SC704/SC705

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Application Information

Operation

The SC704/SC705 are integrated high-side PMOS load

switches that are designed to support up to 500mA con-

tinuous output current and operate from an input voltage

between .V to 3.6V. The internal PMOS pass element has

a very low on resistance of 90mΩ (typical) at .8V. The

Enable pin incorporates a 5MΩ (typical) pull-down resis-

tor. The SC704/SC705 also provides ultra-low low shut-

down and quiescent current for extended battery life

during shutdown and light loading conditions.

The SC705 includes an automatic output discharge func-

tion which employs a 220Ω (typical) discharge path to

ground when the EN pin is disabled. The SC705 is also

designed for longer output rise time to decrease input

inrush current during power on.

Enable

The gate of the internal PMOS FET of SC704/SC705 is con-

trolled by EN pin logic circuitry. If the EN pin is floating,

the internal switch will be turned off. In SC705 the EN pin

also controls the automatic discharge function.

Input Capacitor

In order to improve voltage drop, noise and bounce on

VIN pin, a filter/decoupling capacitor between VIN to GND

is recommended. A uf ceramic capacitor will be suffi-

cient for most application conditions. However it should

be noted that suppressing bounce on input loop after EN

from high to low can require greater capacitor values

depending on the particular design being implemented.

During certain shutdown conditions, as in the case when

input power supply is abruptly removed, the input voltage

may tend to drop faster than the output voltage. In this

event a reverse current through the body diode of inter-

nal PMOS FET from VOUT to VIN can occur. To limit this

reverse current, Cin should be made greater than Cout to

sink current from the output.

Output Capacitor

A uF filter capacitor is added on the VOUT pin to sup-

press noise on the evaluation board. If a larger output

capacitance value is used, then input inrush current

should be considered since the power-on transient is

dependent on the output capacitor size. It should also be

noted that SC705 has longer turn-on delay time and rise

time than SC704 so SC705 will significantly improve input

inrush current during power-on application conditions.

Board Layout Considerations

Input capacitor(C) and output capacitor(C2) should be

placed as close to the SC704/SC705 as possible, and all

traces should be as short as possible and as wide as pos-

sible to minimize the case-to-ambient thermal impedance

and parasitic electrical effects.

Evaluation Board Information

Both T and T2 test points are Kelvin connections which

can be used to minimize R

O.

A jumper can be used

between VIN and EN on J to enable the part. To disable

the part the jumper can be connected between EN and

GND on J.