L6756D STMicroelectronics, L6756D Datasheet - Page 25

• 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
5.6.1
LSLESS start-up
In order to avoid any kind of negative undershoot on the load side during start-up, L6756D
performs a special sequence in enabling the drivers for both sections: during the soft-start
phase, the LS driver results to be disabled (LS = OFF - Gx set to HiZ and DRVON = 0) until
the first PWM pulse. After the first PWM pulse, Gx outputs switches between logic “0” and
logic “1” and DRVON is set to logic “1”.
This particular sequence avoids the dangerous negative spike on the output voltage that
can happen if starting over a pre-biased output.
Low-side MOSFET turn-on is masked only from the control loop point of view: protections
are still allowed to turn-ON the low-side MOSFET in case of overvoltage if needed.
Figure 10. LSLESS start-up: enabled (left) and disabled (right)
Output voltage positioning
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