LM7480 datasheet(17/43 Pages) TI

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and both the gate drivers (DGATE and HGATE) are disabled placing the LM7480 in shutdown mode. If V(ENF) <

V(EN/UVLO) < V(UVLOF) then only HGATE is disabled disconnecting the load from the supply, DGATE remains ON.

The EN/UVLO pin can withstand a maximum voltage of 65 V. For always ON operation connect EN/UVLO pin to

VS.

9.4 Device Functional Modes

Shutdown Mode

The LM7480 enters shutdown mode when the EN/UVLO pin voltage is below the specified input low threshold

V(ENF). Both the gate drivers and the charge pump are disabled in shutdown mode. During shutdown mode the

LM7480 enters low IQ operation with a total input quiescent consumption of 2.87 µA (typ). When the LM7480 is

in shutdown mode, forward current flow to always ON loads connected to the common drain point of the back to

back MOSFETs is not interrupted but is conducted through the MOSFET's body diode.

9.5 Application Examples

9.5.1 Redundant Supply OR-ing with Inrush Current Limiting, Overvoltage Protection and ON/OFF

Control

GND

GATE

ANODE

CATHODE

VIN1

LM74700-Q1

VCAP

SMBJ36CA

ON OFF

GND

DGATE

HGATE

OUT

EN/UVLO

VIN2

VOUT1

VOUT2

LM74800-Q1

CAP VS

ON OFF

SMBJ36CA

VSNS

BATT_MON

Figure 9-5. Redundant Supply OR-ing with Overvoltage Protection and ON/OFF Control

Figure 9-5 shows the implementation of Dual OR-ing with Inrush Current Limiting, overvoltage Protection and

power path ON/OFF control. The input side SMBJ36CA TVS across the ideal diodes is required for ISO7637

Pulse 1 transient suppression to limit the input voltage within the device max voltage rating of –65V.

R1 and R2 are the programming resistors for over voltage protection (OVP) threshold. When the voltage at

OV pin exceeds OV cut-off reference threshold then the HGATE driver turns OFF the FET Q3, disconnecting

the power path and protecting the downstream load. HGATE goes high once the OVP pin voltage goes below

the OVP falling hysteresis threshold. Use 0.1-μF to 1-μF capacitor across VS to CAP pins of the LM7480.

This is the charge pump capacitor and acts as the supply for both the DGATE and HGATE driver stages. The

DGATE driver of the LM7480 is equipped with 20-mA peak source current and 2.6-A peak sink current capability

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LM7480

SNOSDD8 – DECEMBER 2022

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