参数资料
型号: TPS54326RGTR
厂商: TEXAS INSTRUMENTS INC
元件分类: 稳压器
英文描述: 5.5 A SWITCHING REGULATOR, 700 kHz SWITCHING FREQ-MAX, PQCC16
封装: GREEN, PLASTIC, QFN-16
文件页数: 5/26页
文件大小: 911K
代理商: TPS54326RGTR
1
2
P
OUT
F
L
C
p
=
Ilp-p=
V
OUT
V
IN(max)
V
-V
IN(max)
OUT
L
f
O
SW
I
=I +
lpeak
O
Ilp-p
2
I
=
Lo(RMS)
I +
O
2
1
12
Ilp-p
2
I
=
CO(RMS)
V
OUT
(
)
V-V
IN
OUT
V
IN
L
O
f
SW
√12
SLVSA13D
– OCTOBER 2009 – REVISED FEBRUARY 2011
Output Filter Selection
The output filter used with the TPS54326 is an LC circuit. This LC filter has double pole at:
(5)
At low frequencies, the overall loop gain is set by the output set-point resistor divider network and the internal
gain of the TPS54326. 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 Equation 5 is located below the high frequency zero but close enough that the phase boost provided by the
high frequency zero provides adequate phase margin for a stable circuit. To meet this requirement use the
values recommended in Table 1.
Table 1. Recommended Component Values
OUTPUT VOLTAGE
R1 (k
Ω)
R2 (k
Ω)
C4 (pF)(1)
L1 (
H)
C8 + C9 (
F)
(V)
1
6.81
22.1
1.5
22 - 68
1.05
8.25
22.1
1.5
22 - 68
1.2
12.7
22.1
1.5
22 - 68
1.8
30.1
22.1
10 - 47
2.2
22 - 68
2.5
49.9
22.1
10 - 47
2.2
22 - 68
3.3
73.2
22.1
10 - 47
2.2
22 - 68
5
121
22.1
10 - 47
3.3
22 - 68
(1)
Optional
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 Equation 6,
Equation 7, and Equation 8. 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
fSW.
(6)
(7)
(8)
For this design example, the calculated peak current is 3.47 A and the calculated RMS current is 3.01 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.
The capacitor value and ESR determines the amount of output voltage ripple. The TPS54326 is intended for use
with ceramic or other low ESR capacitors. Recommended values range from 22
F to 68 F. Use Equation 9 to
determine the required RMS current rating for the output capacitor.
(9)
For this design two TDK C3216X5R0J226M 22
F output capacitors are used. The typical ESR is 2 mΩ each.
The calculated RMS current is 0.271 A and each output capacitor is rated for 4 A.
2009–2011, Texas Instruments Incorporated
13
Product Folder Link(s) :TPS54326
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