ISL6720A

FN6487 Rev.1.00

Page 9 of 11

August 23, 2007

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VSW

VSW is the switched output and may be turned on and off

using the ENABLE pin (GND = off). The output is adjustable

from 1.5V to 15V, but must always be at least 1.5V lower

than VIO and 5.5V lower than VPWR. VSW uses VIO as its

input source. If the external source applied to VIO is unable

to supply adequate voltage, VPWR will be selected as an

alternate source for VIO (and VSW). VSW is capable of

sourcing up to 50mA continuously, and up to 80mA on a

transient basis.

The output voltage is adjusted using the VSWADJ input. The

voltage applied to this pin, multiplied by an internal gain of 7,

sets the output voltage.

With a 220pF capacitor from VSW to VSWCOMP, the load

capacitance on VSW should be 1.0µF nominal, with a range

of 0.47µF to 1.5µF. VSW requires a minimum load of

500µA. These conditions must be met even if the VSW

output is not used.

VCONT

VCONT, which has a tight tolerance output and can source

25mA, is a continuos output. It remains on during most fault

conditions and precedes VIO and VSW during power-up. It

may be used as reference for other circuitry, or may be used

to power a micro-controller or other similar device.

VCONT selects VIO as its primary source voltage, but also

uses VPWR if VIO is not present or capable.

VIO must have at least 5V of headroom above VCONT or

VPWR is selected as the source. VCONT is enabled when

VPWR exceeds its UVLO threshold and its operation

precedes the enabling of VIO and VSW by 250

s, nominal.

VCONT requires a minimum 250

A load for stability. It

should be bypassed to GND with a 1µF capacitor and

requires a 1nF compensation capacitor between VCOMP

and VCONT. These conditions must be met even if the

VCONT output is not used.

Figure 7 depicts the output deviation on each output when

VSW experiences a 0mA to 50 mA step load. VIO Is

unloaded without back-bias and VCONT has a 250

A

(minimum) load.

Figure 8 depicts the output deviation on each output when

VCONT experiences a 0mA to 25mA step load. VIO Is

unloaded without back-bias and VSW has a 500

A

(minimum) load.

VADJ

ENABLE

VIO

7

9

10

11

8

6

N/C

VSWCOMP

VSW

+

ISL6720A

FIGURE 6. ISOLATING VIO FROM LARGE CAPACITANCES

VSW

7 VSWADJ



=

V

(EQ. 2)

FIGURE 7. VSW TRANSIENT RESPONSE, 0mA to 50mA

STEP, TRACE1: VSW, TRACE2: VCONT,

TRACE3: VIO

TRACE 1

TRACE 1

TRACE 3

TRACE 2

FIGURE 8. VCONT TRANSIENT RESPONSE, 0mA to 25mA

STEP, TRACE1: VSW, TRACE2: VCONT,

TRACE3: VIO

TRACE 1

TRACE 3

TRACE 2