L6712QTR STMicroelectronics, L6712QTR Datasheet - Page 17

• Manufacturer Part Number: L6712QTR
• Description: IC CTRLR DC/DC 2PH SYNC 36VFQFPN
• Manufacturer: STMicroelectronics
• Type: Step-Down (Buck)r

Specifications of L6712QTR

• Internal Switch(s): No
• Synchronous Rectifier: Yes
• Number Of Outputs: 2
• Voltage - Output: 0.9 ~ 3.3 V
• Current - Output: 2A
• Frequency - Switching: 150kHz
• Voltage - Input: 12V
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 36-VFQFN, 36-VFQFPN
• Power - Output: 3.5W
• Operating Temperature Range: - 40 C to + 125 C
• Mounting Style: SMD/SMT
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: 497-4219-2

Figure 13. UVP Protection & Hiccup Mode.
3.8 SOFT START AND INHIBIT
At start-up a ramp is generated increasing the loop reference from 0V to the final value programmed by
VID in 2048 clock periods as shown in Figure 14.
Once the soft start begins, the reference is increased: upper and lower Mosfets begin to switch and the
output voltage starts to increase with closed loop regulation. At the end of the digital soft start, the Power
Good comparator is enabled and the PGOOD signal is then driven high (See Figure 14).
The Under Voltage comparator is enabled when the increasing reference voltage reaches 0.6V while OVP
comparator is always active with a threshold equal to the +15%_min of the final reference.
The Soft-Start will not take place, if both VCC and VCCDR pins are not above their own turn-on thresholds.
During normal operation, if any under-voltage is detected on one of the two supplies the device shuts
down. Forcing the OSC/INH pin to a voltage lower than 0.5V (Typ.) disables the device: all the power mos-
fets and protections are turned off until the condition is removed.
Figure 14. Soft Start.
reference voltage reaches 0.6V). The reference used in this case to determine the UV thresholds is the
increasing voltage driven by the 2048 soft start digital counter while the reference used for the OV
threshold is the final reference programmed by the VID pins or available on the REF_IN/OUT pin.
V
CC
=V
V
PGOOD
LGATEx
V
CCDR
OUT
Timing Diagram
2048 Clock Cycles
CH1=PGOOD; CH2=Vout; CH3=REF_OUT; CH4=Iout
Turn ON threshold
t
t
t
t
CH1=PGOOD; CH2=VOUT; CH3=REF_OUT
Acquisition:
L6712A L6712
17/29