aoz1361di Alpha & Omega Semiconductor, aoz1361di Datasheet - Page 8

• Manufacturer Part Number: aoz1361di
• Description: 28v Programmable Current-limited Load Switch
• Manufacturer: Alpha & Omega Semiconductor

Detailed Description
Introduction
The AOZ1361DI is a 35m
switch with adjustable soft-start slew-rate control,
programmable current limit and thermal shutdown.
It operates with an input voltage range from 4.5V to 28V.
Enable
The EN pin is the ON/OFF control for the output switch.
The device is enabled when EN pin is high and V
above UVLO. The EN pin must be driven to a logic high
or logic low state to guarantee operation. While disabled,
the AOZ1361DI only draws about 1µA supply current.
Under-Voltage Lockout (UVLO)
The under-voltage lockout (UVLO) circuit of AOZ1361DI
monitors the input voltage and prevents the output
MOSFET from turning on until V
Adjustable Soft-Start Slew-Rate Control
When the EN pin is asserted high, the slew rate control
circuitry applies voltage on the gate of the PMOS switch
in a manner such that the output voltage and current is
ramped up linearly until it reaches the steady-state load
current level. The slew rate can be adjusted by an
external capacitor connected to the SS pin to ground.
The slew rate rise time, Ton, can be set using the
following equation:
Programmable Current Limit
The current limit is programmed by an external resistor
connected to the SET pin to ground. This sets a
reference voltage to the current limit error amplifier that
compares it to a sensed voltage that is generated by
passing a small portion of the load current through an
internal amplifier. When the sensed load current exceeds
the set current limit, the load current is then clamped at
the set limit and the Vout drop should be the result of
resistance increasing. The AOZ1361DI will stay in this
condition until the load current no longer exceeds the
current limit or if the thermal shutdown protection is
engaged. To set the current limit use Figure 3 on the
following page.
Ton
Rev. 2.0 October 2010
=
Css
------------------------- -
30μA
×
V
IN
Ω
P-channel high-side load
IN
exceeds 3.9V.
IN
www.aosmd.com
is
Thermal Shut-down Protection
The thermal overload protection of AOZ1361DI is
engaged to protect the device from damage should the
die temperature exceeds safe margins due to a short
circuit, extreme loading or heating from external sources.
1.
2.
FLTB
The FLTB pin is an open drain output that is asserted low
when either an over-current, short-circuit or over-
temperature condition occurs. To prevent false alarm, the
AOZ1361DI implements a fault delay time for over-
temperature, over-current and short-circuit fault
conditions. The FLTB pin becomes high impedance when
the fault conditions are removed. For AOZ1361DI-02, if
the temperature is higher than +130°C, the device will
latch off. After that, if temperature drops below +100°C,
the FLTB pin will pull high, which means the fault
condition has already been removed, although there is
no output voltage due to latch off function. A pull-up
resistor must be connected between FLTB to 5V or 3.3V
to provide a logic signal.
TFLT
TFLT is a fault delay pin, and its delay time is adjustable
by a capacitor connected from TFLT to GND. The delay
time can be calculated by:
C
TLT
AOZ1361DI-01 (
limit or short circuit conditions, the PMOS resistance
is increased to clamp the load current. This increases
the power dissipation in the chip causing the die
temperature to rise. When the die temperature
reaches 130°C the thermal shutdown circuitry will
shutdown the device. There is a 30°C hysterisis. The
device will turn back on and go through soft start
after the temperature drops below +100°C . The
thermal shutdown will cycle repeatedly until the over
temperature condition disappears or the enable pin is
pulled LOW.
AOZ1361DI-02 (
shut-down protection sets a fault latch and shuts off
the internal MOSFET and asserts the FLTB output if
the junction temperature exceeds +130°C. The
AOZ1361DI can be re-enabled by toggling EN pin
after the die temperature drops below +100°C.
(
µs) =
600
µs / nF x
Auto-restart version): During current
Latch-off version): Thermal
C
TFLT
(nF)
AOZ1361DI
Page 8 of 12