DEMO MANUAL DC2056A
LTC3637EMSE
High Efficiency 76V, 1A
Step-Down Converter
DESCRIPTION
Demonstration circuit 2056A is a 76V input, 1A output
DC/DC power supply featuring the
LTC
®
3637.
The IC oper-
ates in a high efficiency Burst Mode
®
operation and includes
an internal high side power MOSFET. The board will accept
an input voltage between 4V and 76V, and provide jumper
selected output voltages of 1.8V, 3.3V, 5V and an option
for additional voltages. The IC includes internal soft-start
and a provision for increasing soft-start time.
Included on the board is an ON/OFF jumper that can also
be configured as a precision undervoltage lockout.
Output voltage between 800mV and V
IN
can be pro-
grammed using optional resistors. (Higher voltage rating
output capacitors may be required.)
The LTC3637 data sheet gives a complete description of the
IC operation and application information. The data sheet
must be read in conjunction with this quick start guide.
Design files for this circuit board are available at
http://www.linear.com/demo
L,
LT, LTC, LTM, Linear Technology, the Linear logo and Burst Mode are registered trademarks
of Linear Technology Corporation. All other trademarks are the property of their respective
owners.
PERFORMANCE SUMMARY
PARAMETER
Input Voltage Range
1.8V Output Voltage
3.3V Output Voltage
5V Output Voltage
Maximum Output Current, I
OUT
Typical Efficiency
Typical Output Ripple
Specifications are at T
A
= 25°C
VALUE
4V to 76V
1.8V ±2%
3.3V ±2%
5V ±2%
1A
85.5%
109mV
P-P
CONDITION
V
IN
= 12V, I
OUT
= 0A to 1A
V
IN
= 12V, I
OUT
= 0A to 1A
V
IN
= 12V, I
OUT
= 0A to 1A
V
IN
= 4V to 76V, V
OUT
= 1.8V, 3.3V or 5V
V
IN
= 12V, V
OUT
= 5V, I
OUT
= 1A
V
IN
= 76V, V
OUT
= 5V, I
OUT
= 1A (20MHz BW)
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DEMO MANUAL DC2056A
QUICK START PROCEDURE
Demonstration circuit 2056A is easy to set up to evaluate
the performance of the LTC3637. Refer to Figure 1 for
the proper measurement equipment setup and follow the
procedure below:
1. With power off, connect the input power supply (set
for 0V) to VIN and GND (input return).
2. Select 5V output using jumper JP1 (B position) and
JP2 (A position). Select ON position for JP3.
3. Connect the 5V output load between VOUT and GND
(Initial load: no load).
4. Connect the DVMs to the input and outputs.
5. Turn on the input power supply and slowly increase to
12V. Check for the proper output voltages. (5V output
should be within 5V ±2%.)
6. Once the proper output voltages are established, ad-
just the loads within the operating range and observe
the output voltage regulation, ripple voltage and other
parameters.
7. With power off, move jumpers JP1 and JP2 to the other
fixed voltage settings (1.8V or 3.3V). Repeat steps 5
and 6. Check for the proper out-put voltage and other
parameters.
Note: When measuring the output or input voltage ripple,
do not use the long ground lead on the oscilloscope probe.
See Figure 2 for the proper scope probe technique. Short,
stiff leads need to be soldered to the (+) and (–) terminals
of an output capacitor. The probe’s ground ring needs to
touch the (–) lead and the probe tip needs to touch the
(+) lead.
Additional Notes
1. CAUTION: Be careful when testing with high voltage.
High voltage can result in an electric shock if care
is not taken.
2. For 5V output, V
IN
input voltage should be at least 5V
or higher.
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