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TEA1024T

High efficiency DC/DC converter

Philips Electronics 

Philips Semiconductors

High efficiency DC/DC converter

Product specification

TEA1204T

A typical component choice for an upconverter from

3 NiCd cells or one LiIon cell to 5.0 V in a GSM handset

(peak power 7.5 W, peak current 2.7 A) is:

• L1; L = 10 µH; Isat >2.3 A; low DC resistance, e.g.

Coilcraft DO3308-103

• C1; C = 100 µF; low ESR capacitor; necessity depends

on type of input voltage source

• C2; C = 330 µF; ESR = 0.1 Ω; e.g. Sprague 595D series

• D1; medium power Schottky diode; e.g. Philips

PRLL5819.

For lower power applications, the Isat and RDC values of

the inductor can be scaled back by the scaling factor of the

output current from the values above. The same holds for

the ESR value of the output capacitor. A further

improvement is increase of inductance and decrease of

output capacitance.

An additional circuit to prevent start-up deadlock in

upconversion is shown in Fig.8. The function of TR1, R1

and R2 is to put the converter into shut-down mode when

the input source is suddenly disconnected. The circuit

operates as follows. When VI is present, TR1 conducts

and the SHDWN pin is kept LOW. As soon as VI falls below

1 V, TR1 no longer conducts and the device is put into

shut-down before VO falls below 2 V. In the event that a

signal is available which indicates the presence of the

input voltage source, this signal should be applied to the

SHDWN pin. TR1, R1 and R2 should be omitted in that

case.

More application information can be found in the

associated application note.

handbook, halfpage

VI

R2

2.7 MΩ

VO

R1

1 MΩ

SHDWN

TR1

MGK930

Fig.8 External deadlock prevention circuit.

1998 Mar 02

11

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