DESCRIPTION
DEMO MANUAL DC2641A
LTC7801EUFD
High Input Voltage
Synchronous Buck Converter
Demonstration circuit 2641A is a single output synchronous buck converter featuring the LTC7801EUFD in the
24-lead QFN package. The input voltage range is from
16V to 100V and the output is 12V/10A. The DC2641A is
configured with a sense resistor for overcurrent protec
tion. Inductor DCR current sensing is optional.
The board has a lot of features including an optional
onboard NMOS LDO for DRVCC, a switch-mode power
clamp or default Burst Mode® operation, a PGOOD output
voltage monitor and PLLIN for PolyPhase® operation.
The LTC7801 data sheet gives a complete description
of the part, operation and application information and
must be read in conjunction with this demo manual for
DC2641A.
Design files for this circuit board are available at
http://www.linear.com/demo/DC2641A
supply for EXTVCC, jumper selectable 100% duty cycle
operation in dropout, a mode selector pin that allows
the converter to run in CCM, pulse-skip, adjustable burst
PERFORMANCE SUMMARY
PARAMETER CONDITIONS VALUE
Input Voltage Range 16V ~ 100V
Output Voltage V
Maximum Output Current I
Default Operating Frequency (Typical) 150kHz
External Clock Sync. Frequency Range 75kHz – 850kHz
Typical Full Load Efficiency (See Figure 4) V
OUT
OUT,MAX
VIN = 16~100V, I
VIN = 16~100V 10A
= 48V, V
IN
Specifications are at TA = 25°C
= 0~10A, JP4: FCM 12V ± 2% (11.76V ~ 12.24V)
OUT
= 12V, I
OUT
OUT
L, LT, LTC, LTM, Linear Technology, Burst Mode, PolyPhase and the Linear logo are registered
trademarks of Analog Devices, Inc. All other trademarks are the property of their respective
owners.
= 10A, fSW = 150 kHz 95.3%
dc2641af
1
DEMO MANUAL DC2641A
QUICK START PROCEDURE
Demonstration circuit DC2641A is easy to set up to
evaluate the performance of the LTC7801EUFD. Refer to
Figure 1 for proper measurement equipment setup and
follow the procedure below:
NOTE: When measuring the input or output voltage ripple,
care must be taken to avoid a long ground lead on the
oscilloscope probe. Measure the input or output voltage
ripple by touching the probe tip directly across the VIN
or V
capacitor. See Figure 2 for proper scope probe technique.
1. Place jumpers in the following positions:
JP1 ON
JP4 FCM
JP5 ON
JP8 OFF
and GND terminals or directly across relevant
OUT
2. With power off, connect the input power supply to V
and GND.
3. Turn on the power at the input.
NOTE: Make sure that the input voltage is higher than
16V and does not exceed 100V.
4. Check the output voltage. The output voltage should
be between 11.76V and 12.24V.
Once the proper output voltage is established, adjust
the load within the operating range and observe the
output voltage regulation, output voltage ripple, efficiency and other parameters.
NOTE: If there is no output, temporarily disconnect the
load to make sure that the load is not set too high.
IN
2
dc2641af
QUICK START PROCEDURE
DEMO MANUAL DC2641A
I
IN
DC2641A F01
+
I
OUT
+
–
–
LOAD
Figure 1. Proper Measurement Equipment Setup
V
IN SUPPLY
+
–
+
–
Figure 2. Measuring Input or Output Ripple Across Terminals or Directly Across Ceramic Capacitor
+ –
C
OUT
V
OUT
GND
dc2641af
3
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