SiP32408, SiP32409

Vishay Siliconix

Document Number: 63717

S13-0971-Rev. F, 06-May-13

www.vishay.com

9

This document is subject to change without notice.

DETAILED DESCRIPTION

SiP32408 and SiP32409 are advanced slew rate controlled

high side load switches consisted of a n-channel power

switch. When the device is enable the gate of the power

switch is turned on at a controlled rate to avoid excessive in-

rush current. Once fully on the gate to source voltage of the

power switch is biased at a constant level. The design gives

a flat on resistance throughout the operating voltages. When

the device is off, the reverse blocking circuitry prevents

current from flowing back to input if output is raised higher

than input. The reverse blocking mechanism also works in

case of no input applied.

APPLICATION INFORMATION

Input Capacitor

SiP32408 and SiP32409 do not require an input capacitor.

To limit the voltage drop on the input supply caused by

transient inrush currents, an input bypass capacitor is

recommended. A 2.2 µF ceramic capacitor placed as close

capacitor can help to further reduce the voltage drop.

Ceramic capacitors are recommended for their ability to

withstand input current surge from low impedance sources

such as batteries in portable devices.

Output Capacitor

While these devices works without an output capacitor,

recommended to accommodate load transient condition. It

GND when switching off. Output capacitor has minimal affect

on device’s turn on slew rate time. There is no requirement

on capacitor type and its ESR.

Enable

The EN pin is compatible with both TTL and CMOS logic

voltage levels. Enable pin voltage can be above IN once it is

within the absolute maximum rating range.

For output voltage slew rate control, EN is required to have

at least 50 µs delay after the input voltage get ready to

enable the device.

Protection Against Reverse Voltage Condition

SiP32408 and SiP32409 contain a reverse blocking circuitry

to protect the current from going to the input from the output

in case where the output voltage is higher than the input

voltage when the main switch is off. Reverse blocking works

for input voltage as low as 0 V.

Thermal Considerations

SiP32408 and SiP32409 are designed to maintain a constant

output load current. Due to physical limitations of the layout

and assembly of the device the maximum switch current is

3.5 A, as stated in the Absolute Maximum Ratings table.

However, another limiting characteristic for the safe

operating load current is the thermal power dissipation of the

package. To obtain the highest power dissipation (and a

thermal resistance of 170 °C/W) the power pad of the device

should be connected to a heat sink on the printed circuit

board. Figure 21 shows a typical PCB layout. All copper

traces and vias for the IN and OUT pins should be sized

adequately to carry the maximum continuous current.

The maximum power dissipation in any application is

dependant

on

the

maximum

junction

temperature,

for the TDFN4 1.2 mm x 1.6 mm package,



expressed as:

Figure 27 - Typical Turn-on Delay, Rise Time

EN

2 V/Div, 0.25 A/Div, 2 ms/Div

Figure 28 - Typical Fall Time

EN

2 V/Div, 0.25 A/Div, 2 ms/Div

170

125

(max.)

(max.)

A

A

J

A

J

T

T

T

P

-

=

-

=

-

θ