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dc1741af
DEMO MANUAL DC1741A
DESCRIPTION
LTC4370
Two-Supply Diode-OR
Current Balancing Controller
Demonstration circuit DC1741A features the LTC4370, a
two supply diode-OR current sharing controller in a typical
2.9V to 18V, 16A sharing application.
The maximum MOSFET voltage drop VFR = VIN – OUT is
set with an external resistor, up to 600mV. A fast gate
turn-on reduces the load voltage droop during supply
switchover. If the input supply fails or is shorted, a fast
turn-off minimizes the transient reverse current.
Disabling the load sharing function turns the LTC4370
into a dual ideal diode controller.
Two enable input pins, EN1 and EN2, allow enabling and
disabling each rail’s MOSFET individually while the MOS-
FETs’ inherent diodes create diode-OR connection when
the MOSFETs are disabled. The LTC4370 provides a rich 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
set of features to support shared current diode-ORed ap-
plications including:
• Load Sharing Between Two Supplies
• Elimination of the Need for Active Control of Input
Supplies
• Elimination of "Share Bus”
• Reverse Current Blocking
• Elimination of Shoot-Through Current During Start-Up
or Faults
Design files for this circuit board are available at
http://www.linear.com/demo
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
VIN VIN1 and VIN2 Input Voltage Operating Range
With External VCC Supply
2.9
0
18
VCC
V
VCC(EXT) VCC External Supply Operating Range VIN1, VIN2 ≤ VCC 2.9 6.0 V
VCC(REG) VCC Regulated Voltage 4.5 5 5.5 V
VEA(OS) Error Amplifier Input Offset 0±2 mV
gm(EA) Error Amplifier Gain 150 µS
VFR Forward Regulation Voltage (VIN – VOUT)V
IN =1.2V, VCC = 5V
VIN =12V
2
2
12
25
25
50
mV
mV
∆VGATE MOSFET Gate Drive (GATE-VIN)V
FWD = 0.2V; I = 0, –1A; Highest VIN = 12V
VFWD = 0.2V; I = 0, –1A; Highest VIN = 2.9V
10
4.5
12
7
14
9
V
V
IGATE GATE1, GATE2 Fast Pull-Up Current
GATE1, GATE2 Fast Down-Up Current
GATE1, GATE2 Off Pull-Down Current
VFWD = 0.4V, ∆VGATE = 0V, CPO = 17V
VFWD = –2V, ∆VGATE = 5V,
Corresponding EN =1V, ∆VGATE = 2.5V
–0.9
0.9
65
–1.4
1.4
110
–1.9
1.9
160
A
A
µA
VEN(TH) EN1, EN2 Threshold Voltage EN Falling 580 600 620 mV
∆VGATE(ON) MOSFET On-Detect Threshold (GATE-VIN) FETON Transitions High 0.28 0.7 1.1 V
IOUT Maximum Continuous Load Current Sharing active, limited by SUM85N03 FET Dissipation 16.6 A
Specifications are at TA = 25°C
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dc1741af
DEMO MANUAL DC1741A
OPERATING PRINCIPLES
The LTC4370 controls N-channel MOSFETs, M1 and
M2, to share the load between two input rails.The error
amplifier compares OUT1 and OUT2, and controls servo
amplifiers which regulate MOSFET forward voltage drop
to VFR. Combined action of the error amplifier and servo
amplifiers forces OUT1 and OUT2 to be equal and as a
result the rail currents are equal. The board RANGE resistor
R3 = 30.1k defines maximum regulation voltage range as
265mV to 375mV.
The board is assembled with SUM85N03-06P N-channel
MOSFETs, which in a single channel application has
current capability up to 20A. In the load share mode the
installed components guarantee continuous proper load
sharing up to 16.6A total load. For a short test time of 3
to 5 seconds it is possible to double this load.
Two LEDs, OFF1 and OFF2, indicate the MOSFETs’ status.
Each LED lights up, when the gate voltage is less than
0.7V above VIN.
Pay special attention to the power supply features used
with the LTC4370.
This controller may not work properly with supplies utilizing
synchronized rectification in the output stage unless the
internal circuit of the supply has the ability to limit negative
current or to block it completely. Exercise caution when
using the controller with this type of supply unless it is
determined that it contains the required circuitry.
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dc1741af
DEMO MANUAL DC1741A
QUICK START PROCEDURE
VARIABLE
LOAD
POWER
SUPPLY 1
mV
+
–
POWER
SUPPLY 2
+
–DC1741A F01
Figure 1. Load Share Performance Measurement
Demonstration circuit DC1741A is easy to set up to evalu-
ate the performance of the LTC4370. Refer to Figure 1
for proper measurement equipment setup for load share
observation.
1. Turn both supplies on. Adjust two 5V supplies’ outputs
to a 215mV difference, which equals the minimum
∆VIN(MIN) load share breakpoint (265mV–50mV).
Load the LTC4370 output with minimal current so that
both supplies contribute current to the common load.
Increase load up to 35A and observe the LTC4370 op-
eration mode with accurate load sharing. It is easy to
estimate load share accuracy by measuring a voltage
between two sense resistors. Since the MOSFETs will
be dissipating excessive power, limit this measurement
to 3 to 5 seconds when at the 35A level.
2. Reduce the load current to a total of 7.5A. Adjust the
two 5V supplies’ outputs to a voltage difference of 373
mV which equals the maximum ∆VIN(MAX) load share
breakpoint (375mV–2mV). As the difference between
power supplies output is greater than the maximum
voltage regulation, the LTC4370 channel with the higher
voltage will provide most of the current. Increase the
voltage until all of the current is provided by the higher
voltage supply. This is the point at which the MOSFET
of the higher voltage channel MOSFET is fully enhanced
while the MOSFET of the lower channel voltage is
completely cut off. Observe that the LED of the lower
supply is illuminated.
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dc1741af
DEMO MANUAL DC1741A
PARTS LIST
ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER
Required Circuit Components
1 1 CC Cap., X7R, 0.18µF, 25V, 10%, 0805 AVX, 08053C184KAT2A
21CV
CC Cap., X7R, 0.1µF, 50V, 10%, 0805 AVX, 08055C104KAT2A
3 2 C1, C2 Cap., X7R, 0.039µF, 50V, 10%, 0805 AVX, 08055C393KAT2A
4 2 D1, D2 LED, RED Panasonic, LN1251C-TR
5 2 D3, D4 Current Limiting Diode, 3.2V, SOD-80 Central Semi. Corp. CCLM3500
6 7 E1, E2, E3, E4, E5, E7, E8 Turret, Testpoint 0.063" Mill-Max, 2308-2-00-80-00-00-07-0
7 4 J1, J2, J4, J5 Connector, Banana Jack Keystone, 575-4
8 2 M1, M2 MOSFET N-Channel, 30V, D2PAK Vishay, SUM85N03-06P-E3
9 2 R1, R2 Res., WSL 0.002 1W, 1%, 2512 Vishay, WSL25122L000FEA
10 1 R3 Res., Chip 30.1k, 0.1W 1%, 0805 Vishay, CRCW080530K1FKEA
11 2 R4, R6 Res., Chip 10k, 0.1W, 5%, 0805 Vishay, CRCW080510K0JNEA
12 0 R5, R7 Res., 0805 OPT
13 1 U1 I.C., Diode-OR Load Share Cont., DFN16DE-4 × 3 Linear Technology Corp., LTC4370CDE
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dc1741af
DEMO MANUAL DC1741A
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 representa-
tion that the interconnection of its circuits as described herein will not infringe on existing patent rights.
SCHEMATIC DIAGRAM
1
1
2
2
3
3
4
4
5
5
A A
B B
C C
D D
NOTES: UNLESS OTHERWISE SPECIFIED
1. ALL RES ARE IN OHMS, 0805.
2. ALL CAP ARE IN MICROFARAD, 0805.
SIZE
DATE:
IC NO. REV.
SHEET OF
TITLE:
APPROVALS
PCB DES.
APP ENG.
TECHNOLOGY Fax: (408)434-0507
Milpitas, CA 95035
Phone: (408)432-1900
1630 McCarthy Blvd.
LTC Confidential-For Customer Use Only
CUSTOMER NOTICE
LINEAR TECHNOLOGY HAS MADE A BEST EFFORT TO DESIGN A
CIRCUIT THAT MEETS CUSTOMER-SUPPLIED SPECIFICATIONS;
HOWEVER, IT REMAINS THE CUSTOMER'S RESPONSIBILITY TO
VERIFY PROPER AND RELIABLE OPERATION IN THE ACTUAL
APPLICATION. COMPONENT SUBSTITUTION AND PRINTED
CIRCUIT BOARD LAYOUT MAY SIGNIFICANTLY AFFECT CIRCUIT
PERFORMANCE OR RELIABILITY. CONTACT LINEAR
TECHNOLOGY APPLICATIONS ENGINEERING FOR ASSISTANCE.
THIS CIRCUIT IS PROPRIETARY TO LINEAR TECHNOLOGY AND
SCHEMATIC
SUPPLIED FOR USE WITH LINEAR TECHNOLOGY PARTS.
SCALE = NONE
www.linear.com
2
DEMO CIRCUIT 1741A
01/17/2012, 11:31 AM
11
TWO-SUPPLY DIODE-OR CURRENT SHARING CONTROLLER
N/A LTC4370CDE
KIM T.
VLADIMIR O.
SIZE
DATE:
IC NO. REV.
SHEET OF
TITLE:
APPROVALS
PCB DES.
APP ENG.
TECHNOLOGY Fax: (408)434-0507
Milpitas, CA 95035
Phone: (408)432-1900
1630 McCarthy Blvd.
LTC Confidential-For Customer Use Only
CUSTOMER NOTICE
LINEAR TECHNOLOGY HAS MADE A BEST EFFORT TO DESIGN A
CIRCUIT THAT MEETS CUSTOMER-SUPPLIED SPECIFICATIONS;
HOWEVER, IT REMAINS THE CUSTOMER'S RESPONSIBILITY TO
VERIFY PROPER AND RELIABLE OPERATION IN THE ACTUAL
APPLICATION. COMPONENT SUBSTITUTION AND PRINTED
CIRCUIT BOARD LAYOUT MAY SIGNIFICANTLY AFFECT CIRCUIT
PERFORMANCE OR RELIABILITY. CONTACT LINEAR
TECHNOLOGY APPLICATIONS ENGINEERING FOR ASSISTANCE.
THIS CIRCUIT IS PROPRIETARY TO LINEAR TECHNOLOGY AND
SCHEMATIC
SUPPLIED FOR USE WITH LINEAR TECHNOLOGY PARTS.
SCALE = NONE
www.linear.com
2
DEMO CIRCUIT 1741A
01/17/2012, 11:31 AM
11
TWO-SUPPLY DIODE-OR CURRENT SHARING CONTROLLER
N/A LTC4370CDE
KIM T.
VLADIMIR O.
SIZE
DATE:
IC NO. REV.
SHEET OF
TITLE:
APPROVALS
PCB DES.
APP ENG.
TECHNOLOGY Fax: (408)434-0507
Milpitas, CA 95035
Phone: (408)432-1900
1630 McCarthy Blvd.
LTC Confidential-For Customer Use Only
CUSTOMER NOTICE
LINEAR TECHNOLOGY HAS MADE A BEST EFFORT TO DESIGN A
CIRCUIT THAT MEETS CUSTOMER-SUPPLIED SPECIFICATIONS;
HOWEVER, IT REMAINS THE CUSTOMER'S RESPONSIBILITY TO
VERIFY PROPER AND RELIABLE OPERATION IN THE ACTUAL
APPLICATION. COMPONENT SUBSTITUTION AND PRINTED
CIRCUIT BOARD LAYOUT MAY SIGNIFICANTLY AFFECT CIRCUIT
PERFORMANCE OR RELIABILITY. CONTACT LINEAR
TECHNOLOGY APPLICATIONS ENGINEERING FOR ASSISTANCE.
THIS CIRCUIT IS PROPRIETARY TO LINEAR TECHNOLOGY AND
SCHEMATIC
SUPPLIED FOR USE WITH LINEAR TECHNOLOGY PARTS.
SCALE = NONE
www.linear.com
2
DEMO CIRCUIT 1741A
01/17/2012, 11:31 AM
11
TWO-SUPPLY DIODE-OR CURRENT SHARING CONTROLLER
N/A LTC4370CDE
KIM T.
VLADIMIR O.
REVISION HISTORY
DESCRIPTION DATEAPPROVEDECO REV
VLADIMIR O.2ND PROTOTYPE
_
2 01-17-12
REVISION HISTORY
DESCRIPTION DATEAPPROVEDECO REV
VLADIMIR O.2ND PROTOTYPE
_
2 01-17-12
REVISION HISTORY
DESCRIPTION DATEAPPROVEDECO REV
VLADIMIR O.2ND PROTOTYPE
_
2 01-17-12
R5
OPT
R5
OPT
D3
CCLM3500
D3
CCLM3500
21
D4
CCLM3500
D4
CCLM3500
21
E2
EN1 E2
EN1
M1
SUM85N03-06P
M1
SUM85N03-06P
M2
SUM85N03-06P
M2
SUM85N03-06P
C1
0.039uF
50V
C1
0.039uF
50V
CVCC
0.1uF
CVCC
0.1uF FETON2FETON2
D1
LN1251C-TR
OFF1
REDD1
LN1251C-TR
OFF1
RED
2 1
FETON1FETON1
E4E4
E7E7
R3 30.1kR3 30.1k
R7
OPT
R7
OPT
J2 OUTPUT
J2 OUTPUT
J4
VINB
18V MAX
J4
VINB
18V MAX
C2
0.039uF
50V
C2
0.039uF
50V
RANGERANGE
E1E1
R6
10K
R6
10K
J1
VINA
18V MAX
J1
VINA
18V MAX
R4
10K
R4
10K
E5
EN2 E5
EN2
R2
0.002
1%1W
2512
R2
0.002
1%1W
2512
E3
VCC E3
VCC
CC
0.18uF
CC
0.18uF
U1
LTC4370CDE
U1
LTC4370CDE
RANGE
2
COMP 3
CPO2
6
OUT2 7
EN2
1
VIN2
4
GATE2
5
FETON2 8
EN1
16
GND
15
VCC
14
VIN1
13
GATE1
12
CPO1
11
OUT1 10
FETON1 9
EP
17
E8E8
J5
GND J5
GND
D2
LN1251C-TR
OFF2
REDD2
LN1251C-TR
OFF2
RED
2 1
R1
0.002
1%1W
2512
R1
0.002
1%1W
2512
6
dc1741af
DEMO MANUAL DC1741A
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com
© LINEAR TECHNOLOGY CORPORATION 2012
LT 0912 • PRINTED IN USA
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
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tion engineer.
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Copyright © 2004, Linear Technology Corporation