2
dc1726f
DEMO MANUAL DC1726
QUICK START PROCEDURE
Figure 1.
Demonstration circuit 1726 allows the user to quickly
evaluate the performance of the LTC3618. Refer to Figure 2
for proper measurement equipment setup and follow the
procedure below
1. Place jumpers in the following positions.
JP1
VOUT 1 Select
1.5V
JP5
Track/SS
INT SS
JP6
PHASE
180°
JP8
MODE
FCM
JP9
COMP 1
INT
JP10
COMP 2
INT
JP11
RUN 1
ON
JP12
RUN 2
ON
JP13
VDDQIN
VDDQ
2. With the input power supply turned down and switched
off, connect the supply and digital voltmeters as shown
in Figure 2.
3. Switch on the input supply and adjust for approximately
3.3V on VIN.
4. Verify that the VDDQ output voltage is within the lim-
its shown in the table on page 1 for each of the three
output voltages as selected by JP1, JP2 and JP2. Note:
moving the jumper to JP3 sets VDDQ to the internal
reference voltage of 600mV. Other output voltages can
be programmed by selecting a suitable resistor for R9.
5. To verify VDDQ output voltage tracking. Move JP5 to the
TRACK position (upper) and remove all VOUT1 SELECT
jumpers. Apply an external reference voltage between
100mV and 600mV to TRACK1 terminal. Verify that the
VDDQ output is within ±11mV of the external reference
voltage.
6. Move JP5 to the INT SS position (lower) and place
a jumper on JP2 (1.8V). Verify that the VTTR output
voltage is equal to VDDQ • 0.5 ±2%. Additional VDDQ
voltages can be selected using JP1 or JP3.
7. Verify that the VTT output voltage is equal to the VTTR
voltage ±6mV. The error voltage can be read differentially
by placing the meter leads between the VTTR and VTT
terminals
8. To evaluate sourcing current from VDDQ or VTT outputs,
connect a suitable 10W load in series with an ammeter
between each output terminal and ground. Resistor.
See Figure 2 for resistor connections and resistor value
equation. Verify that the output voltages still meet the
specifications shown in the Performance Summary
section.
9. To evaluate sinking current into the VTT output, connect
a suitable 10W load resistor in series with an ammeter
between the VTT output and the VIN terminals. Verify
that the output voltages meet the specifications in the
Performance Summary section.
The many jumpers on this board allow the user to evaluate
the various features of the LTC3618. Jumpers are used to
select VDDQ output voltages, switch phasing, soft-start,
tracking, on/off, operating mode and compensation. Refer
to the data sheet for information on these functions.
Extra pads are located on the top and bottom of the board
for adding additional input and output capacitors if desired.
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 1 for proper scope
probe technique.
