LTC3577-3 AND LTC3577-4
2
QUICK START PROCEDURE
Demo Circuit 1592 is designed to be used with a USB
input and/or a 5V adaptor input. Demo Circuit 1592 util-
izes the DC590B, USB to I
2
C interface board, to control
the LED boost driver, LDO enables, and buck modes. It is
also used to monitor the buck and LDO outputs, plus
battery charger status. This circuit may be evaluated us-
ing a lithium ion battery or a battery simulator consist-
ing of a 0V-5V, 3A power supply and a 3.6
Ω
power
resistor.
The DC1592 is easy to set up to evaluate the perform-
ance of the LTC3577-3 and LTC3577-4. Refer to
X
Figure 1
X
and Figure 2 for proper measurement equipment setup
and follow the procedure below to evaluate using the
DC590B board:
NOTE.
When measuring the input or output voltage ripple, 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 VUSB, WALL, or VOUT and GND terminals. See
X
Figure 2
X
for proper
scope probe technique.
1.
Refer to the DC590B Quick Start Guide for QuikEval
TM
setup and software installation details.
2.
Set the VCCIO jumper, JP6, on the DC590B board to
the 3.3V position.
NOTE.
The DVCC voltage level may be selected on the DC590B. This is
done by setting the VCCIO jumper, JP6, on the DC590B board to one of
the following settings: 3.3V, 5V, removed for 2.7V or set to external if an
external supply is desired to be used.
3.
Make sure the USB cable is connected between the
computer and the DC590B controller board.
4.
Set the jumpers on the DC1592 board to the following
settings:
JP1.
ILIM0 to “0” position.
JP2.
ILIM1 to “0” position.
JP3.
NTC to “INT” position.
JP4.
PWR_ON CNTL to “SW” position.
JP5.
VINLDO2 to “VOUT” position.
5.
Connect DC1592 to the DC590B USB Serial Controller
using the supplied 14-conductor ribbon cable as
shown in
X
Figure 1
X
.
6.
With power off, connect a 5V, 1A power supply to
VUSB
and GND with a series ammeter and a voltmeter
as shown in
X
Figure 1
X
.
7.
Connect a battery or a battery simulator set to 3.6V
between BAT
and GND with a series ammeter and a
voltmeter as shown in
X
Figure 1
X
.
8.
Turn on and set the VUSB input power supply to 5V.
The DC590B board gets its power from the USB cable.
9.
Run the QuikEval.exe program. The LTC3577-
3/LTC3577-4 control window (shown in
X
Figure 3
X
)
pops up.
NOTE.
The Status indicators on the software control window may display
“N/A” when an I2C ACK was not received. This occurs when the part is in
the power down (PDN) state or when DVCC is missing. Please refer to
the LTC3577 datasheet for more information on the PDN state.
10.
On the LTC3577-3/LTC3577-4 control window, se-
lect the PWR_ON HI/LOW button. When “HI” is indi-
cated on the button, the PWR_ON pin goes high and
the LDO2, VOUT1, and VOUT2 outputs sequence up.
VOUT POWER GOOD for each output is indicated on
the STATUS section on the control window.
11.
On the LTC3577-3/LTC3577-4 control window, se-
lect the EN3 HI/LOW button. When “HI” is indicated
on the button, the EN3 pin goes high and the VOUT3
powers up. VOUT POWER GOOD for VOUT3 is indi-
cated on the STATUS section on the control window.
12.
On the LTC3577-3/LTC3577-4 control window, se-
lect the BUCK1 through BUCK3 MODE buttons to
switch the bucks into Burst mode. Observe the output
ripple and the quiescent current before and after
switching modes.
13.
Select the desired BUCK SW SLEW RATE option but-
ton to switch between a fast rise-time for best effi-
ciency to a slower rise time with better EMI perform-
ance.
14.
Set the LED DAC REG vertical slider to a desired cur-
rent level. The LED current and the LED DAC register
setting are displayed in the test boxes below the verti-
cal slider. The LED full scale current (I
LED(FS)
) for this
circuit is 20mA.
