MAX6974ATL+ Maxim Integrated Products, MAX6974ATL+ Datasheet - Page 10

• 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

(PWM) value. Each output current driver in the R, G,
and B ports has a unique 12-bit (MAX6974) or 14-bit
(MAX6975) PWM control value providing fine resolution
adjustment of average current output. Each bit time of
the PWM corresponds to one period of CLKI (T
The PWM setting determines the amount of time, out of
the total period, that the output is on. The subframes
have PWM off-zones at the start (t
(t
frame period and PWM off zones are shown in Table 2
for each device.
The MAX6974 subdivides each subframe by 4096
(12-bit) PWM steps and has 16 cycle off zones, leaving
an active PWM region of 4064 PWM steps ranging from
24-Output PWM LED Drivers
for Message Boards
Table 2. Subframe and PWM Timing
Figure 3. Multiplexed and Nonmultiplexed Output Driver Phasing and Example PWM Values
10
EPWM
MAX6974
MAX6975
PART
______________________________________________________________________________________
) of the PWM period (see Figure 3). The sub-
SUBFRAME
(T
16,384
4096
CLKI
)
G0, G2, G4, G6
G1, G3, G5, G7
G0, G2, G4, G6
G1, G3, G5, G7
R0, R2, R4, R6
B0, B2, B4, B6
R1, R3, R5, R7
B1, B3, B5, B7
R0, R2, R4, R6
B0, B2, B4, B6
R1, R3, R5, R7
B1, B3, B5, B7
(T
t
MUX0
MUX1
SPWM
CLKI
16
32
)
MULTIPLEXED
NONMULTIPLEXED
(T
t
t
t
EPWM
SPWM
SPWM
SPWM
CLKI
16
32
50%
SUBFRAME (n), MUX0
ON/OFF PHASING
ON/OFF PHASING
OFF/ON PHASING
OFF/ON PHASING
)
SUBFRAME (n)
75%
) and end
(T
t
EMUX
75%
CLKI
CLKI
16
32
t
)
t
EPWM
).
SPWM
25%
16 to 4079. The MAX6975 subdivides each subframe
by 16,384 (14-bit) PWM steps and has 32 cycle off
zones, leaving an active PWM region of 16,320 PWM
steps ranging from 32 to 16,351. The PWM phase for
outputs R0, R2, R4, R6, G0, G2, G4, G6, B0, B2, B4,
and B6 use phasing with the outputs on first and off
second. Inverse phasing is used for outputs R1, R3,
R5, R7, G1, G3, G5, G7, B1, B3, B5, and B7 as shown
in Figure 3 to balance the timing of loads on the LED
anode power supply.
In multiplexed operation, the subframes are shared
between MUX0 and MUX1 active times, effectively
reducing the number of subframes by 2.
The three levels of intensity control are shown in Figure 2
for one LED output driver in a MAX6974 in nonmulti-
plexed mode. As an example, the CALDAC is set to
169
The global-intensity PDM value is set to 96
an even distribution of ON subframes out of the 128
DEC,
t
EMUX
t
SPWM
setting the port output current level to 21.8mA.
SUBFRAME (n), MUX1
SUBFRAME (n + 1)
75%
75%
100%
75%
LED-Intensity Control Example
t
t
EMUX
EPWM
DEC
, producing