L6718 datasheet(55/71 Pages) STMICROELECTRONICS

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L6718

Output voltage monitoring and protection

The L6718 includes a complete set of protections: overvoltage, undervoltage, feedback

disconnection, overcurrent total and overcurrent per-phase.

The device monitors the voltage on the VSEN pin in order to manage OV, UV and feedback

disconnection while CS1- reads the voltage in order to detect VSEN disconnection. The

IMON pin is used to monitor total overcurrent and it shows different thresholds for different

operative conditions.

The device shows different thresholds when in different operative conditions but the

behavior in response to a protection event is still the same as described below.

Protection is active also during soft-start while it is properly increased during DVID

transitions with an additional delay to avoid false triggering.

Once the protection latches the device, a VCC cycle or enable cycle is needed to restart the

system. If protection occurs while the SMBus interface is used, a VCC cycle is necessary to

discharge the embedded register and reboot the system.

9.1

Overvoltage

During the soft-start or DVID, OVP threshold is fixed to 1.8 V, or 2.4 V if any offset is

present, until the VREADY is set, OVP then moves in tracking mode.

The OVP threshold is in tracking mode for both sections and it considers also an offset set

by SMBus or pinstrapping.

OVP is fixed if VOUT is set lower than 0.5 V. In this case, the OVP is set to 1.8 V with no

offset added or 2.4 V if offset is used.

When the voltage sensed by VSEN and/or SVSEN overcomes the OV threshold, the

controller acts in order to protect the load from excessive voltage levels, avoiding any

Table 18. L6718 protection at a glance

Section

Multi-phase

Single-phase

Overvoltage

(OV)

VSEN, SVSEN = +175/500 mV above Vref + Offset

Action: IC Latch; LS=ON & PWMx = 0 if required to keep the regulation to 250

mV; Other section: HiZ.

Undervoltage (UV)

VSEN, SVSEN = 500 mV below reference. Active after Ref > 500 mV

Action: IC Latch; both sections HiZ.

Overcurrent (OC)

Current monitor across inductor DCR. Dual protection, per-phase and average.

Action: UV-Like.

Feedback

disconnection

VSEN & FBG

VSEN or FBG not connected.

Action: IC Latch HiZ.

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