LTC7067

10

Rev. 0

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OPERATION

Since the power MOSFETs generally account for the

majority of the power loss in a converter, it is important

to turn them on and off quickly, thereby minimizing the

transition time and power loss. The LTC7067’s typical

1.5Ω pull-up resistance and 0.8Ω pull-down resistance

are equivalent to 3A peak pull-up current and 6A peak

pull down current at a 10V driver supply. Both G2 and G1

can produce a rapid turn-on transition for the MOSFETs

with capability of driving a 3nF load with 18ns rise time.

Protection Circuitry

When using the LTC7067, care must be taken not to

exceed any of the Absolute Maximum Ratings. As an

added safeguard, the LTC7067 incorporates an over-

temperature shutdown feature. If the junction tempera-

ture reaches approximately 180°C, the LTC7067 will

enter thermal shutdown mode and G2 will be pulled to

G2RTN; G1 will be pulled to G1RTN. Normal operation

will resume when the junction temperature cools to be

less than 165°C. The overtemperature level is not pro-

duction tested. The LTC7067 is guaranteed to operate at

temperatures below 150°C.

The LTC7067 contains both undervoltage and overvoltage

falls below 4.3V or rises above 14.6V, the output pins G2

and G1 are pulled to G2RTN and G1RTN, respectively.

adequate supply voltage but less than the overvoltage

threshold, normal operation will resume.

Additional undervoltage lockout circuitry is included in

each floating driver supply. The G2 will be pulled down to

falls below 3.3V. Similarly, the G1 will be pulled down to

is less than 3.3V.

The normal operation and undervoltage/overvoltage logic

table is shown in Table 1.

Table 1. Normal Operation and Undervoltage/Overvoltage Logic

G1IN G2IN

UVLO or

OVLO

G1RTN)

UVLO

G2RTN)

UVLO

THERMAL

SHUTDOWN G1 G2 FLTB

X

X

X

X

X

Yes

L

L

L

X

X

Yes

X

X

No

L

L

L

X

H

No

Yes

N

No

L H

L

H

X

No

No

Yes

No

H L

L

L

H

No

No

No

No

L H

H

H

L

No

No

No

No

H L

H

H

H

No

No

No

No

H H

H

L

L

No

No

No

No

L

L

H

Note: “X” means “Don’t Care”, “H” means “High”, and “L” means “Low”.

FAULT FLAG

FLT pin is connected to the open-drain of an internal

N-channel MOSFET. It needs a pull-up resistor (e.g. 51k)

to 15V. The FLT pin is pulled low to SGND immediately if

any of these conditions are met:

threshold.

d. The junction temperature reaches approximately

180°C.

When all the faults are cleared, FLT pin is pulled up by the

external resistor after a built-in 100µs delay.