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MAX6978APE+

P1-P3P4-P6P7-P9P10-P12P13-P13
MAX6978
8-Port, 5.5V Constant-Current LED Driver with
LED Fault Detection and Watchdog
4 _______________________________________________________________________________________
2.5
2.6
2.7
2.8
2.9
3.0
3.1
3.2
3.3
3.0 3.5 4.0 4.5 5.0 5.5
SUPPLY CURRENT vs. SUPPLY VOLTAGE
(INTERFACE IDLE, ALL OUTPUTS
OFF, R
SET
= 720Ω)
MAX6978 toc01
SUPPLY VOLTAGE (V)
SUPPLY CURRENT (mA)
T
A
= +125°C
T
A
= +85°C
T
A
= +25°C
T
A
= -40°C
4.2
4.5
4.4
4.3
4.6
4.7
4.8
4.9
5.0
5.1
5.2
3.0 4.03.5 4.5 5.0 5.5
MAX6978 toc02
SUPPLY VOLTAGE (V)
SUPPLY CURRENT (mA)
T
A
= +125°C
T
A
= +85°C
SUPPLY CURRENT vs. SUPPLY VOLTAGE
(INTERFACE IDLE, ALL OUTPUTS
OFF, R
SET
= 360Ω)
T
A
= -40°C
T
A
= +25°C
Typical Operating Characteristics
(T
A
= +25°C, unless otherwise noted.)
3.3V TIMING CHARACTERISTICS
(Typical Operating Circuit, V+ = 3V 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
52 ns
CLK Pulse-Width High t
CH
24 ns
CLK Pulse-Width Low t
CL
24 ns
DIN Setup Time t
DS
4ns
DIN Hold Time t
DH
8ns
DOUT Propagation Delay t
DO
12 48 ns
DOUT Rise and Fall Time C
DOUT
= 10pF, 20% to 80% 10 ns
LE Pulse-Width High t
LW
20 ns
LE Pulse Width (Fault-Detection
Data Valid)
t
LW
20 ns
LE Setup Time t
LS
15 ns
LE Rising to OUT_ Rising Delay 100 ns
LE Rising to OUT_ Falling Delay 310 ns
CLK Rising to OUT_ Rising Delay
100 ns
CLK Rising to OUT_ Falling Delay
330 ns
OE Rising to OUT_ Rising Delay
t
OEH
100 ns
OE Falling to OUT_ Falling Delay
t
OEL
330 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
Note 1: All parameters tested at T
A
= +25°C. Specifications over temperature are guaranteed by design.
Note 2: See Figure 3.
MAX6978
8-Port, 5.5V Constant-Current LED Driver with
LED Fault Detection and Watchdog
_______________________________________________________________________________________ 5
0
3
9
6
12
15
3.0 4.03.5 4.5 5.0 5.5
MAX6978 toc04
SUPPLY VOLTAGE (V)
SUPPLY CURRENT (mA)
SUPPLY CURRENT vs. SUPPLY VOLTAGE
(INTERFACE IDLE, ALL OUTPUTS
ON, R
SET
= 360Ω)
T
A
= +125°C
T
A
= +85°C
T
A
= +25°C
T
A
= -40°C
0
10
5
20
15
25
30
0 1.0 1.50.5 2.0 2.5 3.0
PORT OUTPUT CURRENT vs. PORT OUTPUT
VOLTAGE (R
SET
= 720Ω, V+ = 3.3V)
MAX6978 toc05
PORT OUTPUT VOLTAGE (V)
PORT OUTPUT CURRENT (mA)
T
A
= +125°C
T
A
= +85°C
T
A
= +25°C
T
A
= -40°C
0
20
10
40
30
50
60
0 1.0 1.50.5 2.0 2.5 3.0
PORT OUTPUT CURRENT vs. PORT OUTPUT
VOLTAGE (R
SET
= 360Ω, V+ = 3.3V)
MAX6978 toc06
PORT OUTPUT VOLTAGE (V)
PORT OUTPUT CURRENT (mA)
T
A
= +125°C
T
A
= +85°C
T
A
= +25°C
T
A
= -40°C
0
10
5
20
15
25
30
0 1.0 1.50.5 2.0 2.5 3.0
PORT OUTPUT CURRENT vs. PORT OUTPUT
VOLTAGE (R
SET
= 720Ω, V+ = 5.0V)
MAX6978 toc07
PORT OUTPUT VOLTAGE (V)
PORT OUTPUT CURRENT (mA)
T
A
= +125°C
T
A
= +85°C
T
A
= +25°C
T
A
= -40°C
0
20
10
40
30
50
60
0 1.0 1.50.5 2.0 2.5 3.0
PORT OUTPUT CURRENT vs. PORT OUTPUT
VOLTAGE (R
SET
= 360Ω, V+ = 5.0V)
MAX6978 toc08
PORT OUTPUT VOLTAGE (V)
PORT OUTPUT CURRENT (mA)
T
A
= +125°C
T
A
= +85°C
T
A
= +25°C
T
A
= -40°C
26.0
25.5
25.0
24.5
24.0
3.0 4.0
3.5
4.5 5.0 5.5
PORT OUTPUT CURRENT vs. SUPPLY
VOLTAGE (R
SET
= 720Ω, V
OUT
= 2V)
MAX6978 toc09
SUPPLY VOLTAGE (V)
PORT OUTPUT CURRENT (mA)
T
A
= +125°C
T
A
= +85°C
T
A
= +25°C
T
A
= -40°C
52
51
50
49
48
3.0 4.0
3.5
4.5 5.0 5.5
PORT OUTPUT CURRENT vs. SUPPLY
VOLTAGE (R
SET
= 360Ω, V
OUT
= 2V)
MAX6978 toc10
SUPPLY VOLTAGE (V)
PORT OUTPUT CURRENT (mA)
T
A
= +125°C
T
A
= +85°C
T
A
= +25°C
T
A
= -40°C
0
10
30
20
40
50
0 40002000 6000 8000 10,000
PORT OUTPUT CURRENT
vs. R
SET
RESISTANCE (V+ = 5.0V)
MAX6978 toc11
R
SET
RESISTANCE (Ω)
PORT OUTPUT CURRENT (mA)
Typical Operating Characteristics (continued)
(T
A
= +25°C, unless otherwise noted.)
MAX6978
8-Port, 5.5V Constant-Current LED Driver with
LED Fault Detection and Watchdog
6 _______________________________________________________________________________________
Pin Description
PIN NAME FUNCTION
1 GND Ground
2 DIN Serial-Data Input. Data is loaded into the internal 8-bit shift register on CLK’s rising edge.
3 CLK Serial-Clock Input. Data is loaded into the internal 8-bit shift register on CLK’s rising edge.
4LE
Load-Enable Input. Data is loaded transparently from the internal shift register to the output latch while
LE is high. Data is latched into the output latch on LE's falling edge, and retained while LE is low.
5–12
OUT0–OUT7
LED Driver Outputs. OUT0–OUT7 are open-drain, constant-current sinking outputs rated to 5.5V.
13 OE
Output-Enable Input. High forces outputs OUT0–OUT7 to high impedance, without altering the contents
of the output latches. Low enables outputs OUT0–OUT7 to follow the state of the output latches.
14 DOUT Serial-Data Output. Data is clocked out of the 8-bit internal shift-register to DOUT on CLK’s rising edge.
15 SET LED Current Setting. Connect SET to GND through a resistor (R
SET
) to set the maximum LED current.
16 V+ Positive Supply Voltage. Bypass V+ to GND with a 0.1µF ceramic capacitor.
PAD
Exposed Pad*
Exposed pad on package underside. Connect to GND.
SERIAL-TO-PARALLEL SHIFT REGISTER
LATCHES
OUT0
OUT1
OUT2
DOUT
DIN
CLK
OUT7
CONSTANT-CURRENT SINKS
OUT5
OUT6
POWER-ON
RESET
V+
CURRENT
REFERENCE
V+
OE
GND
GND
LE
D0 D7
D0 D7
D0 D7
R
SET
MAX6978
FAULT DETECTION
WATCH
DOG
Figure 1. MAX6978 Block Diagram
*TSSOP package only.
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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