4
Pin Descriptions
PWRGD (ISL6142; L Version) Pin 1 - This digital output is
an open-drain pull-down device and can be used to directly
enable an external module. During start-up the DRAIN and
GATE voltages are monitored with two separate comparators.
The first comparator looks at the DRAIN pin voltage compared
to the internal V
PG
reference (1.3V); this measures the
voltage drop across the external FET and sense resistor.
When the DRAIN to V
EE
voltage drop is less than 1.3V, the
first of two conditions required for the power to be considered
good are met. In addition, the GATE voltage monitored by the
second comparator must be within approximately 2.5V of its
normal operating voltage (13.6V). When both criteria are met
the PWRGD
output will transition low and be latched in the
active state, enabling the external module. When this occurs
the two comparators discussed above no longer control the
output. However a third comparator continues to monitor the
DRAIN voltage, and will drive the PWRGD
output inactive if
the DRAIN voltage raises more than 8V above V
EE
. In
addition, any of the signals that shut off the GATE (Over-
Voltage, Under-Voltage, Under-Voltage Lock-Out, Over-
Current time-out, pulling the DIS pin high, or powering down)
will reset the latch and drive the PWRGD
output high to
disable the module. In this case, the output pull-down device
shuts off, and the pin becomes high impedance. Typically an
external pull-up of some kind is used to pull the pin high
(many brick regulators have a pull-up function built in).
PWRGD (ISL6152; H Version) Pin 1 - This digital output is
used to provide an active high signal to enable an external
module. The Power Good comparators are the same as
described above, but the active state of the output is
reversed (reference figure 37).
When power is considered good (both DRAIN and GATE are
normal) the output is latched in the active high state, the
DMOS device (Q3) turns on and sinks current to V
EE
through
a 6.2K resistor. The base of Q2 is clamped to V
EE
to turn it
off. If the external pull-up current is high enough (>1mA, for
example), the voltage drop across the resistor will be large
enough to produce a logic high output and enable the external
module (in this example, 1mA x 6.2K = 6.2V).
Note that for all H versions, although this is a digital pin
functionally, the logic high level is determined by the external
pull-up device, and the power supply to which it is
connected; the IC will not clamp it below the V
DD
voltage.
Therefore, if the external device does not have its own
clamp, or if it would be damaged by a high voltage, an
external clamp might be necessary.
If the power good latch is reset (GATE turns off), the internal
DMOS device (Q3) is turned off, and Q2 (NPN) turns on to
clamp the output one diode drop above the DRAIN voltage
to produce a logic low, indicating power is no longer good.
FAULT
Pin 2- This digital output is an open-drain, pull-down
device, referenced to V
EE
. It is pulled active low whenever
the Over-Current latch is set. It goes to a high impedance
state when the fault latch is reset by toggling the UV or DIS
pins. An external pull-up resistor to a logic supply (5V or
less) is required; the fault outputs of multiple IC’s can be
wire-OR’d together. If the pin is not used it should be left
open.
DIS Pin 3 - This digital input disables the FET when driven to
a logic high state. It has a weak internal pull-up device to an
internal 5V rail (10A), so an open pin will also act as a logic
high. The input has a nominal trip point of 1.6 V while rising,
and a hysteresis of 1.0V. The threshold voltage is referenced
to V
EE
, and is compatible with CMOS logic levels. A logic
low will allow the GATE to turn on (assuming the 4 other
conditions described in the GATE section are also true). The
DIS pin can also be used to reset the Over-Current latch
when toggled high to low. If not used the pin should be tied
to the negative supply rail (-V
IN
).
OV (Over-Voltage) Pin 4 - This analog input compares the
voltage on the pin to an internal voltage reference of 1.255 V
(nominal). When the input goes above the reference the
GATE pin is immediately pulled low to shut off the external
FET. The built in 25mV hysteresis will keep the GATE off
until the OV pin drops below 1.230V (the nominal high to low
threshold). A typical application will use an external resistor
divider from V
DD
to -V
IN
to set the OV trip level. A three-
resistor divider can be used to set both OV and UV trip
points to reduce component count.
UV (Under-Voltage) Pin 5 - This analog input compares the
voltage on the pin to an internal comparator with a built in
hysteresis of 135mv. When the UV input goes below the
nominal reference voltage of 1.120V, the GATE pin is
immediately pulled low to shut off the external FET. The
GATE will remain off until the UV pin rises above a 1.255V
low to high threshold. A typical application will use an
external resistor divider from V
DD
to -V
IN
to set the UV level
as desired. A three-resistor divider can be used to set both
OV and UV trip points to reduce component count.
The UV pin is also used to reset the Over-Current latch. The
pin must be cycled below 1.120V (nominal) and then above
1.255V (nominal) to clear the latch and initiate a normal
start-up sequence.
IS- Pin 6 - This analog pin is the negative input of the current
sense circuit. A sensing resistor (R7) is connected between
this pin and the V
EE
side of resistor R1. The ratio of R1/R7
defines the I
SENSE
to IS
OUT
current scaling factor. If current
sensing is not used in the application, the IS- pin should be
tied directly to the IS+ pin and the node should be left
floating.
ISL6142, ISL6152
