Description
DEMO MANUAL DC2169A
LT8616
Dual 42V Synchronous Monolithic Step-Down
Regulator with 6.5µA Quiescent Current
Demonstration circuit 2169A is a dual monolithic step-down
®
DC/DC switching regulator featuring the LT
8616. The
LT8616 is a high efficiency, high speed, dual synchronous
monolithic step-down switching regulator that consumes
only 6.5μA of quiescent current with both channels enabled.
The demo circuit is designed for 5V, 1.5A and 3.3V, 2.5A
outputs. Both channels contain all switches and neces
sary circuitry to minimize the external components and
solution size. Fast minimum ON time of 35ns enables high
to low V
V
IN
conversion at high switching frequency.
OUT
Independent input voltage, feedback, soft-start and power
good pins for each channel simplify complex power supply
tracking/sequencing requirements.
The inputs of the two channels are connected on the demo
board by default. They can also be separated by removing
the 0Ω resistor (R13) from the board. Each output can
be independently disabled using its own EN/UV pin, while
must be connected to 3.4V or above even if only
V
IN1
channel 2 is in
installed between V
inputs should be tied to V
use. The demo board has an EMI filter
IN2
and V
. To use the EMI filter, the
EMI
.
EMI
The switching frequency of both channels can be programmed either
via an oscillator resistor or a common
external clock up to 3MHz.The SYNC pin on the demo
®
board is grounded by default for Burst Mode
operation.
To synchronize to an external clock, move JP1 to SYNC/
MODE and apply the external clock to the SYNC/MODE
turret. The R
resistor (R5) should be chosen to set the
T
LT8616 internal switching frequency at least 20% below
the lowest synchronization input.
Low ripple Burst Mode operation increases the efficiency
at the light load while keeping the output ripple low.
2
Figure 1 and Figure
show the demo board efficiency for
each channel at 12V input voltage in Burst Mode opera-
3
tion. Figure
shows the temperature rising on DC2169A
demo board with different input voltages under full load
conditions on both channels.
The LT8616 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
DC2169A. The LT8616 is assembled in a 28-lead plastic
TSSOP package. Proper board layout is essential for both
low EMI operation and maximum thermal performance.
See the data sheet sections for details.
Design files for this circuit board are available at
http://www.
L, LT, LTC, LTM, Linear Technology, the Linear logo and Burst Mode are registered trademarks
of Linear Technology Corporation. All other trademarks are the property of their respective
owners.
linear.com/demo/DC2169A
performance summary
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
V
IN1
V
IN2
V
OUT1
V
OUT2
f
SW
I
OUT1
I
OUT2
EFE Efficiency at DC V
Channel 1 Input Supply Range 5.8 42 V
Channel 2 Input Supply Range 4.1 42 V
Channel 1 Output Voltage 4.88 5.02 5.15 V
Channel 2 Output Voltage 3.21 3.29 3.37 V
Switching Frequency RT = 14.7kΩ 1.85 2.05 2.25 MHz
Channel 1 Max Output Current 1.5 A
Channel 2 Max Output Current 2.5 A
IN1
= V
Specifications are at TA = 25°C
= 12V, I
IN2
OUT1
= 1.5A, I
OUT2
= 2.5A 85.1 %
dc2169af
1
DEMO MANUAL DC2169A
performance summary
100
90
80
70
EFFICIENCY (%)
60
50
0.6
LOAD CURRENT (A)
fSW = 2MHz
= 12V
V
IN1
= 5V
V
OUT1
DC2169A F01
1.50.30 0.9 1.2
Figure 1. LT8616 Channel 1 Efficiency vs Load Current
100
90
80
70
EFFICIENCY (%)
60
50
1
LOAD CURRENT (A)
fSW = 2MHz
= 12V
V
IN2
= 3.3V
V
OUT2
DC2169A F02
2.50.50 1.5 2
Figure 2. LT8616 Channel 2 Efficiency vs Load Current
Figure 3. LT8616 Temperature Rising vs Input Voltage
2
100
fSW = 2.05MHz
= 5V, I
V
OUT1
80
60
40
TEMPERATURE RISING (°C)
20
OUT1
INPUT VOLTAGE (V)
= 1.5A
24
40168 32
DC2169A F03
dc2169af
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