l6712a STMicroelectronics, l6712a Datasheet - Page 14

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

L6712A L6712
centage with respect to the load value, it can be simply considered that, for example, to have on OCP
threshold of 200%, this will correspond to I
spond to I
Once the UVP threshold has been intercepted, the device resets with all power mosfets turned OFF. An-
other soft start is then performed allowing the device to recover from OCP once the over load cause has
been removed.
Crossing the UVP threshold causes the device to reset: all mosfets are turned off and a new soft start is
then implemented allowing the device to recover if the over load cause has been removed.
I
The maximum duty cycle is fixed and constant with the delivered current. The device works in constant
current operation once the OCP threshold has overcome. Refer to the above Constant Current section in
which only the different value in the maximum duty has to be considered as follow:
All the above reported relationships about the deliverable current once in quasi-constant current and con-
stant current are still valid in this case.
REMOTE SENSE AMPLIFIER
Remote Sense Amplifier is integrated in order to recover from losses across PCB traces and wiring in high
current DC/DC converter remote sense of the regulated voltage is required to maintain precision in the
regulation. The integrated amplifier is a low-offset error amplifier; external resistors are needed as shown
in figure 7 to implement a differential remote sense amplifier.
Figure 7. Remote Sense Amplifier Connections
Equal resistors give to the resulting amplifier a unity gain: the programmed reference will be regulated
across the remote load.
To regulate output voltages different from the available references, the Remote Amplifier gain can be ad-
justed simply changing the value of the external resistors as follow (see Figure 7):
to regulate a voltage double of the reference, the above reported gain must be equal to ½.
Modifying the Remote Amplifier Gain (in particular with values higher than 1) allows also to regulate volt-
ages lower than the programmed reference.
Since this Amplifier is connected as a differential amplifier, when calculating the offset introduced
14/27
L6712A - Fixed Maximum Duty Cycle Limitation
R2
Remote
V
OUT
R1
INFOx
FBR
I
peak
FBG
R1
Remote
Ground
= 17.5 µ A (IFB = 35 µ A).
R2
=
AMPLIFIER
REMOTE
I
OCPx
RB used
VSEN
RA_Gain
R
FB
+
V
------------------------------------- - Ton
DROOP
IN
I
DROOP
Reference
–
=
Vout
FB
L
----------------------------------------------------------------------------------------
Remote_V
C
F
min
AMPLIFIER
INFOx
ERROR
R
F
⋅
COMP
= 35 µ A (I
OUT
MAX
V
VSEN
–
=
Remote_GND
FB
I
OCPx
= 70 µ A). The full load current will then corre-
V
OUT
FBR
+
FBG
V
-------------------------------------- - 0.85 T
IN
–
AMPLIFIER
REMOTE
Vout
=
L
VSEN
R2
------- -
R1
R
MIN
RB Not Used
FB
DROOP
⋅
I
DROOP
Reference
⋅
FB
C
F
AMPLIFIER
ERROR
R
F
COMP