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 SPITM-compatible 4-wire serial interface.
The MAX6957AAX and MAX6957ATL have 28 ports and
are available in 36-pin SSOP and 40-pin QFN 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.
Applications
Set-Top Boxes
Panel Meters
White Goods
Automotive
Bar Graph Displays
Industrial Controllers
System Monitoring
Features
o High-Speed 26MHz SPI-/QSPI-TM/MICROWIRETM-
Compatible Serial Interface
o 2.5V to 5.5V Operation
o -40°C to +125°C Temperature Range
o 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
MAX6957
4-Wire-Interfaced, 2.5V to 5.5V, 20-Port and
28-Port LED Display Driver and I/O Expander
________________________________________________________________ Maxim Integrated Products
1
28
27
26
25
24
23
22
21
20
19
18
17
16
15
1
2
3
4
5
6
7
8
9
10
11
12
13
14
V+
CS
SCLK
DIN
P31
P30
P22
P29
P28
P27
P26
P25
P24
P23
P21
P20
P19
P18
P17
P16
P15
P14
P13
P12
DOUT
GND
GND
ISET
SSOP/DIP
TOP VIEW
MAX6957
Pin Configurations
19-2429; Rev 2; 2/03
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.
Typical Operating Circuit appears at end of data sheet.
Ordering Information
PART
TEMP RANGE
PIN-PACKAGE
MAX6957ANI
-40
°C to +125°C
28 DIP
MAX6957AAI
-40
°C to +125°C
28 SSOP
MAX6957AAX
-40
°C to +125°C
36 SSOP
MAX6957ATL
-40
°C to +125°C
40 QFN
SPI and QSPI are trademarks of Motorola, Inc.
MICROWIRE is a trademark of National Semiconductor Corp.
Pin Configurations continued at end of data sheet.
MAX6957
4-Wire-Interfaced, 2.5V to 5.5V, 20-Port and
28-Port LED Display Driver and I/O Expander
2
_______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
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.
Voltage (with Respect to GND)
V+ .............................................................................-0.3V to +6V
All Other pins................................................-0.3V to (V+ + 0.3V)
P4P31 Current ................................................................±30mA
GND Current .....................................................................800mA
Continuous Power Dissipation (T
A
= +70°C)
28-Pin PDIP (derate 20.8mW/°C above +70°C)........1667mW
28-Pin SSOP (derate 9.5mW/°C above +70°C) ..........762mW
36-Pin SSOP (derate 11.8mW/°C above +70°C) ........941mW
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
ELECTRICAL CHARACTERISTICS
(Typical Operating Circuit, V+ = 2.5V to 5.5V, T
A
= T
MIN
to T
MAX
, unless otherwise noted.) (Note 1)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
Operating Supply Voltage
V+
2.5
5.5
V
T
A
= +25°C
5.5
8
TA = - 40°C to + 85°C 10
Shutdown Supply Current
I
SHDN
Al l d i g i tal i np uts at
V + or G N D
T
A
= T
MIN
to T
MAX
11
µA
T
A
= +25°C
180
230
TA = - 40°C to + 85°C 250
Operating Supply Current
I
GPOH
Al l p or ts p r og r am m ed
as outp uts hi g h, no l oad ,
al l other i np uts at V + or
G N D
T
A
= T
MIN
to T
MAX
270
µA
T
A
= +25°C
170
210
TA = - 40°C to + 85°C 230
Operating Supply Current
I
GPOL
Al l p or ts p r og r am m ed
as outp uts l ow , no l oad ,
al l other i np uts at V + or
G N D
T
A
= T
MIN
to T
MAX
240
µA
T
A
= +25°C
110
135
T
A
= - 40° C to + 85°C 140
Operating Supply Current
I
LED
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
i np uts at V + or G N D
T
A
= T
MIN
to T
MAX
145
µA
INPUTS AND OUTPUTS
Logic-High Input Voltage
Port Inputs
V
IH
0.7
V+
V
Logic-Low Input Voltage
Port Inputs
V
IL
0.3
V+
V
Input Leakage Current
I
IH
, I
IL
GPIO inputs without pullup,
V
PORT
= V+ to GND
-100
±1
+100
nA
V+ = 2.5V
12
19
30
GPIO Input Internal Pullup to V+
I
PU
V+ = 5.5V
80
120
180
µA
Hysteresis Voltage GPIO Inputs
V
I
0.3
V
GPIO outputs, I
SOURCE
= 2mA, T
A
= -40°C to
+85°C
V+ -
0.7
V
Output High Voltage
V
OH
GPIO outputs, I
SOURCE
= 1mA,
T
A
= T
MIN
to T
MAX
(Note 2)
V+ -
0.7
V
MAX6957
4-Wire-Interfaced, 2.5V to 5.5V, 20-Port and
28-Port LED Display Driver and I/O Expander
_______________________________________________________________________________________
3
Note 1: All parameters tested at T
A
= +25°C. Specifications over temperature are guaranteed by design.
Note 2: Guaranteed by design.
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
MIN
TYP
MAX
UNITS
Port Sink Current
I
OL
V
PORT
= 0.6V
2
10
18
mA
Output Short-Circuit Current
I
OLSC
Port configured output low, shorted to V+
2.75
11
20
mA
V+ = 2.5V, V
LED
= 2.3V at maximum LED
current
9.5
13.5
18
V+ = 3.3V, V
LED
= 2.4V at maximum LED
current (Note 2)
18.5
24
27.5
Port Drive LED Sink Current,
Port Configured as LED Driver
I
PORT
V+ = 5.5V, V
LED
= 2.4V at maximum LED
current
19
25
30
mA
V+ = 2.5V, V
OUT
= 0.6V at maximum LED
current
18.5
23
28.0
Port Drive Logic Sink Current,
Port Configured as LED Driver
I
PORT_SC
V+ = 5.5V, V
OUT
= 0.6V at maximum LED
current
19
24
28
mA
Port LED Sink Current Matching
I
PORT
6
%
V+
3.3V
1.6
Input High-Voltage SCLK, DIN,
CS
V
IH
V+ > 3.3V
2
V
Input Low-Voltage SCLK, DIN, CS
V
IL
0.6
V
Input Leakage Current SCLK,
DIN, CS
I
IH
, I
IL
-50
+50
nA
Output High-Voltage DOUT
V
OH
I
SOURCE
= 1.6mA
V+ -
0.5
V
Output Low-Voltage DOUT
V
OL
I
SINK
= 1.6mA
0.4
V
TIMING CHARACTERISTICS (Figure 3)
(V+ = 2.5V to 5.5V, T
A
= T
MIN
to T
MAX
, unless otherwise noted.) (Note 1)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
CLK Clock Period
t
CP
38.4
ns
CLK Pulse Width High
t
CH
19
ns
CLK Pulse Width Low
t
CL
19
ns
CS Fall to SCLK Rise Setup Time
t
CSS
9.5
ns
CLK Rise to CS Rise Hold Time
t
CSH
0
ns
DIN Setup Time
t
DS
9.5
ns
DIN Hold Time
t
DH
0
ns
Output Data Propagation Delay
t
DO
C
LOAD
= 25pF
21
ns
Minimum CS Pulse High
t
CSW
19
ns
MAX6957
4-Wire-Interfaced, 2.5V to 5.5V, 20-Port and
28-Port LED Display Driver and I/O Expander
4
_______________________________________________________________________________________
OPERATING SUPPLY CURRENT
vs. TEMPERATURE
MAX6957 toc01
TEMPERATURE (
°C)
SUPPLY CURRENT (mA)
97.5
70.0
42.5
15.0
-12.5
0.04
0.08
0.12
0.16
0.20
0.24
0.28
0.32
0.36
0.40
0
-40.0
125.0
V+ = 2.5V TO 5.5V
NO LOAD
ALL PORTS
OUTPUT (1)
ALL PORTS
OUTPUT (0)
ALL PORTS LED (OFF)
SHUTDOWN SUPPLY CURRENT
vs. TEMPERATURE
MAX6957 toc02
TEMPERATURE (
°C)
SUPPLY CURRENT (
µ
A)
97.5
70.0
42.5
15.0
-12.5
4
5
6
7
8
3
-40.0
125.0
V+ = 5.5V
V+ = 3.3V
V+ = 2.5V
OPERATING SUPPLY CURRENT vs. V+
(NO LOADS)
MAX6957 toc03
V+ (V)
SUPPLY CURRENT (mA)
5.0
4.5
4.0
3.5
3.0
2.5
0.1
1
10
100
0.01
2.0
5.5
ALL PORTS LED (ON)
ALL PORTS LED (OFF)
ALL PORTS OUTPUT (1)
ALL PORTS OUTPUT (0)
LED DRIVER SINK CURRENT vs. V+
MAX6957 toc04
V+ (V)
PORT SINK CURRENT (mA)
5.0
4.5
3.5
4.0
3.0
2.5
8
10
12
14
16
18
20
22
24
26
6
2.0
5.5
LED DROP = 2.4V
LED DROP = 1.8V
GPO SOURCE CURRENT vs. TEMPERATURE
(OUTPUT = 1)
MAX6957 toc07
TEMPERATURE (
°C)
PORT SOURCE CURRENT (mA)
97.5
70.0
42.5
15.0
-12.5
3
4
5
6
7
8
9
2
-40.0
125.0
V
PORT
= 1.4V
V+ = 5.5V
V+ = 3.3V
V+ = 2.5V
LED DRIVER SINK CURRENT
vs. TEMPERATURE
MAX6957 toc05
TEMPERATURE (
°C)
PORT SINK CURRENT (mA)
97.5
70.0
42.5
15.0
-12.5
21
22
23
24
25
26
27
20
-40.0
125.0
V
LED
= 2.4V
V+ = 5.5V
V+ = 3.3V
GPO SINK CURRENT vs. TEMPERATURE
(OUTPUT = 0)
MAX6957 toc06
TEMPERATURE (
°C)
PORT SINK CURRENT (mA)
97.5
70.0
-12.5
15.0
42.5
4
6
8
10
12
14
16
18
2
-40.0
125.0
V+ = 2.5V TO 5.5V, V
PORT
= 0.6V
GPI PULLUP CURRENT
vs. TEMPERATURE
MAX6957 toc08
TEMPERATURE (
°C)
PULLUP CURRENT (
µ
A)
97.5
70.0
42.5
15.0
-12.5
100
1000
10
-40.0
125.0
V+ = 5.5V
V+ = 3.3V
V+ = 2.5V
GPO SHORT-CIRCUIT CURRENT
vs. TEMPERATURE
MAX6957 toc09
TEMPERATURE (
°C)
PORT CURRENT (mA)
97.5
70.0
42.5
15.0
-12.5
10
100
1
-40.0
125.0
GPO = 0, PORT
SHORTED TO V+
GPO = 1, PORT
SHORTED TO GND
__________________________________________Typical Operating Characteristics
(R
ISET
= 39k
, T
A
= +25°C, unless otherwise noted.)
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 a status regis-
ter bit, as well as an interrupt pin (port P31), if desired.
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 (P27P31 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.
Register Control of I/O Ports and LEDs
Across Multiple Drivers
The MAX6957 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 2
). This example
requires two MAX6957s, with one digit being driven by
both devices, half by one MAX6957, half by the other
(digit 4 in this example). The two drivers are static, and
therefore do not need to be synchronized. The
MAX6957 sees CA digits as multiple discrete LEDs. To
simplify access to displays that overlap two MAX6957s,
the MAX6957 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-
MAX6957
4-Wire-Interfaced, 2.5V to 5.5V, 20-Port and
28-Port LED Display Driver and I/O Expander
_______________________________________________________________________________________
5
PIN
SSOP
DIP
SSOP
NAME
FUNCTION
1
1
ISET
Segment Current Setting. Connect ISET to GND through a resistor (R
ISET
) to set the
maximum segment current.
2, 3
2, 3
GND
Ground
4
4
DOUT
4-Wire Serial Data Output Port
524
--
P12P31
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.
--
532
P4P31
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.
25
33
SCLK
4-Wire Serial Clock Input Port
26
34
DIN
4-Wire Serial Data Input Port
27
35
CS
4-Wire Chip-Select Input, Active Low
28
36
V+
Positive Supply Voltage. Bypass V+ to GND with a minimum 0.047µF capacitor.
Pin Description
PDF 
ZIP