DC1502A - Demo Manual

DEMO MANUAL DC1502A
LTC4359HDCB
12V/20A Ideal Diode with
Reverse Input Protection
DESCRIPTION
Demonstration circuit 1502A showcases the LTC®4359
ideal diode controller with reverse input protection. The
board includes two independent LTC4359 ideal diode
circuits, sharing a common ground and operating over a
4.5V to 28V range.
Each channel is capable of carrying 20A. Through-hole
pads are included to permit modification for even higher
currents, using an off board power stage.
Design files for this circuit board are available at
http://www.linear.com/demo
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear
Technology Corporation. All other trademarks are the property of their respective owners.
PERFORMANCE SUMMARY
Specifications are at TA = 25°C
PARAMETER
CONDITIONS
MIN
Input Voltage Limits
Operating
DC Survival
1ms Transient
VIN–VOUT
4.5
–40
–60
–60
Output Current Capability
4.5V ≤ VIN ≤ 8V
VIN > 8V
TYP
MAX
UNITS
28
90
250
V
V
V
V
10
20
A
A
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DEMO MANUAL DC1502A
QUICK START PROCEDURE
Overview
DC1502A features two independent LTC4359 ideal diode
circuits sharing a common ground. Each channel handles
up to 20A at room temperature, with no air flow. The board
is double-sided. Reference designators are duplicated for
the two sections of the board; the upper section is suffixed
A while the lower section is suffixed B.
Voltage Capability and Onboard Clamps
The voltage capability of DC1502A is clearly stated on the
top side silkscreen and on the schematic. Several factors
contribute to the listed ranges. First, there are the limits
of the LTC4359 which has a specified operating range of
4V to 80V, and an absolute maximum rating for the IN,
SHDN and SOURCE pins of –40V to 100V.
Second, there is the 60V BVDSS rating of MOSFET Q1 that
limits the VIN–VOUT rating of the board to –60V maximum.
Higher excursions are made possible by operating Q1 in
avalanche, or by replacing it with a higher voltage device.
Third, there are the clamp diodes D1 and D2. Clamping is
necessary to rein in commutation spikes—the LTC4359
behavior is no different in this respect from ordinary
rectifiers.
Fourth, there is the dissipation capability of R1, a component which has been chosen for its pulse capability. It
becomes the limiting factor for DC conditions when the
input voltage exceeds the breakdown of D1 or D2.
These factors combine to produce the INPUT VOLTAGE
LIMITS table shown on the schematic and silkscreened on
to the circuit board. Always bear in mind the VIN–VOUT
limit of –60V which may further restrict the survival and
transient limits.
Current Capability
DC1502A is designed to carry 20A per channel, provided
the LTC4359s are enabled. In the disabled state the associated Q1 MOSFET is turned off, and any forward current
flows through the 0.7V body diode. This limits the current
capability in the disabled state to ≈1A. Do not attempt to
pass 20A forward current in the disabled state, or Q1 will
be destroyed.
The 10A and 20A current limitations in the enabled state
result from MOSFET and board self heating, and from
connector capability.
Circuit Resistances
Typical RDSON for the BCS028N06NS MOSFET is 2.5mΩ,
dropping 50mV and dissipating about 1W at 20A. This
produces a junction temperature rise of 25˚C with the
board lying on a bench top and deprived of air flow.
The circuit traces leading to and from Q1 and the interface between the board and the banana jacks amounts to
500μΩ, adding 200mW dissipation at 20A. The ground path
measures about 350μΩ, which contributes an additional
140mW dissipation. The total board+MOSFET dissipation
for one channel driven is 1.3W and with both channels
driven, the total dissipation approaches 3W. The ground
copper loss may be eliminated by using a single power
ground connection to DC1502A.
The best banana test leads (such as Pomona Model B
banana plug) are rated to only 10A to 15A. For this reason,
and to minimize self heating, all banana connections should
be doubled up and kept as short as possible.
Banana plugs represent a substantial loss. Typical drop
measured from the point where the wire exits a Pomona
B-12 banana plug to the shoulder of the DC1502A banana
jack is in excess of 20mV at 20A, or about 1mΩ. If each
of the eight banana jacks is used to carry 20A, they will
add over 3W, doubling the total dissipation.
If the turrets are removed, 12 AWG bus wire can be
installed in the vacated holes to virtually eliminate any
voltage drop or dissipation associated with connections
to the board. The dissipation is reduced to about 20mW
(50μΩ) per connection. Use the banana jacks for Kelvin
meter connections.
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DEMO MANUAL DC1502A
QUICK START PROCEDURE
At 20A even 12 AWG wire has its limitations: the resistance
is ≈1.6mΩ/foot; one foot dissipates a surprising 640mW at
20A. Some of this heat is conducted into the circuit board.
LTC4359 is enabled. To disable, connect the SHDN turret
to the neighboring VSS turret. SHDN pin level shift circuits
are shown in data sheet Figure 3.
Another means of making connections is to attach ring
terminals or copper terminal lugs to the banana jacks,
using 8-32 screws. A Blackburn/Thomas&Betts BTC1014
terminal lug, enlarged for a number eight screw with a
#15 drill, accepts up to 10 AWG stranded wire; BTC0614
accepts up to 6 AWG wire and needs no machining.
Because the SHDN pin is high impedance, it is subject to
capacitive coupling. A 10nF noise bypass capacitor, CF,
works with R5 to keep noise out of the SHDN pin. R5 also
helps protect the SHDN pin against inadvertent overvoltage
conditions that might arise from use of the SHDN turret.
Various typical circuit resistances are summarized in the
Various Voltage Drops Measured at 10A Load Current table.
Modifying for Higher Current
The resistance issues discussed in the previous section
make obvious that modification of the demo board itself for
higher current is futile. Nevertheless, an off board power
stage may be constructed and connected to DC1502A by
using the SOURCE, DRAIN and GATE test pads. Snub the
MOSFET with a 100Ω, 10nF series network directly across
the device’s drain and source terminals. Do not pass load
current through the DC1502A ground terminals.
Modifying for Other Applications
Pads are provided so that the board may be modified to
match any of the data sheet diode applications. Components used in other applications include D3, D5 and D6, all
located on the bottom of the board. RSNUB and CSNUB are
useful for certain MOSFETs that exhibit parasitic stability
issues, such as the FDMS86101.
Shutdown
The LTC4359 may be shut down by moving the SHDN
jumper to the OFF position, which pulls SHDN to VSS
through 100kΩ (R5). Shutdown reduces the quiescent current to ≈14μA. In the ON position the SHDN pin floats; an
internal 2μA pull up asserts it high, enabling the LTC4359.
In the EXT position, the SHDN pin is connected through
R5 to the SHDN turret. If the SHDN turret is left open, the
It is important to note that shutting down the LTC4359
does not interrupt the forward current path. Even when the
LTC4359 is in the shutdown state and Q1 is off, Q1’s body
diode is still present and will conduct forward current. Do
not shut down the LTC4359 when the MOSFET is carrying
a forward current of more than 1A. High dissipation will
result in rapid destruction of Q1.
How to Operate DC1502A
A simple demonstration of DC1502A’s operation is as
follows (see Figure 1). Connect two adjustable power supplies, each set to 12V. Connect one to VIN A and nearby
GND, the second to VIN B and its associated GND. Place
the SHDN jumpers in the ON position. Join the outputs of
VOUT A and VOUT B together at the input of a DC load of
up to 20A. Slowly adjust one power supply up and down
relative to the other while monitoring the power supply
currents. The higher supply will carry the load current, with
a narrow transition region where the voltages are nearly
identical and the supplies droop share. If one supply is
shorted, the output voltage will not collapse—the other
supply will carry the load.
The forward characteristics of the LTC4359 can be tested
without using a high power load and using only a low voltage 20A supply, as shown in Figure 2. First, DC1502A is
biased with a 12V supply. This supply provides quiescent
current for the two channels, totaling less than 1mA.
Second, connect the two channels in series (VOUT A
connected to VIN B), and connect a 20A, current-limited
low voltage (≈1V) supply to VIN A and VOUT B.
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DEMO MANUAL DC1502A
QUICK START PROCEDURE
Turn on the 12V bias supply first, and then turn on the
20A supply. 20A will flow from the input of channel A,
through Q1A, to the input of channel B, through Q1B,
and back out to the 20A power supply. This arrangement
eliminates the need for high power supplies, eliminates
the need for a second high current supply and eliminates
the need for a high power load, yet the forward behavior
of the LTC4359 and the board, connector and MOSFET
voltage drops are readily examined as though the board
was fully loaded with each channel carrying 20A. Always
remember that the 12V supply must be present whenever
forward current is flowing.
The 20A supply may be adjusted from zero to 20A and the
12V supply may be adjusted from 8.5V to 28V, to observe
operation under any operating condition. At 10A, the 12V
supply may be adjusted to as low as 4.5V.
When powering down, turn off the 20A supply first and
then turn off the 12V supply. Using this sequence precludes
passing 20A through the body diodes of Q1A and Q1B.
Various Voltage Drops Measured at 10A Load Current
MEASURED
COMPUTED
VOLTAGE DROP COMPUTED DISSIPATION
AT 10A
RESISTANCE
AT 20A
PATH
Banana Tip to Banana Jack
Shoulder (Input)
5.6mV
560µΩ
224mW
Banana Jack Shoulder to
SOURCE Pad
0.6mV
60µΩ
Banana Jack Shoulder to
Center Source Lead
2.6mV
260µΩ
104mW
Center Source Lead to
Drain Lead
28.1mV
2.81mΩ
1.12W
Drain Lead to Banana Jack
Shoulder
1.8mV
180µΩ
72mW
Banana Jack Shoulder to
Banana Lead Tip (Output)
2.8mV
280µΩ
112mW
SOURCE Pad to DRAIN Pad
31.4mV
3.14mΩ
LTC4359 IN to OUT Pins
30.5mV
3.05mΩ
Shoulder to Shoulder (Total
Board Drop)
32.7mV
3.27mΩ
1.31W
12V
20A
12V
20A
LOAD
12V
20A
DC1502a F01
Figure 1. Basic Operation of DC1502A
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DEMO MANUAL DC1502A
QUICK START PROCEDURE
+
–
20A
LOW VOLTAGE
(≤ 1V)
12V
LOW
CURRENT
(≤ 1mA)
DC1502a F02
Figure 2. Testing Voltage Drops at High Current without the Need for High Power Supplies
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DEMO MANUAL DC1502A
PARTS LIST
ITEM
QTY
REFERENCE
PART DESCRIPTION
MANUFACTURER/PART NUMBER
Required Circuit Components
1
2
CFB, CFA
CAP, X7R, 10nF, 100V 20% 0805
AVX, 08051C103MAT2A
2
2
COUTB, COUTA
CAP, X7R, 47nF, 200V 20% 1206
AVX, 12062C473MAT2A
3
0
CSNUBB, CSNUBA
CAP, X7R, 10nF, 500V 20% 1206, OPTION
AVX, 12067C103MAT2A
4
2
D1B, D1A
DIODE, TVS, 70V, SMA
DIODES INC/ZETEX, SMAT70A-13-F
5
2
D2B, D2A
DIODE, TVS, 24V, SMA
DIODES INC/ZETEX, SMAJ24A-13-F
6
0
D3B, D3A, D6B, D6A
DIODE, TVS, 70V, SMA, OPTION
DIODES INC/ZETEX, SMAT70A-13-F
7
2
D4B, D4A
DIODE, ZENER 12V 150mW SOD-523
DIODES INC/ZETEX, DDZ9699T-7
8
0
D5B, D5A
DIODE, SWITCHING, 300V, SOD-123, OPTION
DIODES INC/ZETEX, BAV3004W-7-F
9
8
E1B, E1A, E4B, E4A, E6B, BANANA JACK, NON-INSULATED
E6A, E8B, E8A
KEYSTONE, 575-4
10
8
E2B, E2A, E5B, E5A, E7B, TEST POINT, TURRET, 0.094, PBF
E7A, E9B, E9A
MILL-MAX, 2501-2-00-80-00-00-07-0
11
4
E3B, E3A, E10B, E10A
TEST POINT, TURRET, 0.061, PBF
MILL-MAX, 2308-2-00-80-00-00-07-0
12
2
JP1B, JP1A
HEADER, 2X3 PIN, 0.079CC
SAMTEC, TMM-103-02-L-D
13
6
MH1 TO MH6
STANDOFF, NYLON 0.5"
KEYSTONE, 8833 (SNAP ON)
14
2
Q1B, Q1A
TRANSISTOR, POWER MOSFET, N-CH 60V, 100A
TDSON-8
INFINEON, BSC028N06NS
15
0
RSNUBB, RSNUBA
RES, CHIP, 100Ω, 1/2W, 5%, 1210, OPT
NIC, NRCP25J101TRF
16
2
R1B, R1A
RES, CHIP, HIGH POWER, 1k, 1/2W, 5% 1206
VISHAY, CRCW12061K00JNEAHP
17
2
R2B, R2A
RES, CHIP, HIGH POWER, 0Ω, 1/2W, 5% 1206
VISHAY, CRCW12060000Z0EAHP
R2 PART OPTION 2k, 1/2W 5% 1206
VISHAY, CRCW12062K00FKEAHP
18
2
R5B, R5A
RES, CHIP, 100k, 1/8W, 5% 0805
VISHAY, CRCW0805100KJNEA
19
2
U1B, U1A
IC, 28V IDEAL DIODE, DFN-6L
LINEAR TECHNOLOGY, LTC4359HDCB#PBF
20
2
XJP1B, XJP1A
SHUNT, 2MM
SAMTEC, 2SN-BK-G
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6
4
6
E XT 3
OF F 5
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
MH2
MH3
MH4
C S NUB A
10nF
500V
2
1
1
4.5V to 8V
> 8V
5
G AT E
VS S
R 1A
1K
1206
O UT
1
20A
E 8A
E 9A
VOUT A
D3A
S MAT 70A
OP T ION
R 2A
0 OHM
1206
1/2W
MAXIMUM CONTINUOUS LOAD
10A
OUTPUT CURRENT CAPABILITY
T P 4A
E X P O S E D P AD
VS S
T P 3A
G AT E
Q1A
B S C 028N06NS
LT C 4359HDC B
U1A
DDZ9699T
S O UR C E
VIN
3
2
1
D4A
2
1210
1206
OP T ION
OP T ION
T P 2A
T P 1A
D6A
S OUR C E
DR AIN
S MAT 70A
OP T ION
D5A
B AV 3004W
OP T ION
MH6
S HDN
MH5
5
IN
4
S NAP -IN S T ANDOF F S ON P C B OAR D
MH1
1ms TRANSIENT -60V TO 250V
VIN - VOUT
-60V
4.5V TO 28V
-40V TO 90V
OPERATING
CFA
10nF
100V
0805
R 5A
100K
0805
D1A
S MAT 70A
DC SURVIVAL
E 4A
INPUT VOLTAGE LIMITS
2
S HDN
J P 1A
D2A
S MAJ 24A
ON 1
E 5A
GND
E 10A
VS S
S HDN A
E 3A
E 1A
E 2A
VIN A
12V
1
2
2
1
4
6
3
2
1
2
7
1
GND
E 6A
E 7A
2
GND
E 4B
E 5B
CFB
10nF
100V
0805
R 5B
100K
0805
D1B
S MAT 70A
5
S HDN
IN
4
R S NUB B
100
5%
C S NUB B
10nF
500V
2
1
1
5
G AT E
VS S
T P 4B
E X P O S E D P AD
VS S
T P 3B
G AT E
Q1B
B S C 028N06NS
LT C 4359HDC B
U1B
DDZ9699T
S O UR C E
D5B
B AV 3004W
OP T ION
3
2
1
D4B
2
1206
1210
OP T ION
OP T ION
T P 1B
T P 2B
D6B
S OUR C E
DR AIN
S MAT 70A
OP T ION
NOTE: LTC4359HDCB TOP MARK LFKF
6
E 10B
VS S
4
2
OF F 5
S HDN
J P 1B
D2B
S MAJ 24A
C OUT A
47nF
E 3B
ON 1
200V
S HDN B
1206
E XT 3
E 1B
E 2B
VIN B
12V
1
2
2
1
4
6
3
2
1
2
7
1
R 1B
1K
1206
O UT
D3B
S MAT 70A
OP T ION
R 2B
0 OHM
1206
1/2W
E 8B
E 9B
VOUT B
1
GND
E 6B
E 7B
2
R S NUB A
100
5%
C OUT B
47nF
200V
1206
DEMO MANUAL DC1502A
SCHEMATIC DIAGRAM
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7
DEMO MANUAL DC1502A
DEMONSTRATION BOARD IMPORTANT NOTICE
Linear Technology Corporation (LTC) provides the enclosed product(s) under the following AS IS conditions:
This demonstration board (DEMO BOARD) kit being sold or provided by Linear Technology is intended for use for ENGINEERING DEVELOPMENT
OR EVALUATION PURPOSES ONLY and is not provided by LTC for commercial use. As such, the DEMO BOARD herein may not be complete
in terms of required design-, marketing-, and/or manufacturing-related protective considerations, including but not limited to product safety
measures typically found in finished commercial goods. As a prototype, this product does not fall within the scope of the European Union
directive on electromagnetic compatibility and therefore may or may not meet the technical requirements of the directive, or other regulations.
If this evaluation kit does not meet the specifications recited in the DEMO BOARD manual the kit may be returned within 30 days from the date
of delivery for a full refund. THE FOREGOING WARRANTY IS THE EXCLUSIVE WARRANTY MADE BY THE SELLER TO BUYER AND IS IN LIEU
OF ALL OTHER WARRANTIES, EXPRESSED, IMPLIED, OR STATUTORY, INCLUDING ANY WARRANTY OF MERCHANTABILITY OR FITNESS
FOR ANY PARTICULAR PURPOSE. EXCEPT TO THE EXTENT OF THIS INDEMNITY, NEITHER PARTY SHALL BE LIABLE TO THE OTHER FOR
ANY INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES.
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arising from the handling or use of the goods. Due to the open construction of the product, it is the user’s responsibility to take any and all
appropriate precautions with regard to electrostatic discharge. Also be aware that the products herein may not be regulatory compliant or
agency certified (FCC, UL, CE, etc.).
No License is granted under any patent right or other intellectual property whatsoever. LTC assumes no liability for applications assistance,
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Please read the DEMO BOARD manual prior to handling the product. Persons handling this product must have electronics training and
observe good laboratory practice standards. Common sense is encouraged.
This notice contains important safety information about temperatures and voltages. For further safety concerns, please contact a LTC application engineer.
Mailing Address:
Linear Technology
1630 McCarthy Blvd.
Milpitas, CA 95035
Copyright © 2004, Linear Technology Corporation
dc1502af
8
Linear Technology Corporation
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●
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