4
Rev. 0
QUICK START PROCEDURE
Demonstration circuit 2629A is easy to set up and evalu-
ate the performance of the LTC3310S. Refer to Figure 1
for proper measurement equipment setup and follow the
procedure below:
NOTE: For accurate V
IN
, V
OUT
and efficiency measure-
ments, measure V
IN
at the V
IN
SNSE and GND SNSE tur-
rets and V
OUT
at the V
OUT
SNSE and GND SNSE turrets as
illustrated as VM1 and VM2 in Figure 1. When measuring
the input or output voltage ripple, care must be taken
to avoid a long ground lead on the oscilloscope probe.
Measure the output voltage ripple by touching the probe
tip directly across the output turrets or to TP1 as shown
in Figure 2.
1. Set the JP1 Jumper to the HI position.
2. With power off, connect the input power supply to V
IN
and GND. If the input EMI filter is desired, connect the
input power supply to V
IN
EMI and GND.
3. Slowly increase PS1 to 1.0V. If AM1 reads less than
20mA, increase PS1 to 3.3V. Verify that VM1 reads 3.3V
and VM2 reads 1.2V. Record VM1, VM2, VM3 AM1
and AM2. Connect an oscilloscope voltage probe as
shown in Figure 2. Set Channel to AC coupled, voltage
scale to 20mV and time base to 10µs. Record V
OUT
ripple voltage. Verify that PGOOD voltage is above 3V.
Calculate Die temperature using formula below:
T
J
(
°
C)
=
V
SSTT
4mV
−
237
(1)
4. Increase the load by 1A intervals up to 10A and observe
the voltage output regulation, ripple voltage, and the
voltage on the SSTT turret.
5. If Pulse Skip Mode is desired, set PS1 to 0V. Install
a 0Ω resistor in the R6 location or short the MODE/
SYNC turret to GND. Repeat steps 1 through 4. In step
4 observe that the switching waveform is now operating
in Pulse Skip Mode at low currents.
6. To change the frequency, remove R4 and R6 if installed.
Install the desired RT resistor in the R7 location. Note,
the MODE/SYNC pin is an output when R4 is installed
and the MODE/SYNC pin should have high impedance
to GND and V
IN
. Size the inductor, output capacitors and
compensation components to provide the desired induc-
tor ripple and a stable output. Refer to the LTC3310S
datasheet and
choosing the required components.
7. To test the transient response with a base load, add the
desired resistor to produce a minimum load between
V
OUT
and I_STEP turrets (RL shown on Figure 1).
Note that the total load resistance will be RL plus R14
(100mΩ). Adjust a signal generator with a 10ms pe-
riod, 10% duty cycle and an amplitude from 1V to 2V
to start.
8. Measure the I_STEP voltage to observe the current,
VI_STEP/100mΩ. Adjust the amplitude of the pulse
to provide the desired transient. Adjust the rising and
falling edge of the pulse to provide the desired ramp
rate. Figure 3 shows a load step from 2A (RL = 0.51Ω)
to 8A. Refer to the following equations:
I
OUT
=
V
I_STEP
100m
Ω
(2)
V
GS
=
V
SG_INPUT
−
V
I_STEP
(3)
9. When done, turn off SG1, PS1 and Load. Remove all
connections to demo board.
273