rt9703 ETC-unknow, rt9703 Datasheet - Page 12

• Manufacturer Part Number: rt9703
• Description: Smart Universal Power Switch With Flag
• Manufacturer: ETC-unknow

The normal current limit value, I
resistor between IP (pin 8) and GND (pin 4). When a heavy
load or short circuit is applied to an enabled switch, a
large transient current may flow until the current limit
circuitry responds. Once this current limit threshold is
exceeded, the device enters constant current mode until
the thermal shutdown occurred or the fault is removed. It
is important to note that the maximum current limit value
shall be set properly in accordance with its supply voltage
otherwise it may result in the failure occurrence. The graph
below shows the maximum current limit and supply
voltage on the safe operation area.
Thermal Shutdown
Thermal shutdown is employed to protect the device from
damage if the die temperature exceeds approxi- mately
130 C. If enabled, the switch automatically restarts when
the die temperature falls 10 C. The output and FLG signal
will continue to cycle on and off until the device is disabled
or the fault is removed.
Power Dissipation
The device's junction temperature depends on several
factors such as the load, PCB layout, ambient temperature
and package type. The output pin of RT9703 can deliver
a current of up to 3A over the full operating junction
temperature range. However, the maximum output current
must be derated at higher ambient temperature to ensure
RT9703
4.5
3.5
2.5
1.5
0.5
5
4
3
2
1
0
Maximun Current Limit vs. Supply Voltage
2
T
A
= 25 C
2.5
3
Supply Voltage (V)
3.5
LIMIT
4
, is set with an external
4.5
5
Preliminary
5.5
12
the junction temperature does not exceed 100°C. With
all possible conditions, the junction temperature must be
within the range specified under operating conditions.
Power dissipation can be calculated based on the output
current and the R
P
Although the devices are rated for 3A of output current,
but the application may limit the amount of output current
based on the total power dissipation and the ambient
temperature. The final operating junction temperature for
any set of conditions can be estimated by the following
thermal equation:
P
Where T
the die (100° C) and T
temperature. The junction to ambient thermal resistance
(
footprint is 104°C/W (
Supply Filter/Bypass Capacitor
A 10 F low-ESR ceramic capacitor from V
amount of the capacitance may be increased without limit),
located at the device is strongly recommended to prevent
the input voltage drooping during hot-plug events.
However, higher capacitor values will further reduce the
voltage droop on the input. Furthermore, without the
bypass capacitor, an output short may cause sufficient
ringing on the input (from source lead inductance) to
destroy the internal control circuitry. An important note to
be award of is the parasitic inductance of PCB traces can
cause over-voltage transients if the PCB trace has even
a few tens of nH of inductance. It is recommended to use
aluminum electrolytic acted the supply capacitor to prevent
the device from being damaged. The input transient must
not exceed 6.5V of the absolute maximum supply voltage
even for a short duration.
D
D (MAX)
JA
= R
) for SOP-8 package at recommended minimum
DS(ON)
= ( T
J (MAX)
J (MAX)
x I
is the maximum junction temperature of
OUT
DS(ON)
2
- T
A
JA
) /
of switch as below.
is layout dependent).
A
is the maximum ambient
JA
IN
to GND (the