1
dc2317af
DEMO MANUAL
DC2317A
DESCRIPTION
LTC7103
105V, 2.3A Low EMI Synchronous
Step-Down Regulator
Demonstration circuit 2317A is a 100V monolithic DC/
DC step-down regulator featuring the
. The
demo board is designed for a 5V/2.3A output from a 5V
to 100V input at 400kHz switching frequency. The wide
input range makes it suitable for automotive, industrial,
medical instrument, and telecom applications. This buck
regulator has a peak efficiency of 93.5% at 12V
IN
, 88.3%
at 48V
IN
and 81.5% at 100V
IN
(see Figure 3).
The LTC7103 is a compact, high efficiency synchronous
monolithic step-down switching regulator with fast cur-
rent programming. The power switches, compensation
network and other necessary circuits are inside of the
LTC7103 to minimize external components and simplify
design. The LTC7103 has wide operating range from 4.4V
to 105V. A 40ns minimum on-time, together with 100%
maximum duty cycle allow practical use at any output volt-
age between 1V and V
IN
. The switching frequency can be
programmed either via an oscillator resistor or an external
clock over a 200kHz to 2MHz range. Additional features
include a fast and accurate output current programming
and monitoring, and ultralow EMI/EMC emissions.
The demo board has an EMI filter installed. The EMI
performance of the board (with EMI filter) is shown in
Figure 2. The figure shows that the circuit passes the
L
, LT, LTC, LTM, Linear Technology, the Linear logo and Burst Mode are registered trademarks
of Analog Devices, Inc. All other trademarks are the property of their respective owners.
PERFORMANCE SUMMARY
CISPR 25 radiated emission test with a wide margin. To
achieve EMI/EMC performance as shown in Figure 2, the
input EMI filter is required and the input voltage should
be applied at +VIN_EMI turret pin.
The demo board provides current monitor and output
clock signal to interface with an external application cir-
cuit. User selectable mode selection (JP1) is provided and
Burst Mode
®
operation position is selected by default.
Burst Mode operation increases light load efficiency while
pulse-skipping mode allows constant-frequency operation
to a lighter load. This demo board allows phase-locked
loop (PLL) synchronization to an external clock by select-
ing SYNC mode on JP1 and by providing a clock signal
on CLKIN turret.
The LTC7103 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 DC2317A. The LTC7103 is assembled in the 36 (26)
lead QFN package. 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/DC2317A
Specifications are at T
A
= 25°C
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
V
IN
Input Supply Range
5
100
V
V
OUT
Output Voltage
5
V
I
OUT
Output Current Range, Continuous
Free Air
0
2.3
A
f
SW
Switching (Clock) Frequency
400
kHz
V
OUTP-P
Output Ripple
V
IN
= 100V, V
OUT
= 5V, I
OUT
= 2.3A (20MHz BW)
50
mV
P-P
P
OUT
/PIN
Efficiency
V
IN
= 12V, I
OUT
= 1A
V
IN
= 48V, I
OUT
= 1A
92.6
88.1
%
%
Approximate Size
Component Area x Top Component Height
1.0 × 0.7 × 0.3
Inches
