l6712a STMicroelectronics, l6712a Datasheet - Page 20

• Manufacturer Part Number: l6712a
• Description: Two-phase Interleaved Dc/dc Controller
• Manufacturer: STMicroelectronics

L6712A L6712
Figure 13. Current Sharing Control Loop.
Where ∆ I
For R
and R
Average Current Mode (ACM) Control Loop (DROOP=FB)
The average current mode control loop is reported in figure 14. The current information I
the DROOP pin flows into R
The ACM control loop gain results (obtained opening the loop after the COMP pin):
Where:
I
I
I
I
I
I
I
Removing the dependence from the Error Amplifier gain, so assuming this gain high enough, the control
loop gain results:
20/27
Z
load Ro;
Z
Z
A(s) is the error amplifier gain;
and has a typical value of 3V
RA_Gain is the Remote Amplifier Gain.
R
PWM
P
F
L
DROOP
(s) is the compensation network impedance;
(s) is the parallel of the two inductor impedance;
(s) is the impedance resulting by the parallel of the output capacitor (and its ESR) and the applied
SENSE
SENSE
=
READ
= 4m Ω and I
4
-- -
5
mismatches.
=
⋅
------------------ -
∆ V
Rsense
--------------------- - R
is the difference between one phase current and the ideal current (I
V
Rg
G
OSC
IN
LOOP
G
LOOP
is the ACM PWM transfer function where ∆ V
COMP
MAX
⋅
s ( )
FB
FB
= 40A the current sharing error is equal to 2.5%, neglecting errors due to Rg
+
+
s ( )
=
implementing the dependence of the output voltage from the read current.
is the equivalent output resistance determined by the droop function;
–
=
4
-- -
5
⋅
–
------------------ -
∆ V
PWM Z
----------------------------------------------------------------------------------------------------------------------- -
(
PWM1
PWM2
V
Z
1/5
1/5
OSC
IN
P
s ( )
⋅
⋅
+
----------------------------------- -
Z
F
Z
D02IN1393
P
s ( )
L
s ( ) Z
s ( )
CORRECTION
Z
DUTY CYCLE
⋅
F
CURRENT
SHARING
(
+
s ( )
)
R
⋅
DROOP
L
Z
-------------- -
s ( )
A s ( )
F
s ( )
⋅
§
¨
©
Rs
------- -
Rg
+
+
I
I
INFO2
INFO1
RA_Gain Z
§
©
1
+
L 1
L 2
+
RA_Gain Z
-------------------------------------------- -
OSC
----------- -
A s ( )
1
is the oscillator ramp amplitude
V
· R
¹
OUT
R
⋅
⋅
FB
P
⋅
FB
s ( )
P
)
s ( )
MAX
·
¸
¹
/2).
DROOP
sourced by