Datasheet

÷
÷
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÷
ø
ö
ç
ç
ç
ç
è
æ
×
×
-
×=D
SW
IN
OUT
OUT
L
fL
V
V
V
I
(min)
(max)
(max)
1
h
h
TPS62175, TPS62177
www.ti.com SLVSB35B –OCTOBER 2012–REVISED JANUARY 2014
(7)
where
ΔI
L
is the Peak to Peak Inductor Ripple Current,
η is the converter efficiency (see efficiency figures),
L(min) is the minimum inductor value and
f
SW
is the actual PWM Switching Frequency.
Calculating the maximum inductor current using the actual operating conditions gives the minimum saturation
current of the inductor needed. A margin of about 20% is recommended to cover possible load transient
overshoot. A larger inductor value is also useful to get lower ripple current, but increases the transient response
time and solution size as well. The following inductors have been tested with the TPS62175/7:
Table 2. List of Inductors
Type Inductance [µH] Current [A]
(1)
DCR [mΩ] Dimensions [L x B x H] MANUFACTUR
mm ER
LPS4012-103MLC 10µH, ±20% 1.1A 350 (max) 4.0 x 4.0 x 1.2 Coilcraft
LPS4018-103MLC 10µH, ±20% 1.3A 200 (max) 4.0 x 4.0 x 1.8 Coilcraft
VLS4012ET-100M 10µH, ±20% 0.99A 190 (typ) 4.0 x 4.0 x 1.2 TDK
VLCF4020T-100MR85 10µH, ±20% 0.85A 168 (typ) 4.0 x 4.0 x 2.0 TDK
74437324100 10µH, ±20% 1.5 A 215 (typ) 4.5 x 4.1 x 1.8 Wuerth
744025100 10µH, ±20% 1.0A 190 (max) 2.8 x 2.8 x 2.8 Wuerth
IFSC-1515AH-01 10µH, ±20% 1.3A 135 (typ) 3.8 x 3.8 x 1.8 Vishay
ELL-4LG100MA 10µH, ±20% 0.8A 200 (typ) 3.8 x 3.8 x 1.8 Panasonic
(1) I
RMS
at 40°C rise or I
SAT
at 30% drop.
Output Capacitor
The recommended value for the output capacitor is 22uF. To maintain low output voltage ripple during large load
transients, for output voltages below 2V, 2x 22µF is recommended. The architecture of the TPS62175/7 allows
the use of ceramic output capacitors with low equivalent series resistance (ESR). These capacitors provide low
output voltage ripple and are recommended with an X7R or X5R dielectric. Larger capacitance values have the
advantage of smaller output voltage ripple and a tighter DC output accuracy in Power Save Mode.
Note: In Power Save Mode, the output voltage ripple and accuracy depends on the output capacitance and the
inductor value. The larger the capacitance the lower the output voltage ripple and the better the output voltage
accuracy. The same relation applies to the inductor value.
Input Capacitor
Typically, 2.2µF is sufficient and is recommended, though a larger value reduces input current ripple further. The
input capacitor buffers the input voltage during transient events and also decouples the converter from the
supply. A low ESR, multilayer, X5R or X7R dielectric, ceramic capacitor is recommended for best filtering and
should be placed between VIN and PGND as close as possible to those pins.
spacing
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