19-2414; Rev 4; 6/10
KIT
ATION
EVALU
BLE
AVAILA
2-Wire-Interfaced, 2.5V to 5.5V, 20-Port or
28-Port LED Display Driver and I/O Expander
General Description
The 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 I
2
C-compatible 2-wire serial
interface, and uses four-level logic to allow 16 I
2
C
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
MAX6956ANI have 20 ports and are available in 28-pin
SSOP and 28-pin DIP packages, respectively.
For an SPI-interfaced version, refer to the MAX6957
data sheet. For a lower cost pin-compatible port
expander without the constant-current LED drive capa-
bility, refer to the MAX7300 data sheet.
o
o
o
o
2
Features
400kbps I C-Compatible Serial Interface
2.5V to 5.5V Operation
-40°C to +125°C Temperature Range
20 or 28 I/O Ports, Each Configurable as
Constant-Current LED Driver
Push-Pull Logic Output
Schmitt Logic Input
Schmitt Logic Input with Internal Pullup
o
11µA (max) Shutdown Current
o
16-Step Individually Programmable Current
Control for Each LED
o
Logic Transition Detection for Seven I/O Ports
MAX6956
Ordering Information
PART
MAX6956ANI+
MAX6956AAI+
MAX6956AAX+
MAX6956ATL+
MAX6956AAX/V
MAX6956AAX/V+T
TEMP RANGE
-40°C to +125°C
-40°C to +125°C
-40°C to +125°C
-40°C to +125°C
-40°C to +125°C
-40°C to +125°C
PIN-PACKAGE
28 DIP
28 SSOP
36 SSOP
40 Thin QFN-EP*
36 SSOP
36 SSOP
/V denotes an automotive qualified part.
+Denotes
a lead(Pb)-free/RoHS-compliant package.
T = Tape and reel.
*EP
= Exposed pad.
Pin Configurations
Applications
Set-Top Boxes
Panel Meters
White Goods
Automotive
Bar Graph Displays
Industrial Controllers
System Monitoring
TOP VIEW
ISET 1
GND 2
GND 3
AD0 4
P12 5
P13 6
P14 7
28 V+
27 AD1
26 SCL
25 SDA
24 P31
MAX6956
23 P30
22 P29
21 P28
20 P27
19 P26
18 P25
17 P24
16 P23
15 P22
Typical Operating Circuit appears at end of data sheet.
P15 8
P16 9
P17 10
P18 11
P19 12
P20 13
P21 14
SSOP/DIP
Pin Configurations continued at end of data sheet.
________________________________________________________________
Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.
2-Wire-Interfaced, 2.5V to 5.5V, 20-Port or
28-Port LED Display Driver and I/O Expander
MAX6956
ABSOLUTE MAXIMUM RATINGS
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 T
A
= +70°C) 1143mW
28-Pin SSOP (derate 9.1mW/°C above T
A
= +70°C) ...727mW
36-Pin SSOP (derate 11.8mW/°C above T
A
= +70°C) ...941mW
40-Pin TQFN (derate 26.3mW/°C above T
A
= +70°C) 2105mW
Operating Temperature Range
(T
MIN
to T
MAX
) ...............................................-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
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
(Typical
Operating Circuit,
V+ = 2.5V to 5.5V, T
A
= T
MIN
to T
MAX
, unless otherwise noted.) (Note 1)
PARAMETER
Operating Supply Voltage
Shutdown Supply Current
SYMBOL
V+
I
SHDN
CONDITIONS
T
A
= +25°C
T
A
= -40°C to +85°C
T
A
= T
MIN
to T
MAX
All ports programmed
as outputs high, no
load, all other inputs at
V+ or GND
All ports programmed
as outputs low, no
load, all other inputs at
V+ or GND
T
A
= +25°C
T
A
= -40°C to +85°C
T
A
= T
MIN
to T
MAX
T
A
= +25°C
T
A
= -40°C to +85°C
T
A
= T
MIN
to T
MAX
110
170
180
MIN
2.5
TYP
5.5
MAX
5.5
8
10
11
230
250
270
210
230
240
135
140
145
0.7
✕
V+
0.3
✕
V+
GPIO inputs without pullup,
V
PORT
= V+ to GND
V+ = 2.5V
V+ = 5.5V
GPIO outputs, I
SOURCE
= 2mA, T
A
= -40°C to
+85°C
GPIO outputs, I
SOURCE
= 1mA, T
A
= T
MIN
to
T
MAX
(Note 2)
V
PORT
= 0.6V
Port configured output low, shorted to V+
-100
12
80
V+ -
0.7
V+ -
0.7
2
2.75
10
11
18
20
±1
19
120
0.3
+100
30
180
µA
µA
µA
µA
UNITS
V
All digital inputs at V+
or GND
Operating Supply Current
I
GPOH
Operating Supply Current
I
GPOL
Operating Supply Current
I
LED
All ports programmed
T
A
= +25°C
as LED outputs, all LEDs
T
A
= -40°C to +85°C
off, no load, all other
inputs at V+ or GND
T
A
= T
MIN
to T
MAX
INPUTS AND OUTPUTS
Logic-High Input Voltage
Port Inputs
Logic-Low Input Voltage
Port Inputs
Input Leakage Current
GPIO Input Internal Pullup to V+
Hysteresis Voltage GPIO Inputs
V
IH
V
IL
I
IH
, I
IL
I
PU
∆V
I
V
V
nA
µA
V
Output High Voltage
V
OH
V
Port Sink Current
Output Short-Circuit Current
I
OL
I
OLSC
mA
mA
2
_______________________________________________________________________________________
2-Wire-Interfaced, 2.5V to 5.5V, 20-Port or
28-Port LED Display Driver and I/O Expander
ELECTRICAL CHARACTERISTICS (continued)
(Typical
Operating Circuit,
V+ = 2.5V to 5.5V, T
A
= T
MIN
to T
MAX
, unless otherwise noted.) (Note 1)
PARAMETER
SYMBOL
CONDITIONS
V+ = 2.5V, V
LED
= 2.3V at maximum LED
current
V+ = 3.3V, V
LED
= 2.4V at maximum LED
I
DIGIT
current (Note 2)
V+ = 5.5V, V
LED
= 2.4V at maximum LED
current
V+ = 2.5V, V
OUT
= 0.6V at maximum sink
current
I
DIGIT_SC
V+ = 5.5V, V
OUT
= 0.6V at maximum sink
current
V
IH
V
IL
I
IH
, I
IL
V
OL
(Note 2)
I
SINK
= 6mA
-50
MIN
9.5
18.5
19
18.5
19
0.7
✕
V+
0.3
✕
V+
50
10
0.4
TYP
13.5
24
25
23
24
MAX
18
27.5
30
28
mA
28
V
V
nA
pF
V
mA
UNITS
MAX6956
Port Drive LED Sink Current,
Port Configured as LED Driver
Port Drive Logic Sink Current,
Port Configured as LED Driver
Input High-Voltage SDA, SCL,
AD0, AD1
Input Low-Voltage SDA, SCL,
AD0, AD1
Input Leakage Current SDA, SCL
Input Capacitance
Output Low-Voltage SDA
TIMING CHARACTERISTICS (Figure 2)
(V+ = 2.5V to 5.5V, T
A
= T
MIN
to T
MAX
, unless otherwise noted.) (Note 1)
PARAMETER
Serial Clock Frequency
Bus Free Time Between a STOP
and a START Condition
Hold Time (Repeated) START
Condition
Repeated START Condition
Setup Time
STOP Condition Setup Time
Data Hold Time
Data Setup Time
SCL Clock Low Period
SCL Clock High Period
Rise Time of Both SDA and SCL
Signals, Receiving
Fall Time of Both SDA and SCL
Signals, Receiving
Fall Time of SDA Transmitting
SYMBOL
f
SCL
t
BUF
t
HD, STA
t
SU, STA
t
SU, STO
t
HD, DAT
t
SU, DAT
t
LOW
t
HIGH
t
R
t
F
t
F
,
TX
(Note 3)
CONDITIONS
MIN
1.3
0.6
0.6
0.6
15
100
1.3
0.7
20 +
0.1C
b
20 +
0.1C
b
20 +
0.1C
b
900
TYP
MAX
400
UNITS
kHz
µs
µs
µs
µs
ns
ns
µs
µs
ns
ns
ns
(Notes 2, 4)
(Notes 2, 4)
(Notes 2, 5)
300
300
250
Pulse Width of Spike Suppressed
t
SP
(Notes 2, 6)
0
50
ns
Capacitive Load for Each Bus
(Note 2)
400
pF
C
b
Line
Note 1:
All parameters tested at T
A
= +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 V
IL
of the SCL signal) in order to
bridge the undefined region of SCL’s falling edge.
Note 4:
C
b
= total capacitance of one bus line in pF. t
R
and t
F
measured between 0.3V+ and 0.7V+.
Note 5:
I
SINK
≤
6mA. C
b
= total capacitance of one bus line in pF. t
R
and t
F
measured between 0.3V+ and 0.7V+.
Note 6:
Input filters on the SDA and SCL inputs suppress noise spikes less than 50ns.
_______________________________________________________________________________________
3
2-Wire-Interfaced, 2.5V to 5.5V, 20-Port or
28-Port LED Display Driver and I/O Expander
MAX6956
__________________________________________Typical Operating Characteristics
(R
ISET
= 39kΩ, T
A
= +25°C, unless otherwise noted.)
OPERATING SUPPLY CURRENT
vs. TEMPERATURE
MAX6956 toc01
SHUTDOWN SUPPLY CURRENT
vs. TEMPERATURE
MAX6956 toc02
OPERATING SUPPLY CURRENT vs. V+
(NO LOADS)
ALL PORTS LED (ON)
SUPPLY CURRENT (mA)
10
ALL PORTS
OUTPUT
(1)
1
ALL PORTS
OUTPUT
(0)
MAX6956 toc03
0.40
0.36
0.32
SUPPLY CURRENT (mA)
0.28
0.24
0.20
0.16
0.12
0.08
0.04
0
-40.0
-12.5
15.0
42.5
70.0
97.5
ALL PORTS LED (OFF)
ALL PORTS
OUTPUT (1)
ALL PORTS
OUTPUT (0)
V+ = 2.5V TO 5.5V
NO LOAD
8
V+ = 5.5V
7
SUPPLY CURRENT (µA)
V+ = 3.3V
6
100
5
V+ = 2.5V
4
0.1
ALL PORTS LED (OFF)
3
125.0
-40.0
-12.5
15.0
42.5
70.0
97.5
125.0
TEMPERATURE (°C)
TEMPERATURE (°C)
0.01
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
V+ (V)
LED DRIVER SINK CURRENT
vs. V+
MAX6956 toc04
LED DRIVER SINK CURRENT
vs. TEMPERATURE
V
LED
= 2.4V
26
PORT SINK CURRENT (mA)
25
24
23
V+ = 3.3V
22
21
20
V+ = 5.5V
MAX6956 toc05
GPO SINK CURRENT vs. TEMPERATURE
(OUTPUT = 0)
V+ = 2.5V TO 5.5V, V
PORT
= 0.6V
16
PORT SINK CURRENT (mA)
14
12
10
8
6
4
2
-40.0
-12.5
15.0
42.5
70.0
97.5
125.0
MAX6956 toc06
26
24
PORT SINK CURRENT (mA)
22
20
18
16
14
12
10
8
6
2.0
2.5
3.0
3.5
4.0
4.5
5.0
LED DROP = 1.8V
LED DROP = 2.4V
27
18
5.5
-40.0
-12.5
15.0
42.5
70.0
97.5
125.0
V+ (V)
TEMPERATURE (°C)
TEMPERATURE (°C)
GPO SOURCE CURRENT vs. TEMPERATURE
(OUTPUT = 1)
MAX6956 toc07
GPI PULLUP CURRENT
vs. TEMPERATURE
MAX6956 toc08
GPO SHORT-CIRCUIT CURRENT
vs. TEMPERATURE
MAX6956 toc09
9
V
PORT
= 1.4V
8
PORT SOURCE CURRENT (mA)
7
6
5
4
3
2
-40.0
-12.5
15.0
42.5
70.0
97.5
V+ = 5.5V
V+ = 3.3V
V+ = 2.5V
1000
100
PULLUP CURRENT (µA)
V+ = 5.5V
PORT CURRENT (mA)
GPO = 0, PORT
SHORTED TO V+
10
100
V+ = 3.3V
V+ = 2.5V
10
125.0
-40.0
-12.5
15.0
42.5
70.0
97.5
125.0
TEMPERATURE (°C)
TEMPERATURE (°C)
1
-40.0
GPO = 1, PORT
SHORTED TO GND
-12.5
15.0
42.5
70.0
97.5
125.0
TEMPERATURE (°C)
4
_______________________________________________________________________________________
2-Wire-Interfaced, 2.5V to 5.5V, 20-Port or
28-Port LED Display Driver and I/O Expander
Pin Description
PIN
SSOP/DIP
1
2, 3
4
SSOP
1
2, 3
4
TQFN
36
37, 38, 39
40
NAME
ISET
GND
AD0
FUNCTION
Segment Current Setting. Connect ISET to GND through a resistor (R
ISET
) to set
the maximum segment current.
Ground
Address Input 0. Sets device slave address. Connect to either GND, V+, SCL,
SDA to give four logic combinations. See Table 3.
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.
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.
No Connection
I
2
C-Compatible Serial Data I/O
I
2
C-Compatible Serial Clock Input
Address Input 1. Sets device slave address. Connect to either GND, V+, SCL,
SDA to give four logic combinations. See Table 3.
Positive Supply Voltage. Bypass V+ to GND with minimum 0.047µF capacitor.
Exposed Pad (TQFN Only). Not internally connected. Connect EP to ground
plane for maximum thermal performance.
MAX6956
5–24
—
—
1–10,
12–19,
21–30
11, 20, 31
32
33
34
35
—
P12–P31
—
—
25
26
27
28
—
5–32
—
33
34
35
36
—
P4–P31
N.C.
SDA
SCL
AD1
V+
EP
Detailed Description
The MAX6956 LED driver/GPIO peripheral provides up
to 28 I/O ports, P4 to P31, controlled through an I
2
C-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 Circuit
shows 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 Drivers
The 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 sees CA digits as multiple discrete LEDs. To
5
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