2
dc2469af
DEMO MANUAL DC2469A
QUICK START PROCEDURE
Demonstration circuit 2469A is easy to set up to evalu-
ate the performance of the LT8603. Refer to Figure 1 for
proper equipment setup and follow these procedures.
1. With power off, connect the input power supply to the
board through V
IN
and GND terminals on the top layer.
Connect the loads to the terminals VOUT1 and GND,
VOUT2 and GND, VOUT3 and GND on the board. The
default positions of the headers are given in Table 2.
Table 2. Default Positions of the Headers
NAME
POSITION
EN/UVLO
JP4
ON
TRKSS1
JP1
ON
TRKSS2
JP2
ON
RUN3
JP3
RUN
2. Turn on the power at the input. Increase V
IN
to 4.5V.
Make sure that the input voltage is always within spec.
Refer to data sheet on the switching in high V
IN
condi-
tion and the Burst Mode
®
operation in light load. The
minimum start-up voltage for the SEPIC converter (and
the board) is 4.5V. Once it starts, the circuit runs with
input going down below 3V at light load.
3. Check for the proper switching frequency and output
voltage at channel 4. The output is set at 8V (±4%).
The SEPIC converter output current capability depends
on the input voltage. If the 4th output is not regulated,
temporarily disconnect the load, and disable the two
high voltage buck regulators (channels 1, 2) as well.
Check if the EN/UVLO is set in correct position. Check
if too much load is applied to VOUT4. SEPIC does not
have overcurrent or short-circuit protection capability.
NOTE:
By default, the switching frequency of the SEPIC
converter is optimized with 400kHz with FSEL4A low
and FSEL4B high. The switching frequency can be
changed with RT, or different FSEL4A / FSEL4B set-
tings. An accompanying change of inductors might
be necessary to achieve desirable performance of the
converter.
4. Check for the proper output voltages of the buck regu-
lators. The output should be regulated at 5V (±4%),
3.3V (±4%), 1.8V (±4%) for the channels 1, 2 and
3, respectively. Do not overload the buck regulators
simultaneously at high line unless proper thermal cool-
ing method such as air flow or heat sink is applied.
If there is no output, temporarily disconnect the load
of the corresponding channels to make sure that the
PERFORMANCE SUMMARY
Table 1.
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Maximum Output Current, IOUT3
V
IN
= 12V, IOUT2 = 0A
1.8
A
Maximum Output Current, IOUT4
V
IN
= 12V, IOUT1,2,3 = 0A
1.5
A
Switching Frequency, Channel 1~3
V
IN
= 12V, IOUT1,2,3 = 1A
1.85
2
2.15
MHz
Switching Frequency, Channel 4
V
IN
= 6V, IOUT4 = 1A
370
400
430
kHz
Efficiency, Channel 4
V
IN
= 7V, IOUT4 = 2.5A
84
%
Efficiency, CH1, 5V
V
IN
= 12V, IOUT1 = 1.5A
89
%
Efficiency, CH2, 3.3V
V
IN
= 12V, IOUT2 = 2.5A
84
%
Efficiency, CH3, 1.8V
PVIN3 = 3.3V, IOUT3 = 1.8A
83
%
Efficiency, Overall
V
IN
= 14V, IOUT1,2,3 = 1A
75
%
