Datasheet LTC4361-1, LTC4361-2 (Analog Devices) - 9

link to page 9 LTC4361-1/LTC4361-2
APPLICATIONS INFORMATION ON Input
For near zero reverse-leakage current protection when ON is a CMOS compatible, active low enable input. It has GATE is pulled to ground, back-to-back N-channel a default 5µA pull-down to ground. Connect this pin to MOSFETs can be used. Adding an additional P-channel ground or leave open to enable normal device operation. MOSFET controlled by GATEP provides negative input If it is driven high while the external MOSFET is turned voltage protection down to the BVDSS of the P-channel on, GATE is pul ed low with a weak pul -down current MOSFET. Another configuration consists of a P-channel (40µA) to turn off the external MOSFET gradually, mini- MOSFET controlled by GATEP and a N-channel MOSFET mizing input voltage transients. The LTC4361 then goes controlled by GATE. This provides protection against into a low current sleep mode, drawing only 1.5µA at IN. overvoltage and negative voltage but not reverse current. When ON goes back low, the part restarts with a 130ms OVERVOLTAGE delay cycle. PROTECTION R SUPPLY SENSE M1
GATEP Control
IN SENSE OUT GATEP has a 2M resistive pull-down to ground and a 5.8V GATE Zener clamp in series with a 200k resistor to IN. It con- OVERVOLTAGE, REVERSE- trols the gate of an optional external P-channel MOSFET CURRENT PROTECTION RSENSE to provide negative voltage protection. The 2M resistive SUPPLY M1 M3 pull-down turns on the MOSFET once VIN – VGATEP is IN SENSE OUT more than the MOSFET gate threshold voltage. The IN to GATE GATEP Zener protects the MOSFET from gate overvoltage NEGATIVE by clamping its VGS to 5.8V when VIN goes high. VOLTAGE OVERVOLTAGE, REVERSE- PROTECTION CURRENT PROTECTION R SUPPLY M2 SENSE M1 M3
MOSFET Configurations and Selection
The LTC4361 can be used with various external MOSFET IN SENSE OUT configurations (see Figure 3). The simplest configuration GATEP GATE is a single N-channel MOSFET. It has the lowest R NEGATIVE DS(ON) VOLTAGE OVERVOLTAGE and voltage drop and is thus the most power efficient PROTECTION PROTECTION RSENSE solution. When GATE is pulled to ground, the N-channel SUPPLY M2 M1 MOSFET can isolate OUT from a positive voltage at IN up IN SENSE OUT to the BVDSS of the N-channel MOSFET. However, reverse GATEP GATE 436112 F03 current can still flow from OUT to IN via the parasitic body diode of the N-channel MOSFET.
Figure 3. MOSFET Configurations
Rev C For more information www.analog.com 9 Document Outline Features Applications Typical Application Description Absolute Maximum Ratings Pin Configuration Order Information Electrical Characteristics Typical Performance Characteristics Pin Functions Block Diagram Operation Applications Information Package Description Revision History Typical Application Related Parts