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TEA1207T

High efficiency DC/DC converter

Philips Electronics 

Philips Semiconductors

High efficiency DC/DC converter

Product specification

TEA1207T

External component selection

INDUCTOR L1

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 µH

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.

INPUT CAPACITOR C1

The value of capacitor C1 strongly depends on the type of

input source. In general, a 100 µF tantalum capacitor will

do, or a 10 µF ceramic capacitor featuring very low series

resistance (ESR value).

OUTPUT CAPACITOR C2

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.

CURRENT LIMITING RESISTORS

The maximum instantaneous current is set by the external

resistor Rlim. The preferred type is SMD, 1% accurate.

The connection of resistor Rlim differs per mode:

• At upconversion (up mode): resistor Rlim must be

connected between pin 2 (ILIM) and

pin 3 (UPOUT/DNIN).

The current limiting level is defined by: IIim = R-2---3-I-i-m8--

• At downconversion (down mode): resistor Rlim must be

connected between pin 2 (ILIM) and pin 6 (GND).

The current limiting level is defined by: IIim = -R2---7-I-i-m0--

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

Ilim < Isat (saturation current) of the inductor.

DIODE D1

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.

FEEDBACK RESISTORS R1 AND R2

The output voltage is determined by the resistors

R1 and R2. The following conditions apply:

• 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 kΩ when connected in parallel. A higher value will

result in inaccurate operation.

Under these conditions, the output voltage can be

calculated by the formula:

VO

=

1.24

×





1

+

RR-----12--





2000 Nov 27

12

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