STOD03A STMicroelectronics, STOD03A Datasheet - Page 14

• Manufacturer Part Number: STOD03A
• Description: Dual DC-DC converter for powering AMOLED display
• Manufacturer: STMicroelectronics

Specifications of STOD03A

• Typical Efficiency: 85%
• Low Quiescent Current: < 1 μA in shutdown mode
• Temperature Range: - 40 °C to 85 °C

Application information
7
7.1
7.1.1
7.1.2
14/23
Application information
External passive components
Inductor selection
The inductor is the key passive component 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 2.2 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 0.85;
η2: efficiency of inverting converter. Typical value is 0.75.
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 ceramic capacitors with low ESR 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 2 µF must be guaranteed for
C
polarization, a 4.7 µF 10 V capacitor can be used to achieve the required 2 µF.
O
s
O2
MID
IN
: switching frequency. Use the minimum value of 1.2 MHz for the worst case;
MID
: output current for both DC-DC converters;
: input voltage for the STOD03A;
: inverting output voltage including sign (minimum value is the absolute maximum
: step-up output voltage, fixed at 4.6 V;
and C
I
I
PEAK
PEAK
O2
in all conditions. Considering tolerance, temperature variation, and DC
-
-
INVERTING
INVERTING
I
PEAK
=
=
−
(
(
BOOST
VIN
VIN
MIN
MIN
Doc ID 17785 Rev 2
η
η
=
2
2
-
-
η
x
x
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 - 5.4 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
1
VO
VO
MIN
MIN
MIN
2
2
)
)
)
MIN
MIN
x
x
fs
fs
x
x
L
L
2
2
STOD03A