ISL6720A Datasheet, PDF (9/11 Pages) Intersil Corporation – 100V Triple Linear Bias Supply

ISL6720A
.
VIO ¹¹
N/C ¹⁰
ISL6720A
+
VADJ ⁹
VSW ⁸
VSWCOMP ⁷
ENABLE 6
TRTRAACCEE1 ¹
TRACE 3
FIGURE 6. ISOLATING VIO FROM LARGE CAPACITANCES
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.
VSW = 7 × VSWADJ V
(EQ. 2)
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 250μs, nominal.
VCONT requires a minimum 250μA 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.
TRACE 2
FIGURE 7. VSW TRANSIENT RESPONSE, 0mA to 50mA
STEP, TRACE1: VSW, TRACE2: VCONT,
TRACE3: VIO
TRACE 1
TRACE 3
TRACE 2
FIGURE 8. VCONT TRANSIENT RESPONSE, 0mA to 25mA
STEP, TRACE1: VSW, TRACE2: VCONT,
TRACE3: VIO
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 250μA
(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 500μA
(minimum) load.
9
FN6487.1
August 23, 2007