19-3891; Rev 0; 10/05
8-Port, 36V Constant-Current LED Driver
with LED Fault Detection and Watchdog
General Description
The MAX6980 serial-interfaced LED driver provides
eight open-drain, constant-current-sinking LED driver
outputs rated at 36V. The device operates from a 3V to
5.5V supply. The MAX6980 supply and the LEDs’ sup-
ply can power up in any order. The constant-current
outputs are programmed together up to 55mA using a
single external resistor. The MAX6980 operates with a
25Mbps, industry-standard, 4-wire serial interface.
The MAX6980 includes circuitry that automatically
detects open-circuit LEDs. Fault status is loaded into
the serial-interface shift register when LE goes high and
is automatically shifted out on DOUT when the next
data transmission is shifted in.
The MAX6980 includes a fail-safe feature for safety-
related applications, which blanks the display if the ser-
ial interface fails. If the serial interface becomes
inactive for more than 1s, all driver output latches are
automatically cleared. This turns off all LEDs connected
to the outputs. The shift register data is not disturbed.
The outputs remain off until the driver output latches are
updated with data turning them on, so recovery is auto-
matic if the transmission failure is temporary. The
watchdog function requires no software change to the
application driving the MAX6980.
The MAX6980 uses the industry-standard shift-register-
plus-latch-type serial interface. The driver accepts data
shifted into an 8-bit shift register using data input DIN
and clock input CLK. Input data appears at output
DOUT eight clock cycles later to allow cascading of
multiple MAX6980s. The latch-enable input, LE, loads
the 8 bits of shift register data into an 8-bit output latch
to set which LEDs are on and which are off. The output-
enable input,
OE,
gates all eight outputs on and off,
and is fast enough to be used as a PWM input for LED
intensity control.
The MAX6980 is one of a family of 10 shift-register-plus-
latch-type LED drivers. The family includes 8-port and
16-port types, with 5.5V- or 36V-rated LED outputs, with
and without open-circuit LED detection and watchdog.
All versions operate from a 3V to 5.5V supply, and are
specified over the -40°C to +125°C temperature range.
Features
o
25Mbps Industry-Standard 4-Wire Serial Interface
at 5V
o
3V to 5.5V Logic Supply
o
Eight Constant-Current LED Outputs Rated at 36V
o
Up to 55mA Continuous Current per Output
o
Output Current Programmed by Single Resistor
o
3% Current Matching Between Outputs
o
6% Current Matching Between ICs
o
Watchdog Clears Display if Interface Fails
o
Reports Open-Circuit LED Faults
o
-40°C to +125°C Temperature Range
MAX6980
Ordering Information
PART
MAX6980AUE
MAX6980APE
MAX6980AAE
TEMP RANGE
-40°C to +125°C
-40°C to +125°C
-40°C to +125°C
PIN-
PACKAGE
16 TSSOP-EP*
16 PDIP
16 SSOP
PKG
CODE
U16E-3
A16-2
P16-1
*EP
= Exposed pad.
Typical Application Circuit and Selector Guide appear at
end of data sheet.
Pin Configuration
TOP VIEW
GND 1
DIN 2
CLK 3
LE 4
OUT0 5
OUT1 6
OUT2 7
OUT3 8
16 V+
15 SET
14 DOUT
13 OE
Applications
Variable Message Signs
Marquee Displays
Point-of-Order Signs
Traffic Signs
Gaming Features
Architectural Lighting
MAX6980
12 OUT7
11 OUT6
10 OUT5
9
OUT4
TSSOP/PDIP/SSOP
________________________________________________________________
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.
8-Port, 36V Constant-Current LED Driver
with LED Fault Detection and Watchdog
MAX6980
ABSOLUTE MAXIMUM RATINGS
(Voltage with respect to GND.)
V+ ............................................................................-0.3V to +6V
OUT_ .....................................................................-0.3V to +40V
DIN, CLK, LE,
OE,
SET ................................-0.3V to (V+ + 0.3V)
DOUT Current ..................................................................±10mA
OUT_ Sink Current .............................................................60mA
Total GND Current ...........................................................480mA
Continuous Power Dissipation (T
A
= +70°C)
16-Pin TSSOP-EP
(derate 21.3mW/°C above +70°C) .............................1702mW
16-Pin PDIP (derate 10.5mW/°C above +70°C)............842mW
16-Pin SSOP (derate 7.1mW/°C above +70°C) ............571mW
Operating Temperature Range .........................-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+ = 3V to 5.5V, T
A
= T
MIN
to T
MAX
, unless otherwise noted. Typical values are at V+ = 5V, T
A
= +25°C.)
(Note 1)
PARAMETER
Operating Supply Voltage
Output Voltage
Standby Current
(Interface Idle, All Output Ports
High Impedance, R
SET
= 360Ω)
Standby Current
(Interface Running, All Output
Ports High Impedance,
R
SET
= 360Ω)
Supply Current
(All Output Ports Active Low,
R
SET
= 360Ω)
Input High Voltage
DIN, CLK, LE,
OE
Input Low Voltage
DIN, CLK, LE,
OE
Hysteresis Voltage
DIN, CLK, LE,
OE
Input Leakage Current
DIN, CLK, LE,
OE
Pullup Resistor to V+,
OE
Pullup Resistor to GND, LE
Output High Voltage DOUT
Output Low Voltage
Output Current OUT_
Output Leakage Current OUT_
Watchdog Timeout
SYMBOL
V+
V
OUT
I+
All logic inputs at V+ or GND, DOUT
unloaded
3.6
CONDITIONS
MIN
3.0
TYP
MAX
5.5
36
5.6
UNITS
V
V
mA
I+
f
CLK
= 5MHz,
OE
= V+, DIN and LE = V+
or GND, DOUT unloaded
f
CLK
= 5MHz,
OE
= GND, LE and DIN = V+,
DOUT unloaded
0.7 x V+
3.8
6.0
mA
I+
17
30
mA
V
IH
V
IL
∆V
I
I
IH
, I
IL
R
OE
R
LE
V
OH
V
OL
I
OUT
I
LEAK
t
WD
I
SOURCE
= 4mA
I
SINK
= 4mA
V+ = 3.0V to 5.5V, V
OUT
= 0.8V to 2.5V,
R
SET
= 360Ω
OE
= V+
V
0.3 x V+
0.8
V
V
+1
3
3
10.00
10.00
0.5
µA
MΩ
MΩ
V
V
mA
µA
s
-1
0.17
0.17
V+ - 0.5V
36
50
60
1
0.1
1
2.5
2
_______________________________________________________________________________________
8-Port, 36V Constant-Current LED Driver
with LED Fault Detection and Watchdog
5V TIMING CHARACTERISTICS
(Typical
Operating Circuit,
V+ = 4.5V to 5.5V, T
A
= T
MIN
to T
MAX
, unless otherwise noted.) (Notes 1, 2)
PARAMETER
CLK Clock Period
CLK Pulse-Width High
CLK Pulse-Width Low
DIN Setup Time
DIN Hold Time
DOUT Propagation Delay
DOUT Rise and Fall Time
LE Pulse-Width High
LE Setup Time
LE Rising to OUT_ Rising Delay
LE Rising to OUT_ Falling Delay
CLK Rising to OUT_ Rising Delay
CLK Rising to OUT_ Falling Delay
OE
Rising to OUT_ Rising Delay
OE
Falling to OUT_ Falling Delay
LED Output OUT_ Turn-On Fall
Time
LED Output OUT_ Turn-Off Rise
Time
t
LW
t
LS
t
LRR
t
LRF
t
CRR
t
CRF
t
OEH
t
OEL
t
f
t
r
80% to 20% (Note 3)
20% to 80% (Note 3)
(Note 3)
(Note 3)
(Note 3)
(Note 3)
SYMBOL
t
CP
t
CH
t
CL
t
DS
t
DH
t
DO
C
DOUT
= 10pF
20
15
120
300
120
310
130
310
200
120
CONDITIONS
MIN
40
19
19
4
8
12
32
10
TYP
MAX
UNITS
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
MAX6980
_______________________________________________________________________________________
3
8-Port, 36V Constant-Current LED Driver
with LED Fault Detection and Watchdog
MAX6980
3.3V TIMING CHARACTERISTICS
(Typical
Operating Circuit,
V+ = 3V to 5.5V, T
A
= T
MIN
to T
MAX
, unless otherwise noted.) (Notes 1, 2)
PARAMETER
CLK Clock Period
CLK Pulse-Width High
CLK Pulse-Width Low
DIN Setup Time
DIN Hold Time
DOUT Propagation Delay
DOUT Rise and Fall Time
LE Pulse-Width High
LE Setup Time
LE Rising to OUT_ Rising Delay
LE Rising to OUT_ Falling Delay
CLK Rising to OUT_ Rising Delay
CLK Rising to OUT_ Falling Delay
OE
Rising to OUT_ Rising Delay
OE
Falling to OUT_ Falling Delay
LED Output OUT_ Turn-On Fall
Time
LED Output OUT_ Turn-Off Rise
Time
SYMBOL
t
CP
t
CH
t
CL
t
DS
t
DH
t
DO
t
DR
, t
DF
t
LW
t
LS
t
LRR
t
LRF
t
CRR
t
CRF
t
OEH
t
OEL
t
f
t
r
(Note 3)
(Note 3)
(Note 3)
(Note 3)
(Note 3)
(Note 3)
80% to 20%; pullup resistor = 65Ω (Note 3)
20% to 80%; pullup resistor = 65Ω (Note 3)
C
DOUT
= 10pF
20
15
140
310
140
340
140
330
250
150
CONDITIONS
MIN
52
24
24
4
8
12
48
12
TYP
MAX
UNITS
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
Note 1:
All parameters are tested at T
A
= +25°C. Specifications over temperature are guaranteed by design.
Note 2:
See Figure 3.
Note 3:
A 65Ω pullup resistor is connected from OUT_ to 5.5V.
Typical Operating Characteristics
(T
A
= +25°C, unless otherwise noted.)
SUPPLY CURRENT vs. SUPPLY VOLTAGE
(INTERFACE IDLE, ALL OUTPUTS OFF, R
SET
= 720Ω)
MAX6980 toc01
SUPPLY CURRENT vs. SUPPLY VOLTAGE
(INTERFACE IDLE, ALL OUTPUTS OFF, R
SET
= 360Ω)
MAX6980 toc02
SUPPLY CURRENT vs. SUPPLY VOLTAGE
(INTERFACE IDLE, ALL OUTPUTS ON, R
SET
= 720Ω)
T
A
= +125°C T
A
= +85°C
17
SUPPLY CURRENT (mA)
MAX6980 toc03
2.3
2.2
2.1
SUPPLY CURRENT (mA)
2.0
1.9
1.8
1.7
1.6
1.5
1.4
1.3
3.0
3.5
4.0
4.5
5.0
T
A
= -40°C
T
A
= +25°C
T
A
= +125°C
T
A
= +85°C
4.2
4.1
4.0
SUPPLY CURRENT (mA)
3.9
3.8
3.7
3.6
3.5
3.4
3.3
3.2
T
A
= +25°C
T
A
= -40°C
T
A
= +125°C
T
A
= +85°C
20
14
11
T
A
= -40°C
T
A
= +25°C
8
5
3.0
3.5
4.0
4.5
5.0
5.5
3.0
3.5
4.0
4.5
5.0
5.5
SUPPLY VOLTAGE (V)
SUPPLY VOLTAGE (V)
5.5
SUPPLY VOLTAGE (V)
4
_______________________________________________________________________________________
8-Port, 36V Constant-Current LED Driver
with LED Fault Detection and Watchdog
MAX6980
Typical Operating Characteristics (continued)
(T
A
= +25°C, unless otherwise noted.)
SUPPLY CURRENT vs. SUPPLY VOLTAGE
(INTERFACE IDLE, ALL OUTPUTS ON, R
SET
= 360Ω)
MAX6980 toc04
PORT OUTPUT CURRENT vs.
PORT OUTPUT VOLTAGE (R
SET
= 720Ω, V+ = 3.3V)
MAX6980 toc05
PORT OUTPUT CURRENT vs.
PORT OUTPUT VOLTAGE (R
SET
= 360Ω, V+ = 3.3V)
MAX6980 toc06
25
30
25
20
15
10
5
0
T
A
= -40°C
T
A
= +25°C
T
A
= +85°C
T
A
= +125°C
60
50
40
30
20
T
A
= +85°C
10
0
T
A
= +125°C
T
A
= -40°C
T
A
= +25°C
PORT OUTPUT CURRENT (mA)
19
16
13
T
A
= -40°C
10
3.0
3.5
4.0
T
A
= +25°C
4.5
5.0
5.5
0
0.5
1.0
1.5
2.0
2.5
3.0
PORT OUTPUT CURRENT (mA)
22
SUPPLY CURRENT (mA)
T
A
= +125°C T
A
= +85°C
0
0.5
1.0
1.5
2.0
2.5
3.0
SUPPLY VOLTAGE (V)
PORT OUTPUT VOLTAGE (V)
PORT OUTPUT VOLTAGE (V)
PORT OUTPUT CURRENT vs.
PORT OUTPUT VOLTAGE (R
SET
= 720Ω, V+ = 5.0V)
MAX6980 toc07
PORT OUTPUT CURRENT vs.
PORT OUTPUT VOLTAGE (R
SET
= 360Ω, V+ = 5.0V)
MAX6980 toc08
PORT OUTPUT CURRENT vs. SUPPLY VOLTAGE
(R
SET
= 720Ω, V
OUT
= 2V)
MAX6980 toc09
30
25
20
15
T
A
= +85°C
10
5
0
0
0.5
1.0
1.5
2.0
2.5
T
A
= +125°C
T
A
= -40°C
T
A
= +25°C
60
50
40
30
20
10
0
T
A
= -40°C
T
A
= +25°C
T
A
= +85°C
T
A
= +125°C
26.0
PORT OUTPUT CURRENT (mA)
PORT OUTPUT CURRENT (mA)
PORT OUTPUT CURRENT (mA)
25.5
T
A
= +125°C
25.0
T
A
= +85°C
24.5
T
A
= +25°C
T
A
= -40°C
24.0
0
0.5
1.0
1.5
2.0
2.5
3.0
3.0
3.5
4.0
4.5
5.0
5.5
PORT OUTPUT VOLTAGE (V)
SUPPLY VOLTAGE (V)
3.0
PORT OUTPUT VOLTAGE (V)
PORT OUTPUT CURRENT vs. SUPPLY VOLTAGE
(R
SET
= 360Ω, V
OUT
= 2V)
MAX6980 toc10
PORT OUTPUT CURRENT
vs. R
SET
RESISTANCE (V+ = 5.0V)
MAX6980 toc11
52
50
PORT OUTPUT CURRENT (mA)
51
T
A
= +125°C
50
T
A
= +85°C
PORT OUTPUT CURRENT (mA)
40
30
20
49
T
A
= +25°C
T
A
= -40°C
10
48
3.0
3.5
4.0
4.5
5.0
5.5
SUPPLY VOLTAGE (V)
0
0 1000
2000
3000
4000
5000
6000
7000
8000
9000
10,000
R
SET
RESISTANCE (Ω)
_______________________________________________________________________________________
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