NCV8702
APPLICATIONS INFORMATION
Enable Operation
current measured with the output voltage 100 mV lower than
The NCV8702 uses the EN pin to enable/disable its output
and to deactivate/activate the active discharge function.
If the EN pin voltage is <0.4 V the device is guaranteed to
be disabled. The pass transistor is turned−off so that there is
virtually no current flow between the IN and OUT. The
active discharge transistor is active so that the output voltage
the nominal V
. If the Output Voltage is directly shorted
= 0 V), the short circuit protection will
OUT
to ground (V
OUT
limit the output current to 390 mA (typ). The current limit
and short circuit protection will work properly up to V
=
IN
5.5 V at T = 25°C. There is no limitation for the short circuit
A
duration.
V
OUT
is pulled to GND through a 1 kW resistor. In the
Thermal Shutdown
When the die temperature exceeds the Thermal Shutdown
disable state the device consumes as low as typ. 10 nA from
the V .
IN
threshold (T − 160°C typical), Thermal Shutdown event
SD
If the EN pin voltage >0.9 V the device is guaranteed to
be enabled. The NCV8702 regulates the output voltage and
the active discharge transistor is turned−off.
The EN pin has internal pull−down current source with
typ. value of 110 nA which assures that the device is
turned−off when the EN pin is not connected. A build in
2 mV of hysteresis in the EN prevents from periodic on/off
oscillations that can occur due to noise.
is detected and the device is disabled. The IC will remain in
this state until the die temperature decreases below the
Thermal Shutdown Reset threshold (T
− 140°C typical).
SDU
Once the IC temperature falls below the 140°C the LDO is
enabled again. The thermal shutdown feature provides
protection from a catastrophic device failure due to
accidental overheating. This protection is not intended to be
used as a substitute for proper heat sinking.
In the case where the EN function isn’t required the EN
pin should be tied directly to IN.
Power Dissipation
As power dissipated in the NCV8702 increases, it might
become necessary to provide some thermal relief. The
maximum power dissipation supported by the device is
dependent upon board design and layout. Mounting pad
configuration on the PCB, the board material, and the
ambient temperature affect the rate of junction temperature
rise for the part.
Undervoltage Lockout
The internal UVLO circuitry assures that the device
becomes disabled when the V falls below typ. 1.5 V. When
IN
the V voltage ramps−up the NCV8702 becomes enabled,
IN
if V rises above typ. 1.6 V. The 100 mV hysteresis prevents
IN
on/off oscillations that can occur due to noise on V line.
IN
Reverse Current
The PMOS pass transistor has an inherent body diode
which will be forward biased in the case that V
Due to this fact in cases where the extended reverse current
condition is anticipated the device may require additional
external protection.
The maximum power dissipation the NCV8702 can
handle is given by:
> V .
OUT
IN
ƪT
ƫ
J(MAX) * TA
(eq. 1)
PD(MAX)
+
qJA
The power dissipated by the NCV8702 for given
application conditions can be calculated from the following
equations:
Output Current Limit
Output Current is internally limited within the IC to a
typical 380 mA. The NCV8702 will source this amount of
ǒ
Ǔ
ǒV
Ǔ
(eq. 2)
P
D [ VIN IGND@IOUT ) IOUT IN * VOUT
330
310
290
0.65
0.60
0.55
P
, T = 25°C, 2 OZ CU
A
D(MAX)
270
250
230
210
190
0.50
0.45
0.40
0.35
0.30
q
q
, 1 OZ CU
, 2 OZ CU
JA
JA
P
, T = 25°C, 1 OZ CU
A
D(MAX)
170
150
0.25
0.20
700
0
100
200
300
400
500
600
2
PCB COPPER AREA (mm )
Figure 62. qJA and PD(MAX) vs. Copper Area (TSOP5)
http://onsemi.com
16
ONSEMI [ ONSEMI ]
