Texas Instruments Evaluation Module for TPS54528 TPS54528EVM-052 TPS54528EVM-052 데이터 시트
제품 코드
TPS54528EVM-052
IN
OUT
OUT
=
Co(RMS)
IN
O
SW
V
x (V
- V
)
12 x V
x L
x
I
f
2
2
=
IPP
Lo(RMS)
O
1
+
12
I
I
I
lpp
=
+
Ipeak
O
2
I
I
I
V
V
V
IN(max)
OUT
OUT
=
x
IPP
V
L
x
IN(max)
O
SW
-
I
f
F
=
P
OUT
OUT
1
2
L
x C
p
SLVSAY4C – JULY 2011 – REVISED MARCH 2014
Typical Application (continued)
9.2.2.2 Output Filter Selection
The output filter used with the TPS54528 is an LC circuit. This LC filter has double pole at:
(4)
At low frequencies, the overall loop gain is set by the output set-point resistor divider network and the internal
gain of the TPS54528. The low frequency phase is 180 degrees. At the output filter pole frequency, the gain rolls
off at a –40 dB per decade rate and the phase drops rapidly. D-CAP2™ introduces a high frequency zero that
reduces the gain roll off to –20 dB per decade and increases the phase to 90 degrees one decade above the
zero frequency. The inductor and capacitor selected for the output filter must be selected so that the double pole
of
gain of the TPS54528. The low frequency phase is 180 degrees. At the output filter pole frequency, the gain rolls
off at a –40 dB per decade rate and the phase drops rapidly. D-CAP2™ introduces a high frequency zero that
reduces the gain roll off to –20 dB per decade and increases the phase to 90 degrees one decade above the
zero frequency. The inductor and capacitor selected for the output filter must be selected so that the double pole
of
is located below the high frequency zero but close enough that the phase boost provided be the
high frequency zero provides adequate phase margin for a stable circuit. To meet this requirement use the
values recommended in
values recommended in
.
Table 1. Recommended Component Values
Output Voltage (V)
R1 (k
Ω)
R2 (k
Ω)
C4 (pF)
(1)
L1 (µH)
C8 + C9 (µF)
1
6.81
22.1
1.0 - 1.5
22 - 68
1.05
8.25
22.1
1.0 - 1.5
22 - 68
1.2
12.7
22.1
1.0 - 1.5
22 - 68
1.5
21.5
22.1
1.5
22 - 68
1.8
30.1
22.1
5 - 22
1.5
22 - 68
2.5
49.9
22.1
5 - 22
2.2
22 - 68
3.3
73.2
22.1
5 - 22
2.2
22 - 68
5
124
22.1
5 - 22
3.3
22 - 68
(1)
Optional
Since the DC gain is dependent on the output voltage, the required inductor value increases as the output
voltage increases. For higher output voltages at or above 1.8 V, additional phase boost can be achieved by
adding a feed forward capacitor (C4) in parallel with R1
voltage increases. For higher output voltages at or above 1.8 V, additional phase boost can be achieved by
adding a feed forward capacitor (C4) in parallel with R1
The inductor peak-to-peak ripple current, peak current and RMS current are calculated using
,
and
. The inductor saturation current rating must be greater than the calculated peak
current and the RMS or heating current rating must be greater than the calculated RMS current. Use 700 kHz for
f
f
SW
.
Use 650 kHz for f
SW
. Make sure the chosen inductor is rated for the peak current of
and the RMS
current of
.
(5)
(6)
(7)
For this design example, the calculated peak current is 5.51 A and the calculated RMS current is 5.01 A. The
inductor used is a TDK SPM6530-1R5M100 with a peak current rating of 11.5 A and an RMS current rating of
11 A.
inductor used is a TDK SPM6530-1R5M100 with a peak current rating of 11.5 A and an RMS current rating of
11 A.
The capacitor value and ESR determines the amount of output voltage ripple. The TPS54528 is intended for use
with ceramic or other low ESR capacitors. Recommended values range from 22µF to 68µF. Use
with ceramic or other low ESR capacitors. Recommended values range from 22µF to 68µF. Use
to
determine the required RMS current rating for the output capacitor.
(8)
Copyright © 2011–2014, Texas Instruments Incorporated
13
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