l6706 STMicroelectronics, l6706 Datasheet - Page 34

• Manufacturer Part Number: l6706
• Description: Vr11.1 Single Phase Controller With Integrated Driver
• Manufacturer: STMicroelectronics

Output voltage monitor and protections
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15.1
15.2
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Output voltage monitor and protections
L6706 monitors through pin VSEN the regulated voltage in order to manage the OVP and
UVP conditions. Protections are active also during soft-start
they are masked during D-VID transitions with an additional 67µs delay after the transition
has finished to avoid false triggering.
Undervoltage
If the output voltage monitored by VSEN drops more than 600 mV (typ) below the
programmed reference for more than one clock period, the L6706:
Preliminary overvoltage
To provide a protection while VCC is below the UVLO
damage to the CPU in case of failed HS MOSFETs. In fact, since the device is supplied from
the 12 V bus, it is basically “blind” for any voltage below the turn-on threshold (UVLO
order to give full protection to the load, a preliminary-OVP protection is provided while VCC
is within UVLO
This protection turns-on the low side MOSFETs as long as the VSEN pin voltage is greater
than 1.800 V with a 350 mV hysteresis. When set, the protection drives the LS MOSFET
with a gate-to-source voltage depending on the voltage applied to VCC. This protection
depends also on the OUTEN pin status as detailed in
A simple way to provide protection to the output in all conditions when the device is OFF
(then avoiding the unprotected red region in
controller through the 5 V
+12 V and, in case of HS short, the LS MOSFET is driven with 5V assuring a reliable
protection of the load.
Figure 18. Output voltage protections and typical principle connections
–
–
–
UVLO
UVLO
Permanently turns OFF the MOSFETs
Drives the OSC/ FAULT pin high (3.3 V typ).
Power supply or OUTEN pin cycling is required to restart operations.
VCC
OVP
V cc
VCC
VSEN Monitored
Preliminary OVP
(OUTEN = 0)
and UVLO
Preliminary OVP Enabled
SB
VSEN Monitored
No Protection
Provided
bus as shown in
Pre-OVP
Programmable OVP
Doc ID 15698 Rev 1
VSEN Monitored
(OUTEN = 1)
.
Figure
Figure
18-Left) consists in supplying the
18-Right: 5V
+12V
+5V
VCC
Figure
SB
threshold is fundamental to avoid
BAT54C
(See “Soft-start”
18.
SB
is always present before
2.2Ω
10Ω
1μF
1μF
Section) while
VCC
VCCDR
VCC
L6706
). In