LM5080
Modular Current Sharing Controller
General Description
The LM5080 is a simple and cost effective load share con-
troller that provides all functions required to balance the
currents delivered from multiple power converters operated
in parallel. The LM5080 implements an average program
(AP) method of active load share control which adjusts the
output voltage of individual power stages either up or down
to deliver nearly equal currents to a common load. The
average program method improves stability and reduces the
output voltage tolerance when compared to other common
load sharing methods. The LM5080 supports two common
applications for load share controllers: external control in
which the load share circuit balances currents between
separate power modules (bricks), and internal control where
the load share circuit is integrated into the voltage regulation
loop of each power converter module or circuit.
Features
n
Average program current share method
n
Single-wire star link current share bus
n
No precision external resistors necessary
n
3V to 15V bias voltage range
n
Adaptable for high or low side current sensing
n
Flexible architecture allows 4 modes of operation:
Negative remote sense adjustment
Positive remote sense adjustment
Trim or reference adjustment
Feedback divider adjustment
Packages
n
MSOP-8
n
RoHS compliant Pb free available
LM5080 Typical Application
20157801
Remote Sense Adjust Mode
January 2006
LM5080
Modular
Current
Sharing
Controller
2006 National Semiconductor Corporation
DS201578
www.national.com
Connection Diagram
20157802
8-Lead MSOP
See NS Package Number MUA08A
Ordering Information
Order Number
Description
NSC Package Drawing
Supplied As
LM5080MM
MSOP-8
MUA08A
1000 Units on Tape and Reel
LM5080MMX
MSOP-8
MUA08A
3500 Units on Tape and Reel
Pin Descriptions
Pin
Name
Description
1
SHR
Current Share Bus. The SHR pins of each LM5080 device are connected together.
2
CSM
Current Sense Amplifier Minus Input.
3
TRO
Transconductance Output. One of two outputs of the current sense transconductance amplifier.
4
GND
Ground. Connect to negative terminal of the LM5080 bias supply.
5
RSO
Remote Sense Output. Capable of driving the low impedance remote sense pin of a power
converter.
6
VCC
Bias Supply. VCC can be connected to the output of the power converter that the LM5080
controls if greater than 3V, or it can be connected to another bias source for lower voltage
systems.
7
CSO
Current Sense Output. One of two outputs of the current sense transconductance amplifier.
8
CSP
Current Sense Amplifier Positive Input.
LM5080
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2
Absolute Maximum Ratings
(Note 1)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
V
CC
to GND
-0.3V to 15V
RSO to GND (Note 2)
-0.3V to 5V
All other pins to GND
-0.3V to 5V
ESD Rating (Note 3)
Human Body Model
2kV
Storage Temperature
-55C to +150C
Junction Temperature
150C
Operating Ratings
(Note 1)
VCC to GND
3V to 14 V
Operating Junction Temperature
-40C to +125C
Electrical Characteristics
Limits in standard type are for T
J
= 25C only; limits in boldface type apply over
the junction temperature range of 40C to +125C and are provided for reference only. Unless otherwise specified, the fol-
lowing conditions apply: CSM = 0, VCC = 5V, RSO unloaded.
Symbol
Parameter
Conditions
Min
Typ
Max
Units
ICC
VCC Quiescent Current
RSO shorted to CSO
CSP = 50 mV
CTRO = 10nF
3.7
5.5
mA
CSP Input open circuit voltage ratio
Specified as a percentage of VCC
19
20
21
%
CSP mode threshold ratio- Rising
Specified as a percentage of VCC
8.5
10.5
12.5
%
CSP mode threshold ratio - Falling
Specified as a percentage of VCC
7.0
9.5
11
%
Current Share Amplifier
VIO
Input Offset Voltage (RSO-CSP)
RSO shorted to CSO
CSP = 50 mV
CTRO = 10nF
-2.5
-3.5
0
2.5
3.5
mV
RSO shorted to CSO
CSP = 600 mV
CTRO = 10nF, VCC = 3V
-1
-2
0
1
2
mV
CSM
MAX
Input Common Mode Voltage
Range
CSP - CSM = 50 mV
RSO shorted to CSO
CSO-CSP
<
1 mV
CTRO = 10 nF
VCC-2V
V
CSM
MIN
0
V
GM
TRO
Current Share Amplifier
Transconductance
GM
TRO
=
ITRO / VSHR
CTRO = 10 nF
8.7
mA/V
I
TRO_SRC
TRO sourcing current limit
TRO = 500 mV
CSO open, CSP = 1.1V
9
11
14
A
I
TRO_SINK
TRO sinking current limit
TRO = 500 mV
CSO open, CSP=0.9V
8.2
11
13.5
A
I
TRO_OS
TRO offset current
TRO = 750 mV
CSP, CSO Open Circuit
1
0
1
A
V
TRO_MIN
TRO Output Range
CSP, CSO, SHA open circuit
ITRO_OS
<
500 nA
450
mV
V
TRO_MAX
2.75
V
RSO Buffer
VIO
RSO
RSO Buffer Input offset Voltage
Offset = TRO-RSO, TR0 = 750 mV
CSO, CSP open circuit
-4
0
4
mV
I
LIMSRC
RSO source current limit
18
26
35
mA
I
LIMSNK
RSO sink current limit
18
26
35
mA
VOL
RSO
RSO output low voltage
CSP = 0V, Sinking 10 mA
12
28
mV
Thermal Resistance
JA
Junction to Ambient
MSOP-8 Package
190
C/W
LM5080
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3
Electrical Characteristics
Limits in standard type are for T
J
= 25C only; limits in boldface type apply over
the junction temperature range of 40C to +125C and are provided for reference only. Unless otherwise specified, the
following conditions apply: CSM = 0, VCC = 5V, RSO unloaded. (Continued)
Note 1: Absolute Maximum Ratings are limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the device is intended
to be functional, but does not guarantee specific perfromance limits. For guaranteed specifications and test conditions see the Electrical Characteristics.
Note 2: Maximum recommended operating voltage not to exceed VCC - 2V or 5V, whichever is lower.
Note 3: The human body model is a 100 pF capacitor discharged through a 1.5 k
resistor into each pin.
Typical Performance Characteristics
I
CC
vs V
CC
Current Share Amplifier Transconductance vs VCC
20157817
20157818
RSO Sink Current Limit vs VCC
RSO Source Current Limit vs VCC
20157819
20157820
LM5080
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4
Typical Performance Characteristics
(Continued)
RSO Buffer Input Offset Voltage vs VCC
RSO VOL vs VCC
20157821
20157822
TRO Current Limit vs VCC
TRO Offset Current vs TRO Voltage
20157823
20157824
CSP Input Open Circuit Voltage vs VCC
CSP Mode Thresholds vs VCC
20157826
20157827
LM5080
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5
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