LTC4367 datasheet(17/30 Pages) AD

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LTC7000A

Rev. 0

For more information www.analog.com

APPLICATIONS INFORMATION

7000A F06

TIMER

∆VSNS

V(TG-TS)

(TGUP SHORTED TO TGDN)

FAULT

>30mV

<30mV

0.4V

1ST

31ST

32ND

INP

1.30V

1.40V

Figure 6. Auto Retry with INP Cycling Low

Fast Turn-Off Mode

If the TIMER pin is connected to VCC or any other supply

greater than 3.5V (abs max 15V), an overcurrent event

will immediately pull TGDN to TS and the LTC7000A/

LTC7000A-1 will remain there until the INP signal has

cycled low and then back high. In fast turn-off mode, the

typical delay from a ΔVSNS overcurrent step to TG going

low is around 70ns, so very fast short-circuit events can

be detected. Also, when the TIMER pin is connected to a

voltage greater than 3.5V, the FAULT signal is redefined to

be the inverse state of the high side pull-up (VTGUP – VTS).

The FAULT signal can be used in this application as low-

voltage digital information that has been level shifted

down from the high side MOSFET. An application for this

could include using this signal to wait until VTGUP–VTS has

gone low before turning on a redundant power MOSFET.

High Side Current Monitor Output (LTC7000A Only)

The LTC7000A contains a high side current monitor output.

The high side differential voltage sensed across the SNS+

and SNS– pins (ΔVSNS) is multiplied by 20 and ground

referenced on the IMON pin which makes it suitable for

monitoring and regulating the MOSFET current. The work-

ing range of IMON is 0V to 1.5V as ΔVSNS varies from 0mV

to 75mV. The IMON pin is a voltage output whose nominal

output impedance is 100kΩ and should not be resistively

loaded. The current monitor output is only available after

the INP signal has been high for 0.5µs (typical), other-

wise the IMON pin is pulled to ground. A block diagram of

the IMON circuit is shown in Figure 7. The gm of the tran-

simpedance amplifier tracks the 100kΩ internal resistor

to ground which makes variations over process minimal.

IMON

gm = 200µA/V

7000A F07

LTC7000A

SNS+

SNS–

–

100k

INP

Figure 7. IMON Block diagram

RUN Pin and External Input Overvoltage/Undervoltage

Lockout (LTC7000A Only)

The RUN pin has two different threshold voltage levels.

Pulling RUN below 0.7V puts the LTC7000A into a low

quiescent current shutdown mode (IQ ~ 1µA). When

the RUN pin is greater than 1.21V, the part is enabled.

Figure 8 shows examples of configurations for driving

the RUN pin from logic.

The RUN and OVLO pins can alternatively be configured

as precise undervoltage (UVLO) and overvoltage (OVLO)

lockouts on the VIN supply with a resistive divider

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