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KIT
ATION
EVALU
BLE
AVAILA
2-Wire Interfaced, 2.7V to 5.5V LED Display
Driver with I/O Expander and Key Scan
General Description
The MAX6955 is a compact display driver that interfaces
microprocessors to a mix of 7-segment, 14-segment,
and 16-segment LED displays through an I
2
C-compati-
ble 2-wire serial interface. The MAX6955 drives up to 16
digits 7-segment, 8 digits 14-segment, 8 digits 16-seg-
ment, or 128 discrete LEDs, while functioning from a
supply voltage as low as 2.7V. The driver includes five
I/O expander or general-purpose I/O (GPIO) lines, some
or all of which can be configured as a key-switch reader.
The key-switch reader automatically scans and
debounces a matrix of up to 32 switches.
Included on chip are full 14- and 16-segment ASCII
104-character fonts, a hexadecimal font for 7-segment
displays, multiplex scan circuitry, anode and cathode
drivers, and static RAM that stores each digit. The max-
imum segment current for the display digits is set using
a single external resistor. Digit intensity can be inde-
pendently adjusted using the 16-step internal digital
brightness control. The MAX6955 includes a low-power
shutdown mode, a scan-limit register that allows the
user to display from 1 to 16 digits, segment blinking
(synchronized across multiple drivers, if desired), and a
test mode, which forces all LEDs on. The LED drivers
are slew-rate limited to reduce EMI.
For an SPI™-compatible version, refer to the MAX6954
data sheet. An evaluation kit (EV kit) for the MAX6955 is
available.
Features
♦
400kbps 2-Wire I
2
C-Compatible Interface
♦
2.7V to 5.5V Operation
♦
Drives Up to 16 Digits 7-Segment, 8 Digits
14-Segment, 8 Digits 16-Segment, 128 Discrete
LEDs, or a Combination of Digit Types
♦
Drives Common-Cathode Monocolor and Bicolor
LED Displays
♦
Built-In ASCII 104-Character Font for 14-Segment
and 16-Segment Digits and Hexadecimal Font for
7-Segment Digits
♦
Automatic Blinking Control for Each Segment
♦
10µA (typ) Low-Power Shutdown (Data Retained)
♦
16-Step Digit-by-Digit Digital Brightness Control
♦
Display Blanked on Power-Up
♦
Slew-Rate-Limited Segment Drivers for Lower EMI
♦
Five GPIO Port Pins Can Be Configured as Key-
Switch Reader to Scan and Debounce Up to 32
Switches with n-Key Rollover
♦
IRQ Output when a Key Input is Debounced
♦
36-Pin SSOP and 40-Pin TQFN Packages
♦
Automotive Temperature Range Standard
MAX6955
Functional Diagram
Applications
Set-Top Boxes
Panel Meters
White Goods
Automotive
Bar Graph Displays
Audio/Video Equipment
OSC
ISET
CURRENT
SOURCE
GPIO
AND KEY-SCAN
CONTROL
PWM
BRIGHTNESS
CONTROL
DIGIT
MULTIPLEXER
P0 TO P4
LED
DRIVERS
O0 TO O18
Ordering Information
OSC_OUT
DIVIDER/
COUNTER
NETWORK
PART
MAX6955AAX
TEMP RANGE
-40°C to +125°C
PIN-
PACKAGE
36 SSOP
40 TQFN-EP*
(6mm x 6mm)
PKG
CODE
A36-2
T4066-5
BLINK
BLINK
CONTROL
MAX6955
CHARACTER
GENERATOR
ROM
MAX6955ATL+ -40°C to +125°C
*EP
= Exposed paddle.
+Denotes
lead-free package.
SCL
AD0
AD1
SDA
RAM
CONFIGURATION
REGISTER
Pin Configurations and Typical Operating Circuits appear
at end of data sheet.
SPI is a trademark of Motorola, Inc.
2-WIRE SERIAL INTERFACE
________________________________________________________________
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.
2-Wire Interfaced, 2.7V to 5.5V LED Display
Driver with I/O Expander and Key Scan
MAX6955
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)
Current
O0–O7 Sink Current ......................................................935mA
O0–O18 Source Current .................................................55mA
SCL, SDA, AD0, AD1, BLINK, OSC, OSC_OUT, ISET ....20mA
P0, P1, P2, P3, P4 ...........................................................40mA
GND .....................................................................................1A
Continuous Power Dissipation (T
A
= +70°C)
36-Pin SSOP (derate at 11.8mW/°C above +70°C) .....941mW
40-Pin TQFN (derate at 25.6mW/°C above +70°C)....2051.3mW
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
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.
DC ELECTRICAL CHARACTERISTICS
(Typical Operating Circuit, V+ = 2.7V 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
Shutdown mode, all
digital inputs at V+
or GND
T
A
= +25°C
T
A
= T
MIN
to T
MAX
22
CONDITIONS
MIN
2.7
10
TYP
MAX
5.5
35
µA
40
30
mA
35
UNITS
V
Operating Supply Current
I+
All segments on, all
T
A
= +25°C
digits scanned,
intensity set to full,
internal oscillator, no
display or OSC_OUT T
A
= T
MIN
to T
MAX
load connected
OSC = RC oscillator, R
SET
= 56kΩ,
C
SET
= 22pF, V+ = 3.3V
OSC driven externally
1
Master Clock Frequency
Dead Clock Protection Frequency
OSC Internal/External Detection
Threshold
OSC High Time
OSC Low Time
Slow Segment Blink Period
Fast Segment Blink Period
Fast or Slow Segment Blink Duty
Cycle
f
OSC
f
OSC
V
OSC
t
CH
t
CL
4
8
95
1.7
50
50
1
0.5
49.5
50.5
MHz
kHz
V
ns
ns
s
s
%
OSC = RC oscillator, R
SET
= 56kΩ,
f
SLOWBLINK
C
SET
= 22pF, V+ = 3.3V
f
FASTBLINK
OSC = RC oscillator, R
SET
= 56kΩ,
C
SET
= 22pF, V+ = 3.3V
2
_______________________________________________________________________________________
2-Wire Interfaced, 2.7V to 5.5V LED Display
Driver with I/O Expander and Key Scan
DC ELECTRICAL CHARACTERISTICS (continued)
(Typical Operating Circuit, V+ = 2.7V to 5.5V, T
A
= T
MIN
to T
MAX
, unless otherwise noted.) (Note 1)
PARAMETER
SYMBOL
V
LED
= 2.2V,
V+ = 3.3V
Segment Drive Source Current
I
SEG
V
LED
= 2.2V,
V+ = 2.7V
T
A
= +25°C
-32
-40
-48
mA
CONDITIONS
MIN
TYP
MAX
UNITS
MAX6955
Segment Current Slew Rate
Segment Drive Current Matching
LOGIC INPUTS AND OUTPUTS
Input High Voltage
SDA, SCL, AD0, AD1
Input Low Voltage
SDA, SCL, AD0, AD1
Input Leakage Current
SDA, SCL, AD0, AD1, OSC, P0,
P1, P2, P3, P4
SDA Output Low Voltage
Port Logic-High Input Voltage
P0, P1, P2, P3, P4
Port Logic-Low Input Voltage
P0, P1, P2, P3, P4
Port Hysteresis Voltage
P0, P1, P2, P3, P4
Port Input Pullup Current from V+
Port Output Low Voltage
Blink Output Low Voltage
OSC_OUT Output High Voltage
OSC_OUT Output Low Voltage
∆I
SEG
/∆t
∆I
SEG
T
A
= +25°C, V+ = 3.3V
T
A
= +25°C, V+ = 3.3V
0.7 x
V+
11
5
mA/µs
%
V
IH
V
IL
V
0.3 x
V+
V
I
IH
, I
IL
V
OLSDA
V
IHP
V
ILP
∆V
IP
I
IPU
V
OLP
V
OLBK
V
OHOSC
V
OLOSC
P0 to P3 configured as key-scan inputs,
V+ = 3.3V
I
SINK
= 8mA
I
SINK
= 0.6mA
I
SOURCE
= 1.6mA
I
SINK
= 1.6mA
I
SINK
= 6mA
-1
+1
0.4
µA
V
V
0.7 x
V+
0.3 x
V+
0.03 x
V+
75
0.3
0.1
V+ -
0.4
0.4
0.5
0.3
V
V
µA
V
V
V
V
_______________________________________________________________________________________
3
2-Wire Interfaced, 2.7V to 5.5V LED Display
Driver with I/O Expander and Key Scan
MAX6955
TIMING CHARACTERISTICS
(Typical Operating Circuit, V+ = 2.7V to 5.5V, T
A
= T
MIN
to T
MAX
, unless otherwise noted.) (Note 1)
PARAMETER
TIMING CHARACTERISTICS
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
Pulse Width of Spike Suppressed
Capacitive Load for Each
Bus Line
f
SCL
t
BUF
t
HD,
t
STA
t
SU
, t
STA
t
SU:STO
t
HD
, t
DAT
t
SU
, t
DAT
t
LOW
t
HIGH
t
R
t
F
t
F
, t
X
t
SP
C
B
(Notes 2, 4)
(Notes 2, 4)
(Notes 2, 5)
(Notes 2, 6)
(Note 2)
0
400
(Note 3)
100
1.3
0.6
20 +
0.1C
B
20 +
0.1C
B
20 +
0.1C
B
300
300
300
50
1.3
0.6
0.6
0.6
0.9
400
kHz
µs
µs
µs
µs
µs
ns
µs
µs
ns
ns
ns
ns
pF
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
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.
4
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