Description
DEMO MANUAL DC2012A
LT8610AB
42V, 3.5A Micropower Synchronous
Step-Down Regulator
Demonstration circuit 2012A is a 42V, 3.5A micropower synchronous
®
8610AB. The LT8610AB is a compact, high efficiency,
LT
step-down regulator featuring the
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
can be applied
CC
to the SYNC turret for pulse-skipping operation. Figure 1
shows the efficiency of the circuit at 12V input.
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
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.
performance summary
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
* Input Supply Range 5.5 42 V
V
IN
V
OUT
I
OUT
f
SW
EFE Efficiency at DC I
* Refer to Figure 2 to determine the maximum input voltage. If IC temperature exceeds target, reduce input voltage, output current or switching
frequency.
Output Voltage 4.8 5 5.2 V
Maximum Output Current 3.5 A
Switching Frequency 1.85 2 2.15 MHz
Specifications are at TA = 25°C
= 1A 91 %
OUT
dc2012af
1
DEMO MANUAL DC2012A
DC2012A F03
Quick start proceDure
DC2012A is easy to set up to evaluate the performance of
the LT8610AB. Refer to Figure 4 and Figure 5 for proper
measurement equipment setup and follow the procedure
below:
1. With power off, connect the input power supply to V
IN
and GND.
100
95
90
85
80
75
EFFICIENCY (%)
70
65
60
0 0.01 1 100.1
LOAD CURRENT (A)
DC2012A F01
2. With power off, connect the load V
and GND.
OUT
3. Check JP1 setting
4. Turn on the power at the input.
5. Carefully evaluate other design parameters as needed.
140
120
100
80
60
40
CASE TEMPERATURE RISE (°C)
20
2MHz, 2.5A
0
6 11 21 3616 3126
2MHz, 3.5A
VIN (V)
700kHz, 3.5A
DC2012A F02
Figure 1. LT8610AB 12VIN to 5V
2MHz Switching Frequency
Figure 3. LT8610AB Demo Circuit Conducted EMI Performance
Efficiency at
OUT
70
60
50
40
30
20
dBµV
10
0
–10
–20
–30
START 150kHz
RES BW 9kHz
Figure 2. LT8610AB Case Temperature Rise.
V
= 5V, TA = 25°C
OUT
EN55022 CLASS B
VBW 62kHz STOP 30MHz
2
dc2012af
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