LX1671 EVA KIT Microsemi Analog Mixed Signal Group, LX1671 EVA KIT Datasheet - Page 6

• Manufacturer Part Number: LX1671 EVA KIT
• Description: KIT EVAL FOR SWITCHING REGULATOR
• Manufacturer: Microsemi Analog Mixed Signal Group
• Series: LoadSHARE™r

Specifications of LX1671 EVA KIT

• Main Purpose: DC/DC, Step Down with LDO
• Regulator Topology: Buck
• Frequency - Switching: 300kHz
• Board Type: Fully Populated
• Utilized Ic / Part: LX1671, LX1672
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Current - Output: -
• Voltage - Output: -
• Voltage - Input: -
• Power - Output: -
• Outputs And Type: -
• Other names: LX1671EVAKIT; LXE1671 EVAL KIT; LXE1671 EVAL KIT

LX1671 EVALUATION BOARD
LoadSHARE Methods
There are four basic methods used for LoadSHARE
that are described in the LX1671 Product Design
Guide. Numerous components are related to the
implementation of these various methods.
LoadSHARE Filters
The low pass filters used for LoadSHARE operation
are made up of
R23-C6 for the RF2 input. Typical values are 61.9K
and 4700pf.
Proportional LoadSHARE
U2 and U3 are only used if proportional LoadSHARE
is desired. Several other components around U2
and U3 are also used only with proportional
LoadSHARE control.
LDO Soft Start
CR6-C27-R27 can be used to ramp the LDO output
up slowly if desired. The primary reason for this is to
prevent a possible UVLO condition if 5 volts is used
for the LDO input. If 5 volts is used for the LDO input
and a sudden current demand is placed on it by the
LDO load it can result in a transient on the 5 volts
that will trigger the UVLO.
Frequency Compensation
Three resistors R8-13-22 set the gain of the PWM
error amplifiers, these are typically 200K ohm and
three capacitors C23-31-32 can be placed in parallel
with the feedback resistors to lower the error
amplifier bandwidth.
Bulk Capacitors
There are a number of output bulk capacitors.
Phase one output C10-11; phase 2 output C12-13;
phase 3 output C19-26. These are chosen to
provide the required output filtering at the output
voltage.
S
Copyright © 2002
Rev 1.0, 2/24/2006
INGLE
• LoadSHARE operation of phases 1 and 2
• Remove R6 (jumper wire) - Connects phase 1
• Remove R23 and C6 - Feedback filter to RF2·
• Remove C5 and replace with a jumper -
• Change R22 to 200K - Phase 2 error amplifier
requires several component selections that
are factory installed (if ordered for Bi-Phase
operation). If single-phase operation of phase
1 and 2 is desired than modifications must be
made as follows.·
and 2 outputs together
Phase 2 feedback integrator capacitor
gain·
P
HASE
/ B
R18-C22 for the FB2 input and
I
-P
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, FAX: [phone]
HASE
Integrated Products
Microsemi
This equation is simplified and does not account for
drop across the input resistors due to error amplifier
input current. It is suggested that input resistors be
kept between 1K ohm and 10K ohm to minimize
error and noise coupling from surrounding circuits.
R
Resistive loads for all outputs at the required power
levels for each output
O
E
Once all components have been installed power can
be applied to the input terminal blocks and initial
operation checked with no load. It is recommended
that the power supplies used on the input have
adjustable current limits that can be set to a low
value for initial turn on of a new board. Apply all
input voltages with current limits set below 1A and
enable each output independently to verify that all
outputs are functional and have the correct output
voltage.
Once every output has been verified for proper
operation at no-load, a resistive load can be
connected to each output (up to the desired output
level). It is recommended that each output be loaded
individually the first time to insure normal operation
VALUATION
EQUIRED
• Install a jumper for R26 - Connects the
• Remove R18 and C22 - Filtered feedback to
• Change R21 to 4.02K
• Phase 2 voltage feedback
• Select R17 and R20 to give the desired output
• Multiple channel Oscilloscope with ten to one
• Digital Multimeter
• Power source (3.3 volts) if required for PWM
• Power source (5 volts) with sufficient current
• Power Source (12 volts) if required for PWM
PTIONAL
• Oscilloscope current probe with amplifier
• Electronic loads
reference to phase 2 error amplifier positive
input RF2·
FB2·
voltage for phase 2
probes having short ground leads
input (factory configuration requires +3.3)
for loads (factory configuration requires +5)
input or VCX (factory configuration requires
+12)
Input power sequencing is not critical.
T
T
EST
EST
B
V
OUT
OARD
E
E
QUIPMENT
QUIPMENT
=
0.8
O
⎛
⎜
⎝
PERATION
R17
R20
+
R20
USER GUIDE
⎞
⎟
⎠
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