
                                           AT1605 
High-Side Power Switch IC 
Function Description 
Enable Control 
Digital logic of EN provides an electrical ON/OFF control of the power supply. Connecting this pin to 
ground or to any voltage less than EN input threshold will completely turn OFF the Bias. In this state, 
current drain from the input supply is less than 1μA; the internal reference, comparators, and biasing 
circuitry turn off. EN works as a simple on/off control. Drive EN high to enable the device, or drive EN 
low for shutdown. 
Charge Pump 
The higher of supply battery powers the internal charge pump. The charge pump provides power to the 
current limit amplifier and allows the N-MOS gate voltage to be higher the battery supply voltage. A 
gate voltage that is higher than the source voltage is necessary to turn on the N-MOS. 
Under-Voltage Lockout (UVLO) 
The under voltage lockout prevents the device from misoperation at low input voltage.  
Soft-Start 
Soft-start is built-in on chip. When power up, the soft-start function is immediately active to nominal 
voltage by a constant current. During this time, the soft-start voltage directly controls the N-MOS 
on-time to reduce input surge currents. The maximum load current is available after the soft-start cycle 
is completed.  
Over-Current Limit 
The AT1605 provides cycle-by-cycle over-current protection. Current limit is accomplished using a 
separate dedicated comparator. The current limit signals control logic block to limit current of N-MOS 
in event that the current of flowing N-MOS is greater than the current limit value. The current-limit 
feature protection against a hard short or over-current fault at the output. 
Thermal-Overload Protection 
Thermal-overload protection limits total power dissipation in the AT1605. When the junction 
temperature exceeds Tj=130
°
C, a thermal sensor activates the thermal protection, which shuts down the 
IC, allowing the IC to cool. Once the device cools down by 20
°
C, IC will automatically recover normal 
operation. For continuous operation, do not exceed the absolute maximum junction-temperature rating 
of Tj=150
°
C. 
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4/26/2006 REV:1.1                                        Email: 
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