Datasheet

( ) ( )
( )
IMON
LOAD
IMON
63,000 V
63,000 1.8
I 1.81 A
R 62,500
´
´
= = =
( )
(
)
( )
( )
( )
AD _IN max
IMON
LOAD max
63,000 V
63,000 2.5
R 63 k
I 2.5
´
´
= = = W
3
3 6
FAULT
CT
3
T
10
C 20 10 0.514 10
38.9
38.9 10
-
-
= = ´ ´ = ´
´
TPS2420
www.ti.com SLUS903E –JANUARY 2009–REVISED MAY 2013
Because I
FAULT
satisfies the spin up current, the timer can be set for the additional loading of charging the
capacitor. Estimate approximately 20 ms. Use either Equation 12 or Table 2 to estimate the capacitance.
(12)
For a scaled analog readback of the current from V
IN
, set the I
MON
resistor. In Equation 13 , the V
AD_INMAX
is the
desired full scale A/D converter voltage. The largest value of V
AD_INMAX
2.5 V. I
LOADMAX
is the full scale current,
2.5 A.
(13)
The read-back voltage at the IMON pin, V
IMON
, indicates the instantaneous current output. Using equation
Equation 14 again, determine the current output for example, a 1.8-V V
IMON
. Substitute V
IMON
for V
AD_INMAX
and
I
LOAD
for I
LOADMAX
and solve for I
LOAD
, (Equation 14).
(14)
Layout
Support Components
Locate all TPS2420 support components, R
SET
, C
T
, etc. or any input or output voltage clamps, close to their
connection pin. Connect the other end of the component to the inner layer GND without trace length.
PowerPad™
When properly mounted the PowerPad package provides significantly greater cooling ability than an ordinary
package. To operate at rated power the Power Pad must be soldered directly to the PC board GND plane
directly under the device. The PowerPad is at GND potential and can be connected using multiple vias to inner
layer GND. Other planes, such as the bottom side of the circuit board can be used to increase heat sinking in
higher current applications.
Refer to Technical Briefs: PowerPAD™ Thermally Enhanced Package (TI Literature Number SLMA002) and
PowerPAD™ Made Easy (TI Literature Number SLMA004) for more information on using this PowerPadTM
package.These documents are available at www.ti.com (Search by Keyword).
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