L6756D STMicroelectronics, L6756D Datasheet - Page 24

• 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

Output voltage positioning
5.6
Note:
Note:
24/36
Soft-start
L6756D implements a soft-start to smoothly charge the output filter avoiding high in-rush
currents to be required to the input power supply. During this phase, the device increases
the reference from zero up to the programmed reference in closed loop regulation. Soft-start
is implemented only when all the power supplies are above their own turn-on thresholds and
the EN pin is set free. At the end of the digital soft-start, VR_RDY signal is set free.
Soft-start phase is initiated with a T1 = 2 ms (min) delay. After that, the reference ramps up
to V
during which the device reads the VID lines. Output voltage will then ramps up to the
programmed value in T4 with the same slope as before (See
SS sets the output voltage dv/dt during soft-start according to the resistor R
SGND. soft-start time T
27 kΩ resistor to program T2 = 500 µs.
Protections are active during soft-start, UVP is enabled after the reference reaches 0.5 V
while OVP is always active with a fixed 1.24 V threshold before V
threshold coming from the VID after V
If during T3 the programmed VID selects an output voltage lower than V
voltage will ramp to the programmed voltage starting from V
The VID code is checked at the end of T3. In case the device is enabled over an OFF code,
the output voltage will rise up to V
any pull-up and/or pull-down before T3.
Figure 9.
BOOT
= 1.081 V in T2 according to the R
Soft-start timings
SS
will proportionally change with a gain of 18.52 [µs / kΩ]. Connect
BOOT
BOOT
and then device will latch. VID lines does not show
(See red-dashed line in
SS
settings and waits for T3 = 200 μsec (typ)
BOOT
Figure
.
BOOT
Figure
9).
and with the
BOOT
9).
SS
, the output
connected to
L6756D