Linear Technology DC2012A Demo Manual

Description
Demonstration circuit 2012A is a 42V, 3.5A micro-
power synchronous step-down regulator featuring the
LT 8610AB. The LT8610AB is a compact, high efficiency,
®
high speed synchronous monolithic step-down switching
regulator that consumes only 2.5µA of quiescent current
when output is regulated at 5V. The efficiency of the circuit
is greater than 90% at light load up to 1.5A. This is a 10%
improvement over competing parts. Top and bottom power
switches, compensation components and other necessary
circuits are inside of the LT8610AB to minimize external
components and simplify design.
The SYNC pin on the demo board is grounded by default
for low ripple burst mode operation. To synchronous to an
external clock, move JP1 to SYNC and apply the external
clock to the SYNC turret. Once JP1 is on SYNC position,
a DC voltage of higher than 2V or INTV
to the SYNC turret for pulse-skipping operation. Figure 1
shows the efficiency of the circuit at 12V input.
performance summary
SYMBOL PARAMETER
V * Input Supply Range
IN
V Output Voltage
OUT
I Maximum Output Current
OUT
f Switching Frequency
SW
EFE Efficiency at DC
* Refer to Figure 2 to determine the maximum input voltage. If IC temperature exceeds target, reduce input voltage, output current or switching
frequency.
DEMO MANUAL DC2012A
42V, 3.5A Micropower Synchronous
Figure 2 shows the thermal performance of the circuit.
When running at input voltage greater than 30V, 3.5A
output current and 2MHz switching frequency, the tem-
perature rise will be significant. Either reducing the input
voltage, the output current or the switching frequency will
bring the temperature down to acceptable level without
external cooling.
The demo board has an EMI filter installed. The board
and the IC are designed to minimize conducted and radi-
ated EMI. The conducted EMI performance of the board
is shown on Figure 3. The limit in Figure 3 is EN55022
class B, average. It shows the circuit passes the test with
a wide margin.
The LT8610AB data sheet gives a complete description of
the part, operation and application information. The data
can be applied
CC
sheet must be read in conjunction with this quick start
guide for DC2012A.
Design files for this circuit board are available at
http://www.linear.com/demo/DC2012A
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.
Specifications are at T
CONDITIONS
I = 1A
OUT
Step-Down Regulator
= 25°C
A
MIN
5.5
4.8
3.5
1.85
LT8610AB
TYP MAX UNITS
42 V
5 5.2 V
A
2 2.15 MHz
91 %
dc2012af
1