L6615 STMicroelectronics, L6615 Datasheet - Page 12

• Manufacturer Part Number: L6615
• Description: High/low side load share controller
• Manufacturer: STMicroelectronics

L6615
Figure 12. ADJ network
To set the R
(V
represents the voltage that the L6615 must be able to correct.
Now two different approaches are feasible depending on whether the SMPS (whose output current must
be shared) has to be completely designed or it is an "off the shelf" component and only the current sharing
section must be designed.
In the first case, the adjustment resistor (R
feedback divider R
state condition, through the feedback divider I
we will have:
It can be an useful rule of thumb to use R
worst case condition, it will be:
This value must not exceed the one indicated in the "Electrical characteristic section" but this is very easy
to meet, as one can easily see by using sensible values for
In the second case (fig 12.b), the feedback divider has been already designed by the SMPS manufacturer
and it is not possible to modify it: the design of R
maximum spread without significantly shifting the SMPS regulation point. A minimum R
found by:
where I
Especially for low voltage output buses it is important to avoid adjustment network saturation; the design
must satisfy the following relationship:
where V
12/20
OUT
± V
ADJ(max)
ADJ(MIN)
O
); the maximum difference between master and slave output voltage is 2* V
ADJ
is 8mA.
value it is necessary to know the tolerance required of the power supply output voltage
can be found in the "Electrical characteristic section" for different I
H
(see fig.12.a): typically the first step consist of fixing the current flowing, under steady
E/A
E/A
V
V
REF
REF
R
R
R
R
ADJ
ADJ
1
1
V
a)
a)
V
V
OUT
OUT
OUT
R
H
R
R
2
2
=
I
I
–
ADJ
ADJ
R
R
R
to L6615
to L6615
ADJ pin
ADJ pin
ADJ
I
ADJ
ADJ min
1
ADJ max
ADJ
+
lower than (or equal to) one tenth of R1, considering that, in
R
FB
I
) can be considered as a fraction of the high resistor of the
FB
ADJ
; by choosing the value for R
I
ADJ
ADJ
=
=
=
must be done to make the L6615 able to correct the
V
------------- -
=
+
R
------------------------- -
I
REF



ADJ max
I
POWER SUPPLY
POWER SUPPLY
------------------
V
-------------- - 1
V
FB
2
R
V
V
Off the shelf
Off the shelf
OUT
REF
E/A
E/A
ADJ
OUT
OUT
V
V
–
b)
b)
A DJ MIN
OUT
V
V



REF
REF
R
and R
R
R
ADJ
ADJ
2
V
V
OUT
OUT
2
.
I
I
ADJ
ADJ
2
:
to L6615
to L6615
ADJ pin
ADJ pin
ADJ
O
values.
ADJ
and this amount
value can be