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NCV47710 View Datasheet(PDF) - ON Semiconductor

Part Name
Description
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NCV47710 Datasheet PDF : 12 Pages
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NCV47710
ǒ Ǔ Vout + VREF1
1 ) R1
R2
(eq. 2)
Use R2 < 50 kW to avoid significant voltage output errors
due to ADJ bias current.
Designers should consider the tolerance of R1 and R2 during
the design phase.
Setting the Output Current Limit
The output current limit can be set between 10 mA and
350 mA by external resistor RCSO (see Figure 1). Capacitor
CCSO of 1 mF in parallel with RCSO is required for stability
of current limit control circuitry (see Figure 1).
ǒ Ǔ VCSO + Iout RCSO
1
100
(eq. 3)
ILIM
+
100
1
2.55
RCSO
(eq. 4)
RCSO
+
100
1
2.55
ILIM
(eq. 5)
Where
RCSO
− current limit setting resistor
VCSO
− voltage at CSO pin proportional to Iout
ILIM
− current limit value
Iout
− output current actual value
CSO pin provides information about output current actual
value. The CSO voltage is proportional to output current
according to Equation 3.
Once output current reaches its limit value (ILIM) set by
external resistor RCSO than voltage at CSO pin is typically
2.55 V. Calculations of ILIM or RCSO values can be done
using equations Equation 4 and Equation 5, respectively.
Thermal Considerations
As power in the NCV47710 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. When
the NCV47710 has good thermal conductivity through the
PCB, the junction temperature will be relatively low with
high power applications. The maximum dissipation the
NCV47710 can handle is given by:
ƪ ƫ TJ(MAX) * TA
PD(MAX) +
RqJA
(eq. 6)
Since TJ is not recommended to exceed 150°C, then the
NCV47710 soldered on 645 mm2, 1 oz copper area, FR4
can dissipate up to 1.8 W (SOIC−8 EP) or 1 W (SOIC−8) and
up to 4.3 W (SOIC−8 EP) or 1.6 W (SOIC−8) for 4 layers
PCB (all layers are 1 oz) when the ambient temperature (TA)
is 25°C. See Figure 18 for RthJA versus PCB area. The power
dissipated by the NCV47710 can be calculated from the
following equations:
PD + VinǒIq@IoutǓ ) IoutǒVin * VoutǓ
(eq. 7)
or
PD(MAX) ) ǒVout
Vin(MAX) [
Iout ) Iq
IoutǓ
(eq. 8)
Hints
Vin and GND printed circuit board traces should be as
wide as possible. When the impedance of these traces is
high, there is a chance to pick up noise or cause the regulator
to malfunction. Place external components, especially the
output capacitor, as close as possible to the NCV47710 and
make traces as short as possible.
220
200
180
160
140
120
100
1 oz
80
1 oz
2 oz
1 oz
2 oz 2 oz
SO−8 single layer PCB
SO−8 EP single layer PCB
60 SO−8 4 layers PCB
40 SO−8 EP 4 layers PCB
1 oz 2 oz
20
0 100 200 300 400 500 600 700
COPPER HEAT SPREADER AREA (mm2)
Figure 18. Thermal Resistance vs. PCB Copper Area
ORDERING INFORMATION
Device
Output Voltage
Marking
Package
Shipping
NCV47710PDAJR2G
Adjustable
47710
SOIC−8 EP
(Pb−Free)
2500 / Tape & Reel
NCV47710DAJR2G
Adjustable
47710
SOIC−8
(Pb−Free)
2500 / Tape & Reel
†For information on tape and reel specifications,including part orientation and tape sizes, please refer to our Tape and Reel Packaging
Specifications Brochure, BRD8011/D.
www.onsemi.com
10
 

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