STOD13AS STMicroelectronics, STOD13AS Datasheet - Page 15

• Manufacturer Part Number: STOD13AS
• Description: 250 mA dual DC-DC converter for powering AMOLED display
• Manufacturer: STMicroelectronics

Specifications of STOD13AS

• Typical Efficiency: 85%
• Temperature Range: -40 °C to 85 °C

STOD13AS
7
7.1
7.1.1
7.1.2
Application information
External passive components
Inductor selection
Magnetic shielded low ESR power inductors must be chosen as the key passive
components for switching converters.
For the step-up converter an inductance between 4.7 µH and 6.8 µH is recommended.
For the inverting stage the suggested inductance ranges from 3.3 µH to 4.7 µH.
It is very important to select the right inductor according to the maximum current the
inductor can handle to avoid saturation. The step-up and the inverting peak current can be
calculated as follows:
Equation 1
Equation 2
where
V
V
value);
I
V
f
η1: efficiency of step-up converter. Typical value is 0.70;
η2: efficiency of inverting converter. Typical value is 0.60.
The negative output voltage can be set via S
current, at the maximum load condition, increases. A proper inductor, with a saturation
current as a minimum of 1 A, is preferred.
Input and output capacitor selection
It is recommended to use X5R or X7R low ESR ceramic capacitors as input and output
capacitors in order to filter any disturbance present in the input line and to obtain stable
operation for the two switching converters. A minimum real capacitance value of 6 µF must
be guaranteed for C
variation and DC polarization, a 10 µF, 10 V ±10% capacitor as C
±10% as C
O
s
O2
MID
IN
: switching frequency. Use the minimum value of 1.35 MHz for the worst case;
: output current for both DC-DC converters;
: input voltage of the STOD13AS;
: inverting output voltage including sign (minimum value is the absolute maximum
: step-up output voltage, fixed at 4.6 V;
I
I
O2
PEAK
PEAK
, can be used to achieve the required 6 µF.
-
-
INVERTING
INVERTING
I
MID
PEAK
=
=
and C
−
(
(
BOOST
VIN
VIN
MIN
MIN
Doc ID 022733 Rev 1
O2
η
η
=
2
2
-
-
in all conditions. Considering tolerance, temperature
x
x
η
V
VO
VO
1
VIN
VIN
MID
×
2
2
VIN
×
MIN
MIN
MIN
MIN
I
OUT
)
)
MIN
x
x
I
I
WIRE
+
OUT
OUT
VIN
+
+
at -6.4 V. Accordingly, the inductor peak
2
2
MIN
2
x
x
×
(
(
×
VO
VO
V
V (
MID
VIN
VIN
MID
2
2
×
MIN
MIN
fs
MIN
MIN
−
-
-
×
VIN
VIN
VIN
x
x
L
MID
Application information
1
VO
VO
MIN
MIN
MIN
and 2 x 10 µF, 10 V
2
2
)
)
)
MIN
MIN
x
x
fs
fs
x
x
L
L
2
2
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