Quick Start Procedure - Analog Devices DC2874A-A Demo Manual

QUICK START PROCEDURE

Demonstration circuit 2874A is easy to set up and evalu-
ate the performance of the LTC3310S in multiphase
operation. Refer to Figure 1 for the proper measurement
equipment setup and jumper settings. Follow the proce-
dure below to familiarize yourself with the DC2874A.
NOTE: For accurate V , V
IN
ments, measure V at the VIN SNSE and GND SNSE tur-
IN
rets and V at the VOUT SNSE and GND SNSE turrets as
OUT
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 VIN
and GND. If the input EMI filter is desired, connect the
input power supply to VIN 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, volt-
age scale to 10mV and time base to 100ns. Record
V ripple voltage. Verify that PGOOD voltage is above
OUT
3V. Set the EN Jumper, JP1, to the HI position.
4. Increase the load by 1A intervals up to full load and
observe the voltage output regulation, ripple voltage.
5. To test the transient response with a base load, turn
off LD1 and add the desired resistor to produce a
minimum load between VOUT and I_STEP turrets (RL
shown on Figure 1).
Note that the total load resistance will be RL plus the
parallel combination of R16 and R18 (10mΩ).
and efficiency measure-
OUT
DEMO MANUAL DC2874A-A/
DC2874A-B/DC2874A-C
The DC2874A uses a buffered signal generator input
to drive a source follower circuit and control the slew
rate and amplitude of the current transient. The source
follower FET, Q1, is operated in the linear region dur-
ing the load step. The current step is measured as the
voltage across the parallel combination of R16 and R18
(10mΩ), V .
I_STEP
6. Connect PS2 to the DRIVER BIAS and GND turrets.
Turn on and set PS2 to 8V.
7. Measure the I_STEP voltage to observe the current,
VI_STEP/10mΩ. Adjust the amplitude of the pulse to
provide the desired transient. Adjust the rising and fall-
ing edge of the pulse to provide the desired ramp rate.
Figure 3 shows a load step from 8A (RL = 150mΩ) to
36A. Refer to the following equations:
V
I _ STEP
I
=
OUT
10mΩ
Where:
V = V
I _ STEP SGINPUT
8. Set a signal generator with a 1ms pulse width, a 10ms
period and an amplitude from 0V to 3V, and then con-
nect it to the SG_INPUT turret.
NOTE: Do not allow the pulse generator to have more
than a 20% duty cycle. This can allow too much power
to be dissipated in Q1 and can damage the FET.
9. Connect an oscilloscope with a horizontal scale of
200us/Div with one channel having a vertical scale of
2V/Div on the SG_INPUT and another with a vertical
scale of 50mV/Div to the I_STEP turret.
10. Adjust the amplitude of the SG_INPUT pulse to obtain
the desired load pulse observed on the I_STEP turret.
11. Turn off PS1, PS2 and the signal generator. Remove
all connections from demo board.
− V
GS
(1)
(2)
Rev. 0
3