3
DEMO MANUAL DC242
DC/DC CONVERTER
Refer to Figure 2 for proper measurement equipment
set-up and follow the procedure outlined below:
1. Connect the input power supply to the V
IN
and GND
terminals. Input voltage is limited to between 7.4V and
48V.
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 V
OUT
and GND terminals.
4. Connect an ammeter in series with the output load to
measure output current.
5. The SHDN pin should be left floating for normal
operation or tied to GND for shutdown.
6. Leave jumper JP2 connected for switching the LT1777
at its nominal frequency of 100kHz.
7. Set the output voltage with jumper JP1, as shown in
Table 1.
8. After all connections are made, turn on the input
power and verify that the output voltage is correct.
Table 1
POSITION
OUTPUT VOLTAGE
Jumper JP1 Closed
5V
Jumper JP1 Open
3.3V
VOUT
GND
DC242 F02
GND
VIN
LT1777CS
DC242
A
LOAD
A
Figure 2. Proper Measurement Set-Up
PARTS LIST
REFERENCE
DESIGNATOR
QUANTITY
PART NUMBER
DESCRIPTION
VENDOR
TELEPHONE
L3
1
DT1608C-152
1.5
µ
H Inductor (Alternate for L2)
Coilcraft
(847) 639-6400
R1
1
CR16-2152FM
21.5k 1/16W 1% Chip Resistor
Tad
(714) 255-9123
R2
1
CR16-2612FM
26.1k 1/16W 1% Chip Resistor
Tad
(714) 255-9123
R3
1
CR16-3572FM
35.7k 1/16W 1% Chip Resistor
Tad
(714) 255-9123
R4
1
CR16-683JM
68k 1/16W 5%
Tad
(714) 255-9123
TP1 to TP6
6
2501-2
0.090 Turret Testpoint
Mill-Max
(516) 922-6000
U1
1
LT1777CS
16-Lead SO DC/DC Controller IC
LTC
(408) 432-1900
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