L6615D STMicroelectronics, L6615D Datasheet - Page 15

• 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

Figure 15. Distributed power system for +48V bus
In this application is inserted also a circuit for the square current limit protection in case of overcurrent (R1-
Q1): being the voltage at the CGA pin directly proportional to the current carried by the relevant section,
it is possible to set the CGA resistor such that, until the output current is in the right range, the CGA voltage
is lower than V
path, reducing the duty cycle and consequently the output voltage.
Current sharing can be required in AC to DC application like distributed power system (DPS) for telecom
applications: if the output voltage is higher than the absolute maximum rating for the current sense pins
(CS+ and CS-) high side sensing can not be performed unless adding other components; the current
sense is performed on the ground return.
To maintain high side sensing two resistor dividers (between the edge of R
introduced to translate the sense signal in the L6615 input pin common mode range.
In fig.15 two AC-DC converters supply the same load through a +48V bus; these converters usually exhibit
also a +12V auxiliary output useful to supply the L6615 whose ADJ pin works on the +48V feedback sec-
tion (COMP pin and CGA pin connections are not showed) in figure 15.
7
The L6615 has a "doubled" sense structure, designed to perform both high side and low side sensing: the
first solution is usually considered more convenient. Actually low side sensing means to split the ground
return as many times as the power supplies paralleled are: on each of these paths it is then necessary to
place the sense resistor introducing a drop between the power supply ground and the common load neg-
ative reference.
The voltage at CS+ pin is read by an internal comparator and compared with a reference corresponding
to the switchover threshold V
parator triggers the High Side Amplifier (HSA); being the threshold provided by hysteresis, then the Low
Side Amplifier (LSA) will be triggered as VCS+ is lower than 1.44V (typ.).
Hence V
erating range of HSA; usually LSA is operating when the sense resistor is placed on the ground return,
between the negative load terminal and the negative power supply output (fig 10.b) and HSA when the
sense resistor is placed between the power supply positive output and the load.
It is however possible to perform high side sensing for applications whose output voltage is close to V
threshold (or even lower) exploiting the low sense internal structure (LSA).
LOW VOLTAGE BUSES
(*) the center of the
output feedback divider
is usually connected to
a voltage compatible
with L6615 AMR
Mains
Mains
THcs+
AC
AC
REF
defines the threshold between the operating range of LSA, (referring to fig.10) and the op-
+0.7. As soon as this value is overcome, then the bipolar pushes current in the feedback
+48V GND
+48V (*)
feedback
DPS1
+48V
+12V
THcs+
whose value is typically 1.6V. If such value is overcome, then the com-
Vcc
ADJ
CS-
R
L6615
G
R
SNS
R
CS+
GND
I
G
OUT1
SH
SH bus
O
A
D
L
I
OUT2
SH
GND
CS+
R
L6615
G
R
SNS
R
CS-
ADJ
Vcc
G
SENSE
+48V GND
+12V
+48V
+48V (*)
feedback
DPS2
and ground) could be
Mains
AC
L6615
THcs+
15/20