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dc1552af
DEMO MANUAL DC1552A
DESCRIPTION
LT8500/LT3595A
48-Channel LED Driver with PWM
Generator and Serial Interface
This demonstration circuit showcases the LT8500, a
48-channel LED driver with a PWM generator and serial
interface. It operates from a 30V to 45V input power sup-
ply and drives 48 channels of LED strings at 30mA and
up to 32V each, although it can be adjusted for 50mA per
string. The LT8500 drives 48 PWM channels that are tied
directly to the PWM inputs of the three separate LT3595As.
The LT3595A is a 16-channel step-down LED driver that
can operate up to 45V input and up to 50mA per channel.
The input to the LT8500 is a serial interface that can run
up to 50MHz. The DC1552A has both an input and output
connector and can be cascaded in a chain of two or more
while being driven from a single serial interface. DC1552A
is assembled as a solo 48-channel LED driver, but with a
few simple modifications, it can be turned into one of the
elements in a cascaded chain of DC1552As.
The LT8500 is a pulse width modulation (PWM) genera-
tor with 48 independent channels. Each channel has an
individually adjustable 12-bit (4096-step) PWM register
and a 6-bit (64-step) ±50% correction register. All controls
are programmable via a simple serial data interface. Three
banks of 16-channels each can be configured such that
they operate 120 degrees out-of-phase with each other.
The LT8500 features two diagnostic information flags:
synchronization error and open LED. The flags are sent,
with additional state information, on the serial data interface
L
, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear
Technology Corporation. All other trademarks are the property of their respective owners.
during status read back. The 50MHz cascadable serial data
interface includes buffering and skew-balancing, making
the chip suitable for PWM intensive applications such as
large screen LCD dynamic backlighting and mono-, multi-
and full-color LED displays. The LT8500 is also ideally
suited to control three LT3595A LED drivers.
The LT3990 is a small 350mA step-down regulator with
integrated power switch and diodes that operates up
to 62V
IN
. Its 3mm
×
3mm 16 pin MSOP and integrated
components are a good housekeeping power supply to be
used for 3.3V power on the LT8500 and it’s surrounding
logic buffers.
The LT8500, LT3595A, and LT3990 data sheets give complete
descriptions of the parts, operation and applications infor-
mation. The data sheets must be read in conjunction with
this demo manual for DC1552A. The LT8500 and LT3595A
are both assembled in 56 pin (5mm
×
9mm
×
0.75mm)
QFN packages. Proper board layout is essential for both
maximum thermal performance and signal noise immunity.
See the layout considerations sections in the data sheets
for more details.
Design files for this circuit board are available at
http://www.linear.com/demo
