MAX6974ATL+ Maxim Integrated Products, MAX6974ATL+ Datasheet - Page 9

• 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

The MAX6974/MAX6975 provide three levels of output
current control for LED drive: calibration DACs
(CALDACs), global-intensity control, and individual-
intensity control. The CALDACs set the port output cur-
rent levels, while the global-intensity and individual-
intensity controls modulate the output current on/off
times, providing a fine-resolution control of average
output currents (see Figure 2). The individual-intensity
control operates on each output independently to set
each individual LED intensity level. The global-intensity
controls modulate MAX6974/MAX6975 outputs simulta-
neously for a uniform brightness control without affect-
ing color. Using a fixed output current level that is
modulated only by on/off control leaves the LED color
unaffected while precisely controlling intensity. Finally,
all outputs can be turned on and off simultaneously by
setting or clearing configuration bit D3 (PWM-ON).
The 8-bit R, G, and B CALDACs set the output current
level for all eight outputs in the R, G, and B ports,
respectively (see the MAX6974 Block Diagram and
MAX6975 Block Diagram ). The R CALDAC, G
CALDAC, and B CALDAC range from a low of 6mA
(0x00) to a maximum of 30mA (0xFF), providing
94µA/step of current trimming. The CALDACs are
loaded by the serial interface using command 01 (see
Table 4). The B CALDAC data is loaded first, followed
by the G CALDAC data, and then the R CALDAC data
(see the Serial Interface section). The loaded data takes
effect immediately.
Figure 2. Relationship Among the CALDACs, Global-Intensity, and Individual-Intensity PWM Controls
(mA)
30
25
20
15
10
100%
5
50%
0%
0
_______________________________________________________________________________________
6mA MIN
CURRENT
CALDAC
LED-Intensity Control
CALDAC
= 169
30mA MAX
Calibration DACs
21.8mA
255
100%
50%
0%
0
GLOBAL-INTENSITY
24-Output PWM LED Drivers
PDM
GLOBAL
= 96
The MAX6974/MAX6975 adjust global and individual
intensities over a time period called a frame. One frame
requires 2
sponds to one video-frame time. Video frames generally
contain consecutive images displayed rapidly to yield
a motion picture display. Running the MAX6974/
MAX6975 at f
update rate of 60fps for full-motion video (see the
MAX6974 Video-Frame Timing and MAX6975 Video-
Frame Timing sections).
The MAX6974/MAX6975 further divide frames into sub-
frames to allow a unique combination of global- and
individual-intensity controls. The number of subframes
is equal to the number of global-intensity control steps.
The MAX6974 uses 128 subframes per frame in
nonmultiplexed mode (corresponding to 7-bit global-
intensity PDM control) and 64 subframes in multiplexed
mode (corresponding to 6-bit global-intensity PDM
control). The MAX6975 features 5-, 4-, 3-, and 2-bit
global-intensity control to yield 32, 16, 8, and 4 sub-
frames per frame, respectively.
The MAX6974/MAX6975 control global intensity by
driving subframes on and off. When a subframe is on, it
allows the individual PWM intensity control to be driven
on the outputs. Subframes that are off do not have any
PWM modulation on the outputs.
The MAX6974/MAX6975 further modulate the time that
each subframe is ON by a pulse-width modulation
127
100%
50%
0%
0
for Message Boards
INDIVIDUAL-INTENSITY
19
Rn, Gn, OR Bn PWM
(524,288) periods of CLKI and corre-
CLKI
PWM
= 2560
= 31.5MHz allows a video-frame
Global-Intensity Control
Individual PWM Control
4095
Rn, Gn, OR Bn I
AVE
= 10.22mA
9