General Description
The MAX6954 is a compact display driver that inter-
faces microprocessors to a mix of 7-segment, 14-seg-
ment, and 16-segment LED displays through an SPITM-
or QSPITM-compatible 4-wire serial interface. The serial
interface may be cascaded through multiple devices.
The MAX6954 drives up to 16 digits 7-segment, 8 digits
14-segment, 8 digits 16-segment, or 128 discrete
LEDs, while functioning from a supply voltage as low as
2.7V. The driver includes five I/O expander (or GPIO)
lines, some or all or which may be configured as a key-
switch reader, which 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 MAX6954 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 a 2-wire interfaced version, refer to the MAX6955*
data sheet. An evaluation kit* (EV kit) for the MAX6955
is available.
*Future product--contact factory for availability.
Applications
Set-Top Boxes
Automotive
Panel Meters
Bar Graph Displays
White Goods
Audio/Video Equipment
Features
o
High-Speed 26MHz SPI/QSPI/MICROWIRETM-
Compatible Serial Interface
o
2.7V to 5.5V Operation
o
Drives Up to 16 Digits 7-Segment, 8 Digits
14-Segment, 8 Digits 16-Segment, 128 Discrete
LEDs, or a Combination of Digit Types
o
Drives Common-Cathode Monocolor and Bicolor
LED Displays
o
Built-In ASCII 104-Character Font for 14-Segment
and 16-Segment Digits and Hexadecimal Font for
7-Segment Digits
o
Automatic Blinking Control for each Segment
o
10µA (typ) Low-Power Shutdown (Data Retained)
o
16-Step Digit-by-Digit Digital Brightness Control
o
Display Blanked on Power-Up
o
Slew-Rate Limited Segment Drivers for Lower EMI
o
Five GPIO Port Pins Can Be Configured as Key-
Switch Reader to Scan and Debounce Up to 32
Switches with n-Key Rollover
o
IRQ Output when a Key Input Is Debounced
o
36-Pin SSOP and 40-Pin DIP Packages
o
Automotive Temperature Range Standard
MAX6954
4-Wire Interfaced, 2.7V to 5.5V LED Display
Driver with I/O Expander and Key Scan
________________________________________________________________ Maxim Integrated Products
1
Ordering Information
19-2460; Rev 1; 10/02
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.
PART
TEMP RANGE
PIN-PACKAGE
MAX6954AAX
-40°C to +125°C
36 SSOP
MAX6954APL
-40°C to +125°C
40 PDIP
SPI and QSPI are trademarks of Motorola, Inc.
MICROWIRE is a trademark of National Semiconductor Corp.
Pin Configurations and Typical Operating Circuits appear
at end of data sheet.
ISET
OSC
OSC_OUT
BLINK
CLK
CS
DIN
DOUT
4-WIRE SERIAL INTERFACE
RAM
BLINK
CONTROL
CONFIGURATION
REGISTER
CHARACTER
GENERATOR
ROM
CURRENT
SOURCE
DIVIDER/
COUNTER
NETWORK
DIGIT
MULTIPLEXER
PWM
BRIGHTNESS
CONTROL
GPIO
AND KEY-SCAN
CONTROL
LED
DRIVERS
O0 TO O23
P0 TO P4
MAX6954
Functional Diagram
MAX6954
4-Wire Interfaced, 2.7V to 5.5V LED Display
Driver with I/O Expander and Key Scan
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)
Current
O0O7 Sink Current ......................................................935mA
O0O18 Source Current .................................................55mA
DIN, CLK, CS, OSC, DOUT, BLINK, 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 PDIP (derate at 16.7mW/°C above +70°C).....1333mW
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
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
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
Operating Supply Voltage
V+
2.7
5.5
V
T
A
= +25°C
10
35
Shutdown Supply Current
I
SHDN
Shutdown mode, all
digital inputs at V+
or GND
T
A
= T
MIN
to T
MAX
40
µA
T
A
= +25°C
22
30
Operating Supply Current
I+
All segments on, all
digits scanned,
intensity set to full,
internal oscillator,
DOUT open circuit,
no display or
OSC_OUT load
connected
T
A
= T
MIN
to T
MAX
35
mA
OSC = RC oscillator, R
SET
= 56k
,
C
SET
= 22pF, V+ = 3.3V
4
Master Clock Frequency
f
OSC
OSC driven externally
1
8
MHz
Dead Clock Protection Frequency
f
OSC
95
kHz
OSC Internal/External Detection
Threshold
V
OSC
1.7
V
OSC High Time
t
CH
50
ns
OSC Low Time
t
CL
50
ns
Slow Segment Blink Period
f
SLOWBLINK
OSC = RC oscillator, R
SET
= 56k
,
C
SET
= 22pF, V+ = 3.3V
1
s
Fast Segment Blink Period
f
FASTBLINK
OSC = RC oscillator, R
SET
= 56k
,
C
SET
= 22pF, V+ = 3.3V
0.5
s
Fast or Slow Segment Blink Duty
Cycle
49.5
50.5
%
MAX6954
4-Wire Interfaced, 2.7V to 5.5V LED Display
Driver with I/O Expander and Key Scan
_______________________________________________________________________________________
3
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
CONDITIONS
MIN
TYP
MAX
UNITS
Segment Drive Source Current
I
SEG
V
LED
= 2.2V,
V+
= 3.3V
T
A
= +25°C
-34.5
-40
-46.5
mA
Segment Current Slew Rate
I
SEG
/
t
T
A
= +25°C, V+ = 3.3V
11
mA/µs
Segment Drive Current Matching
I
SEG
T
A
= +25°C, V+ = 3.3V
5
10
%
LOGIC INPUTS AND OUTPUTS
Input Leakage Current
DIN, CLK, CS, OSC, P0, P1, P2,
P3, P4
I
IH
, I
IL
-1
+1
µA
4-Wire Logic-High Input Voltage
DIN, CLK, CS
V
IHSPI
1.8
V
4-Wire Logic-Low Input Voltage
DIN, CLK, CS
V
ILSPI
0.6
V
Port Logic-High Input Voltage
P0, P1, P2, P3, P4
V
IHP
0.7 x
V+
V
Port Logic-Low Input Voltage
P0, P1, P2, P3, P4
V
ILP
0.3 x
V+
V
Port Hysteresis Voltage P0, P1,
P2, P3, P4
V
IP
0.03 x
V+
V
Port Input Pullup Current from V+
I
IPU
P0 to P3 configured as keyscan input, V+ =
3.3V
75
µA
Port Output Low Voltage
V
OLP
I
SINK
= 8mA
0.3
0.5
V
Blink Output Low Voltage
V
OLBK
I
SINK
= 0.6mA
0.1
0.3
V
DOUT Output High Voltage
V
OHDO
I
SOURCE
= 1.6mA
V+ -
0.2
V
DOUT Output Low Voltage
V
OLDO
I
SINK
= 1.6mA
0.2
V
OSC_OUT Output High Voltage
V
OHOSC
I
SOURCE
= 1.6mA
V+ -
0.4
V
OSC_OUT Output Low Voltage
V
OLOSC
I
SINK
= 1.6mA
0.4
V
MAX6954
4-Wire Interfaced, 2.7V to 5.5V LED Display
Driver with I/O Expander and Key Scan
4
_______________________________________________________________________________________
Typical Operating Characteristics
(V+ = 3.3V, LED forward voltage = 2.4V, typical application circuit, T
A
= +25°C, unless otherwise noted.)
TIMING CHARACTERISTICS
(Typical Operating Circuit, V+ = 2.7V to 5.5V, T
A
= T
MIN
to T
MAX
, unless otherwise noted.) (Note 1)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
TIMING CHARACTERISTICS
CLK Clock Period
t
CP
38.4
ns
CLK Pulse Width High
t
CH
16
ns
CLK Pulse Width Low
t
CL
16
ns
CS Fall to CLK 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
V+ = 3.0V to 5.5V
19
Output Data Propagation Delay
t
DO
V+ = 2.7V
25
ns
DOUT Output Rise and Fall Times
t
FT
C
LOAD
= 10pF, V+ = 3.0V to 5.5V
10
Minimum CS Pulse High
t
CSW
19.5
ns
Note 1:
All parameters tested at T
A
= +25°C. Specifications over temperature are guaranteed by design.
INTERNAL OSCILLATOR FREQUENCY
vs. TEMPERATURE
MAX6954 toc01
TEMPERATURE (
°
C)
OSCILLATOR FREQUENCY (MHz)
110
80
50
20
-10
3.8
4.0
4.2
4.4
3.6
-40
R
SET
= 56k
C
SET
= 22pF
INTERNAL OSCILLATOR FREQUENCY
vs. SUPPLY VOLTAGE
MAX6954 toc02
SUPPLY VOLTAGE (V)
OSCILLATOR FREQUENCY (MHz)
5.0
4.5
4.0
3.5
3.0
3.8
4.2
4.4
3.6
2.5
5.5
R
SET
= 56k
C
SET
= 22pF
4.0
100ns/div
OSC: 500mV/div
OSC_OUT: 2V/div
MAX6954 toc03
OSC
0V
0V
OSC_OUT
INTERNAL OSCILLATOR WAVEFORM
AT OSC AND OSC_OUT PINS
R
SET
= 56k
C
SET
= 22pF
MAX6954
4-Wire Interfaced, 2.7V to 5.5V LED Display
Driver with I/O Expander and Key Scan
_______________________________________________________________________________________
5
Typical Operating Characteristics (continued)
(V+ = 3.3V, LED forward voltage = 2.4V, typical application circuit, T
A
= +25°C, unless otherwise noted.)
DEAD CLOCK OSCILLATOR FREQUENCY
vs. SUPPLY VOLTAGE
MAX6954 toc04
SUPPLY VOLTAGE (V)
OSCILLATOR FREQUENCY (kHz)
5.0
4.5
4.0
3.5
3.0
85
95
105
110
80
2.5
5.5
R
SET
= 56k
OSC = GND
100
90
SEGMENT SOURCE CURRENT
vs. SUPPLY VOLTAGE
MAX6954 toc05
SUPPLY VOLTAGE (V)
CURRENT NORMALIZED TO 40mA
5.0
4.5
4.0
3.5
3.0
0.94
0.98
1.00
1.02
0.92
2.5
5.5
V
LED
= 1.8V
0.96
1V/div
200
µ
s/div
MAX6954 toc06
O0
O18
WAVEFORM AT PINS O0 AND O18,
MAXIMUM INTENSITY
0V
0V
GPIO SINK CURRENT
vs. TEMPERATURE
MAX6954 toc07
TEMPERATURE (
°
C)
GPIO SINK CURRENT (mA)
110
50
80
20
-10
5
10
15
20
25
30
35
40
45
0
-40
V
CC
= 3.3V
V
CC
= 2.5V
V
CC
= 5.5V
OUTPUT = LOW
V
PORT
= 0.6V
PORT INPUT PULLUP CURRENT
vs. TEMPERATURE
MAX6954 toc08
TEMPERATURE (
°
C)
KEY-SCAN SOURCE CURRENT (mA)
110
50
80
20
-10
0.05
0.10
0.15
0.20
0.25
0.30
0
-40
V
CC
= 3.3V
V
CC
= 2.5V
V
CC
= 5.5V
OUTPUT = HIGH
V
PORT
= 1.4V
400
µ
s/div
KEY_A: 1V/div
IRQ: 2V/div
MAX6954 toc09
KEY_A
0V
0V
IRQ
KEYSCAN OPERATION
(KEY_A AND IRQ)
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