tea1205at NXP Semiconductors, tea1205at Datasheet - Page 11

• Manufacturer Part Number: tea1205at
• Description: High Efficiency Dc/dc Converter
• Manufacturer: NXP Semiconductors

Philips Semiconductors
APPLICATION INFORMATION
A typical component choice for an upconverter from
3 NiCd cells or one Li-ion cell to 5.0 V in a GSM handset
(peak power 7.5 W, peak current 2.7 A) is (see Fig.8):
For lower power applications, the I
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.9. 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 V
and the SHDWN pin is kept LOW. As soon as V
1 V, TR1 no longer conducts and the device is put into
shut-down before V
signal is available which indicates the presence of the
input voltage source, this signal should be applied to the
1998 Mar 24
handbook, full pagewidth
L1 = 10 H; I
Coilcraft DO3308-103
C1 = 100 F; low ESR capacitor; necessity depends on
type of input voltage source
C2 = 330 F; ESR = 0.1 ; e.g. Sprague 595D series
D1; medium power Schottky diode; e.g. Philips
PRLL5819.
High efficiency DC/DC converter
sat
> 2.3 A; low DC resistance, e.g.
O
falls below 2 V. In the event that a
V I
I
is present, TR1 conducts
C1
sat
L1
Fig.8 Complete application for upconversion.
and R
DC
LX
I
values of
falls below
GND
ILIM
R lim
TEA1205AT
11
VSEL SYNC SHDWN
D1
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
Fig.9 External deadlock prevention circuit.
SENSE
OUT
V I
2.7 M
R2
C2
MGM701
V O
V O
TR1
R1
1 M
Preliminary specification
SHDWN
TEA1205AT
MGK930