USER GUIDE | UG:019
Analog LV ChiP™ NBM™ Bus Converter Module
Evaluation Board
Contents
Introduction
Contents
Features
Board Description
General Components
Test Points Description
Bill of Materials
Recommended
Test Equipment
Basic Connections
Board Operation Details
Thermal Considerations
Paralleling
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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 powertrain is disabled by any protection, and V
SEC
is present, then
voltage equal to V
SEC
minus two diode drops will appear on the primary side.
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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.
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During operation, the power devices and surrounding structures can be operated safely
at high temperatures.
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Remove power and use caution when connecting and disconnecting test probes and interface lines to
avoid inadvertent short circuits and contact with hot surfaces.
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Never use a jumper in place of the fuse.
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When testing electronic products always use approved safety glasses.
Follow good laboratory practice and procedures.
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Avoid creating ground loops between the SGND and PGND pins when making measurements.
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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.
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product evaluation boards described in this document are designed for general laboratory
The
evaluation and are not suitable for installation in end-user equipment.
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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 NBM
products. Kelvin connections are provided for accurate voltage measurements 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.
2.
3.
Apply input voltage to the NBM primary or secondary pins greater than the
undervoltage lockout. (Default)
On-board mechanical switch.
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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Contents
The evaluation board ships with the following contents:
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x NBM™ evaluation board
1
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x Top heat sink pre-installed
1
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x hardware kit:
1
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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 powertrain 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 (VOUT / VIN).
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).
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.
2.
3.
4.
5.
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6.
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.
Figure 1
NBM™ signal connector (J102)
2
SGND
1
4
SGND
3
6
SGND
5
EN
8
SGND
7
VAUX
TM_PWM TM_DC
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Temperature Monitor (TM):
The NBM (TM) pin outputs a 250kHz PWM signal. A 1kΩ and
a 10nF is the recommended low-pass filtering solution. (TM_PWM) and filtered (TM_DC) are
both accessible on (J102) connector header. (TM_DC) measures 1.27V for a 27°C internal
temperature corresponding to a (TM_PWM) duty cycle of 38.48%
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Enable Control (EN):
Connecting the NBM (EN) pin to (SGND) will disable the module.
(SW101) can be used to turn off the powertrain 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 VµC_ACTIVE. This connector can be used to bus the (EN) pin in an
array allowing array synchronous start up.
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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 2ms delay from powertrain 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
4mA max load.
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.
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.
9.
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
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Test Points Description
Test nodes are labeled and include an SMT test point for attaching miniature probes, clips or hooks.
Table 1
Test point descriptions
Name
+VIN, PGND
EN, SGND
TM_DC, SGND
TM_PWM, SGND
VAUX, SGND
+VOUT, PGND
Description
Provide measurement test points for the input voltage of the NBM™ module.
Test points are Kelvin connected to the module input pins.
Used to measure the NBM EN pin relative to SGND pin.
Used to measure the filtered NBM TM signal using a recommended low pass
filter relative to SGND pin.
Used to measure the NBM TM pin which is a pulse width modulated output
signal relative to SGND pin.
Used to measure the NBM VAUX pin output signal relative to SGND pin.
Provide measurement test points for the output voltage of the NBM module.
Test points are Kelvin connected to the module output pins.
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