L6722TR STMicroelectronics, L6722TR Datasheet - Page 16

• Manufacturer Part Number: L6722TR
• Description: IC BUCK ADJ 2A TRPL 36VFQFPN
• Manufacturer: STMicroelectronics
• Type: Step-Down (Buck)r

Specifications of L6722TR

• Internal Switch(s): No
• Synchronous Rectifier: No
• Number Of Outputs: 3
• Voltage - Output: Adj to 0.8V
• Current - Output: 2A
• Frequency - Switching: 100kHz
• Voltage - Input: 12V
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 36-VFQFN, 36-VFQFPN
• Power - Output: 3.5W
• Operating Temperature Range: - 40 C to + 125 C
• Mounting Style: SMD/SMT
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: 497-5904-2

6 Current sharing loop and current reading
6
Caution:
16/34
Current sharing loop and current reading
L6722 embeds two separate Current-Reading circuitries used to perform Current-Sharing and
OCP through ISENx pins and Voltage-Positioning through CS+ and CS- pins (See
Current-sharing control-loop and connections are reported in
the I
phase and the information about the average current I
device. The error between the read current I
a voltage that with a proper gain is used to adjust the duty cycle whose dominant value is set by
the voltage error amplifier in order to equalize the current carried by each phase.
The current flowing trough each phase is read using the voltage drop across the low-side
mosfets R
current. The trans-conductance ratio is issued by the external resistor R
chip between I
The current sense circuit tracks the current information for a time T
middle of the LS conduction time and holds the tracked information during the rest of the
period. The current that flows from the I
perform current sharing and OCP and it is given by:
where R
resistor connected between the ISENx pins and the LS Drain; I
the relative phase and I
R
Asymmetries in the R
so that one phase can carry higher currents or support different cooling. To increase the current
in any of the phases, the value of the related R
theoretical value extracted from the above reported relationships. Start from the coolest phase
first to get the thermal balance.
Figure 6.
ISENx
AVG
SENx
is designed according to the Over Current Protection: see
dsON
pins is converted into a current I
dsON
Current sharing loop and current reading connections
is the ON resistance of the low side mosfet and R
SENx
or across a sense resistor in its series and it is internally converted into a
and the reading point (usually the LS mosfet Drain).
I
I
I
From EA
I
ISENx
INFO1
AVG
INFO2
INFO3
INFOx
values are allowed in order to create intentional current-unbalance
I
ISENx
is the current information signal reproduced internally.
=
R
-----------------
R
SENx
dsON
ISEN
INFOx
INFOx
pin is the current information used by the device to
⋅
PWM1 Out
PWM2 Out
PWM3 Out
ISEN
I
proportional to the current delivered by each
PHASEx
and the reference I
can be slightly increased starting from the
AVG
=
= ΣI
I
I
INFOx
ISENx
Figure
INFOx
PHASEx
ISEN
LGATEx
Section 9.6
ISENx
TRACK
/ 3 is internally built into the
6: the current read through
is the trans-conductance
AVG
is the current carried by
ISEN
is then converted into
centered in the
R
ISEN
placed outside the
for details.
Section
L6722
I
PHASEx
7).