L6615D STMicroelectronics, L6615D Datasheet - Page 11

• Manufacturer Part Number: L6615D
• Description: IC CTRLR LOAD SHARE HI/LO 8-SOIC
• Manufacturer: STMicroelectronics

Specifications of L6615D

• Applications: Power Supplies, Converters, Controllers
• Current - Supply: 5mA
• Voltage - Supply: 2.7 V ~ 22 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (3.9mm Width)
• Operating Temperature Range: - 40 C to + 125 C
• Mounting Style: SMD/SMT
• For Use With: 497-5498 - EVAL BOARD FOR L6615
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

At full load, V
R
I
tems composed by N power supplies, each of them works at its nominal current, so:
This relationship is true also in N+M redundant system, even if under normal condition each power supply
provides I
For example in a system composed by two paralleled power supplies 100% redundant (N=M=1), each
module is sized to sustain the entire load current (in normal operation it carries only one half): for this rea-
son the sense resistor must be sized considering the whole load current.
The temperature variation of the sense resistor (hence of its resistance value) has to be taken into ac-
count, so R
Once fixed V
culated:
where V
A small capacitor in parallel to R
The effect of current sharing feedback loop is to force the voltages of the slave's CGA pins to be equal to
V
simplicity we consider 2 paralleled power supplies (as in fig. 11): under closed loop condition:
Ideally all the external component and
Any mismatch will have repercussion on the sharing precision: in particular the maximum difference be-
tween the output currents (sharing error) will be given by the sum of the mismatches amongst the relevant
values.
OUT(MAX)
SH
SENSE
– maximum share bus voltage is internally limited up to 2.2V below L6615 V
– V
– maximum share drive amplifier current capability (I
– for safety reasons the following relation must be met:
This condition is not tough to meet in normal applications, as one can easily see by using sensible
values for N (number of paralleled power supplies) and V
solving for N, we obtain Nmax=20;
keeping in mind that every Volt on the share bus will increase the master controller's supply current
by approximately 45 A for each slave unit connected in parallel; this total current, provided by the
master share drive amplifier, must be lower than its minimum output capabilty (8mA) so
(that is to reduce the voltage difference at the inputs of the L6615 error amplifier). For the sake of
in this way no fault will cause I
SH(MAX)
(typically few hundreds of millivolt).
SH(MAX)
LOAD
is the maximum current carried by each of the paralleled power supply; in non redundant sys-
SENSE(MAX)
SENSE(MAX)
/(N+M).
represents an upper limit but the designer should select the full scale share bus voltage
SENSE(MAX)
is defined by the application.
I
OUT 1
is the value at maximum operating temperature to avoid saturating the share bus.
, the ratio R
= I
OUT(MAX
R
--------------------- - R
CGA
R
SNS 1
G 1
CS+
CGA
is useful to reduce the noise.
I
) · R
OUT 1
V
(or I
/R
R
---------------
SH MA X
are matched so:
R
R
I
CGA
G
OUT MAX
G
SENSE(MAX)
G
CGA 1
CS-
(gain from the sensing section to the share bus) can be cal-
=
1
-- -
2
) to overcome its absolute maximum ratings.
=
I


-------------------------------------
V
OUT 2
--------------- - 40
10mA
R
------------------ - 8mA
SENSE MAX
=
V
V
i MIN
out
SH MAX
=
I
N
OUT 2
is the maximum voltage drop across the resistor
CGA(MAX)
I
--------------- -
LOAD
=
–
N
I
--------------- -
LOAD


SH(MAX)
2
R
--------------------- - R
R
=2mA);
SNS 2
G 2
. For example, with V
CGA 2
CC
voltage (pin#8);
SH(MAX)
L6615
11/20
=8V,