QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 476
1.25MHZ 3A PEAK SWITCH CURRENT MONOLITHIC STEP-DOWN CONVERTER
TYPICAL PERFORMANCE SUMMARY (T
A
= 25
°
C)
Table 1.
Step-Down Converter (V
OUT
= 5V)
PARAMETER VALUE
V
IN
7V to 25V
V
OUT
5.0V
I
OUT
2A(max)
Efficiency
Up to 90% at 1A out and up to 89% at
2A output
EFFICIENCY (%)
LOAD CURRENT (mA)
10k
10
90
45
100
1k
50
55
60
65
70
75
80
85
V
IN
= 24V
V
IN
= 18V
V
IN
= 12V
V
IN
= 8V
Figure 2.
Typical Efficiency of DC476A LT1765EFE, V
OUT
= 5V
Table 2.
Step-Down Converter (with V
OUT
= 3.3V)
PARAMETER VALUE
V
IN
4.7V to 18V (up to 25V)
V
OUT
3.3V
I
OUT
2A(max)
Efficiency
Up to 88% at 1A out and up to 85%
at 2A output
EFFICIENCY (%)
LOAD CURRENT (mA)
10k
10
90
45
100
1k
50
55
60
65
70
75
80
85
V
IN
= 18V
V
IN
= 12V
V
IN
= 8V
V
IN
= 5V
Figure 3.
Typical Efficiency of DC476A LT1765EFE, V
OUT
= 3.3V
QUICK START PROCEDURE
Demonstration circuit 476 is easy to set up to evaluate
the performance of the LT1765EFE. Refer to Figure 4 for
proper measurement equipment setup and follow the
procedure below:
1.
Connect the 7–25V or 4.7–18V input power supply to
the VIN and GND terminals on the board.
2.
Connect an ammeter in series with the input supply to
measure input current.
3.
Connect either power resistors or an electronic load
to the VOUT and GND terminals on the board.
4.
Connect an ammeter in series with output load to
measure output current.
5.
Connect a voltmeter across the VIN and GND termi-
nals to measure input voltage.
6.
Connect a voltmeter across the VOUT and GND termi-
nal to measure output voltage.
7.
After all connections are made, turn on input power
and verify that the output voltage is either 5.0V or
3.3V (the output voltage jumper setting).
8.
The synchronization and shutdown functions are op-
tional and their terminals can be left floating (discon-
nected) if their functions are not being used.
MINIMUM INPUT VOLTAGE
The minimum LT1765EFE operating input voltage is
3.0V. Nevertheless, a DC/DC buck converter must have
an input voltage that is greater than the output voltage
by a certain margin in order to provide the desired regu-
lated output voltage. Maximum duty cycle, switch on-
resistance, and inductor and diode DC losses all play a
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