L6756D STMicroelectronics, L6756D Datasheet - Page 33

• Manufacturer Part Number: L6756D
• Description: IC CTLR 2/3/4PH BUCK 40-VFQFPN
• Manufacturer: STMicroelectronics

Specifications of L6756D

• Applications: Controller, Intel VR10, VR11, VR11.1
• Voltage - Input: 12V
• Number Of Outputs: 4
• Voltage - Output: 0.3 ~ 1.6 V
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 40-VFQFN, 40-VFQFPN
• Output Voltage: 3 V
• Input Voltage: - 0.3 V to + 15 V
• Switching Frequency: 185 KHz to 215 KHz
• Operating Temperature Range: - 40 C to + 150 C
• Mounting Style: SMD/SMT
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

L6756D
Sensitivity of the load transient detector and the gain of the LTB ramp can be programmed in
order to control precisely both the undershoot and the ring-back.
●
●
LTB Technology
Detector design. R
which is desired the controller to be sensitive as follow:
Gain design. Through the LTBGAIN pin it is possible to modify the slope of the LTB
Ramp in order to modulate the entity of the LTB response once the LT has been
detected. In fact, the response depends on the board design and its parasites requiring
different actions from the controller.
Leaving the LTBGAIN pin floating, the maximum pulse-width is programmed. The slope
of the LTB ramp will be equal to 1/2 of the OSC ramp slope.
Connecting R
Where I
(20μA plus the current coming from the OSC pin).
–
–
–
R
LTBRamp
LTB
Descries R
smaller dV
Increase C
higher dV/dt.
Increase R
=
LTBGAIN
dV
----------------- -
25μA
Slope
OUT
®
design tips.
LTBGAIN
OUT
=
LTB
LTBGAIN
LTB
is the current sunk from LTBGAIN pin and I
OSC
LTB
.
to increase the system sensitivity making the system sensitive to
C
to increase the system sensitivity making the system sensitive to
LTB
to GND, the LTB Ramp slope can be modified as follow:
- C
Slope
to increase the width of the LTB pulse.
=
LTB
--------------------------------------------- -
2πN R
⋅
⎛
⎝
is design according to the output voltage deviation dV
1
+
⋅
I
----------------------- -
LTBGAIN
LTB
1
I
OSC
⋅
F
SW
⎞
⎠
System control loop compensation
OSC
is the OSC current
33/36
OUT