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Linear Technology DC2243A Demo Manual

Lt3668 40v step-down regulator with dual tracking ldos
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Description
Demonstration circuit 2243A is a triple power supply that
includes one 400mA step-down regulator and two 200mA
low dropout (LDO) linear tracking regulators featuring the
LT
3668. The demo circuit is designed for one 6V and dual
®
5V outputs from a 7V to 40V input. Two LDO outputs are
configured as post-regulators of the switching regulator
output. The total current capability of three output chan-
nels is up to 400mA, while the two LDO regulators are
capable of 200mA each.
The switching frequency of the step-down regulator can be
programmed via an oscillator resistor (R8) over a 250kHz
to 2.2 MHz range. The default setting is 600kHz.
The LT3668 internal boost diode and loop compensation
reduce the components count and solution size. The cur-
rent mode control scheme creates fast transient response
performance summary
SYMBOL
PARAMETER
V
Input Supply Range of V
IN1
f
Switching Frequency
SW
V
Output Voltage 1
OUT1
V
Output Voltage 2
OUT2
V
Output Voltage 3
OUT3
I
+ I
+ I
Maximum Total Output Current
OUT1
OUT2
OUT3
I
, I
Maximum LDO Output Current
OUT2
OUT3
DEMO MANUAL DC2243A
40V Step-Down Regulator
and good loop stability. The switching regulator has cycle-
by-cycle current limit and diode current sense, providing
protection against shorted outputs.
JP1 can be used to set the whole LT3668 in shutdown
mode. JP3 and JP4 enable and disable the outputs of the
dual 5V tracking LDOs respectively.
The LT3668 data sheet gives a complete description of
the part, operation and application information. The data
sheet must be read in conjunction with this quick start
guide for demo circuit 2243A. Proper board layout is es-
sential for both proper operation and maximum thermal
performance. See the data sheet section "PCB Layout".
Design files for this circuit board are available at
http://www.linear.com/demo/DC2243A
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.
Specifications are at T
CONDITIONS
IN1
V
= 12V, V
= 6V/I
IN1
OUT1
V
= 5V/I
= 0
OUT2
OUT2
V
= 5V/I
= 0
OUT3
OUT3
V
= 12V, V
= 6V/I
IN1
OUT1
V
= 5V/I
= 0
OUT2
OUT2
V
= 5V/I
= 0
OUT3
OUT3
V
= 12V, V
= 6V/I
IN1
OUT1
V
= 5V/I
= 0 ~ 190mA
OUT2
OUT2
V
= 5V/I
= 0
OUT3
OUT3
V
= 12V, V
= 6V/I
IN1
OUT1
V
= 5V/I
= 0
OUT2
OUT2
V
= 5V/I
= 0 ~ 190mA
OUT3
OUT3
with Dual Tracking LDOs
= 25°C
A
MIN
7
= 400mA
510
OUT1
= 0 ~ 400mA
5.88
OUT1
= 0
4.9
OUT1
= 0
4.9
OUT1
400
190
LT3668
TYP
MAX
UNITS
40
V
690
kHz
6.12
V
5.1
V
5.1
V
mA
200
mA
dc2243af
1

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Summary of Contents for Linear Technology DC2243A

  • Page 1 The cur- http://www.linear.com/demo/DC2243A rent mode control scheme creates fast transient response 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. performance summary Specifications are at T = 25°C...

  • Page 2: Quick Start Procedure

    DEMO MANUAL DC2243A Description = 6V OUT1 = 600kHz = 0A = 12V OUT2 = 0A = 24V OUT3 LOAD CURRENT (A) OUT1 DC2234 F01 Figure 1. V Typical Efficiency vs. Load Current OUT1 Quick start proceDure Demonstration circuit 2243A is easy to set up to evalu- 4.
  • Page 3 DEMO MANUAL DC2243A Quick start proceDure – – LOAD OUT2 – – – OUT1 OUT3 – – – – – – LOAD LOAD Figure 2. Proper Measurement Equipment Setup Figure 3. Measuring Input or Output Ripple dc2243af...

  • Page 4: Parts List

    DEMO MANUAL DC2243A parts List ITEM REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER Required Circuit Components CAP ., X7R 2.2µF 100V 10% 1206 AVX, 12061C225KAT2A CAP ., X7R 0.22µF 25V 10% 0603 AVX, 06033C224KAT2A CAP ., NPO 22pF 25V 5% 0603 AVX, 06033A220JAT2A CAP ., X5R 22µF 25V 20% 1210...

  • Page 5: 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 6 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.
  • Page 7 Mouser Electronics Authorized Distributor Click to View Pricing, Inventory, Delivery & Lifecycle Information: Analog Devices Inc. DC2243A...