UCC28056CDBVT datasheet(23/55 Pages) TI2

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DRV

Ovp2Fltb

Zcdb

TOvp2Blk

TOvp2En

IL(t)

VZC(t) ± Cold NTC

VZC(t) ± Hot NTC

VOvp2Th

UCC28056

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SLUSD37E – OCTOBER 2017 – REVISED NOVEMBER 2019

Product Folder Links: UCC28056

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Feature Description (continued)

The UCC28056 triggers an Ovp2 fault if the time between the falling edge of the Ovp2 comparator output and the

Zcdb signal is less than TOvp2En for three consecutive switching cycles. The series impedance required to trigger

a false Ovp2 fault is greatly increased because the Ovp2 comparator must be tripped close to the Zcdb point

when the current flowing through the NTC resistor is small.

An internal discharge resistor (RCODisch) between the COMP and GND pins connected for each switching cycle

causes the Ovp2 comparator to trip. This internal resistance discharges the external compensation network

reducing power demand and therefore the peak current flowing through the NTC resistor. The internal COMP

discharge resistor remains connected for any switching cycle that triggers the Ovp2 comparator. The internal

COMP discharge resistor becomes disconnected after the first switching cycle that does not trigger the Ovp2

comparator. By limiting the peak current flowing through the cold NTC resistor, the effect of this circuit is to limit

the peak voltage stress applied to the Boost MOSFET during a cold start.

Figure 24. Waveforms to Illustrate Ovp2 Operation

8.3.5.4 Thermal Shutdown Protection

The controller includes an internal temperature sensor. During the switching period, the controller triggers a

Thermal ShutDown (TSD) fault if the internal silicon temperature exceeds TTSDRise for three consecutive switching

cycles. The TSD fault halts switching operation and causes the controller to transition to its Stopb state for a

period TLongFlt. After this delay the controller continues the normal start-up process.

The controller does not exit the Stopb state to begin switching operation while the internal silicon temperature is

above TTSDFall.

UCC28056CDBVT Datasheet(PDF) 23 Page - Texas Instruments