DC740A - Demo Manual

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 740
TRACKER/SEQUENCER DEMO BOARD
LTC2922
DESCRIPTION
Demonstration circuit 740 is a tracker/sequencer
demo board featuring the LTC2922 that monitors up
to five external power supplies and ramps up their
load voltages by controlling external N-channel MOSFETs. Automatic remote sense switching allows supply generators with sense inputs to compensate for
voltage drops across the controlling FETs. Excessive
current on the primary supply (Supply #0) trips an
electronic circuit breaker that will disconnect all of the
loads. Four jumpers (block JP1) are provided to select which non-primary supplies are monitored. The
resistors that set the supply monitoring levels may be
replaced to customize the board for other supply
voltage combinations (see the LTC2922 Datasheet).
Five other jumpers (blocks JP2, JP3, and JP4) allow
the board to demonstrate supply sequencing. With
the proper jumper settings, supplies #3 and #4 will
track up together a selectable time after supplies #0,
#1, and #2 track up together. The board includes a
power-on LED that, when lit, indicates that the primary supply’s load is energized. Oversized solder
pads under the load resistors and the circuit breaker
current sense resistor accommodate a wide range of
component footprints. Solder pads on the back of
the board accommodate extra load capacitors or resistors. In addition to providing near-by ground connections for each supply input and output, the board
has metal ground strips that are convenient clip
points for meter leads.
Design files for this circuit board are available. Call
the LTC factory.
LTC is a registered trademark of Linear Technology Corporation
Table 1. Performance Summary (TA = 25°C)
PARAMETER
MIN
TYP
MAX
UNITS
VCC (Supply #0) Voltage Typical Board DC740A-A
Operating Range
Board DC740A-B
4.50
5.00
5.50
V
2.97
3.30
3.63
V
Board DC740A-C
2.37
2.50
2.63
V
Load ramp rate
CONDITION
Tracking
0.10
V/ms
Sequencing, first set of loads
0.10
V/ms
Sequencing, delayed set of loads
0.12
V/ms
Monitor-to-Tracking Delay
All monitors in compliance to start of GATE ramp
20
ms
Sequencing Delay
Final GATE voltage to start of PG ramp
20
ms
Circuit Breaker Trip Current
3.7
4.2
4.7
A
OPERATING PRINCIPLES
This board may be configured to demonstrate supply
tracking or supply sequencing. In tracking mode, all
supplies are ramped up simultaneously a selectable
delay after all monitoring requirements are met. Supply #0, the VCC supply, is always monitored; monitoring of other supplies is selectable by means of jumper
block JP1.
In sequencing mode, the ramping of one set of supplies follows the ramping of another set of supplies.
This demonstration board limits the possible delayed
supplies to #3 and/or #4. The delayed supplies may
not take advantage or automatic remote sense
switching.
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QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 740
TRACKER/SEQUENCER DEMO BOARD
Table 2. Supply Requirements for Demo Board 740A with Factory Jumper Settings
SUPPLY NUMBER
SUPPLY
VOLTAGE
SUPPLY
VARIATION
DEMO BOARD
VERSION
LOAD CURRENT
COMPLIANCE
5.0V
±10% max.
740A-A
>95mA
3.3V
±10% max.
740A-B
>75mA
2.5V
±5% max.
740A-C
>65mA
#1
2.5V
±7.5% max.
740A-A, -B, -C
>30mA
4.0A max.
#2
1.8V
±7.5% max.
740A-A, -B, -C
>25mA
4.0A max.
#3
1.5V
±7.5% max.
740A-A, -B, -C
>20mA
3.5A max.
#4
1.2V
±5% max.
740A-A, -B, -C
>15mA
3.5A max.
#0
(Primary Supply =
VCC Voltage)
ADDITIONAL
LOAD CURRENT
3.7A min.
4.2A typ.
4.7A max.
QUICK START PROCEDURE
Demonstration circuit 740 is easy to set up to evaluate the operation of the LTC2922. Refer to Figure 1
for proper measurement equipment setup. To test
tracking operation, follow steps 1 through 3 below,
then proceed to step 7. To test sequencing operation,
follow steps 4 through 6, then proceed to step 7.
TRACKING
1. Set the jumpers of block JP1 to choose which supplies, in addition to the primary supply, will be
monitored. For example, to monitor all supplies
set:
Use of remote sense switching is optional on a per
supply basis (see Figure 1). It is available for all supplies in tracking applications, but only for supplies 0
through 2 in sequencing applications.
The demo board is shipped with the jumpers set for
monitoring all five supplies and tracking of all the
loads. In addition, a resistor pull-up to VCC from the
PG pin makes the power good output a proper logic
signal.
The voltage and current requirements for supply generators when the board has factory jumper settings,
and the factory installed values for monitoring resistors RA1-RA4 and RB1-RB4 are summarized in
Table 2. Consult the LTC2922 Datasheet to calculate
new resistor values to monitor supplies with different
voltages or tolerances.
External loads may be added at the load terminals.
Make the wires as short as possible to reduce inductance and resistance, and use a gauge proper for the
expected load currents.
2.
JP1 Supply#1
Monitor
JP1 Supply#2
Monitor
JP1 Supply#3
Monitor
JP1 Supply#4
Monitor
Set jumper JP2 to select the resistive pull-up on
the PG pin:
JP2 PG Function
3.
Pull-up
Set the upper and lower jumpers of blocks JP3 and
JP4 to select tracking and automatic remote sense
switching:
JP3 Load#3
JP3 Load#3
Track
Remote Sense
JP4 Load#4
JP4 Load#4
Track
Remote Sense
NOTE: Remote
sense switching will have no effect if
supply generators’ sense inputs are not connected
to the board’s FB turret posts.
Proceed to step 7.
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QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 740
TRACKER/SEQUENCER DEMO BOARD
SEQUENCING
4. Set the jumpers of block JP1 to choose which supplies, in addition to the primary supply, will be
monitored. For example, to monitor all supplies,
set:
5.
JP1 Supply#1
Monitor
JP1 Supply#2
Monitor
JP1 Supply#3
Monitor
JP1 Supply#4
Monitor
Leave one supply off, turn on all the other supplies.
This supply must be selected as a monitored supply, and should be the trigger signal for the oscilloscope.
9.
Turn on the final supply and capture selected supply voltage and load voltage waveforms.
10.
Make sure that the Load #0 Power On indicator
LED is lighted, and that the load voltages nearly
equal the supply voltages. (Small differences will
occur due to the voltage drop across the controlling FETs.)
Sequence
Set the upper and lower jumpers of blocks JP3 and
JP4 to choose which supplies get a sequencing delay. For example, to sequence both supply #3 and
supply #4, set:
JP3 Load#3
JP3 Load#3
Sequence
Sequence/No Sense
JP4 Load#4
JP4 Load#4
Sequence
Sequence/No Sense
NOTE: When
a supply is sequenced, remote sense
switching is not available for that supply.
7.
8.
Set jumper JP2 to select the sequencing function
of the PG pin:
JP2 PG Function
6.
ply generators (if available) to the FB terminals on
the left side of the board.
With the power off, connect supply generators to
the Supply and GND terminal pairs on the left side
of the board. Connect sense terminals of the sup-
NOTE: If
the loads do not power up, double check the
voltage levels and current compliances of the supplies against the required values in Table 2.
11.
When the load voltages have successfully ramped,
view the scope trace to measure the monitor-toramp start delay, the supply ramp rate, and other
parameters in Table 1. Note the compensating effect of automatic remote sense switching if supply
sense inputs are connected.
12.
Check the operation of the electronic circuit
breaker by loading the primary supply and noting
the disconnection of all supplies. Pulse supply #1
low or short pin “V1 In” to ground momentarily to
reset the breaker and initiate tracking or sequencing.
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QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 740
TRACKER/SEQUENCER DEMO BOARD
Figure 1. Proper Measurement Equipment Setup
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QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 740
TRACKER/SEQUENCER DEMO BOARD
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