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MAX6978APE+

P1-P3P4-P6P7-P9P10-P12P13-P13
General Description
The MAX6978 serial-interfaced LED driver provides
eight open-drain, constant-current sinking LED driver
outputs rated at 5.5V. The MAX6978 operates from a 3V
to 5.5V supply. The MAX6978 supply and the LEDs’
supply can power up in any order. The constant-current
outputs are programmed together to up to 55mA using
a single external resistor. The MAX6978 operates with a
25Mb, industry-standard, 4-wire serial interface.
The MAX6978 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 MAX6978 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 MAX6978.
The MAX6978 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 the output
DOUT eight clock cycles later to allow cascading of
multiple MAX6978s. 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 MAX6978 is one of a family of 12 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
♦ 25Mb Industry-Standard 4-Wire Serial Interface at 5V
♦ 3V to 5.5V Logic Supply
♦ 8 Constant-Current LED Outputs Rated at 5.5V
♦ Up to 55mA Continuous Current per Output
♦ Output Current Programmed by Single Resistor
♦ 3% Current Matching Between Outputs
♦ 6% Current Matching Between ICs
♦ Watchdog Clears Display if Interface Fails
♦ Reports Open-Circuit LED Faults
♦ -40°C to +125°C Temperature Range
MAX6978
8-Port, 5.5V Constant-Current LED Driver with
LED Fault Detection and Watchdog
________________________________________________________________ Maxim Integrated Products 1
16
15
14
13
12
11
10
9
1
2
3
4
5
6
7
8
GND
V+
SET
DOUT
OE
OUT7
OUT6
OUT5
OUT4
TOP VIEW
MAX6978AUE
MAX6978APE
MAX6978AAE
TSSOP/PDIP/SSOP
DIN
CLK
OUT1
LE
OUT0
OUT2
OUT3
Pin Configuration
Ordering Information
19-3578; Rev 2; 7/05
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 Application Circuit and Selector Guide appear at
end of data sheet.
Applications
Variable Message Signs
Marquee Displays
Point-of-Order Signs
Traffic Signs
Gaming Features
Architectural Lighting
PART TEMP RANGE PIN-PACKAGE
MAX6978AUE
-40°C to +125°C
16 TSSOP-EP*
MAX6978APE
-40°C to +125°C
16 PDIP
MAX6978AAE
-40°C to +125°C
16 SSOP
*EP = Exposed pad.
MAX6978
8-Port, 5.5V Constant-Current LED Driver with
LED Fault Detection and Watchdog
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
OUT_ .......................................................................-0.3V to +6V
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 SSOP (derate 7.1mW/°C above +70°C) ............571mW
16-Pin PDIP (derate 10.5mW/°C above +70°C)............842mW
16-Pin TSSOP (derate 21.3mW/°C over
T
A
= +70°C) ..............................................................1702mW
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
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
SYMBOL
CONDITIONS
MIN TYP MAX
UNITS
Operating Supply Voltage V+ 3.0 5.5 V
Output Voltage V
OUT
5.5 V
Standby Current
(Interface Idle, All Output Ports
High Impedance, R
SET
= 360Ω)
I
+
All logic inputs at V+ or GND, DOUT
unloaded
4.5 5.6 mA
Standby Current
(Interface Running, All Output
Ports High Impedance,
R
SET
= 360Ω)
I
+
f
CLK
= 5MHz, OE = V+, DIN and LE = V+
or GND, DOUT unloaded
4.7 6 mA
Supply Current
(Interface Idle, All Output Ports
Active Low, R
SET
= 360Ω)
I
+
All logic inputs at V+ or GND,
DOUT unloaded
10 25 mA
Input High Voltage
DIN, CLK, LE, OE
V
IH
0.7 V+
V
Input Low Voltage
DIN, CLK, LE, OE
V
IL
0.3 V+
V
Hysteresis Voltage
DIN, CLK, LE, OE
∆V
I
0.8 V
Input Leakage Current
DIN, CLK, LE, OE
I
IH
, I
IL
-1 +1 µA
Output-High Voltage DOUT V
OH
I
SOURCE
= 4mA
V +
- 0.5V
V
Output Low Voltage V
OL
I
SINK
= 4mA 0.5 V
Output Current
OUT_
I
OUT
V+ = 3V to 5.5V, V
OUT
= 0.8V to 2.5V,
R
SET
= 360Ω
42 50 56 mA
Output Leakage Current OUT_ I
LEAK
OE = V+, V
OUT
= V+ 1 µA
Watchdog Timeout t
WD
1s
MAX6978
8-Port, 5.5V Constant-Current LED Driver with
LED Fault Detection and Watchdog
_______________________________________________________________________________________ 3
5V TIMING CHARACTERISTICS
(Typical Operating Circuit, V+ = 4.5V 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
40 ns
CLK Pulse-Width High t
CH
19 ns
CLK Pulse-Width Low t
CL
19 ns
DIN Setup Time t
DS
4ns
DIN Hold Time t
DH
8ns
DOUT Propagation Delay t
DO
12 32 ns
DOUT Rise and Fall Time
t
DR
, t
DF
C
DOUT
= 10pF, 20% to 80% 10 ns
LE Pulse-Width High t
LW
20 ns
LE Pulse Width (Fault-Detection
Data Valid)
t
LF
20 ns
LE Setup Time t
LS
10 ns
LE Rising to OUT_ Rising Delay t
LRR
(Note 2) 100 ns
LE Rising to OUT_ Falling Delay t
LRF
(Note 2) 280 ns
CLK Rising to OUT_ Rising Delay
t
CRR
(Note 2) 100 ns
CLK Rising to OUT_ Falling Delay
t
CRF
(Note 2) 310 ns
OE Rising to OUT_ Rising Delay
t
OEH
100 ns
OE Falling to OUT_ Falling Delay
t
OEL
300 ns
LED Output OUT_ Turn-On Fall
Time
t
f
80% to 20% 200 ns
LED Output OUT_ Turn-Off Rise
Time
t
r
20% to 80% 120 ns
P1-P3P4-P6P7-P9P10-P12P13-P13

MAX6978APE+

Mfr. #:
Buy MAX6978APE+
Manufacturer:
Maxim Integrated
Description:
LED Display Drivers 8-Port, 5.5V Constant-Current LED Driver with LED Fault Detection and Watchdog
Lifecycle:
New from this manufacturer.
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