LTC3577 AND LTC3577-1
QUICK START PROCEDURE
Demo Circuit 1402 is designed to be used with a USB
input and/or an external HV buck demo board, such as
the DC1325A, DC1394A, or DC1395A featuring the
LT3653, LT3480 and the LT3505 respectively. Demo Cir-
cuit 1402 utilizes 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 using a lithium ion battery or a battery simula-
tor consisting of a 0V-5V, 3A power supply and a
3.6
Ω
power resistor.
The DC1402 is easy to set up to evaluate the perform-
ance of the LTC3577 and LTC3577-1. Refer to
Figure 1
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 Vin or Vout and GND terminals. See
Figure 2 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 DC1402-2 board to the follow-
ing settings:
JP1.
PWR_ON CNTL to “SW” position.
JP2.
ILIM1 to “1” position.
JP3.
ILIM0 to “1” position.
JP4.
STATUS PIN PULL-UP to “VOUT” position.
JP5.
NTC to “INT” position.
JP6.
VINLDO2 to “VOUT” position.
JP7.
VINLDO1 to “VOUT” position.
5.
Connect DC1402 to the DC590B USB Serial Controller
using the supplied 14-conductor ribbon cable as
shown in
Figure 1.
6.
With power off, connect a 5V, 1A power supply to
VUSB
and GND with a series ammeter and a voltmeter
as shown in
Figure 1.
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
Figure 1.
8.
Turn on and set the VUSB input power supply to 5V.
The DC590B board gets its power from the USB cable.
NOTE.
Make sure that the input voltage does not exceed 6V.
9.
Run the QuikEval.exe program. The LTC3577 control
window (shown in
Figure 3) 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 control window, select the PWR_ON
HI/LOW button. When “HI” is indicated on the button,
the PWR_ON pin goes high and the VOUT1, VOUT2,
and VOUT3 outputs sequence up. VOUT POWER
GOOD for each output is indicated on the STATUS
section on the control window.
11.
Select 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.
12.
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.
13.
Select the LDO1 and LDO2 EN/DIS buttons to enable
LDO1 and LDO2 via the I
2
C bus.
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.
2
Summary of Contents for Demo Circuit 1402A
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