L6722 STMicroelectronics, L6722 Datasheet - Page 27

• Manufacturer Part Number: L6722
• Description: IC BUCK ADJ 2A TRPL 36VFQFPN
• Manufacturer: STMicroelectronics
• Type: Step-Down (Buck)r

Specifications of L6722

• 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
• Output Voltage: 0.8 V to 1.85 V
• Output Current: 95 A
• Input Voltage: 13.8 V
• Mounting Style: SMD/SMT
• Maximum Operating Temperature: + 125 C
• Minimum Operating Temperature: - 40 C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

L6722
11
System control loop compensation
The control loop is composed by the Current Sharing control loop (See
Voltage control loop. Each loop gives, with a proper gain, the correction to the PWM in order to
minimize the error in its regulation: the Current Sharing control loop equalize the currents in the
inductors while the Voltage control loop fixes the output voltage equal to the reference.
Figure 16
The system Control Loop is reported in
the DROOP pin flows into R
read current (when DROOP is enabled).
Figure 16. Main control loop
The system can be modeled with an equivalent single phase converter which only difference is
the equivalent inductor L/3 (where each phase has an L inductor).
The Control Loop gain results (obtained opening the loop after the COMP pin):
Where:
●
●
●
●
●
R
function;
Z
the applied load R
Z
Z
A(s) is the error amplifier gain;
DROOP
P
F
L
(s) is the parallel of the three inductor impedance;
(s) is the impedance resulting by the parallel of the output capacitor (and its ESR) and
(s) is the compensation network impedance;
shows the block diagram of the system control loop.
=
DCR
------------ -
Rg
G
LOOP
CURRENT SHARING
⋅
CORRECTION
DUTY CYCLE
R
1 / 5
1 / 5
1 / 5
O
s ( )
FB
;
is the equivalent output resistance determined by the droop
FB
=
–
implementing the dependence of the output voltage from the
------------------------------------------------------------------------------------------------------------------------ -
[
Z
P
s ( )
I
I
I
INFO1
INFO2
INFO3
PWM
+
Figure
Z
L
⋅
PWM3
PWM2
PWM1
s ( )
4 / 5
Z
ERROR AMPLIFIER
17. The current information I
]
F
⋅
s ( )
COMP
Z
-------------- -
⋅
A s ( )
F
(
s ( )
R
DROOP
L3
L2
L1
Z
+
F
(s)
⎛
⎝
1
11 System control loop compensation
+
Reference
FB
----------- -
A s ( )
+
1
Z
P
⎞
⎠
s ( )
I
DROOP
⋅
C
Figure
OUT
)
R
Z
FB
F
DROOP
(s)
R
OUT
16) and the
sourced by
27/34