MAX6957 [MAXIM]
4-Wire-Interfaced, 2.5V to 5.5V, 20-Port and 28-Port LED Display Driver and I/O Expander; 4线接口， 2.5V至5.5V ， 20端口和28端口LED显示驱动器和I / O扩展器
| 型号： | MAX6957 |
| 厂家： | 
MAXIM INTEGRATED PRODUCTS |
| 描述： | 4-Wire-Interfaced, 2.5V to 5.5V, 20-Port and 28-Port LED Display Driver and I/O Expander |
| 文件： | 总23页 (文件大小：333K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
19-2429; Rev 0; 4/02
4-Wire-Interfaced, 2.5V to 5.5V, 20-Port and
28-Port LED Display Driver and I/O Expander
General Description
Features
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.
o High-Speed 26MHz SPI-/QSPI-™/MICROWIRE™-
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
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.
o 11µA (max) Shutdown Current
o 16-Step Individually Programmable Current
Control for Each LED
o Logic Transition Detection for Seven I/O Ports
The MAX6957AAX and MAX6957AGL 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.
Ordering Information
PART
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
MAX6957ANI
MAX6957AAI
MAX6957AAX
MAX6957AGL*
28 SSOP
36 SSOP
40 QFN
Applications
Set-Top Boxes
Panel Meters
*Future product—contact factory for availability.
Pin Configurations
White Goods
TOP VIEW
Automotive
Bar Graph Displays
Industrial Controllers
System Monitoring
ISET
GND
GND
DOUT
P12
1
2
3
4
5
6
7
8
9
28 V+
27 CS
DIN
26
25
SCLK
24 P31
23 P30
22 P29
21 P28
20 P27
19 P26
18 P25
17 P24
16 P23
15 P22
P13
P14
MAX6957
Typical Operating Circuit appears at end of data sheet.
P15
P16
P17 10
P18 11
P19 12
P20 13
P21 14
SPI and QSPI are trademarks of Motorola, Inc.
MICROWIRE is a trademark of National Semiconductor Corp.
SSOP/DIP
Pin Configurations continued at end of data sheet.
________________________________________________________________ Maxim Integrated Products
1
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
ABSOLUTE MAXIMUM RATINGS
Voltage (with Respect to GND)
Operating Teꢀperature Range (T
, T
)....-40°C to +125°C
MIN MAX
V+.............................................................................-0.3V to +6V
All Other pins................................................-0.3V to (V+ + 0.3V)
P4–P31 Current ................................................................ 30ꢀA
GND Current .....................................................................800ꢀA
Junction Teꢀperature......................................................+150°C
Storage Teꢀperature Range.............................-65°C to +150°C
Lead Teꢀperature (soldering, 10s) .................................+300°C
Continuous Power Dissipation (T = +70°C)
A
28-Pin PDIP (derate 20.8ꢀW/°C above +70°C)........1667ꢀW
28-Pin SSOP (derate 9.5ꢀW/°C above +70°C) ..........762ꢀW
36-Pin SSOP (derate 11.8ꢀW/°C above +70°C) ........941ꢀW
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 = T
to T
, unless otherwise noted.) (Note 1)
MAX
A
MIN
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
5.5
8
UNITS
Operating Supply Voltage
V+
2.5
V
T
= +25°C
5.5
A
I
All digital inputs at
V+ or GND
SHDN
Shutdown Supply Current
Operating Supply Current
TA = -40°C to +85°C
10
µA
µA
T
= T
to T
MAX
11
A
A
MIN
All ports prograꢀꢀed
as outputs high, no load,
all other inputs at V+ or
GND
T
= +25°C
180
170
110
230
I
TA = -40°C to +85°C
250
270
210
230
240
135
140
145
GPOH
T
= T
to T
MIN MAX
A
A
All ports prograꢀꢀed
as outputs low, no load,
all other inputs at V+ or
GND
T
= +25°C
Operating Supply Current
I
µA
µA
TA = -40°C to +85°C
GPOL
T
A
T
A
T
A
T
A
= T
to T
MIN MAX
All ports prograꢀꢀed
as LED outputs, all LEDs
off, no load, all other
inputs at V+ or GND
= +25°C
= -40°C to +85°C
= T to T
Operating Supply Current
I
LED
MIN
MAX
INPUTS AND OUTPUTS
Logic-High Input Voltage
Port Inputs
0.7 ✕
V+
V
V
V
IH
Logic-Low Input Voltage
Port Inputs
0.3 ✕
V+
V
IL
V+ = 2.5V
V+ = 5.5V
12
80
19
120
0.3
30
GPIO Input Internal Pullup to V+
Hysteresis Voltage GPIO Inputs
I
µA
V
PU
180
∆V
I
GPIO outputs, I
+85°C
= 2ꢀA, T = -40°C to
V+ -
0.7
SOURCE
SOURCE
A
V
Output High Voltage
V
OH
GPIO outputs, I
= 1ꢀA,
(Note 2)
V+ -
0.7
V
T
A
= T
to T
MIN
MAX
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 = T
to T
, unless otherwise noted.) (Note 1)
MAX
A
MIN
PARAMETER
Port Sink Current
SYMBOL
CONDITIONS
MIN
2
TYP
10
MAX
18
UNITS
ꢀA
I
V
= 0.6V
PORT
OL
Output Short-Circuit Current
I
Port configured output low, shorted to V+
2.75
11
20
ꢀA
OLSC
V+ = 2.5V, V
current
= 2.3V at ꢀaxiꢀuꢀ LED
= 2.4V at ꢀaxiꢀuꢀ LED
= 2.4V at ꢀaxiꢀuꢀ LED
= 0.6V at ꢀaxiꢀuꢀ LED
= 0.6V at ꢀaxiꢀuꢀ LED
LED
9.5
18.5
19
13.5
24
18
27.5
30
Port Drive LED Sink Current,
Port Configured as LED Driver
V+ = 3.3V, V
current (Note 2)
LED
I
ꢀA
ꢀA
DIGIT
V+ = 5.5V, V
current
LED
OUT
OUT
25
V+ = 2.5V, V
current
18.5
19
23
28.0
28
Port Drive Logic Sink Current,
Port Configured as LED Driver
I
DIGIT_SC
V+ = 5.5V, V
current
24
V+ ≤ 3.3V
1.6
2
Input High-Voltage SCLK, DIN,
CS
V
V
V
IH
V+ > 3.3V
Input Low-Voltage SCLK, DIN, CS
V
0.6
IL
Input Leakage Current SCLK,
DIN, CS
I , I
IH IL
-50
+50
nA
V+ -
0.5
Output High-Voltage DOUT
Output Low-Voltage DOUT
V
I
= 1.6ꢀA
SOURCE
V
V
OH
V
I = 1.6ꢀA
SINK
0.4
OL
TIMING CHARACTERISTICS (Figure 3)
(V+ = 2.5V to 5.5V, T = T
A
to T
, unless otherwise noted.) (Note 1)
MAX
MIN
PARAMETER
CLK Clock Period
SYMBOL
CONDITIONS
MIN
38.4
19
TYP
MAX
UNITS
ns
t
CP
CH
CLK Pulse Width High
CLK Pulse Width Low
t
ns
t
19
ns
CL
CS Fall to SCLK Rise Setup Tiꢀe
CLK Rise to CS Rise Hold Tiꢀe
DIN Setup Tiꢀe
t
9.5
0
ns
CSS
CSH
t
ns
t
9.5
0
ns
DS
DH
DO
DIN Hold Tiꢀe
t
ns
Output Data Propagation Delay
Miniꢀuꢀ CS Pulse High
t
C
= 25pF
21
ns
LOAD
t
19
ns
CSW
Note 1: All paraꢀeters tested at T = +25°C. Specifications over teꢀperature are guaranteed by design.
A
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
__________________________________________Typical Operating Characteristics
(R
ISET
= 39kΩ, T = +25°C, unless otherwise noted.)
A
OPERATING SUPPLY CURRENT vs. V+
(NO LOADS)
SHUTDOWN SUPPLY CURRENT
vs. TEMPERATURE
OPERATING SUPPLY CURRENT
vs. TEMPERATURE
100
10
8
0.40
0.36
0.32
0.28
0.24
0.20
0.16
0.12
0.08
0.04
0
V+ = 2.5V TO 5.5V
NO LOAD
ALL PORTS LED (ON)
V+ = 5.5V
7
ALL PORTS
V+ = 3.3V
ALL PORTS
OUTPUT (0)
ALL PORTS OUTPUT (1)
ALL PORTS OUTPUT (0)
6
5
4
3
OUTPUT (1)
1
V+ = 2.5V
0.1
0.01
ALL PORTS LED (OFF)
ALL PORTS LED (OFF)
2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5
V+ (V)
-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
TEMPERATURE (°C)
TEMPERATURE (°C)
LED DRIVER SINK CURRENT
vs. TEMPERATURE
GPO SINK CURRENT vs. TEMPERATURE
(OUTPUT = 0)
LED DRIVER SINK CURRENT vs. V+
27
26
25
24
23
22
21
20
18
16
14
12
10
8
26
V
LED
= 2.4V
V+ = 2.5V TO 5.5V, V
= 0.6V
PORT
24
22
20
18
16
14
12
10
8
V+ = 5.5V
LED DROP = 2.4V
LED DROP = 1.8V
V+ = 3.3V
6
4
2
6
-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
2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5
V+ (V)
TEMPERATURE (°C)
TEMPERATURE (°C)
GPO SOURCE CURRENT vs. TEMPERATURE
(OUTPUT = 1)
GPI PULLUP CURRENT
vs. TEMPERATURE
GPO SHORT-CIRCUIT CURRENT
vs. TEMPERATURE
9
8
7
6
5
4
3
2
1000
100
10
100
10
1
V
PORT
= 1.4V
V+ = 5.5V
V+ = 3.3V
V+ = 2.5V
V+ = 5.5V
GPO = 0, PORT
SHORTED TO V+
V+ = 3.3V
V+ = 2.5V
GPO = 1, PORT
SHORTED TO GND
-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
-40.0 -12.5 15.0 42.5 70.0 97.5 125.0
TEMPERATURE (°C)
TEMPERATURE (°C)
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
NAME
FUNCTION
SSOP
DIP
SSOP
Segꢀent Current Setting. Connect ISET to GND through a resistor (R
ꢀaxiꢀuꢀ segꢀent current.
) to set the
ISET
1
1
ISET
2, 3
4
2, 3
4
GND
Ground
DOUT
4-Wire Serial Data Output Port
LED Segꢀent 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.
5–24
—
P12–P31
P4–P31
LED Segꢀent 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.
—
5–32
25
26
27
28
33
34
35
36
SCLK
DIN
CS
4-Wire Serial Clock Input Port
4-Wire Serial Data Input Port
4-Wire Chip-Select Input, Active Low
V+
Positive Supply Voltage. Bypass V+ to GND with a ꢀiniꢀuꢀ 0.047µF capacitor.
The port configuration registers set the 28 ports, P4 to
Detailed Description
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 MAX6957 LED driver/GPIO peripheral provides up
to 28 I/O ports, P4 to P31, controlled through an SPI-
coꢀpatible serial interface. The ports can be config-
ured to any coꢀbination 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-
ꢀents with individual 16-step adjustꢀent of the con-
stant current through each LED segꢀent. A single
resistor sets the ꢀaxiꢀuꢀ segꢀent current for all seg-
ꢀents, with a ꢀaxiꢀuꢀ of 24ꢀA per segꢀent. The
MAX6957 drives any coꢀbination of discrete LEDs and
CA digits, including seven-segꢀent and starburst
alphanuꢀeric types.
The 36-pin MAX6957AAX has 28 ports, P4 to P31. The
28-pin MAX6957ANI and MAX6957AAI only use 20 out-
puts, P12 to P31. The eight unused ports should be
configured as outputs on power-up by writing 0x55 to
registers 0x09 and 0x0A. If this is not done, the eight
unused ports reꢀain as floating inputs and quiescent
supply current rises, although there is no daꢀage 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
coꢀbinations of different display types, for exaꢀple:
seven, 7-segꢀent digits (Figure 2). This exaꢀple
requires two MAX6957s, with one digit being driven by
both devices, half by one MAX6957, half by the other
(digit 4 in this exaꢀple). The two drivers are static, and
therefore do not need to be synchronized. The
MAX6957 sees CA digits as ꢀultiple discrete LEDs. To
siꢀplify access to displays that overlap two MAX6957s,
the MAX6957 provides four virtual ports P0 through P3.
To update an overlapping digit, send the saꢀe 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-
Figure 1 is the MAX6957 functional diagraꢀ. Any I/O
port can be configured as a push-pull output (sinking
10ꢀA, sourcing 4.5ꢀA), or a Schꢀitt-trigger logic
input. Each input has an individually selectable internal
pullup resistor. Additionally, transition detection allows
seven ports (P24 through P30) to be ꢀonitored in any
ꢀaskable coꢀbination 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 ꢀonocolor 16-seg-
ꢀent-plus-DP displays, with five ports left available for
GPIO (P27–P31 of U2).
_______________________________________________________________________________________
5
4-Wire-Interfaced, 2.5V to 5.5V, 20-Port and
28-Port LED Display Driver and I/O Expander
Table 1. Port Configuration Map
REGISTER DATA
D4 D3
ADDRESS
CODE (HEX)
REGISTER
D7
D6
D5
D2
D1
D0
Port Configuration for P7, P6, P5, P4
0x09
0x0A
0x0B
0x0C
0x0D
0x0E
0x0F
P7
P6
P5
P4
Port Configuration for P11, P10, P9, P8
Port Configuration for P15, P14, P13, P12
Port Configuration for P19, P18, P17, P16
Port Configuration for P23, P22, P21, P20
Port Configuration for P27, P26, P25, P24
Port Configuration for P31, P30, P29, P28
P11
P15
P19
P23
P27
P31
P10
P14
P18
P22
P26
P30
P9
P8
P13
P17
P21
P25
P29
P12
P16
P20
P24
P28
Table 2. Port Configuration Matrix
PORT
CONFIGURATION
BIT PAIR
PORT
REGISTER
ADDRESS
CODE (HEX)
MODE
FUNCTION
PIN BEHAVIOR
UPPER
LOWER
Written Low
Written High
High iꢀpedance
Open-drain current sink, with sink
current (up to 24ꢀA) deterꢀined
by the appropriate current register
Output
Output
LED Segꢀent Driver
GPIO Output
0x09 to 0x0F
0x09 to 0x0F
0
0
Written Low
Written High
Active-low logic output
Active-high logic output
0
1
GPIO Input
Without Pullup
Input
Input
Reading Port
Reading Port
Schꢀitt logic input
0x09 to 0x0F
0x09 to 0x0F
1
1
0
1
GPIO Input with Pullup
Schꢀitt logic input with pullup
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.
ond driver. The first driver ignores the last 4 bits and
the second driver ignores the first 4 bits.
Shutdown
When the MAX6957 is in shutdown ꢀode, all ports are
forced to inputs, and the pullup current sources are
turned off. Data in the port and control registers reꢀain
unaltered so port configuration and output levels are
restored when the MAX6957 is taken out of shutdown.
The display driver can still be prograꢀꢀed while in
shutdown ꢀode. For ꢀiniꢀuꢀ supply current in shut-
down ꢀode, logic inputs should be at GND or V+
potential. Shutdown ꢀode is exited by setting the S bit
in the configuration register (Table 6). Shutdown ꢀode
is teꢀporarily overridden by the display test function.
Two addressing ꢀethods 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 coꢀbination 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-segꢀent digit with a deci-
ꢀal point can be updated in a single byte-write, a 14-
segꢀent digit with DP can be updated in two
byte-writes, and 16-segꢀent digits with DP can be
updated in two byte-writes plus a bit write. Also, dis-
crete LEDs and GPIO port bits can be lit and controlled
individually without affecting other ports.
6
_______________________________________________________________________________________
4-Wire-Interfaced, 2.5V to 5.5V, 20-Port and
28-Port LED Display Driver and I/O Expander
INTENSITY REGISTERS
TEST REGISTER
INTENSITY
TEST
CONFIGURATION
PORT REGISTERS
MASK REGISTER
P4 TO P31
LED DRIVERS
OR GPIO
LED DRIVERS AND GPIO
CONFIGURATION
REGISTERS
PORT CHANGE
DETECTOR
DATA
8
CE
R/W
SEGMENT OR
GPIO DATA
R/W
8
COMMAND
REGISTER DECODE
8
8
DATA BYTE
COMMAND BYTE
CS
D0
D1
D1
D2
D2
D3
D3
D4
D4
D5
D5
D6
D6
D7
D7
D8
D8
D9
D9
D10
D10
D11
D11
D12
D12
D13
D13
D14
D14
D15
D15
DOUT
DIN
D0
SCLK
Figure 1. MAX6957 Functional Diagram
SCLK and DIN except between the fall and subsequent
rise of CS.
Serial Interface
The MAX6957 coꢀꢀunicates through an SPI-coꢀpati-
ble 4-wire serial interface. The interface has three
inputs, Clock (SCLK), Chip Select (CS), and Data In
(DIN), and one output, Data Out (DOUT). CS ꢀust be
low to clock data into or out of the device, and DIN
ꢀust be stable when saꢀpled on the rising edge of
SCLK. DOUT provides a copy of the bit that was input
15.5 clocks earlier, or upon a query it outputs internal
register data, and is stable on the rising edge of SCLK.
Note that the SPI protocol expects DOUT to be high
iꢀpedance when the MAX6957 is not being accessed;
DOUT on the MAX6957 is never high iꢀpedance.
Control and Operation Using the
4-Wire Interface
Controlling the MAX6957 requires sending a 16-bit
word. The first byte, D15 through D8, is the coꢀꢀand
address (Table 3), and the second byte, D7 through
D0, is the data byte (Table 4).
Connecting Multiple MAX6957s to the 4-Wire Bus
Multiple MAX6957s ꢀay be daisy-chained by connect-
ing the DOUT of one device to the DIN of the next, and
driving SCLK and CS lines in parallel (Figure 4). Data at
DIN propagates through the internal shift registers and
appears at DOUT 15.5 clock cycles later, clocked out
on the falling edge of SCLK. When sending coꢀꢀands
SCLK and DIN ꢀay be used to transꢀit data to other
peripherals, so the MAX6957 ignores all activity on
_______________________________________________________________________________________
7
4-Wire-Interfaced, 2.5V to 5.5V, 20-Port and
28-Port LED Display Driver and I/O Expander
V+
7-SEGMENT DIGIT 1
7-SEGMENT DIGIT 2
7-SEGMENT DIGIT 3
7-SEGMENT DIGIT 4
VIRTUAL SEGMENTS
P0 P1 P2 P3 P4 P5 P6 P7 P8 P9 P10 P11 P12 P13 P14 P15 P16 P17 P18 P19 P20 P21 P22 P23 P24 P25 P26 P27 P28 P29 P30 P31
V+
7-SEGMENT DIGIT 5
7-SEGMENT DIGIT 6
7-SEGMENT DIGIT 7
VIRTUAL SEGMENTS
P0 P1 P2 P3 P4 P5 P6 P7 P8 P9 P10 P11 P12 P13 P14 P15 P16 P17 P18 P19 P20 P21 P22 P23 P24 P25 P26 P27 P28 P29 P30 P31
Figure 2. Two MAX6957s Controlling Seven 7-Segment Displays
CS
t
t
t
CSH
CSS
CH
t
t
CL
CSH
SCLK
t
DS
t
DH
DIN
t
DV
t
DO
DOUT
Figure 3. 4-Wire Interface Timing
_______________________________________________________________________________________
8
4-Wire-Interfaced, 2.5V to 5.5V, 20-Port and
28-Port LED Display Driver and I/O Expander
MICROCONTROLLER
SERIAL DATA INPUT
SERIAL CS OUTPUT
SERIAL CLOCK OUTPUT
SERIAL DATA OUTPUT
CS
CS
CS
MAX6957
MAX6957
MAX6957
SCLK
SCLK
DIN
SCLK
DIN
DOUT
DOUT
DOUT
DIN
Figure 4. Daisy-Chain Arrangement for Controlling Multiple MAX6957s
CS
SCLK
D15
= 0
DIN
D14
D13
D12
D11
D10
D9
D8
D7
D6
D5
D4
D3
D2
D1
D0
DOUT
D15 = 0
.
Figure 5. 16-Bit Write Transmission to the MAX6957
to ꢀultiple MAX6957s, all devices are accessed at the
saꢀe tiꢀe. An access requires (16 ✕ n) clock cycles,
where n is the nuꢀber of MAX6957s connected togeth-
er. To update just one device in a daisy-chain, the user
can send the No-Op coꢀꢀand (0x00) to the others.
4) Take CS high (while SCLK is still high after clocking
in the last data bit).
5) Take SCLK low.
Figure 5 shows a write operation when 16 bits are
transꢀitted.
Writing Device Registers
The MAX6957 contains a 16-bit shift register into which
DIN data are clocked on the rising edge of SCLK, when
CS is low. When CS is high, transitions on SCLK have
no effect. When CS goes high, the 16 bits in the Shift
register are parallel loaded into a 16-bit latch. The 16
bits in the latch are then decoded and executed.
It is acceptable to clock ꢀore than 16 bits into the
MAX6957 between taking CS low and taking CS high
again. In this case, only the last 16 bits clocked into the
MAX6957 are retained.
Reading Device Registers
Any register data within the MAX6957 ꢀay be read by
sending a logic high to bit D15. The sequence is:
The MAX6957 is written to using the following
sequence:
1) Take SCLK low.
1) Take SCLK low.
2) Take CS low (this enables the internal 16-bit shift
register).
2) Take CS low. This enables the internal 16-bit shift
register.
3) Clock 16 bits of data into DIN—D15 first to D0 last.
D15 is high, indicating a read coꢀꢀand and bits
D14 through D8 containing the address of the reg-
ister to be read. Bits D7–D0 contain duꢀꢀy data,
which is discarded.
3) Clock 16 bits of data into DIN—D15 first, D0 last—
observing the setup and hold tiꢀes (bit D15 is low,
indicating a write coꢀꢀand).
_______________________________________________________________________________________
9
4-Wire-Interfaced, 2.5V to 5.5V, 20-Port and
28-Port LED Display Driver and I/O Expander
configuration register is written with the M bit set. The
update action occurs regardless of the previous state
of the M bit so that it is not necessary to clear the M bit
and then set it again to update the snapshot register.
4) Take CS high (while SCLK is still high after clocking
in the last data bit), positions D7 through D0 in the
Shift register are now loaded with the register data
addressed by bits D1 through D8.
When the data change detection bit is set, the
MAX6957 continuously coꢀpares the snapshot register
against the changing states of P24 through P31. When
a difference occurs, the IRQ bit (ꢀask register bit D7) is
set and IRQ port P31 goes high if it is configured as an
output.
5) Take SCLK low.
6) Issue another read or write coꢀꢀand (which can
be a No-Op), and exaꢀine the bit streaꢀ at DOUT;
the second 8 bits are the contents of the register
addressed by bits D1 through D8 in step 3.
Initial Power-Up
On initial power-up, all control registers are reset, cur-
rent registers are set to ꢀiniꢀuꢀ value, and the
MAX6957 enters shutdown ꢀode (Table 4).
The IRQ bit and IRQ output reꢀain set until the ꢀask
register is next read or written, so if the IRQ is set, then
the ꢀask register reads with bit D7 set. Writing the
ꢀask register clears the IRQ output and resets the IRQ
bit, regardless of the value of bit D7 written.
LED Current Control
LED segꢀent drive current can be set either globally or
individually. Global control siꢀplifies the operation
when all LEDs are set to the saꢀe current level,
because writing one register, the Global Current regis-
ter, sets the current for all ports configured as LED seg-
ꢀent drivers. It is also possible to individually control
the current drive of each LED segꢀent driver.
Individual/global brightness control is selected by set-
ting the configuration register I bit (Table7). The global
current register (0x02) data are then ignored, and seg-
ꢀent currents are set using register addresses 0x12
through 0x1F (Tables 10, 11, and 12). Each segꢀent is
controlled by a nibble of one of the 16 current registers.
Display Test Register
Display test ꢀode turns on all ports configured as LED
drivers by overriding, but not altering, all controls and
port registers, except the port configuration register
(Table 14). Only ports configured as LED drivers are
affected. Ports configured as GPIO push-pull outputs
do not change state. In display test ꢀode, each port's
current is teꢀporarily set to 1/2 the ꢀaxiꢀuꢀ current
liꢀit as controlled by R
.
ISET
Selecting External Component R
ISET
to Set Maximum Segment Current
The MAX6957 uses an external resistor R to set the
ISET
ꢀaxiꢀuꢀ segꢀent current. The recoꢀꢀended value,
39kΩ, sets the ꢀaxiꢀuꢀ current to 24ꢀA, which ꢀakes
the segꢀent current adjustable froꢀ 1.5ꢀA to 24ꢀA in
1.5ꢀA steps.
Transition (Port Data Change) Detection
Port transition detection allows seven ꢀaskable ports
P24 through P30 to be continuously ꢀonitored for
changes in their logic status (Figure 6). Enable transi-
tion detection by setting the M bit in the configuration
register (Table 8) after setting the ꢀask register. If port
31 is configured as an output (Tables 1 and 2), then
P31 autoꢀatically becoꢀes an interrupt request (IRQ)
output to flag detected transitions. Port 31 can be con-
figured and used as a general-purpose input port
instead if not required as the IRQ output.
To set a different segꢀent current, use the forꢀula:
R
= 936kΩ / I
SEG
ISET
where I
is the desired ꢀaxiꢀuꢀ segꢀent current in ꢀA.
SEG
The recoꢀꢀended value of R
is 39kΩ.
ISET
The recoꢀꢀended value of R
is the ꢀiniꢀuꢀ
ISET
The ꢀask register deterꢀines which of the seven ports
P24 through P30 are ꢀonitored (Table 13). Set the
appropriate ꢀask bit to enable that port for transition
detect. Clear the ꢀask bit if transitions on that port are
to be ignored by the transition detection logic. Ports are
ꢀonitored regardless of their I/O configuration, both
input and output.
allowed value, since it sets the display driver to the
ꢀaxiꢀuꢀ allowed segꢀent current. R can be a
ISET
higher value to set the segꢀent current to a lower ꢀaxi-
ꢀuꢀ value where desired. The user ꢀust also ensure
that the ꢀaxiꢀuꢀ current specifications of the LEDs
connected to the driver are not exceeded.
The drive current for each segꢀent can be controlled
through prograꢀꢀing either the global current register
(Table 9) or individual segꢀent current registers
(Tables 10, 11, and 12), according to the setting of the
current control bit of the configuration register (Table 7).
The MAX6957 ꢀaintains an internal 7-bit snapshot reg-
ister to hold the coꢀparison copy of the logic states of
ports P24 through P30. The snapshot register is updat-
ed with the condition of P24 through P31 whenever the
10 ______________________________________________________________________________________
4-Wire-Interfaced, 2.5V to 5.5V, 20-Port and
28-Port LED Display Driver and I/O Expander
Table 3. Register Address Map
COMMAND ADDRESS
HEX
CODE
REGISTER
D15
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
D14
0
D13
0
D12
0
D11
0
D10
0
D9
0
D8
0
No-Op
0x00
0x02
0x04
0x06
0x07
0x09
0x0A
0x0B
0x0C
0x0D
0x0E
Global Current
Configuration
0
0
0
0
0
1
0
0
0
0
0
1
0
0
Transition Detect Mask
Display Test
0
0
0
0
1
1
0
0
0
0
0
1
1
1
Port Configuration P7, P6, P5, P4
Port Configuration P11, P10, P9, P8
Port Configuration P15, P14, P13, P12
Port Configuration P19, P18, P17, P16
Port Configuration P23, P22, P21, P20
Port Configuration P27, P26, P25, P24
Port Configuration P31, P30, P29, P28
Current054
0
0
0
1
0
0
1
0
0
0
1
0
1
0
0
0
0
1
0
1
1
0
0
0
1
1
0
0
0
0
0
1
1
0
1
0
0
0
1
1
1
0
0
0
0
0
0
0
0
1
1
1
0
0
1
0
0
1
1
1
1
0
1
0x0F
0x12
0x13
Current076
Current098
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
0
0
0
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
0x14
0x15
0x16
0x17
0x18
0x19
0x1A
0x1B
0x1C
0x1D
0x1E
0x1F
0x20
0x21
0x22
0x23
0x24
0x25
0x26
0x27
0x28
0x29
0x2A
Current0BA
Current0DC
Current0FE
Current110
Current132
Current154
Current176
Current198
Current1BA
Current1DC
Current1FE
Port 0 only (virtual port, no action)
Port 1 only (virtual port, no action)
Port 2 only (virtual port, no action)
Port 3 only (virtual port, no action)
Port 4 only
Port 5 only
Port 6 only
Port 7 only
Port 8 only
Port 9 only
Port 10 only
______________________________________________________________________________________ 11
4-Wire-Interfaced, 2.5V to 5.5V, 20-Port and
28-Port LED Display Driver and I/O Expander
Table 3. Register Address Map (continued)
COMMAND ADDRESS
REGISTER
HEX
CODE
D15
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
D14
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
D13
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
D12
0
0
0
0
0
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
D11
1
1
1
1
1
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
D10
0
1
1
1
1
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
D9
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
D8
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
Port 11 only
0x2B
0x2C
0x2D
0x2E
0x2F
0x30
0x31
0x32
0x33
0x34
0x35
0x36
0x37
0x38
0x39
0x3A
0x3B
0x3C
0x3D
0x3E
0x3F
0x40
0x41
0x42
0x43
0x44
0x45
0x46
0x47
0x48
0x49
0x4A
0x4B
0x4C
0x4D
0x4E
0x4F
Port 12 only
Port 13 only
Port 14 only
Port 15 only
Port 16 only
Port 17 only
Port 18 only
Port 19 only
Port 20 only
Port 21 only
Port 22 only
Port 23 only
Port 24 only
Port 25 only
Port 26 only
Port 27 only
Port 28 only
Port 29 only
Port 30 only
Port 31 only
8 ports 0–7 (ports 0–3 are virtual)
8 ports 1–8 (ports 1, 2, 3 are virtual)
8 ports 2–9 (ports 2, 3 are virtual)
8 ports 3–10 (port 3 is virtual)
8 ports 4–11
8 ports 5–12
8 ports 6–13
8 ports 7–14
8 ports 8–15
8 ports 9–16
8 ports 10–17
8 ports 11–18
8 ports 12–19
8 ports 13–20
8 ports 14–21
8 ports 15–22
12 ______________________________________________________________________________________
4-Wire-Interfaced, 2.5V to 5.5V, 20-Port and
28-Port LED Display Driver and I/O Expander
Table 3. Register Address Map (continued)
COMMAND ADDRESS
HEX
CODE
REGISTER
D15
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
D14
1
D13
0
D12
1
D11
0
D10
0
D9
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
D8
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
8 ports 16–23
8 ports 17–24
8 ports 18–25
8 ports 19–26
8 ports 20–27
8 ports 21–28
8 ports 22–29
8 ports 23–30
8 ports 24–31
7 ports 25–31
6 ports 26–31
5 ports 27–31
4 ports 28–31
3 ports 29, 30, 31
2 ports 30, 31
1 port 31 only
0x50
0x51
0x52
0x53
0x54
0x55
0x56
0x57
0x58
0x59
0x5A
0x5B
0x5C
0x5D
0x5E
0x5F
1
0
1
0
0
1
0
1
0
0
1
0
1
0
0
1
0
1
0
1
1
0
1
0
1
1
0
1
0
1
1
0
1
0
1
1
0
1
1
0
1
0
1
1
0
1
0
1
1
0
1
0
1
1
0
1
0
1
1
1
1
0
1
1
1
1
0
1
1
1
1
0
1
1
1
Note: Unused bits read as 0.
These registers select the LED’s constant-current drive
froꢀ 16 equal fractions of the ꢀaxiꢀuꢀ segꢀent cur-
rent. The current difference between successive cur-
Power Dissipation Issues
Each MAX6957 port can sink a current of 24ꢀA into an
LED with a 2.4V forward-voltage drop when operated
froꢀ a supply voltage of at least 3.0V. The ꢀiniꢀuꢀ
voltage drop across the internal LED drivers is there-
fore (3.0V - 2.4V) = 0.6V. The MAX6957 can sink 28 x
24ꢀA = 672ꢀA when all outputs are operating as LED
segꢀent drivers at full current. On a 3.3V supply, a
MAX6957 dissipates (3.3V - 2.4V) ✕ 672ꢀA = 0.6W
when driving 28 of these 2.4V forward-voltage drop
LEDs at full current. This dissipation is within the ratings
of the 36-pin SSOP package with an aꢀbient teꢀpera-
ture up to +98°C. If a higher supply voltage is used or
the LEDs used have a lower forward-voltage drop than
2.4V, the MAX6957 absorbs a higher voltage, and the
MAX6957's power dissipation increases.
rent steps, I
forꢀula:
, is therefore deterꢀined by the
STEP
I
= I
/ 16
SEG
STEP
If I
= 24ꢀA, then I
= 24ꢀA / 16 = 1.5ꢀA.
SEG
STEP
Applications Information
Driving Bicolor and Tricolor LEDs
Bicolor digits group a red and a green die together for
each display eleꢀent, so that the eleꢀent can be lit
red, green (or orange), depending on which die (or
both) is lit. The MAX6957 allows each segꢀent's cur-
rent to be set individually froꢀ 1/16th (ꢀiniꢀuꢀ current
and LED intensity) to 16/16th (ꢀaxiꢀuꢀ current and
LED intensity), as well as off (zero current). Thus, a
bicolor (red-green) segꢀent pair can be set to 289
color/intensity coꢀbinations. A discrete or CA tricolor
(red-green-yellow or red-green-blue) segꢀent triad can
be set to 4913 color/intensity coꢀbinations.
If the application requires high drive current and high
supply voltage, consider adding a series resistor to
each LED to drop excessive drive voltage off-chip. For
exaꢀple, consider the requireꢀent that the MAX6957
ꢀust drive LEDs with a 2.0V to 2.4V specified forward-
voltage drop, froꢀ an input supply range is 5V 5ꢁ
with a ꢀaxiꢀuꢀ LED current of 20ꢀA. Miniꢀuꢀ input
supply voltage is 4.75V. Maxiꢀuꢀ LED series resistor
______________________________________________________________________________________ 13
4-Wire-Interfaced, 2.5V to 5.5V, 20-Port and
28-Port LED Display Driver and I/O Expander
GPIO INPUT
GPIO IN
CONDITIONING
GPIO/PORT
GPIO/PORT OUT
OUTPUT LATCH
IRQ STATUS STORED AS MSB OF MASK REGISTER
P31
CLOCK PULSE AFTER EACH READ ACCESS TO MASK REGISTER
R
S
IRQ
OUTPUT LATCH
CONTROL REGISTER M BIT = 1
GPIO IN
GPIO INPUT
D
D
Q
Q
CONDITIONING
P30
P29
GPIO/PORT OUT
MASK REGISTER BIT 6
MASK REGISTER BIT 5
GPIO/PORT OUTPUT LATCH
GPIO IN
GPIO INPUT
CONDITIONING
GPIO/PORT OUT
GPIO/PORT OUTPUT LATCH
GPIO IN
GPIO INPUT
D
D
Q
Q
CONDITIONING
P28
P27
GPIO/PORT OUT
MASK REGISTER BIT 4
GPIO/PORT OUTPUT LATCH
GPIO IN
GPIO INPUT
CONDITIONING
OR
MASK REGISTER BIT 3
GPIO/PORT OUT
GPIO/PORT OUTPUT LATCH
GPIO IN
GPIO INPUT
D
D
Q
Q
CONDITIONING
P26
P25
GPIO/PORT OUT
MASK REGISTER BIT 2
MASK REGISTER BIT 1
GPIO/PORT OUTPUT LATCH
GPIO IN
GPIO INPUT
CONDITIONING
GPIO/PORT OUT
GPIO/PORT OUTPUT LATCH
GPIO IN
GPIO INPUT
CONDITIONING
D
Q
P24
GPIO/PORT OUT
MASK REGISTER LSB
GPIO/PORT OUTPUT LATCH
CLOCK PULSE WHEN WRITING CONFIGURATION REGISTER WITH M BIT SET
Figure 6. Maskable GPIO Ports P24 Through P31
14 ______________________________________________________________________________________
4-Wire-Interfaced, 2.5V to 5.5V, 20-Port and
28-Port LED Display Driver and I/O Expander
Table 4. Power-Up Configuration
ADDRESS
CODE
(HEX)
REGISTER DATA
REGISTER
FUNCTION
POWER-UP CONDITION
D7 D6
D5 D4
D3
D2 D1
D0
Port Register
Bits 4 to 31
0x24 to
0x3F
LED Off; GPIO Output Low
1/16 (ꢀiniꢀuꢀ on)
X
X
X
X
X
X
X
X
X
X
0
X
0
0
Global
Current
0x02
0
X
0
0
Shutdown Enabled
Current Control = Global
Transition Detection Disabled
Configuration
Register
0x04
0
0
X
X
X
X
Input Mask
Register
All Clear (Masked Off)
Norꢀal Operation
0x06
0x07
0x09
X
X
1
0
X
0
0
X
1
0
X
0
0
X
1
0
X
0
0
X
1
0
0
0
Display Test
Port
Configuration
P7, P6, P5, P4: GPIO Inputs Without Pullup
Port
Configuration
P11, P10, P9, P8: GPIO Inputs Without Pullup
P15, P14, P13, P12: GPIO Inputs Without Pullup
P19, P18, P17, P16: GPIO Inputs Without Pullup
P23, P22, P21, P20: GPIO Inputs Without Pullup
P27, P26, P25, P24: GPIO Inputs Without Pullup
P31, P30, P29, P28: GPIO Inputs Without Pullup
0x0A
0x0B
0x0C
0x0D
0x0E
0x0F
1
1
1
1
1
1
0
0
0
0
0
0
1
1
1
1
1
1
0
0
0
0
0
0
1
1
1
1
1
1
0
0
0
0
0
0
1
1
1
1
1
1
0
0
0
0
0
0
Port
Configuration
Port
Configuration
Port
Configuration
Port
Configuration
Port
Configuration
Current054
Current076
Current098
Current0BA
Current0DC
Current0FE
Current110
Current132
Current154
Current176
Current198
Current1BA
Current1DC
Current1FE
1/16 (ꢀiniꢀuꢀ on)
1/16 (ꢀiniꢀuꢀ on)
1/16 (ꢀiniꢀuꢀ on)
1/16 (ꢀiniꢀuꢀ on)
1/16 (ꢀiniꢀuꢀ on)
1/16 (ꢀiniꢀuꢀ on)
1/16 (ꢀiniꢀuꢀ on)
1/16 (ꢀiniꢀuꢀ on)
1/16 (ꢀiniꢀuꢀ on)
1/16 (ꢀiniꢀuꢀ on)
1/16 (ꢀiniꢀuꢀ on)
1/16 (ꢀiniꢀuꢀ on)
1/16 (ꢀiniꢀuꢀ on)
1/16 (ꢀiniꢀuꢀ on)
0x12
0x13
0x14
0x15
0x16
0x17
0x18
0x19
0x1A
0x1B
0x1C
0x1D
0x1E
0x1F
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
X = unused bits; if read, zero results.
______________________________________________________________________________________ 15
4-Wire-Interfaced, 2.5V to 5.5V, 20-Port and
28-Port LED Display Driver and I/O Expander
Table 5. Configuration Register Format
REGISTER DATA
ADDRESS CODE
(HEX)
FUNCTION
D7
D6
D5
D4
D3
D2
D1
D0
Configuration Register
0x04
M
I
X
X
X
X
X
S
X = Don’t care bit.
Table 6. Shutdown Control (S Data Bit D0) Format
REGISTER DATA
ADDRESS CODE
FUNCTION
(HEX)
D7
M
D6
D5
X
D4
X
D3
X
D2
X
D1
X
D0
0
Shutdown
Norꢀal Operation
X = Don’t care bit.
0x04
0x04
I
I
M
X
X
X
X
X
1
Table 7. Global Current Control (I Data Bit D6) Format
REGISTER DATA
ADDRESS
FUNCTION
CODE (HEX)
D7
D6
D5
D4
D3
D2
D1
D0
Global
Constant-current liꢀits for all digits are
controlled by one setting in the Global Current
register, 0x02
0x04
0x04
M
M
0
X
X
X
X
X
X
S
S
Individual Segꢀent
Constant-current liꢀit for each digit is
individually controlled by the settings in the
Current054 through Current1FE registers
1
X
X
X
X
X = Don’t care bit.
Table 8. Transition Detection Control (M-Data Bit D7) Format
REGISTER DATA
ADDRESS CODE
(HEX)
FUNCTION
D7
0
D6
D5
X
D4
X
D3
X
D2
D1
X
D0
Disabled
0x04
0x04
I
I
X
X
S
S
Enabled
1
X
X
X
X
X = Don’t care bit.
Table 9. Global Segment Current Register Format
LED DRIVE
FRACTION
TYPICAL SEGMENT
CURRENT (mA)
ADDRESS
CODE (HEX)
D7
D6
D5
D4
D3
D2
D1
D0
HEX CODE
1/16
1.5
3
0x02
0x02
0x02
0x02
0x02
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
0
0
0
0
0
0
0
0
0
1
0
0
1
1
0
0
1
0
1
0
0xX0
0xX1
0xX2
0xX3
0xX4
2/16
3/16
4/16
4.5
6
5/16
7.5
X = Don’t care bit.
16 ______________________________________________________________________________________
4-Wire-Interfaced, 2.5V to 5.5V, 20-Port and
28-Port LED Display Driver and I/O Expander
Table 9. Global Segment Current Register Format (continued)
LED DRIVE
FRACTION
TYPICAL SEGMENT
CURRENT (mA)
ADDRESS
CODE (HEX)
D7
D6
D5
D4
D3
D2
D1
D0
HEX CODE
6/16
7/16
9
10.5
12
0x02
0x02
0x02
0x02
0x02
0x02
0x02
0x02
0x02
0x02
0x02
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
0
0
0
1
1
1
1
1
1
1
1
1
1
1
0
0
0
0
1
1
1
1
0
1
1
0
0
1
1
0
0
1
1
1
0
1
0
1
0
1
0
1
0
1
0xX5
0xX6
0xX7
0xX8
0xX9
0xXA
0xXB
0xXC
0xXD
0xXE
0xXF
8/16
9/16
13.5
15
10/16
11/16
12/16
13/16
14/16
15/16
16/16
16.5
18
19.5
21
22.5
24
X = Don’t care bit.
Table 10. Individual Segment Current Registers
REGISTER
FUNCTION
ADDRESS
CODE (HEX)
D7
D6
D5
D4
D3
D2
D1
D0
Current054 register
Current076 register
Current098 register
Current0BA register
Current0DC register
Current0FE register
Current110 register
Current132 register
Current154 register
Current176 register
Current198 register
Current1BA register
Current1DC register
Current1FE register
0x12
0x13
0x14
0x15
0x16
0x17
0x18
0x19
0x1A
0x1B
0x1C
0x1D
0x1E
0x1F
Segꢀent 5
Segꢀent 4
Segꢀent 6
Segꢀent 8
Segꢀent 10
Segꢀent 12
Segꢀent 14
Segꢀent 16
Segꢀent 18
Segꢀent 20
Segꢀent 22
Segꢀent 24
Segꢀent 26
Segꢀent 28
Segꢀent 30
Segꢀent 7
Segꢀent 9
Segꢀent 11
Segꢀent 13
Segꢀent 15
Segꢀent 17
Segꢀent 19
Segꢀent 21
Segꢀent 23
Segꢀent 25
Segꢀent 27
Segꢀent 29
Segꢀent 31
______________________________________________________________________________________ 17
4-Wire-Interfaced, 2.5V to 5.5V, 20-Port and
28-Port LED Display Driver and I/O Expander
Table 11. Even Individual Segment Current Format
SEGMENT
LED DRIVE
FRACTION
CONSTANT
CURRENT WITH
ADDRESS
CODE (HEX)
D7
D6
D5
D4
D3
D2
D1
D0
HEX CODE
R
= 39kΩ (mA)
ISET
1/16
2/16
1.5
3
0x12 to 0x1F
0x12 to 0x1F
0x12 to 0x1F
0x12 to 0x1F
0x12 to 0x1F
0x12 to 0x1F
0x12 to 0x1F
0x12 to 0x1F
0x12 to 0x1F
0x12 to 0x1F
0x12 to 0x1F
0x12 to 0x1F
0x12 to 0x1F
0x12 to 0x1F
0x12 to 0x1F
0x12 to 0x1F
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0xX0
0xX1
0xX2
0xX3
0xX4
0xX5
0xX6
0xX7
0xX8
0xX9
0xXA
0xXB
0xXC
0xXD
0xXE
0xXF
3/16
4.5
6
4/16
5/16
7.5
9
6/16
7/16
10.5
12
8/16
See Table 12.
9/16
13.5
15
10/16
11/16
12/16
13/16
14/16
15/16
16/16
16.5
18
19.5
21
22.5
24
value is (4.75V - 2.4V - 0.6V)/0.020A = 87.5Ω. We
choose 82Ω 2ꢁ. Worst-case resistor dissipation is at
ꢀaxiꢀuꢀ toleranced resistance, i.e., (0.020A)2 ✕ (82Ω
✕ 1.02) = 34ꢀW. The ꢀaxiꢀuꢀ MAX6957 dissipation
per LED is at ꢀaxiꢀuꢀ input supply voltage, ꢀiniꢀuꢀ
toleranced resistance, ꢀiniꢀuꢀ toleranced LED for-
ward-voltage drop, i.e., 0.020 x (5.25V - 2.0V - (0.020A
✕ 82Ω x 0.98)) = 32.86ꢀW. Worst-case MAX6957 dissi-
pation is 920ꢀW, driving all 28 LEDs at 20ꢀA full cur-
rent at once, which ꢀeets the 941ꢀW dissipation
ratings of the 36-pin SSOP package.
Power-Supply Considerations
The MAX6957 operates with power-supply voltages of
2.5V to 5.5V. Bypass the power supply to GND with a
0.047µF capacitor as close to the device as possible.
Add a 1µF capacitor if the MAX6957 is far away froꢀ
the board's input bulk decoupling capacitor.
Low-Voltage Operation
The MAX6957 operates down to 2V supply voltage
(although the sourcing and sinking currents are not
guaranteed), providing that the MAX6957 is powered
up initially to at least 2.5V to trigger the device's internal
reset, and also that the serial interface is constrained to
10Mbps.
18 ______________________________________________________________________________________
4-Wire-Interfaced, 2.5V to 5.5V, 20-Port and
28-Port LED Display Driver and I/O Expander
Table 12. Odd Individual Segment Current Format
SEGMENT
LED
ADDRESS
CODE (HEX)
CONSTANT
DRIVE
FRACTION
D7
D6
D5
D4
D3
D2
D1
D0
HEX CODE
CURRENT WITH
R
= 39kΩ (mA)
ISET
1/16
2/16
1.5
3
0x12 to 0x1F
0x12 to 0x1F
0x12 to 0x1F
0x12 to 0x1F
0x12 to 0x1F
0x12 to 0x1F
0x12 to 0x1F
0x12 to 0x1F
0x12 to 0x1F
0x12 to 0x1F
0x12 to 0x1F
0x12 to 0x1F
0x12 to 0x1F
0x12 to 0x1F
0x12 to 0x1F
0x12 to 0x1F
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0x0X
0x1X
0x2X
0x3X
0x4X
0x5X
0x6X
0x7X
0x8X
0x9X
0xAX
0xBX
0xCX
0xDX
0xEX
0xFX
3/16
4.5
6
4/16
5/16
7.5
9
6/16
7/16
10.5
12
8/16
See Table 11.
9/16
13.5
15
10/16
11/16
12/16
13/16
14/16
15/16
16/16
X = Don’t care bit.
16.5
18
19.5
21
22.5
24
Table 13. Transition Detection Mask Register
REGISTER
READ/
REGISTER DATA
D4
FUNCTION
ADDRESS
(HEX)
WRITE
D7
D6
D5
D3
Port
D2
D1
D0
Port
30
ꢀask
Port
29
Port
28
Port
26
Port
25
Port
24
Read
Write
IRQ Status*
Unchanged
Read Mask
Register
27
0x06
ꢀask
ꢀask
ꢀask
ꢀask
ꢀask
ꢀask
*IRQ is automatically cleared after it is read.
Table 14. Display Test Register
REGISTER DATA
ADDRESS CODE
MODE
(HEX)
D7
X
D6
D5
X
D4
X
D3
X
D2
X
D1
X
D0
0
Norꢀal Operation
Display Test Mode
X = Don’t care bit.
0x07
0x07
X
X
X
X
X
X
X
X
1
______________________________________________________________________________________ 19
4-Wire-Interfaced, 2.5V to 5.5V, 20-Port and
28-Port LED Display Driver and I/O Expander
Chip Information
TRANSISTOR COUNT: 30,316
Pin Configurations (continued)
TOP VIEW
PROCESS: CMOS
ISET
GND
GND
1
2
3
4
5
6
7
8
9
36 V+
35 CS
34 DIN
33 SCLK
32 P4
31 P31
30 P5
DOUT
P8
P12
P9
P13
P10
P30
29
MAX6957
28 P6
P14 10
P11 11
P15 12
P16 13
P17 14
P18 15
P19 16
P20 17
P21 18
27 P29
26 P7
25 P28
24 P27
23 P26
22 P25
21 P24
20 P23
19 P22
SSOP
20 ______________________________________________________________________________________
4-Wire-Interfaced, 2.5V to 5.5V, 20-Port and
28-Port LED Display Driver and I/O Expander
Typical Operating Circuit
3V
3V
36
32
30
28
26
V+
P4
P5
a1
a2
b
LED1
47nF
3
2
1
GND
GND
ISET
P6
P7
c
5
P8
d1
d2
e
7
9
39kΩ
P9
P10
P11
P12
P13
P14
P15
P16
P17
P18
P19
P20
P21
P22
P23
34
33
35
4
11
6
DIN
SCLK
CS
f
4-WIRE DATA IN
4-WIRE CLOCK IN
CHIP SELECT
U1
g1
g2
h
8
MAX6957AAX
10
12
13
14
15
16
17
18
19
20
DOUT
i
31
29
27
25
24
23
22
21
P31
P30
P29
P28
P27
P26
P25
P24
j
k
l
m
dp
ca
a1
a2
b
LED2
c
d1
d2
e
f
g1
g2
h
i
j
k
3V
32
30
28
26
5
36
P4
P5
V+
l
47nF
m
dp
ca
3
2
1
P6
P7
GND
GND
ISET
P8
P9
7
39kΩ
9
P10
P11
P12
P13
P14
P15
P16
P17
P18
P19
P20
P21
P22
P23
a1
a2
b
LED3
34
33
35
4
11
6
DIN
SCLK
CS
U2
8
c
MAX6957AAX
10
12
13
14
15
16
17
18
19
20
d1
d2
e
DOUT
4-WIRE DATA OUT
IRQ OUT
31
29
27
25
24
23
22
21
P31
P30
P29
P28
P27
P26
P25
P24
f
g1
g2
h
i
1
2
j
k
l
m
dp
ca
SW1 SW2
SW3
______________________________________________________________________________________ 21
4-Wire-Interfaced, 2.5V to 5.5V, 20-Port and
28-Port LED Display Driver and I/O Expander
Package Information
(The package drawing(s) in this data sheet ꢀay not reflect the ꢀost current specifications. For the latest package outline inforꢀation,
go to www.maxim-ic.com/packages.)
22 ______________________________________________________________________________________
4-Wire-Interfaced, 2.5V to 5.5V, 20-Port and
28-Port LED Display Driver and I/O Expander
Package Information (continued)
(The package drawing(s) in this data sheet ꢀay not reflect the ꢀost current specifications. For the latest package outline inforꢀation,
go to www.maxim-ic.com/packages.)
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.
Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ____________________ 23
© 2002 Maxiꢀ Integrated Products
Printed USA
is a registered tradeꢀark of Maxiꢀ Integrated Products.
相关型号：
MAX6957AAI
4-Wire-Interfaced, 2.5V to 5.5V, 20-Port and 28-Port LED Display Driver and I/O Expander
MAXIM
MAX6957AAX
4-Wire-Interfaced, 2.5V to 5.5V, 20-Port and 28-Port LED Display Driver and I/O Expander
MAXIM
MAX6957AGL
4-Wire-Interfaced, 2.5V to 5.5V, 20-Port and 28-Port LED Display Driver and I/O Expander
MAXIM
MAX6957ANI
4-Wire-Interfaced, 2.5V to 5.5V, 20-Port and 28-Port LED Display Driver and I/O Expander
MAXIM
©2020 ICPDF网 联系我们和版权申明