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Linear Technology DC2257A Demo Manual

Ltm8005 38vin, 38vout boost µmodule led driver with 40v switch
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DESCRIPTION
Demonstration circuit 2257A features the
38V
, 38V
boost μModule
IN
OUT
connect the output to protect against faults and provides
spread spectrum switching to simplify emissions compli-
ance. DC2257A is an LED driver with an input range for
normal operation from 6V to 27V. OVLO becomes active for
inputs above 29V and the maximum input voltage is 38V.
The LED current is 1.2A and the base switching frequency
is 350kHz. The efficiency is 92% when the input is 12V
with a 35V LED load. 35V is the maximum LED voltage.
The demo circuit requires application of an external voltage
to the PWM terminal for operation. The external voltage
can be a DC level or an appropriate PWM dimming signal.
Common frequencies for PWM dimming are 100Hz or
higher. Analog dimming is achieved using the CTRL inputs.
DC2257A allows adjustments to output voltage, output
current, input current, switching frequency, frequency
BOARD PHOTO
38V
LTM
8005
– a
®
LED driver that can dis-
®
DEMO MANUAL DC2257A
, 38V
Boost µModule
IN
OUT
LED Driver with 40V Switch
modulation rate including disable, feedback loop com-
pensation, EN/UVLO threshold, OVLO threshold, soft-
start period, and fault latch-off or hiccup. In most cases,
adjustment is made by modifying the appropriate resistor
or capacitor component(s).
DC2257A provides outputs for input and output current
monitoring and fault status for short and open LEDs.
The demo circuit is designed to be easily reconfigured
to buck mode, buck-boost mode and SEPIC topologies.
There are placeholders to mount optional LC input filter
components.
The LTM8005 data sheet must be read in conjunction with
this demo manual to properly use or modify DC2257A.
Design files for this circuit board are available at
http://www.linear.com/demo/DC2257A
L, LT, LTC, LTM, Linear Technology, the Linear logo and μModule are registered trademarks of
Linear Technology Corporation. All other trademarks are the property of their respective owners.
LTM8005
dc2257af
1

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Summary of Contents for Linear Technology DC2257A

  • Page 1 DC2257A allows adjustments to output voltage, output current, input current, switching frequency, frequency L, LT, LTC, LTM, Linear Technology, the Linear logo and μModule are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners.

  • Page 2: Quick Start Procedure

    RS1 = 0.008Ω 7.5A Peak QUICK START PROCEDURE To use DC2257A to evaluate the performance of the supply voltage does not exceed the forward voltage of LTM8005, refer to Figure 1 for the proper measurement the LED string. OVLO becomes active to inhibit switch- equipment setup and then follow the procedure below.
  • Page 3 DEMO MANUAL DC2257A QUICK START PROCEDURE Figure 1. Proper Measurement Equipment Setup dc2257af...
  • Page 4 DEMO MANUAL DC2257A QUICK START PROCEDURE Output Current Noise Spectrum –10 –20 DETECTOR = PEAK–HOLD –30 RBW = 9kHz CT–1 CURRENT TRANSFORMER –40 SPREAD SPECTRUM = OFF –50 FREQUENCY (MHz) DC2257A F02 Figure 2. Output Current Noise Spectrum with Spread Spectrum = OFF , V...

  • Page 5: Parts List

    DEMO MANUAL DC2257A PARTS LIST ITEM REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER Required Circuit Components CAP ., X7R, 1μF, 50V, 10%, 0805 MURATA, GRM21BR71H105KA12L C2, C3, C4, C7, C8 CAP ., X7R, 4.7μF, 50V, 10%, 1210 MURATA, GRM32ER71H475KA88L CAP ., X7R, 0.022μF, 16V, 10%, 0603 MURATA, GRM188R71C223KA01D CAP ., X7R, 0.1μF, 25V, 10%, 0603...
  • Page 6 DEMO MANUAL DC2257A SCHEMATIC DIAGRAM dc2257af...

  • Page 7: Schematic Diagram

    Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representa- tion that the interconnection of its circuits as described herein will not infringe on existing patent rights.
  • Page 8 Linear Technology Corporation (LTC) provides the enclosed product(s) under the following AS IS conditions: This demonstration board (DEMO BOARD) kit being sold or provided by Linear Technology is intended for use for ENGINEERING DEVELOPMENT OR EVALUATION PURPOSES ONLY and is not provided by LTC for commercial use. As such, the DEMO BOARD herein may not be complete in terms of required design-, marketing-, and/or manufacturing-related protective considerations, including but not limited to product safety measures typically found in finished commercial goods.