LM51772 datasheet(11/112 Pages) TI

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Typical values correspond to TJ=25°C. Minimum and maximum limits apply over TJ=0°C to 70°C. Unless otherwise stated,

V(BIAS) =12 V

PARAMETER

MIN

TYP

MAX UNIT

VT-(SYNC)

Sync input negative going threshold

0.41

td(Det,Sync)

Sync activity detection frequency

threshold

refered to f(SYNC)

cycle

Sync PLL lock time

refered to f(SYNC)

until f(SYNC) - 5% < f(sw)

< f(SYNC) + 5%

cycle

SYNC high level output voltage drop

EN_SYNC_OUT = 0b1

I(SYNC) = 2 mA, V(VCC2) ≥

3.5 V,

Referenced to V(VCC2)

0.4

SYNC low level output voltage

0.3

SYNC output drive strength

EN_SYNC_OUT = 0b1

V(VCC2) = 5 V

sink

–42

–31

–22 mA

source

42 mA

SOFT-START

I(SS)

Soft-start current

SS pull-down switch RDS(on)

V(SS) = 1 V

td(DISCH;SS) SS Pin discharge time

Time from internal SS

discharge until the soft-

start current can charge

the pin again

500

µs

td(EN_SS)

SS Pin ramp start delay time

Internal delay until soft-

start current starts

2.5

µs

VOUT TRACKING

VT+(DTRK)

DTRK positive-going threshold

V(DTRK) rising

1.19

VT-(DTRK)

DTRK negative-going threshold

V(DTRK) falling

0.41

DTRK activity dectection

frequency

DTRK

activity

detection

frequency

148

kHz

td(DTRK)

DTRK detection delay time

cycle

fc(LPF)

Corner frequency of

internal low pass

kHz

V(REF)voltage offset error

V(REF)voltag

e offset

error

f(DTRK) = 500kHz, duty =

50%, V(REF) = 1V

±10 mV

PULSE WIDTH MODULATION

Switching frequency

RRT = 316kΩ,

100

110 kHz

Minimum controllable on-time

fPWM, RRT = 14 kΩ,

positive inductor current

Boost Mode

Buck Mode

107

Minimum controllable off-time

Boost Mode

Buck Mode

RT regulation voltage

0.75

MODE SELECTION

VT+(MODE)

Mode input positive going threshold

1.19

VT-(MODE)

Mode input negative going threshold

0.41

CURRENT SENSE

Positive peak

current limit threshold

55 mV

Negative peak current

limit threshold

–56

–50

–44 mV

AVERAGE CURRENT LIMIT

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