Linear Technology DC2110A Demo Manual

Description
Demonstration circuit 2110A is a monolithic step-down
converter featuring LT 8631. The demo board is designed
®
for 5V output from a 6.5V to 100V input at 400kHz switch-
ing frequency. The wide input range makes it suitable for
regulating power from a wide variety of sources, includ-
ing automotive, industrial systems and telecom supplies.
The LT8631 is a compact, high efficiency synchronous
monolithic step-down switching regulator. The power
switch, compensation and other necessary circuits are
inside of the LT8631 to minimize external components
and simplify design.
The LT8631 switching frequency can be programmed
either via oscillator resistor or external clock over a
100kHz to 1MHz range. The SYNC pin on the demo board
is grounded (JP1 at Burst Mode
low ripple Burst Mode operation. To synchronize to an
external clock, move JP1 to SYNC and apply the external
clock to the SYNC turret. If the pulse-skipping operation
is required, move JP1 to fixed frequency position. Figure 1
shows the efficiency of the circuit at 12V input at the Burst
Mode selection.
The demo board has an EMI filter installed. The EMI per-
formance of the board (with EMI filter) is shown in Figure
2. The red line in Figure 2 is CISPR25 Class 5 peak limit.
The figure shows that the circuit passes the test with a
wide margin. To achieve EMI/EMC performance as shown
performance summary
SYMBOL PARAMETER
V Input Supply Range
IN
V Output Voltage
OUT
f Switching Frequency
SW
I Max Output Current
OUT
E Efficiency at DC
FE
Micropower Step-Down Regulator
position) by default for
®
Specifications are at T
CONDITIONS
R = 25.5kΩ
T
V = 12V
IN
V = 12V, I
IN
V = 12V, I
IN
DEMO MANUAL DC2110A
100V, 1A Synchronous
95
90
85
80
75
70
65
60
55
50
0 0.1 0.2 0.3
Figure 1. LT8631 Efficiency vs Load Current
in Figure 2, the input EMI filter is required and the input
voltage should be applied at V
The LT8631 data sheet gives a complete description of
the part, operation and application information. The data
sheet must be read in conjunction with this demo manual
for demo circuit 2110A. The LT8631 is assembled in a
20-lead TSSOP packages. Proper board layout is essential
for maximum thermal and electrical performance. See the
data sheet sections for details.
Design files for this circuit board are available at
http://www.linear.com/demo/DC2110A
L, LT, LTC, LTM, Linear Technology, Burst Mode and the Linear logo are registered trademarks
of Linear Technology Corporation. All other trademarks are the property of their respective
owners.
= 25°C
A
= 1A
OUT
= 0.4A
OUT
LT8631
f = 400kHz
SW
V = 12V
IN
V = 5V
OUT
0.4 0.5 0.6 0.7 0.8 0.9 1
LOAD CURRENT (A)
DC2110a F01
turret pin, not V
EMI
MIN TYP MAX
6.5 100
4.88 5.04 5.2
370 400 430
1
82.6
89.5
.
IN
UNITS
V
V
kHz
A
%
%
dc2110af
1