2
Rev. 0
Demonstration circuit 2728A is easy to set up to evaluate
the performance of the LTC7880. Refer to Figure 2 for
the proper measurement equipment setup and follow the
procedure below.
1. With power off, connect the input power supply to V
IN
(12V to 24V) and GND (input return). Make sure the
input power supply is capable of 35A at 12V.
2. Connect the 24V output load between V
OUT0
and GND
(Initial Load: no load).
3. Connect the 48V output load between V
OUT1
and GND
(Initial Load: no load).
4. Connect the DVMs to the input and outputs. Set default
jumper position: SW1: ON; SW2: ON; JP1: OFF; JP2:
NC; JP3: NC.
5. Turn on the input power supply and check for the
proper output voltages. V
OUT0
should be 24V ± 0.5%,
and V
OUT1
should be 48V ± 0.5%.
PARAMETER
CONDITIONS
VALUE
Input Voltage Range
12V to 24V
Output Voltage, V
OUT0
V
IN
= 12V to 24V, I
OUT0
= 0A to 5A
24V to 48V, Default: 24V
Maximum Output Current, I
OUT0
V
IN
= 12V to 24V, V
OUT0
= 24V to 48V
5A
Output Voltage, V
OUT1
V
IN
= 12V to 24V, I
OUT1
= 0A to 5A
24V to 48V, Default: 48V
Maximum Output Current, I
OUT1
V
IN
= 12V to 24V, V
OUT1
= 24V to 48V
5A
Typical Efficiency of CH0
V
IN
=12V, V
OUT0
= 24V, I
OUT0
= 5A
Typical Efficiency of CH1
V
IN
= 12V, V
OUT1
= 48V, I
OUT1
= 5A
Default Switching Frequency
150kHz
6. Once the proper output voltages are established, adjust
the loads within the operating range and observe
the output voltage regulation, ripple voltage and
other parameters.
7. Connect the dongle and control the output voltages
from the GUI. See the LTpowerPlay GUI for the LTC7880
Quick Start Guide for details.
NOTE:
When measuring the output or input voltage
ripple, do not use the long ground lead on the oscil-
loscope probe. See Figure 3 for the proper scope probe
technique. Short, stiff leads need to be soldered to
the (+) and (–) terminals of an output capacitor. The
probe’s ground ring needs to touch the (–) lead and
the probe tip needs to touch the (+) lead.
QUICK START PROCEDURE
PERFORMANCE SUMMARY
Specifications are at T
A
= 25°C
