TEA1207T Philips Semiconductors, TEA1207T Datasheet - Page 12

• Manufacturer Part Number: TEA1207T
• Description: High efficiency DC/DC converter
• Manufacturer: Philips Semiconductors

Philips Semiconductors
External component selection
I
The performance of the TEA1207T is not very sensitive to
the inductance value. Best efficiency performance over a
wide load current range is achieved by using e.g.
TDK SLF7032-6R8M1R6, having an inductance of 6.8 H
and a saturation current level of 1.6 A. In case the
maximum output current is lower, other inductors are also
suitable such as the small sized Coilcraft DT1608 range.
I
The value of capacitor C1 strongly depends on the type of
input source. In general, a 100 F tantalum capacitor will
do, or a 10 F ceramic capacitor featuring very low series
resistance (ESR value).
O
The value and type of capacitor C2 depend on the
maximum output current and the ripple voltage which is
allowed in the application. Low-ESR tantalum as well as
ceramic capacitors show good results. The most important
specification of capacitor C2 is its ESR, which mainly
determines the output voltage ripple.
D
The Schottky diode is only used a short time during
takeover from N-type power MOSFET and P-type power
MOSFET and vice versa. Therefore, a medium-power
diode such as Philips PRLL5819 is sufficient.
F
The output voltage is determined by the resistors
R1 and R2. The following conditions apply:
Under these conditions, the output voltage can be
calculated by the formula:
1999 Oct 21
NDUCTOR
NPUT CAPACITOR
EEDBACK RESISTORS
IODE
UTPUT CAPACITOR
Use 1% accurate SMD type resistors only. In case larger
body resistors are used, the capacitance on pin 7
(feedback input) will be too large, causing inaccurate
operation.
Resistors R1 and R2 should have a maximum value of
50 k when connected in parallel. A higher value will
result in inaccurate operation.
High efficiency DC/DC converter
D1
L1
C1
C2
R1
AND
V
O
R2
=
1.24
1
+
R1
------- -
R2
12
C
The maximum instantaneous current is set by the external
resistor R
The connection of resistor R
The average inductor current during limited current
operation also depends on the inductance value, input
voltage, output voltage and resistive losses in all
components in the power path. Ensure that
I
lim
URRENT LIMITING RESISTORS
At upconversion (up mode): resistor R
connected between pin 2 (ILIM) and
pin 3 (UPOUT/DNIN).
The current limiting level is defined by:
At downconversion (down mode): resistor R
connected between pin 2 (ILIM) and pin 6 (GND).
The current limiting level is defined by:
< I
sat
(saturation current) of the inductor.
lim
. The preferred type is SMD, 1% accurate.
lim
differs per mode:
Preliminary specification
TEA1207T
lim
I
I
Iim
Iim
must be
lim
=
=
--------- -
R
270
--------- -
R
238
must be
Iim
Iim