USER GUIDE | UG:019
Analog LV ChiP NBM™ Bus Converter Module
Evaluation Board
Written by: Peter Makrum
Applications Engineer
June 2015
Contents
Introduction
Contents
Features
Board Description
General Components
Test Points Description
Schematics
Bill of Materials
Recommended Test
Equipment
Basic Connections
Page
1
3
3
3
3
6
7
9
10
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10
11
11
Board Operation Details
Thermal Considerations
Paralleling
Introduction
The Converter housed in a Package (ChiP) Bus Converter Module (BCM) evaluation
board described in this document is designed to be used with the NBM family of
non-isolated, DC-DC Bus converters. The Evaluation board is used for both the analog
control, and digital control NBM products.
The focus of this document is to assist the user in evaluating the analog control
version of the NBM family.
The NBM evaluation board can be configured for various enabling and fault
monitoring schemes, as well as to exercise various loading conditions depending on
the application requirements. The evaluation board can be used to evaluate NBMs in
either a stand-alone configuration, or as an array of modules.
It is important to remember the fast response of NBMs can readily show the
limitations of the source, load, and associated wiring connected to the evaluation
board. Care should be exercised to minimize the stray source and load impedance in
order to fully exercise the NBM.
The NBM non-isolated topology allows start up in forward and reverse directions and
provides bidirectional protections. However if power train is disabled by any protection,
and V
SEC
is present, then voltage equal to V
SEC
minus two diode drops will appear on
primary side.
UG:019
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Applications Engineering: 800 927.9474
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IMPORTANT NOTICE:
Read the precautions below entirely BEFORE using the NBM Evaluation Board. Do not
operate the evaluation board unless you have the appropriate safety precautions in
place on your bench to guarantee safety.
The list below is not comprehensive and is not a substitute for common sense
and good practice.
n
During operation, the power devices and surrounding structures can be operated
safely at high temperatures.
n
Remove power and use caution when connecting and disconnecting test probes
and interface lines to avoid inadvertent short circuits and contact with hot surfaces.
n
Never use a jumper in place of the fuse.
n
When testing electronic products always use approved safety glasses. Follow good
laboratory practice and procedures.
n
Avoid creating ground loops between the SGND and PGND pins when
making measurements.
n
Care should be taken to protect the user from accidental contact when
under power.
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Care should be taken to avoid reversing polarities if connecting to the opposite
(solder) side of the board.
n
The product evaluation boards described in this document are designed for general
laboratory evaluation, and are not suitable for installation in end user equipment.
n
Refer to the specific NBM module data sheet for electrical, thermal, and mechanical
product details.
This board provides a convenient way to evaluate or demonstrate the performance of
Vicor’s NBM products. Kelvin connections are provided for accurate voltage measure-
ments on power nodes. Sockets are provided to permit quick installation and changing
of bulk filtering capacitors. The evaluation board also provides lugs for input / output
connections, test points and sockets for easy connection to standard test equipment, and
a high performance air-cooled heat sink assembly.
Enable Options:
1.
Apply input voltage to the NBM primary or secondary pins greater than the
under voltage lockout. (Default)
2.
On-board mechanical switch
3.
External control using available test point
Fault Monitor Options:
1.
On-board LED: the VAUX pin drives a visible LED for visual feedback on the NBM
status such as enabled or fault condition.
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Applications Engineering: 800 927.9474
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Contents
The evaluation board ships with the following contents:
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n
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1 x NBM evaluation board
1 x Top heat sink pre-installed
1 x hardware kit:
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1 x through-hole aluminum electrolytic output capacitor (C121)
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3 x Connector Receptacle 8 position
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2 x Connector socket 2 position
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5 x size 10 screws, lugs and washers
Features
The NBM evaluation board has the following features:
1.
2.
3.
4.
5.
6.
7.
8.
Input and output lugs for source and load connections
Appropriately rated input fuse
Input aluminum electrolytic capacitor for additional source decoupling
Basic output filtering footprint, including sockets to add through-hole output
aluminum electrolytic capacitors
Toggle switch for enabling and disabling the NBM via the enable (EN) pin
Oscilloscope probe jack for accurate, high frequency output voltage measurements
Connectors for NBM signal pins (TM, EN, and VAUX) and temperature monitor
filtered signal
Kelvin voltage test points for all power pins
Board Description
The following section provides a detailed description of the evaluation board
components, test points and sockets.
General Components
1.
(PS01) The NBM is inherently a reversible product. This means that a voltage source
placed at the secondary will bias the power train and allow the units to power up.
Note if the units is held in a disabled state using the EN pin any voltage applied to
the secondary pins of NBM will appear on the primary pins minus two diode drops.
Loading the primary in this state may permanently damage the unit since the load
current path would be through the body diode of the primary stage FETs . See the
NBM data sheet for additional insight.
Input lugs: Sized for #10 hardware. Use for making connection to the input source.
This board does not contain reverse polarity protection. Check for proper polarity
before applying the power. It is important to remember that noise from the source
and voltage drops, will appear at the output of the bus converter multiplied by
transformation ratio (K). The K factor is the ratio of the output voltage to the input
voltage (V
OUT
/ V
IN
).
Input fuse (F101 & F102): Appropriately rated for the NBM model installed on the
board. The fuse is meant to protect against excessive damage in a
short-circuit event.
Input filtering: aluminum electrolytic input capacitor (C101).
2.
3.
4.
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Applications Engineering: 800 927.9474
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5.
Enable / Disable switch (SW101): When actuator is towards “ON” text on the board,
the (EN) pin will be open and the NBM will be enabled. When actuator is towards
“OFF” text on the board, the (EN) pin will be connected to (SGND) pin and the NBM
will be disabled. When switch (SW101) is “ON”, an external voltage source can
control the EN pin state.
Signal connector (J102): provides access to the bus converter signal pins (TM, EN,
and VAUX) as well as (TM_DC) externally filtered signal. All signal pins are reference
to the primary non-isolated voltage return (SGND) pin.
6.
Figure 1.
NBM signal connector (J102)
2
SGND
1
4
SGND
3
6
SGND
5
EN
8
SGND
7
VAUX
TM_PWM TM_DC
n
Temperature Monitor (TM): The NBM (TM) pin outputs a 250 kHz PWM signal.
A 1 kΩ and a 10 nF is the recommended low pass filtering solution. (TM_PWM)
and filtered (TM_DC) are both accessible on (J102) connector header. (TM_DC)
measures 1.27 V for a 27 °C internal temperature corresponding to a (TM_PWM)
duty cycle of 38.48%
Enable Control (EN): Connecting the NBM (EN) pin to (SGND) will disable the
module. (SW101) can be used to turn off the power train and disable
the module. The (EN) pin is internally pulled up. During a fault condition,
this signal and will remain high while input voltage is applied and greater than
V
µC_ACTIVE
. This connector can be used to bus the (EN) pin in an array allowing
array synchronous startup.
Auxiliary Voltage Source (VAUX): The NBM (VAUX) can be used as a fault flag it
is internally driven low during a fault condition. The (VAUX) pin can also be
used as a ready to process full power flag. A 2 ms delay from power train active
is introduced on this pin signaling the end of soft-start. During normal operation
this pin can be used as an auxiliary supply up to 4 mA max load.
n
n
7.
8.
Output lugs: Sized for #10 hardware. Use these lugs to connect the output directly
to the load.
Output oscilloscope probe Jack (J101): Used for making accurate scope
measurements of the output voltage (e.g. ripple). The jack is directly compatible
with many common passive voltage probes models. Remove the grounding lead and
insulating barrel of the probe and insert the probe tip and barrel directly into the
jack, insuring that the probe tip sits in the center socket of the jack. To avoid the risk
of an inadvertent short circuit, do not attempt to install while power is applied. This
Johnson Jack is kelvin connected to the module output pins. The effect of the output
capacitors will not be noticeable.
UG:019
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Applications Engineering: 800 927.9474
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9.
Output filter: 10x output ceramic capacitors 1206 footprint provision (C103, C104,
and C113 - C120). In addition to socket (C121) that can be used for easy installation
of an aluminum electrolytic output capacitor included with in hardware kit of the
evaluation board.
10.
Chassis ground: (R106) is a 2010 package. The footprint can be used to provide
a convenient means to short the chassis and heat sink common ground to the
power ground plane.
Figure 2.
PCB#42142 evaluation board
photo, top side
UG:019
vicorpower.com
Applications Engineering: 800 927.9474
Page 5
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