QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 392
HIGH EFFICIENCY DUAL REGULATOR
LTC1628 or LTC3728
DESCRIPTION
Demonstration circuit 392 is a dual output, step-down,
synchronous buck converter featuring either the 150kHz
to 300kHz LTC1628EUH controller (DC392A-A), the
250kHz to 550kHz LTC3728EUH (DC392A-B) or 250kHz
to 550kHz LTC3728LUH (DC392A-C). All three ICs come
in a 5mm×5mm QFN package with an exposed pad for
Table 1. Performance Summary
PARAMETER
Minimum Input Voltage
Maximum Input Voltage
V
OUT1
V
OUT2
Switching Frequency (LTC1628)
Switching Frequency (LTC3728)
V
IN
= 7V to 24V, I
OUT1
= 0A to 4A
V
IN
= 7V to 24V, I
OUT1
= 0A to 5A
Jumper selectable
Jumper selectable
CONDITION
VALUE
7V
24V
5V ±1%
3.3V ±1%
150kHz–300kHz
250kHz–550kHz
low thermal impedance. The input voltage is from 7V up
to 24V. Output 1 is 5V with loads up to 4A and output 2
is 3.3V with loads up to 5A.
Design files for this circuit board are available. Call
the LTC factory.
QUICK START PROCEDURE
Demonstration circuit 392 is easy to set up to evaluate
the performance of the LTC1628 or LTC3728. Refer to
Figure 1 for proper measurement equipment setup and
follow the procedure below:
NOTE:
The input voltage range should be 7V–24V in-
3.
Set Vin to 12V (recommended). The rated input
voltage range is from 7V to 24V.
4.
Remove the RUN1 jumper to switch on the Vout1
channel. The nominal output voltage of Vout1
should be 5V ±0.1V.
Increase load current on Vout1 to 4A. At 12V input
voltage, the input current should be less than 2A.
Slowly increase the input voltage to 24V. At 24V in-
put, the input current should be less than 1.1A.
5.
Decrease the load current of Vout1 to 0A. Reduce
stead of 5V-24V as shown on the board.
NOTE:
When measuring the input or output voltage rip-
ple, care must be taken to avoid a long ground lead on
the oscilloscope probe. Measure the input or output
voltage ripple by touching the probe tip directly across
the Vin or Vout and GND terminals. See Figure 2 for
proper scope probe technique.
1.
With the power off, place the jumpers as shown in
the input voltage to 12V.
6.
Remove the RUN2 jumper to switch on the Vout2
Figure 1.
NOTE:
The STBY and FLTCPL jumpers apply only to
channel. The output voltage of Vout2 should be
3.3V ±0.05V.
7.
Increase load current on Vout2 to 5A. At 12V input
demo circuit 392A-A (featuring the LTC1628). These
jumpers are not used for the DC392A-B or
DC392A-C which feature the LTC3728.
2.
Connect the loads at Vout1 and Vout2. The loads
voltage, the input current should be less than 1.8A.
Slowly increase the input voltage to 24V. At 24V in-
put, the input current should be less than 1.0A.
can be up to 4A for Vout1 and 5A for Vout2. Pre-set
the loads to 0A.
1
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