ISL80101IRAJZ-TK Intersil, ISL80101IRAJZ-TK Datasheet - Page 7

• Manufacturer Part Number: ISL80101IRAJZ-TK
• Description: IC REG LDO ADJ 1A 10DFN
• Manufacturer: Intersil

Specifications of ISL80101IRAJZ-TK

• Regulator Topology: Positive Adjustable
• Voltage - Output: 0.8 ~ 5 V
• Voltage - Input: 2.2 ~ 6 V
• Voltage - Dropout (typical): 0.13V @ 1A
• Number Of Regulators: 1
• Current - Output: 1A (Max)
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 10-DFN
• Rohs Compliant: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Current - Limit (min): -
• Other names: ISL80101IRAJZ-TK; ISL80101IRAJZ-TKTR

Functional Description
Enable Operation
The Enable turn-on threshold is typically 0.8V with a
hysteresis of 80mV. The Enable pin doesn't have an
internal pull-up or pull-down resistor. As a result, this pin
must not be left floating. This pin must be tied to V
is not used. A pull-up resistor (typically 1k
be required for applications that use open collector or
open drain outputs to control the Enable pin. The Enable
pin may be connected directly to V
are always on.
Soft-Start Operation
The soft-start circuit controls the rate at which the output
voltage comes up to regulation at power-up or coming
out of a chip disable. A constant current charges an
external soft-start capacitor. The external capacitor
always gets discharged to 0V at start-up of after coming
out of a chip disable. The discharge rate is the RC time
constant of an internal resistance and C
function effectively limits the amount of in-rush current
below the programmed current limit during start-up or
an enable sequence to avoid an overcurrent fault
condition. This can be an issue for applications that
require large, external bulk capacitances on V
high levels of charging current can be seen for a
significant period of time. High in-rush currents can
cause V
V
C
output voltage, C
output and I
The following scope in Figure 3 captures the response for
the soft-start function.The output voltage is set to 1.8V.
C
FIGURE 3. IN-RUSH CURRENT WITH NO C
OUT
SS
SS
for a desired in-rush current
=
to shutdown. Equation 3 can be used to calculate
(
-----------------------------------------------------------
V
IN
OUT
I
INRUSH
to drop below minimum which could cause
INRUSH
C
xC
OUT
OUT
OUT
x0.5V
= 1000µF, IN-RUSH CURRENT = 1.8A
x2μA )
is the desired in-rush current.
is the total capacitance on the
)
7
.
Where V
IN
for applications that
SS
. The soft-start
Ω
OUT
SS
to 10k
OUT
,
is the
(EQ. 1)
where
IN
Ω)
ISL80101
will
if it
The rise time of the regulator output voltage for a given
Also
C
Power-Good Operation
The PGOOD circuit monitors V
condition when V
voltage. The PGOOD flag is an open-drain NMOS that can
sink 10mA during a fault condition. The PGOOD pin
requires an external pull up resistor which is typically
connected to the VOUT pin. The PGOOD pin should not
be pulled up to a voltage source greater than V
a fault condition, the PGOOD output is pulled low. The
PGOOD fault can be caused by the current limit fault or
low input voltage. The PGOOD does not function during
thermal shutdown and when the part is disabled.
t
RAMP
FIGURE 4. IN-RUSH CURRENT WITH C
FIGURE 5. IN-RUSH CURRENT WITH C
SS
value can be calculated using Equation 2.
=
C
--------------------------- -
SS
2μA
C
C
x0.5V
OUT
OUT
OUT
= 1000µF, IN-RUSH CURRENT = 0.5A
= 1000µF, IN-RUSH CURRENT = 0.2A
is below 85% of the nominal output
OUT
and signals a fault
SS
SS
December 21, 2009
= 15nF,
= 33nF,
IN
. During
(EQ. 2)
FN6931.0