19-2429; Rev 4; 2/07
4-Wire-Interfaced, 2.5V to 5.5V, 20-Port and
28-Port LED Display Driver and I/O Expander
General Description
The MAX6957 compact, serial-interfaced LED display
driver general-purpose I/O (GPIO) peripheral provides
microprocessors with up to 28 ports. Each port is indi-
vidually user configurable to either a logic input, logic
output, or common-anode (CA) LED constant-current
segment driver. Each port configured as an LED seg-
ment 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 GPIO can be either a push-
pull logic output capable of sinking 10mA and sourcing
4.5mA, or a Schmitt logic input with optional internal
pullup. Seven ports feature configurable transition
detection logic, which generates an interrupt upon
change of port logic level. The MAX6957 is controlled
through an SPI™-compatible 4-wire serial interface.
The MAX6957AAX and MAX6957ATL have 28 ports and
are available in 36-pin SSOP and 40-pin TQFN (6mm x
6mm) packages, respectively. The MAX6957AAI and
MAX6957ANI have 20 ports and are available in 28-pin
SSOP and 28-pin DIP packages, respectively.
For a 2-wire interfaced version, refer to the MAX6956
data sheet.
For a lower cost pin-compatible port expander without
the constant-current LED drive capability, refer to the
MAX7301 data sheet.
♦
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
♦
11µA (max) Shutdown Current
♦
16-Step Individually Programmable Current
Control for Each LED
♦
Logic Transition Detection for Seven I/O Ports
Features
♦
High-Speed 26MHz SPI-/QSPI-™/MICROWIRE™-
Compatible Serial Interface
MAX6957
Ordering Information
PART
MAX6957ANI
MAX6957AAI
MAX6957AAX
MAX6957ATL
TEMP RANGE
-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
PKG
CODE
N28-2
A28-1
A36-4
T4066-5
Pin Configurations
TOP VIEW
ISET 1
GND 2
GND 3
DOUT 4
P12 5
P13 6
P14 7
P15 8
P16 9
P17 10
P18 11
P19 12
P20 13
28 V+
27 CS
26 DIN
25 SCLK
24 P31
23 P30
Applications
Set-Top Boxes
Panel Meters
White Goods
Automotive
Bar Graph Displays
Industrial Controllers
System Monitoring
MAX6957
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.
SPI and QSPI are trademarks of Motorola, Inc.
MICROWIRE is a trademark of National Semiconductor Corp.
P21 14
SSOP/DIP
Pin Configurations continued at end of data sheet.
1
________________________________________________________________
Maxim Integrated Products
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
4-Wire-Interfaced, 2.5V to 5.5V, 20-Port and
28-Port LED Display Driver and I/O Expander
MAX6957
ABSOLUTE MAXIMUM RATINGS
Voltage (with Respect to GND)
V+ .............................................................................-0.3V to +6V
All Other pins................................................-0.3V to (V+ + 0.3V)
P4–P31 Current ................................................................±30mA
GND Current .....................................................................800mA
Continuous Power Dissipation (T
A
= +70°C)
28-Pin PDIP (derate 14.3mW/°C above +70°C)........1143mW
28-Pin SSOP (derate 9.1mW/°C above +70°C) ..........727mW
36-Pin SSOP (derate 11.8mW/°C above +70°C) ........941mW
40-Pin TQFN (derate 37.0mW/°C above +70°C) ......2963mW
Operating Temperature Range (T
MIN
, T
MAX
) ....-40°C to +125°C
Junction Temperature ......................................................+150°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°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
All digital inputs at
V+ or GND
T
A
= +25°C
TA = -40°C to +85°C
T
A
= T
MIN
to T
MAX
All ports programmed
T
A
= +25°C
as outputs high, no load,
TA = -40°C to +85°C
all other inputs at V+ or
T
A
= T
MIN
to T
MAX
GND
All ports programmed
as outputs low, no load,
all other inputs at V+ or
GND
T
A
= +25°C
TA = -40°C to +85°C
T
A
= T
MIN
to T
MAX
110
180
CONDITIONS
MIN
2.5
5.5
TYP
MAX
5.5
8
10
11
230
250
270
170
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
Output High Voltage
V
OH
GPIO outputs, I
SOURCE
= 1mA,
T
A
= T
MIN
to T
MAX
(Note 2)
-100
12
80
V+ -
0.7
V+ -
0.7
±1
19
120
0.3
+100
30
180
µA
µA
µA
µA
UNITS
V
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
T
A
= T
MIN
to T
MAX
inputs at V+ or GND
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
ΔV
I
V
V
nA
µA
V
V
V
2
_______________________________________________________________________________________
4-Wire-Interfaced, 2.5V to 5.5V, 20-Port and
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
Port Sink Current
Output Short-Circuit Current
SYMBOL
I
OL
I
OLSC
V
PORT
= 0.6V
Port configured output low, shorted to V+
V+ = 2.5V, V
LED
= 2.3V at maximum LED
current
Port Drive LED Sink Current,
Port Configured as LED Driver
I
PORT
V+ = 3.3V, V
LED
= 2.4V at maximum LED
current (Note 2)
V+ = 5.5V, V
LED
= 2.4V at maximum LED
current
V+ = 2.5V, V
OUT
= 0.6V at maximum LED
current
I
PORT_SC
V+ = 5.5V, V
OUT
= 0.6V at maximum LED
current
V+
≤
3.3V
V+ > 3.3V
CONDITIONS
MIN
2
2.75
9.5
18.5
19
18.5
19
TYP
10
11
13.5
24
25
23
24
6
1.6
2
0.6
-50
I
SOURCE
= 1.6mA
I
SINK
= 1.6mA
V+ -
0.5
0.4
+50
MAX
18
20
18
27.5
30
28.0
mA
28
%
V
V
nA
V
V
mA
UNITS
mA
mA
MAX6957
Port Drive Logic Sink Current,
Port Configured as LED Driver
Port LED Sink Current Matching
Input High-Voltage SCLK, DIN,
CS
Input Low-Voltage SCLK, DIN,
CS
Input Leakage Current SCLK,
DIN,
CS
Output High-Voltage DOUT
Output Low-Voltage DOUT
ΔI
PORT
V
IH
V
IL
I
IH
, I
IL
V
OH
V
OL
TIMING CHARACTERISTICS (Figure 3)
(V+ = 2.5V to 5.5V, T
A
= T
MIN
to T
MAX
, unless otherwise noted.) (Note 1)
PARAMETER
CLK Clock Period
CLK Pulse Width High
CLK Pulse Width Low
CS
Fall to SCLK Rise Setup Time
CLK Rise to
CS
Rise Hold Time
DIN Setup Time
DIN Hold Time
Output Data Propagation Delay
Minimum
CS
Pulse High
SYMBOL
t
CP
t
CH
t
CL
t
CSS
t
CSH
t
DS
t
DH
t
DO
t
CSW
C
LOAD
= 25pF
19
CONDITIONS
MIN
38.4
19
19
9.5
0
9.5
0
21
TYP
MAX
UNITS
ns
ns
ns
ns
ns
ns
ns
ns
ns
Note 1:
All parameters tested at T
A
= +25°C. Specifications over temperature are guaranteed by design.
Note 2:
Guaranteed by design.
_______________________________________________________________________________________
3
4-Wire-Interfaced, 2.5V to 5.5V, 20-Port and
28-Port LED Display Driver and I/O Expander
MAX6957
__________________________________________Typical Operating Characteristics
(R
ISET
= 39kΩ, T
A
= +25°C, unless otherwise noted.)
OPERATING SUPPLY CURRENT
vs. TEMPERATURE
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
125.0
TEMPERATURE (°C)
ALL PORTS LED (OFF)
3
-40.0
-12.5
15.0
42.5
70.0
97.5
125.0
TEMPERATURE (°C)
0.01
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
V+ (V)
ALL PORTS
OUTPUT (1)
ALL PORTS
OUTPUT (0)
V+ = 2.5V TO 5.5V
NO LOAD
MAX6957 toc01
SHUTDOWN SUPPLY CURRENT
vs. TEMPERATURE
MAX6957 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)
MAX6957 toc03
0.40
8
V+ = 5.5V
7
SUPPLY CURRENT (μA)
V+ = 3.3V
6
100
5
V+ = 2.5V
0.1
4
ALL PORTS LED (OFF)
LED DRIVER SINK CURRENT vs. V+
MAX6957 toc04
LED DRIVER SINK CURRENT
vs. TEMPERATURE
MAX6957 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
MAX6957 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
V
LED
= 2.4V
26
PORT SINK CURRENT (mA)
25
24
23
V+ = 3.3V
22
21
20
V+ = 5.5V
18
5.5
-40.0
-12.5
15.0
42.5
70.0
97.5
125.0
-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)
MAX6957 toc07
GPI PULLUP CURRENT
vs. TEMPERATURE
MAX6957 toc08
GPO SHORT-CIRCUIT CURRENT
vs. TEMPERATURE
MAX6957 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)
GPO = 1, PORT
SHORTED TO GND
1
-40.0
-12.5
15.0
42.5
70.0
97.5
125.0
TEMPERATURE (°C)
4
_______________________________________________________________________________________
4-Wire-Interfaced, 2.5V to 5.5V, 20-Port and
28-Port LED Display Driver and I/O Expander
Pin Description
PIN
28 SSOP
28 DIP
1
2, 3
4
5–24
36
SSOP
1
2, 3
4
—
40
TQFN
36
37, 38,
39
40
—
1–10,
12–19,
21–30
32
33
34
35
11, 20,
31
EP
NAME
FUNCTION
Segment Current Setting. Connect ISET to GND through a resistor (R
ISET
) to set
the maximum segment current.
Ground
4-Wire Serial Data Output Port
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.
4-Wire Serial Clock Input Port
4-Wire Serial Data Input Port
4-Wire Chip-Select Input, Active Low
Positive Supply Voltage. Bypass V+ to GND with a minimum 0.047µF capacitor.
No Connection. Not internally connected.
Exposed Paddle. Internally connected to GND. Connect to large ground plane for
maximum thermal dissipation. Do not use as sole ground connection.
MAX6957
ISET
GND
DOUT
P12–P31
—
25
26
27
28
—
—
5–32
33
34
35
36
—
—
P4–P31
SCLK
DIN
CS
V+
N.C.
EP
Detailed Description
The MAX6957 LED driver/GPIO peripheral provides up
to 28 I/O ports, P4 to P31, controlled through an SPI-
compatible serial interface. The ports can be config-
ured 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 MAX6957 controls up to 28 LED seg-
ments with individual 16-step adjustment of the con-
stant current through each LED segment. A single
resistor sets the maximum segment current for all seg-
ments, with a maximum of 24mA per segment. The
MAX6957 drives any combination of discrete LEDs and
CA digits, including seven-segment and starburst
alphanumeric types.
Figure 1 is the MAX6957 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
maskable combination for changes in their logic status.
A detected transition is flagged through an interrupt pin
(port P31).
The
Typical Operating Circuit
shows two MAX6957s
working together controlling three monocolor 16-seg-
ment-plus-DP displays, with five ports left available for
GPIO (P27–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 MAX6957AAX has 28 ports, P4 to P31. The
28-pin MAX6957ANI and MAX6957AAI make only 20
ports available. The eight unused ports should be con-
figured as outputs on power-up by writing 0x55 to reg-
isters 0x09 and 0x0A. If this is not done, the eight
unused ports remain as floating inputs and quiescent
supply current rises, although there is no damage to
the part.
_______________________________________________________________________________________
5
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