MAX6974ATL+ Maxim Integrated Products, MAX6974ATL+ Datasheet - Page 13

• Manufacturer Part Number: MAX6974ATL+
• Description: IC LED DRIVER LINEAR 40-TQFN
• Manufacturer: Maxim Integrated Products
• Type: Linear (Serial Interface)r

Specifications of MAX6974ATL+

• Topology: PWM
• Number Of Outputs: 24
• Internal Driver: Yes
• Type - Primary: General Purpose
• Type - Secondary: RGB
• Frequency: 33MHz
• Voltage - Supply: 3 V ~ 3.6 V
• Voltage - Output: 7V
• Mounting Type: Surface Mount
• Package / Case: 40-TQFN Exposed Pad
• Operating Temperature: -40°C ~ 125°C
• Current - Output / Channel: 30mA
• Internal Switch(s): Yes
• Low Level Output Current: 6 mA
• High Level Output Current: 30 mA
• Operating Supply Voltage: 3 V to 3.6 V
• Maximum Supply Current: 77 mA
• Maximum Power Dissipation: 2963 mW
• Maximum Operating Temperature: + 125 C
• Mounting Style: SMD/SMT
• Minimum Operating Temperature: - 40 C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Efficiency: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

MUX cycles as shown in Figure 3. The alternating MUX
cycles reduce the global-intensity resolution (the num-
ber of subframes) by half, which reduces the average
LED current by half.
A selectable watchdog timer monitors serial-interface
inputs CLKI, DIN, and LOADI. Enabling the watchdog
timer requires that CLKI, DIN, and LOADI toggle at
least once every 40ms. If any of these transitions fails to
occur, then the individual-intensity PWM data latches
clear. This condition effectively blanks the LEDs.
Update the individual-intensity PWM data registers to
turn the LEDs back on. The watchdog timeout does not
affect the calibration or global-intensity data, the clock
synchronization, or multiplexed/nonmultiplexed setting.
Use the watchdog functionality in safety-critical appli-
cations where a blanked display is safer than an incor-
rect display.
The MAX6974/MAX6975 feature two fault detection func-
tions: open-circuit LED outputs and overtemperature. An
Table 3. MAX6974/MAX6975 Timing Comparison
MAX6974
MAX6975
MAX6974
MAX6975
PART
PART
GLB4
BIT
MUX
X
X
0
1
BIT
0
1
0
1
______________________________________________________________________________________
MUX
BIT
Overtemperature Detection
OPERATION
Nonmultiplex
Nonmultiplex
0
1
0
1
0
1
Multiplex
Multiplex
OPERATION
Nonmultiplex
Nonmultiplex
Nonmultiplex
LED Open-Circuit and
Multiplex
Multiplex
Multiplex
12 bits
14 bits
PWM
RES.
GLOBAL
7 bits
3 bits
RES.
6 bits
5 bits
4 bits
2 bits
PDM
Watchdog
TOTAL CLOCKS PER
PWM SUBFRAME
24-Output PWM LED Drivers
SUBFRAMES
PER FRAME
16,384
4096
128
64
32
16
8
4
LED open circuit is detected on driver outputs by moni-
toring for output voltages below 200mV. When an open
circuit is detected, the MAX6974/MAX6975 increments
a fault counter included in the serial-interface protocol
that can be routed back to the host transmitter for diag-
nostics. Any number of open-circuit LEDS, multiplexed
or nonmultiplexed, can be detected, however, only one
counter increment occurs per device.
The MAX6974/MAX6975 detect die temperatures
above T
setting all PWM data to zero. The fault counter in the
serial-interface protocol is incremented by one count
for each cascaded device with an overtemperature
condition. The output drivers are turned back on when
the die temperature falls below T
fault counter value is distinguished between LED open-
circuit and overtemperature conditions by the serial-
interface command used at the time of detection (see
the Serial Interface section for more details).
The MAX6974/MAX6975 have four commands used to
load all operating mode and LED output current data.
CLOCKS
524,288
524,288
131,072
FRAME
for Message Boards
USEABLE CLOCKS PER
PER
DIE
PWM SUBFRAME
= +165°C and disable all output drivers by
16,320
4064
FREQUENCY (MHz)
FOR 50fps
CLOCK
26.2144
26.2144
6.5536
16,320 / 16,384 = 99.61%
4064 / 4096 = 99.22%
DIE
MAXIMUM PWM
FREQUENCY (MHz)
DUTY CYCLE
= +150°C. The
FOR 60fps
Commands
31.45728
31.45728
CLOCK
7.8643
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