External high side switch MOSFET
External reverse polarity protection MOSFET
The LM74502, LM74502H is a controller which operates in conjunction with an external back-to-back connected N-channel MOSFETs to realize a low loss reverse polarity protection and load disconnect solution. The device can also be configured to drive high side MOSFET as a load switch with overvoltage protection . The wide supply input range of 3.2 V to 65 V allows control of many popular DC bus voltages such as 12-V, 24-V and 48-V input systems. The device can withstand and protect the loads from negative supply voltages down to –65 V. The LM74502, LM74502H does not have reverse current blocking and is suitable for input reverse polarity protection only.
The LM74502 controller provides a charge pump gate drive for an external N-channel MOSFET. with the enable pin low, the controller is off and draws approximately 1 µA of current, thus offering low system current when put into sleep mode. LM74502 and LM74502H offers programmable overvoltage and undervoltage protection which cuts off the load from the input source in case of these fault events. The devices are available in a 2.9 mm × 1.6 mm 8-pin DDF package and are specified over a –40°C to +125°C temperature range.
PART NUMBER | PACKAGE | BODY SIZE (NOM) |
---|---|---|
LM74502 | SOT-23 (8) | 2.90 mm × 1.60 mm |
LM74502H |
PIN | I/O(1) | DESCRIPTION | |
---|---|---|---|
NO. | NAME | ||
1 | EN/UVLO | I | EN/UVLO Input. Connect to VS pin for always ON operation. Can be driven externally from a micro controller I/O. Pulling the pin low below V(ENF) makes the device enter into low Iq shutdown mode. For UVLO, connect an external resistor ladder from input supply to EN/UVLO to ground. |
2 | GND | G | Ground pin |
3 | N.C | — | No connection |
4 | VCAP | O | Charge pump output. Connect to external charge pump capacitor. |
5 | VS | I | Input power supply pin to the controller. Connect a 100-nF capacitor across VS and GND pins. |
6 | GATE | O | Gate drive output. Connect to gate of the external N-channel MOSFET. |
7 | OV | I | Adjustable overvoltage threshold input. Connect a resistor ladder from input supply to OV pin to ground. When the voltage at OV pin exceeds the overvoltage cutoff threshold then the GATE is pulled low. GATE turns ON when the OV pin voltage goes below the OVP falling threshold. Connect OV pin to ground when OV feature is not used. |
8 | SRC | I | Source pin. Connect to common source point of external back-to-back connected N-channel MOSFETs or the source pin of the high side switch MOSFET. |