DESCRIPTION
DEMO MANUAL DC2049A
LT3999EMSE
Low Noise Isolated
Power Supply
The DC2049A demonstrates how a power supply regulates
®
two output voltage by using the LT
3999 and low dropout
(LDO) regulators.
The LT3999 is a monolithic push-pull DC/DC driver which
features wide input range and small external passive
components.
The LT3999 has duty circle control for ΔV
compensa-
IN
tion, which allows for a wide input voltage range and low
LDO losses.
DC2049A employs a push-pull topology that inherently
The
provides a low-noise solution. The design is well suited
to noise sensitive systems such as medical instruments,
industrial sensing and control, data conversion and wide
band communications. The post regulator LDOs reduce
output noise further. For more details about the LDOs,
please check the LT3065 and LT3090 data sheets.
PERFORMANCE SUMMARY
Specifications are at TA = 25°C
The DC2049A produces an isolated 12V
and –12V
OUT
OUT
at
up to 200mA each from a 10V ~ 15.5V input voltage range.
This board can be modified, by changing the transformer
(and duty cycle), to produce other output voltages.
The DC2049A features a small transformer, small inductors
and capacitors that work at a 1MHz switching frequency.
The LT3999 data sheet gives a complete description of the
part, operation and applications information. The data sheet
must be read in conjunction with this demo manual. The
LT3999EMSE is assembled in a 10-lead plastic MSE pack
-
age with a thermally enhanced ground pad. Proper board
is essential for maximum thermal performance. See
layout
the data sheet section Layout Consideration Check List.
Design files for this circuit board are available at
http://www.linear.com/demo/DC2049A
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.
PARAMETERS MIN TYP MAX UNITS
Input Voltage Range 10.0 15.5 VDC
Output Voltage 1 (VOUT1) 11.64 12.0 12.3 VDC
Output Voltage 2 (VOUT2) –12.36 –12.0 –11.64 VDC
Output Current 1 0 200 mA
Output Current 2 0 200 mA
Switching Frequency 1.0 MHz
Isolation 1000 VDC
dc2049af
1
DEMO MANUAL DC2049A
QUICK START PROCEDURE
DC2049A is easy to set up to evaluate the performance of
the LT3999EMSE. Refer to Figure 1 for proper measurement equipment setup and follow the procedure below:
Connect Load 1 (positive) between the VOUT1 and GND
1.
terminals and another Load 2 (negative) between the
VOUT2 and GND terminals.
2. With power off, connect the input power supply to the
+VIN and –VIN terminals.
3. Turn the input power supply on and make sure the
voltage is between 10V and 15.5V.
4. To measure the output noise, connect one end of a BNC
connector J1. Connect the other end of the BNC cable
to an oscilloscope with a 50Ω input impedance. Refer
to Application Note 70 for more precise techniques for
measuring the output noise.
*J1 is the BNC connector to coaxial
cable for noise measurement, please
refer to AN70 Appendix B for details.
Figure 1. Test Procedure Setup Drawing for DC2049A
2
dc2049af
Loading...