Texas Instruments TPS61150A-150 Evaluation Board TPS61150AEVM-150 TPS61150AEVM-150 TPS61150AEVM-150 Datenbogen
Produktcode
TPS61150AEVM-150
www.ti.com
I
L_DC
+
V
iout
Iout
V
in
h
(7)
INPUT AND OUTPUT CAPACITOR SELECTION
Cout
+
ǒ
V
iout
*
V
in
Ǔ
Iout
V
iout
Fs
V
ripple
(8)
SLVS706 – OCTOBER 2006
APPLICATION INFORMATION (continued)
Use the maximum load current and minimum V
I
for calculation.
The internal loop compensation for PWM control is optimized for the external component shown in the typical
application circuit with consideration of component tolerance. Inductor values can have
application circuit with consideration of component tolerance. Inductor values can have
±
20% tolerance with no
current bias. When the inductor current approaches saturation level, its inductance can decrease 20 to 35%
from the 0A value depending on how the inductor vendor defines saturation. Using an inductor with a smaller
inductance value forces discontinuous PWM in which inductor current ramps down to zero before the end of
each switching cycle. It reduces the boost converter’s maximum output current, and causes large input voltage
ripple. An inductor with larger inductance reduces the gain and phase margin of the feedback loop, possibly
resulting in instability
from the 0A value depending on how the inductor vendor defines saturation. Using an inductor with a smaller
inductance value forces discontinuous PWM in which inductor current ramps down to zero before the end of
each switching cycle. It reduces the boost converter’s maximum output current, and causes large input voltage
ripple. An inductor with larger inductance reduces the gain and phase margin of the feedback loop, possibly
resulting in instability
Regulator efficiency is dependent on the resistance of its high current path and switching losses associated with
the PWM switch and power diode. Although the TPS61150A has optimized the internal switches, the overall
efficiency still relies on inductors DC resistance (DCR); Lower DCR improves efficiency. However, there is a
trade off between DCR and inductor size, and shielded inductors typically have higher DCR than unshielded
ones. DCR in range of 150m
the PWM switch and power diode. Although the TPS61150A has optimized the internal switches, the overall
efficiency still relies on inductors DC resistance (DCR); Lower DCR improves efficiency. However, there is a
trade off between DCR and inductor size, and shielded inductors typically have higher DCR than unshielded
ones. DCR in range of 150m
Ω
to 350m
Ω
is suitable for applications requiring both on mode. DCR is the range
of 250m
Ω
to 450m
Ω
is a good choice for single output application.
and
list recommended
inductor models.
Table 2. Recommended Inductors for Single Output
L
DCR Typ
Isat
SIZE
(
µ
H)
(m
Ω
)
(A)
(L
×
W
×
H mm)
TDK
VLF3012AT-100MR49
10
360
0.49
2.8
×
3.0
×
1.2
VLCF4018T-100MR74-2
10
163
0.74
4.0
×
4.0
×
1.8
Sumida
CDRH2D11/HP
10
447
0.52
3.2
×
3.2
×
1.2
CDRH3D16/HP
10
230
0.84
4.0
×
4.0
×
1.8
Table 3. Recommended Inductors for Dual Output
L
DCR Typ
Isat
SIZE
(
µ
H)
(m
Ω
)
(A)
(L
×
W
×
H mm)
TDK
VLCF4018T-100MR74-2
10
163
0.74
4.0
×
4.0
×
1.8
VLF4012AT-100MR79
10
300
0.85
3.5
×
3.7
×
1.2
Sumida
CDRH3D16/HP
10
230
0.84
4.0
×
4.0
×
1.8
CDRH4D11/HP
10
340
0.85
4.8
×
4.8
×
1.2
The output capacitor is mainly selected for the output ripple of the converter. This ripple voltage is the sum of the
ripple caused by the capacitor’s capacitance and its equivalent series resistance (ESR). Assuming a capacitor
with zero ESR, the minimum capacitance needed for a given ripple can be calculated by
ripple caused by the capacitor’s capacitance and its equivalent series resistance (ESR). Assuming a capacitor
with zero ESR, the minimum capacitance needed for a given ripple can be calculated by
V
ripple
= Peak-to-peak output ripple.
14