interfaced, 2.5V to 5.5V, 20-Port and 28-Port LED Display Driver and I/O ExpanderFeatures®The MAX6957 compact, serial-interfaced LED display ● High-Speed 26MHz SPI-/QSPI™-/MICROWI ..
MAX6957AAX ,4-Wire-Interfaced, 2.5V to 5.5V, 20-Port and 28-Port LED Display Driver and I/O ExpanderApplicationsMAX6957AGL* -40°C to +125°C 40 QFNSet-Top Boxes*Future product—contact factory for avai ..
MB401 , 40 Amp Single Phase Bridge Rectifier 50 to 1000 Volts
MB401 , 40 Amp Single Phase Bridge Rectifier 50 to 1000 Volts
MB401 , 40 Amp Single Phase Bridge Rectifier 50 to 1000 Volts
MB40166 ,AD/DA CONVERTERFUJITSU SEMICONDUCTORDS04-28500-5EDATA SHEETASSPAD/DA CONVERTERMB40166/MB401761-CHANNEL 6-BIT AD/DA ..
MB40176 ,AD/DA CONVERTERFUJITSU SEMICONDUCTORDS04-28500-5EDATA SHEETASSPAD/DA CONVERTERMB40166/MB401761-CHANNEL 6-BIT AD/DA ..
MB40176 ,AD/DA CONVERTERFUJITSU SEMICONDUCTORDS04-28500-5EDATA SHEETASSPAD/DA CONVERTERMB40166/MB401761-CHANNEL 6-BIT AD/DA ..
MAX6956AAI+-MAX6956AAX/V+T-MAX6956AAX+
2-Wire-Interfaced, 2.5V to 5.5V, 20-Port or 28-Port LED Display Driver and I/O Expander
General DescriptionThe MAX6956 compact, serial-interfaced LED display
driver/I/O expander provide microprocessors with up to
28 ports. Each port is individually user configurable to
either a logic input, logic output, or common-anode
(CA) LED constant-current segment driver. Each port
configured as an LED segment driver behaves as a
digitally controlled constant-current sink, with 16 equal
current steps from 1.5mA to 24mA. The LED drivers are
suitable for both discrete LEDs and CA numeric and
alphanumeric LED digits.
Each port configured as a general-purpose I/O (GPIO)
can be either a push-pull logic output capable of sink-
ing 10mA and sourcing 4.5mA, or a Schmitt logic input
with optional internal pullup. Seven ports feature config-
urable transition detection logic, which generates an
interrupt upon change of port logic level. The MAX6956
is controlled through an I2C-compatible 2-wire serial
interface, and uses four-level logic to allow 16 I2C
addresses from only 2 select pins.
The MAX6956AAX and MAX6956ATL have 28 ports
and are available in 36-pin SSOP and 40-pin thin QFN
packages, respectively. The MAX6956AAI and
MAX6956ANIhave 20 ports and are available in 28-pin
SSOP and 28-pin DIP packages, respectively.
For an SPI-interfaced version, refer to the MAX6957data sheet. For a lower cost pin-compatible port
expander without the constant-current LED drive capa-bility, refer to the MAX7300 data sheet.
ApplicationsSet-Top BoxesBar Graph Displays
Panel MetersIndustrial Controllers
White GoodsSystem Monitoring
Automotive
Features400kbps I2C-Compatible Serial Interface2.5V to 5.5V Operation-40°C to +125°C Temperature Range20 or 28 I/O Ports, Each Configurable as
Constant-Current LED Driver
Push-Pull Logic Output
Schmitt Logic Input
Schmitt Logic Input with Internal Pullup11µA (max) Shutdown Current16-Step Individually Programmable Current
Control for Each LEDLogic Transition Detection for Seven I/O Ports
MAX6956
2-Wire-Interfaced, 2.5V to 5.5V, 20-Port or
28-Port LED Display Driver and I/O Expander AD1
SCL
SDA
P31
P30
P22
P29
P28
P27
P26
P25
P24
P23
P21
P20
P19
P18
P17
P16
P15
P14
P13
P12
AD0
GND
GND
ISET
SSOP/DIPTOP VIEW
MAX6956
Pin Configurations19-2414; Rev 4; 6/10
Typical Operating Circuit appears at end of data sheet.
Ordering Information
PARTTEMP RANGEPIN-PACKAGEMAX6956ANI+-40°C to +125°C28 DIP
MAX6956AAI+-40°C to +125°C28 SSOP
MAX6956AAX+-40°C to +125°C36 SSOP
MAX6956ATL+-40°C to +125°C40 Thin QFN-EP*
MAX6956AAX/V-40°C to +125°C36 SSOP
MAX6956AAX/V+T-40°C to +125°C36 SSOP
Pin Configurations continued at end of data sheet.
/V denotes an automotive qualified part.
+Denotes a lead(Pb)-free/RoHS-compliant package.
T = Tape and reel.
*EP = Exposed pad.
EVALUATION KIT
AVAILABLE
MAX6956
2-Wire-Interfaced, 2.5V to 5.5V, 20-Port or
28-Port LED Display Driver and I/O Expander
ABSOLUTE MAXIMUM RATINGSStresses 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.
Voltage (with Respect to GND)
V+.............................................................................-0.3V to +6V
SCL, SDA, AD0, AD1................................................-0.3V to +6V
All Other Pins................................................-0.3V to (V+ + 0.3V)
P4–P31 Current ................................................................±30mA
GND Current.....................................................................800mA
Continuous Power Dissipation
28-Pin PDIP (derate 14.3mW/°C above TA= +70°C)1143mW
28-Pin SSOP (derate 9.1mW/°C above TA= +70°C)...727mW
36-Pin SSOP (derate 11.8mW/°C above TA= +70°C)...941mW
40-Pin TQFN (derate 26.3mW/°C above TA= +70°C) 2105mW
Operating Temperature Range
(TMINto TMAX)...............................................-40°C to +125°C
Junction Temperature......................................................+150°C
Storage Temperature Range.............................-65°C to +150°C
Soldering Temperature (reflow)
Lead(Pb)-free packages...............................................+260°C
Packages containing lead(Pb)......................................+240°C
ELECTRICAL CHARACTERISTICS(Typical Operating Circuit, V+ = 2.5V to 5.5V, TA= TMINto TMAX, unless otherwise noted.) (Note 1)
PARAMETERSYMBOLCONDITIONSMINTYPMAXUNITSOperating Supply VoltageV+2.55.5V
TA = +25°C5.58
TA = -40°C to +85°C10Shutdown Supply CurrentISHDNAll digital inputs at V+
or GND
TA = TMIN to TMAX11
TA = +25°C180230
TA = -40°C to +85°C250Operating Supply CurrentIGPOH
All ports programmed
as outputs high, no
load, all other inputs at
V+ or GNDTA = TMIN to TMAX270
TA = +25°C170210
TA = -40°C to +85°C230Operating Supply CurrentIGPOL
All ports programmed
as outputs low, no
load, all other inputs at
V+ or GNDTA = TMIN to TMAX240
TA = +25°C110135
TA = -40°C to +85°C140Operating Supply CurrentILED
Al l p or ts p r og r am m ed
as LE D outp uts, al l LE D s
off, no l oad , al l other np uts at V + or GN D TA = TMIN to TMAX145
INPUTS AND OUTPUTSLogic-High Input Voltage
Port InputsVIH0.7 ✕V
Logic-Low Input Voltage
Port InputsVIL0.3 ✕V
Input Leakage CurrentIIH, IILGPIO inputs without pullup,
VPORT = V+ to GND-100±1+100nA
V+ = 2.5V121930GPIO Input Internal Pullup to V+IPUV+ = 5.5V80120180µA
Hysteresis Voltage GPIO InputsΔVI0.3V
GPIO outputs, ISOURCE = 2mA, TA = -40°C to
+85°C
V+ -
0.7Output High VoltageVOHGPIO outputs, ISOURCE = 1mA, TA = TMIN to
TMAX (Note 2)
V+ -
Port Sink CurrentIOLVPORT = 0.6V21018mA
MAX6956
2-Wire-Interfaced, 2.5V to 5.5V, 20-Port or
28-Port LED Display Driver and I/O Expander
Note 1:All parameters tested at TA= +25°C. Specifications over temperature are guaranteed by design.
Note 2:Guaranteed by design.
Note 3:A master device must provide a hold time of at least 300ns for the SDA signal (referred to VILof the SCL signal) in order to
bridge the undefined region of SCL’s falling edge.
Note 4:Cb= total capacitance of one bus line in pF. tRand tFmeasured between 0.3V+ and 0.7V+.
Note 5:ISINK≤6mA. Cb= total capacitance of one bus line in pF. tRand tFmeasured between 0.3V+ and 0.7V+.
ELECTRICAL CHARACTERISTICS (continued)(Typical Operating Circuit, V+ = 2.5V to 5.5V, TA= TMINto TMAX, unless otherwise noted.) (Note 1)
PARAMETERSYMBOLCONDITIONSMINTYPMAXUNITSV+ = 2.5V, VLED = 2.3V at maximum LED
current9.513.518
V+ = 3.3V, VLED = 2.4V at maximum LED
current (Note 2)18.52427.5Port Drive LED Sink Current,
Port Configured as LED DriverIDIGIT
V+ = 5.5V, VLED = 2.4V at maximum LED
current192530
V+ = 2.5V, VOUT = 0.6V at maximum sink
current18.52328Port Drive Logic Sink Current,
Port Configured as LED DriverIDIGIT_SCV+ = 5.5V, VOUT = 0.6V at maximum sink
current192428
Input High-Voltage SDA, SCL,
AD0, AD1VIH0.7 ✕V
Input Low-Voltage SDA, SCL,
AD0, AD1VIL0.3 ✕V
Input Leakage Current SDA, SCLIIH, IIL-5050nA
Input Capacitance(Note 2)10pF
Output Low-Voltage SDAVOLISINK = 6mA0.4V
TIMING CHARACTERISTICS (Figure 2)(V+ = 2.5V to 5.5V, TA= TMINto TMAX, unless otherwise noted.) (Note 1)
PARAMETERSYMBOLCONDITIONSMINTYPMAXUNITSSerial Clock FrequencyfSCL400kHz
Bus Free Time Between a STOP
and a START ConditiontBUF1.3µs
Hold Time (Repeated) START
ConditiontHD, STA0.6µs
Repeated START Condition
Setup TimetSU, STA0.6µs
STOP Condition Setup TimetSU, STO0.6µs
Data Hold TimetHD, DAT(Note 3)15900ns
Data Setup TimetSU, DAT100ns
SCL Clock Low PeriodtLOW1.3µs
SCL Clock High PeriodtHIGH0.7µs
Rise Time of Both SDA and SCL
Signals, ReceivingtR(Notes 2, 4)20 +
0.1Cb300ns
Fall Time of Both SDA and SCL
Signals, ReceivingtF(Notes 2, 4)20 +
0.1Cb300ns
Fall Time of SDA TransmittingtF,TX(Notes 2, 5)20 +
0.1Cb250ns
Pulse Width of Spike SuppressedtSP(Notes 2, 6)050ns
Capacitive Load for Each Bus
LineCb(Note 2)400pF
MAX6956
2-Wire-Interfaced, 2.5V to 5.5V, 20-Port or
28-Port LED Display Driver and I/O Expander
OPERATING SUPPLY CURRENT
vs. TEMPERATUREMAX6956 toc01
TEMPERATURE (°C)
SUPPLY CURRENT (mA)
V+ = 2.5V TO 5.5V
NO LOAD
ALL PORTS
OUTPUT (1)
ALL PORTS
OUTPUT (0)
ALL PORTS LED (OFF)
SHUTDOWN SUPPLY CURRENT
vs. TEMPERATUREMAX6956 toc02
TEMPERATURE (°C)
SUPPLY CURRENT (
V+ = 5.5V
V+ = 3.3V
V+ = 2.5V
OPERATING SUPPLY CURRENT vs. V+
(NO LOADS)MAX6956 toc03
V+ (V)
SUPPLY CURRENT (mA)
ALL PORTS LED (ON)
ALL PORTS LED (OFF)
ALL PORTS OUTPUT (1)
ALL PORTS OUTPUT (0)
LED DRIVER SINK CURRENT
vs. V+MAX6956 toc04
V+ (V)
PORT SINK CURRENT (mA)
LED DROP = 2.4V
LED DROP = 1.8V
GPO SOURCE CURRENT vs. TEMPERATURE
(OUTPUT = 1)MAX6956 toc07
TEMPERATURE (°C)
PORT SOURCE CURRENT (mA)
VPORT = 1.4V
V+ = 5.5V
V+ = 3.3V
V+ = 2.5V
LED DRIVER SINK CURRENT
vs. TEMPERATUREMAX6956 toc05
TEMPERATURE (°C)
PORT SINK CURRENT (mA)
VLED = 2.4V
V+ = 5.5V
V+ = 3.3V
GPO SINK CURRENT vs. TEMPERATURE
(OUTPUT = 0)MAX6956 toc06
TEMPERATURE (°C)
PORT SINK CURRENT (mA)
V+ = 2.5V TO 5.5V, VPORT = 0.6V
GPI PULLUP CURRENT
vs. TEMPERATUREMAX6956 toc08
TEMPERATURE (°C)
PULLUP CURRENT (
V+ = 5.5V
V+ = 3.3V
V+ = 2.5V
GPO SHORT-CIRCUIT CURRENT
vs. TEMPERATUREMAX6956 toc09
TEMPERATURE (°C)
PORT CURRENT (mA)
GPO = 0, PORT
SHORTED TO V+
GPO = 1, PORT
SHORTED TO GND
__________________________________________Typical Operating Characteristics(RISET= 39kΩ, TA = +25°C, unless otherwise noted.)
Detailed DescriptionThe MAX6956 LED driver/GPIO peripheral provides up
to 28 I/O ports, P4 to P31, controlled through an I2C-com-
patible serial interface. The ports can be configured to
any combination of constant-current LED drivers, logic
inputs and logic outputs, and default to logic inputs on
power-up. When fully configured as an LED driver, the
MAX6956 controls up to 28 LED segments with individual
16-step adjustment of the constant current through each
LED segment. A single resistor sets the maximum seg-
ment current for all segments, with a maximum of 24mA
per segment. The MAX6956 drives any combination of
discrete LEDs and CA digits, including seven-segment
and starburst alphanumeric types.
Figure 1 is the MAX6956 functional diagram. Any I/O
port can be configured as a push-pull output (sinking
10mA, sourcing 4.5mA), or a Schmitt-trigger logic input.
Each input has an individually selectable internal pullup
resistor. Additionally, transition detection allows seven
ports (P24 through P30) to be monitored in any mask-
able combination for changes in their logic status. A
detected transition is flagged through a status register
bit, as well as an interrupt pin (port P31), if desired.
The Typical Operating Circuitshows two MAX6956s
working together controlling three monocolor 16-seg-
ment-plus-DP displays, with five ports left available for
GPIO (P26–P31 of U2).
The port configuration registers set the 28 ports, P4 to
P31, individually as either LED drivers or GPIO. A pair
of bits in registers 0x09 through 0x0F sets each port’s
configuration (Tables 1 and 2).
The 36-pin MAX6956AAX has 28 ports, P4 to P31. The
28-pin MAX6956ANI and MAX6956AAI make only 20
ports available, P12 to P31. The eight unused ports
should be configured as outputs on power-up by writ-
ing 0x55 to registers 0x09 and 0x0A. If this is not done,
the eight unused ports remain as unconnected inputs
and quiescent supply current rises, although there is no
damage to the part.
Register Control of I/O Ports and LEDs
Across Multiple DriversThe MAX6956 offers 20 or 28 I/O ports, depending on
package choice. These can be applied to a variety of
combinations of different display types, for example:
seven, 7-segment digits (Figure 7). This example
requires two MAX6956s, with one digit being driven by
both devices, half by one MAX6956, half by the other
(digit 4 in this example). The two drivers are static, and
therefore do not need to be synchronized. The
MAX6956
2-Wire-Interfaced, 2.5V to 5.5V, 20-Port or
28-Port LED Display Driver and I/O Expander
PIN
SSO P/D IPSSOPT Q F N NAMEFUNCTION136ISETSegment Current Setting. Connect ISET to GND through a resistor (RISET) to set
the maximum segment current.
2, 32, 337, 38, 39GNDGround440AD0Address Input 0. Sets device slave address. Connect to either GND, V+, SCL,
SDA to give four logic combinations. See Table 3.
5–24——P 12–P 31
LED Segment Drivers and GPIO. P12 to P31 can be configured as CA LED
drivers, GPIO outputs, CMOS logic inputs, or CMOS logic inputs with weak
pullup resistor.5–32
1–10,
12–19,
P4–P31
LED Segment Drivers and GPIO. P4 to P31 can be configured as CA LED
drivers, GPIO outputs, CMOS logic inputs, or CMOS logic inputs with weak
pullup resistor.—11, 20, 31N.C.No Connection3332SDAI2C-Compatible Serial Data I/O3433SCLI2C-Compatible Serial Clock Input3534AD1Address Input 1. Sets device slave address. Connect to either GND, V+, SCL,
SDA to give four logic combinations. See Table 3.3635V+Positive Supply Voltage. Bypass V+ to GND with minimum 0.047µF capacitor.
———EPExposed Pad (TQFN Only). Not internally connected. Connect EP to ground
plane for maximum thermal performance.
Pin Description
MAX6956simplify access to displays that overlap two MAX6956s,
the MAX6956 provides four virtual ports, P0 through P3.
To update an overlapping digit, send the same code
twice as an eight-port write, once to P28 through P35 of
the first driver, and again to P0 through P7 of the sec-
ond driver. The first driver ignores the last 4 bits and
the second driver ignores the first 4 bits.
Two addressing methods are available. Any single port
(bit) can be written (set/cleared) at once; or, any
sequence of eight ports can be written (set/cleared) in
any combination at once. There are no boundaries; it is
equally acceptable to write P0 through P7, P1 through
P8, or P31 through P38 (P32 through P38 are nonexis-
tent, so the instructions to these bits are ignored).
Using 8-bit control, a seven-segment digit with a deci-
mal point can be updated in a single byte-write, a 14-
segment digit with DP can be updated in two byte-
writes, and 16-segment digits with DP can be updated
in two byte-writes plus a bit write. Also, discrete LEDs
and GPIO port bits can be lit and controlled individually
without affecting other ports.
ShutdownWhen the MAX6956 is in shutdown mode, all ports are
forced to inputs (which an be read), and the pullup cur-
rent sources are turned off. Data in the port and control
registers remain unaltered, so port configuration and
output levels are restored when the MAX6956 is taken
out of shutdown. The display driver can still be pro-
grammed while in shutdown mode. For minimum sup-
ply current in shutdown mode, logic inputs should be at
GND or V+ potential. Shutdown mode is exited by set-
ting the S bit in the configuration register (Table 8).
2-Wire-Interfaced, 2.5V to 5.5V, 20-Port or
28-Port LED Display Driver and I/O Expander
Table 1. Port Configuration Map
REGISTER DATAREGISTERADDRESS
CODE (HEX)D7D6D5D4D3D2D1D0Port Configuration for P7, P6, P5, P40x09P7P6P5P4
Port Configuration for P11, P10, P9, P80x0AP11P10P9P8
Port Configuration for P15, P14, P13, P120x0BP15P14P13P12
Port Configuration for P19, P18, P17, P160x0CP19P18P17P16
Port Configuration for P23, P22, P21, P200x0DP23P22P21P20
Port Configuration for P27, P26, P25, P240x0EP27P26P25P24
Port Configuration for P31, P30, P29, P280x0FP31P30P29P28
Table 2. Port Configuration Matrix
Note:The logic is inverted between the two output modes; a high makes the output go low in LED segment driver mode (0x00) to
turn that segment on; in GPIO output mode (0x01), a high makes the output go high.
PORT
CONFIGURATION
BIT PAIRMODEFUNCTION
PORT
REGISTER
(0x20–0x5F)
PIN BEHAVIORADDRESS
CODE (HEX)
UPPERLOWERRegister bit = 0High impedance
OutputLED Segment DriverRegister bit = 1
Open-drain current sink, with sink
current (up to 24mA) determined
by the appropriate current register
0x09 to 0x0F00
Register bit = 0Active-low logic outputOutputGPIO OutputRegister bit = 1Active-high logic output0x09 to 0x0F01
InputGPIO Input
Without PullupSchmitt logic input0x09 to 0x0F10
InputGPIO Input with Pullup
Register bit =
input logic levelSchmitt logic input with pullup0x09 to 0x0F11
Shutdown mode is temporarily overridden by the dis-
play test function.
Serial Interface
Serial AddressingThe MAX6956 operates as a slave that sends and
receives data through an I2C-compatible 2-wire inter-
face. The interface uses a serial data line (SDA) and a
serial clock line (SCL) to achieve bidirectional commu-
nication between master(s) and slave(s). A master (typ-
ically a microcontroller) initiates all data transfers to and
from the MAX6956, and generates the SCL clock that
synchronizes the data transfer (Figure 2).
The MAX6956 SDA line operates as both an input and
an open-drain output. A pullup resistor, typically 4.7kΩ,
is required on SDA. The MAX6956 SCL line operates
only as an input. A pullup resistor, typically 4.7kΩ, is
required on SCL if there are multiple masters on the 2-
wire interface, or if the master in a single-master system
has an open-drain SCL output.
Each transmission consists of a START condition
(Figure 3) sent by a master, followed by the MAX6956
7-bit slave address plus R/Wbit (Figure 6), a register
address byte, one or more data bytes, and finally a
STOP condition (Figure 3).
Start and Stop ConditionsBoth SCL and SDA remain high when the interface is
not busy. A master signals the beginning of a transmis-
sion with a START (S) condition by transitioning SDA
MAX6956
2-Wire-Interfaced, 2.5V to 5.5V, 20-Port or
28-Port LED Display Driver and I/O Expander SLAVE ADDRESS BYTED1D2D3D4D5D6D7D8D9D10D11D12D13D14D15
R/WDATA
SDA
SCL
TEST REGISTER
INTENSITY REGISTERS
PORT REGISTERS
LED DRIVERS AND GPIO
INTENSITY
CONFIGURATION
TEST
P4 TO P31
LED DRIVERS
OR GPIO
ADDRESS
MATCHER
AD0
AD1
COMMAND BYTEDATA BYTE
R/W7-BIT DEVICE ADDRESS
TO COMMAND REGISTERSTO/FROM DATA REGISTERS
SEGMENT OR
GPIO DATAR/W
CONFIGURATION
REGISTERSPORT CHANGE
DETECTOR
MASK REGISTER
COMMAND
REGISTER DECODE
DATA BYTECOMMAND BYTE
MAX6956
Figure 1. MAX6956 Functional Diagram
MAX6956has finished communicating with the slave, it issues a
STOP (P) condition by transitioning SDA from low to
high while SCL is high. The bus is then free for another
transmission (Figure 3).
Bit TransferOne data bit is transferred during each clock pulse.
The data on SDA must remain stable while SCL is high
(Figure 4).
AcknowledgeThe acknowledge bit is a clocked 9th bit, which the
recipient uses to handshake receipt of each byte of
data (Figure 5). Thus, each byte transferred effectively
requires 9 bits. The master generates the 9th clock
pulse, and the recipient pulls down SDA during the
acknowledge clock pulse, such that the SDA line is sta-
ble low during the high period of the clock pulse. When
the master is transmitting to the MAX6956, the
MAX6956 generates the acknowledge bit because the
2-Wire-Interfaced, 2.5V to 5.5V, 20-Port or
28-Port LED Display Driver and I/O Expander Figure 2. 2-Wire Serial Interface Timing Details
SCL
SDA
START CONDITIONSTOP CONDITIONREPEATED START CONDITIONSTART CONDITION
tSU, DAT
tHD, DATtLOW
tHD, STA
tHIGHtF
tSU, STA
tHD, STA
tSU, STO
tBUF
Figure 3. Standard Stop Conditions
SDA
SCLS
START
CONDITION
STOP
CONDITION
SDA
SCLDATA LINE STABLE;
DATA VALIDCHANGE OF DATA ALLOWED
Figure 4. Bit Transfer
MAX6956 is the recipient. When the MAX6956 is trans-
mitting to the master, the master generates the
acknowledge bit because the master is the recipient.
Slave AddressThe MAX6956 has a 7-bit-long slave address (Figure 6).
The eighth bit following the 7-bit slave address is the
R/Wbit. It is low for a write command, high for a read
command.
The first 3 bits (MSBs) of the MAX6956 slave address
are always 100. Slave address bits A3, A2, A1, and A0
are selected by address inputs, AD1 and AD0. These
two input pins may be connected to GND, V+, SDA, or
SCL. The MAX6956 has 16 possible slave addresses
(Table 3) and therefore, a maximum of 16 MAX6956
devices may share the same interface.
Message Format for Writing
the MAX6956A write to the MAX6956 comprises the transmission of
the MAX6956’s slave address with the R/Wbit set to
zero, followed by at least 1 byte of information. The first
byte of information is the command byte. The com-
mand byte determines which register of the MAX6956
is to be written by the next byte, if received. If a STOP
condition is detected after the command byte is
received, then the MAX6956 takes no further action
(Figure 8) beyond storing the command byte.
Any bytes received after the command byte are data
bytes. The first data byte goes into the internal register of
the MAX6956 selected by the command byte (Figure 9). If
multiple data bytes are transmitted before a STOP condi-
tion is detected, these bytes are generally stored in subse-
quent MAX6956 internal registers because the command
byte address generally autoincrements (Table 4).
Message Format for Reading The MAX6956 is read using the MAX6956’s internally
stored command byte as address pointer, the same
way the stored command byte is used as address
pointer for a write. The pointer generally autoincre-
ments after each data byte is read using the same rules
as for a write (Table 4). Thus, a read is initiated by first
configuring the MAX6956’s command byte by perform-
MAX6956
2-Wire-Interfaced, 2.5V to 5.5V, 20-Port or
28-Port LED Display Driver and I/O Expander SCL
SDA
BY TRANSMITTER
CLOCK PULSE FOR ACKNOWLEDGMENTSTART CONDITION
SDA
BY RECEIVER89
Figure 5. Acknowledge
SDA
SCL0A3A2A1A00
MSBLSB
R/WACK
Figure 6. Slave Address
MAX6956
2-Wire-Interfaced, 2.5V to 5.5V, 20-Port or
28-Port LED Display Driver and I/O Expander P1P2P3P4P5P6P7P8P9P10P11P12P13P14P15P16P17P18P19P20P21P22P23P24P25P26P27P28P29P30P31
7-SEGMENT DIGIT 1
VIRTUAL SEGMENTS
VIRTUAL SEGMENTS
7-SEGMENT DIGIT 57-SEGMENT DIGIT 67-SEGMENT DIGIT 7
7-SEGMENT DIGIT 27-SEGMENT DIGIT 37-SEGMENT DIGIT 4V+P1P2P3P4P5P6P7P8P9P10P11P12P13P14P15P16P17P18P19P20P21P22P23P24P25P26P27P28P29P30P31
Figure 7. Two MAX6956s Controlling Seven 7-Segment DisplaysAP0SLAVE ADDRESSCOMMAND BYTE
ACKNOWLEDGE FROM MAX6956
R/WACKNOWLEDGE FROM MAX6956
D15D14D13D12D11D10D9D8COMMAND BYTE IS STORED ON RECEIPT OF STOP CONDITION
COMMAND BYTE RECEIVED
Figure 8. Command Byte ReceivedAAP0SLAVE ADDRESSCOMMAND BYTEDATA BYTE
ACKNOWLEDGE FROM MAX6956
1 BYTE
D15D14D13D12D11D10D9D8D1D0D3D2D5D4D7D6HOW COMMAND BYTE AND DATA BYTE MAP INTO MAX6956's REGISTER
ACKNOWLEDGE FROM MAX6956ACKNOWLEDGE FROM MAX6956
R/W
Figure 9. Command and Single Data Byte Received
ing a write (Figure 8). The master can now read n con-
secutive bytes from the MAX6956, with the first data
byte being read from the register addressed by the ini-
tialized command byte. When performing read-after-
write verification, remember to reset the command
byte’s address because the stored control byte
address generally has been autoincremented after the
write (Table 4). Table 5 is the register address map.
Operation with Multiple MastersIf the MAX6956 is operated on a 2-wire interface with
multiple masters, a master reading the MAX6956
should use a repeated start between the write, which
sets the MAX6956’s address pointer, and the read(s)
that takes the data from the location(s). This is because
it is possible for master 2 to take over the bus after
master 1 has set up the MAX6956’s address pointer but
MAX6956
2-Wire-Interfaced, 2.5V to 5.5V, 20-Port or
28-Port LED Display Driver and I/O Expander
COMMAND BYTE ADDRESS RANGEAUTOINCREMENT BEHAVIORx0000000 to x1111110Command address autoincrements after byte read or written
x1111111Command address remains at x1111111 after byte written or read
PIN
CONNECTIONDEVICE ADDRESS
AD1AD0A6A5A4A3A2A1A0GNDGND1000000
GNDV+1000001
GNDSDA1000010
GNDSCL1000011GND1000100V+1000101SDA1000110SCL1000111
SDAGND1001000
SDAV+1001001
SDASDA1001010
SDASCL1001011
SCLGND1001100
SCLV+1001101
SCLSDA1001110
SCLSCL1001111AAP0SLAVE ADDRESSCOMMAND BYTEDATA BYTE
ACKNOWLEDGE FROM MAX6956
D15D14D13D12D11D10D9D8D1D0D3D2D5D4D7D6HOW COMMAND BYTE AND DATA BYTE MAP INTO MAX6956's REGISTER
ACKNOWLEDGE FROM MAX6956
R/Wn BYTES
AUTOINCREMENT MEMORY WORD ADDRESS
ACKNOWLEDGE FROM MAX6956
Figure 10. n Data Bytes Received
Table 3. MAX6956 Address Map
Table 4. Autoincrement Rules
MAX6956
2-Wire-Interfaced, 2.5V to 5.5V, 20-Port or
28-Port LED Display Driver and I/O Expander
Table 5. Register Address Map
COMMAND ADDRESSREGISTERD15D14D13D12D11D10D9D8
HEX
CODENo-OpX00000000x00
Global CurrentX00000100x02
ConfigurationX00001000x04
Transition Detect MaskX00001100x06
Display TestX00001110x07
Port Configuration P7, P6, P5, P4X00010010x09
Port Configuration P11, P10, P9, P8X00010100x0A
Port Configuration P15, P14, P13, P12X00010110x0B
Port Configuration P19, P18, P17, P16X00011000x0C
Port Configuration P23, P22, P21, P20X00011010x0D
Port Configuration P27, P26, P25, P24X00011100x0E
Port Configuration P31, P30, P29, P28X00011110x0F
Current054X00100100x12
Current076X00100110x13
Current098X00101000x14
Current0BAX00101010x15
Current0DCX00101100x16
Current0FEX00101110x17
Current110X00110000x18
Current132X00110010x19
Current154X00110100x1A
Current176X00110110x1B
Current198X00111000x1C
Current1BAX00111010x1D
Current1DCX00111100x1E
Current1FEX00111110x1F
Port 0 only (virtual port, no action)X01000000x20
Port 1 only (virtual port, no action)X01000010x21
Port 2 only (virtual port, no action)X01000100x22
Port 3 only (virtual port, no action)X01000110x23
Port 4 only (data bit D0; D7–D1 read as 0)X01001000x24
Port 5 only (data bit D0; D7–D1 read as 0)X01001010x25
Port 6 only (data bit D0; D7–D1 read as 0)X01001100x26
Port 7 only (data bit D0; D7–D1 read as 0)X01001110x27
Port 8 only (data bit D0; D7–D1 read as 0)X01010000x28
Port 9 only (data bit D0; D7–D1 read as 0)X01010010x29
Port 10 only (data bit D0; D7–D1 read as 0)X01010100x2A
