Si91861

Features:

·Single Fixed 3.3-V Output
·Linear Regulator for 5-V Power Input
·Auxilliary Input Can Be Bypassed
·Automatically Switches Between Linear Regulator and Bypass Mode
·Linear Regulator: 3.3-V
3% Output at 400-mA Current; 600-mA Peak Output Current
·Low Bypass Switch Voltage-Drop: <55-mV at 150 mA
·Built-in Short Circuit and Thermal Shutdown Protection
· Low Supply Current
·SOIC-8 Package




Application

·Network Interface Cards (NIC)
·PCMCIA Cards
·Cardbus
·Desktop Computers/Workstations




Pinout






Specifications

Pin 2, 4 Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..−0.3 V to 6 V
Linear Regulator Output Current . . . . . . . . . . . . . . . . . . . . . . . . . . .600 mA
Bypass Switch Current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .600 mA
Maximum Junction Temperature, T_J(max) . . . . . . . . . . . . . . . . . . . . . . .150
Storage Temperature, T_STG . . . . . . . . . . . . . . . . . . . . . . . . . .−55 to 150
ESD (Human Body Model). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2 kV
Package Power Dissipationb
P_D . . . . . . . . . . . . . . . . . . . . . . .2W (internally limited via thermal shutdown)
Thermal Impedance (JA)a . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .62.5/W
Notes
a. Device mounted with all leads soldered or welded to PC board.
b. Derate 16 mW/C above T_A = 25




Description

The Si91861 provides a constant 3.3-V output with multiple inputs. This function is required in many power interface applications, such as the Network Interface Card (NIC). The Si91861 is offered in small SOIC-8 package with up to 2-W power handling capability. The complete application circuit uses only three external components.

The linear regulator steps down from the 5-V supply (5 VIN) to 3.3 V. A 200-m bypass switch is integrated to connect the 3.3-VAUX input to the output. The power drawn priority is 5 VIN > 3.3 VAUX, where the selection is done internally and automatically by the Si91861. The power handling capability is as such as to carry at least 400-mA continuous load current for any power input condition.

In order to satisfy the stringent ambient temperature requirements in many applications, the Si91861 is rated for the industrial temperature range of -40 to 85.

The Si91861 is available in both standard and lead (Pb)-free packages.