Rev. B 11/05/10

3

SEN012-013

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Applications Considerations

The maximum voltage that the device can sustain across the

VCC and G pin is 16 V. The maximum voltage that any of the

source channels can be at with respect to the ground terminal

is 6.5 V. SENZero has a typical on state resistance of approxi-

mately 500

W at room temperature. The device is therefore

typically used in series with high ohmic value resistors where

this on resistance is a small percentage of the total series

impedance.

It is not necessary to provide a local bypass capacitor on the

VCC pin.

Operating Configurations for the SENZero

One configuration to power up the SENZero is shown in Figure 7.

In this circuit, SENZero is powered up from an unregulated bias

winding through a simple series pass regulator formed by Q1,

R

even if the maximum bias voltage exceeds 16 V. During power

down, as soon as the bias voltage falls below V

turn off.

The series pass transistor Q1 is necessary only if the bias

winding voltage regulation is not tight enough (unregulated). If

the voltage on the bias winding is regulated or is such that the

voltage on the VCC pin can be maintained in the range 6 V <

VCC < 16 V, then the series pass transistor (Q1, R

be eliminated.

Figure 7.

SENZero Powered from an Unregulated Bias Winding Through a Series

Pass Regulator. Device is Enabled When Bias Voltage is Present.

PI-6052-072010

Unregulated

Bias

Q1

(2N3904)

SENZero

VCC

G

D1

D2

S1

S2

(2 k

Ω)

PI-6051-072010

ON/OFF

Disable

Regulated

Auxiliary

Q1

(2N3906)

(2 k

Ω)

SENZero

VCC

G

(20 k

Ω)

D1

D2

S1

S2

PI-6053-110510

Unregulated

Bias

Q1

(2N3904)

SENZero

VCC

G

D1

D2

S1

S2

(2 k

Ω)

(100 k

Ω)

ON/OFF

Enable

Q2

(2N3906)

A configuration that can be used to trigger remote-off

functionality is shown in Figure 8. In this configuration, a

regulated auxiliary output is used to power the IC. Transistor

Q1 serves as the ON/OFF switch which is commanded by the

Enable/Disable signal at its base.

Figure 8.

SENZero Powered From a Regulated Auxiliary Winding.

An alternative remote-off configuration is shown in Figure 9

where an unregulated bias voltage supplies the SENZero

through a series pass regulator similar to the one shown in

Figure 7. However the circuit of Figure 9 includes an ON/OFF

transistor Q2. In other versions of this circuit Q2 can be

replaced by an optocoupler allowing the ON/OFF disable signal

to be communicated from a secondary of the power supply

such as in PC power supplies.

Figure 9.

A Modified Version of an Unregulated Bias Winding Supplying Power

Through a Series Pass Regulator. Transistor Q2 Provides Remote-Off

Functionality.