Datasheet

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Designing for Load Transients
PTH04000W
SLTS247B – JUNE 2005 – REVISED OCTOBER 2007
The transient response of the dc/dc converter has been characterized using a load transient with a di/dt of 1 A/s.
The typical voltage deviation for this load transient is given in the data sheet specification table using the optional
value of output capacitance. As the di/dt of a transient is increased, the response of a converter's regulation
circuit ultimately depends on its output capacitor decoupling network. This is an inherent limitation with any dc/dc
converter once the speed of the transient exceeds its bandwidth capability. If the target application specifies a
higher di/dt or lower voltage deviation, the requirement can only be met with additional output capacitor
decoupling. In these cases, special attention must be paid to the type, value, and ESR of the capacitors selected.
If the transient performance requirements exceed those specified in the data sheet, the selection of output
capacitors becomes more important. Review the minimum ESR in the characteristic data sheet for details on the
capacitance maximum.
Table 3. Recommended Input/Output Capacitors
(1)
CAPACITOR CHARACTERISTICS QUANTITY
85C
CAPACITOR VENDOR/
EQUIVALENT
VENDOR
MAXIMUM PHYSICAL
COMPONENT
WORKING VALUE SERIES INPUT OUTPUT
NUMBER
RIPPLE SIZE
SERIES
VOLTAGE (F) RESISTANCE BUS
(2)
BUS
CURRENT (mm)
(ESR)
(I
rms
)
Panasonic WA (SMT) 10 V 120 0.035 Ω 2800 mA 8 × 6,9 1 ≤ 4
(2)
EEFWA1A121P
(3)
FC (SMT) 25 V 47 0.400 Ω 230 mA 8 × 6,2 1 1
(2)
EEVFC1E470P
(3)
6.3 V 47 0.018 Ω 2500 mA 7,3 × 4,3 1 ≤ 2 EEFCD0J470R
Panasonic SL SP-cap(SMT)
6.3 V 56 0.009 Ω 3000 mA 7,3 × 4,3 1 ≤ 1 EEFSL0J560R
United Chemi-con PXA (SMT) 10 V 47 0.031 Ω 2250 mA 6,3 × 5,7 1 1 PXA10VC470MF60TP
FS 10 V 100 0.040 Ω 2100 mA 6,3 × 9,8 1 ≤ 3 10FS100M
LXZ 16 V 100 0.250 Ω 290 mA 6,3 × 11,5 1 1 LXZ16VB101M6X11LL
MVZ (SMT) 16 V 100 0.440 Ω 230 mA 6,3 × 5,7 1 1 MVZ16VC101MF60TP
Nichicon UWG (SMT) 16 V 100 0.400 Ω 230 mA 8 × 6,2 1 1 UWG1C101MCR1GS
F559(Tantalum) 10 V 100 0.055 Ω 2000 mA 7,7 × 4,3 1 ≤ 3 F551A107MN
PM 10 V 100 0.550 Ω 210 mA 6 × 11 1 1 UPM1A101MEH
Sanyo Os-con\ POS-Cap SVP 10 V 68 0.025 Ω 2400 mA 7,3 × 4,3 1 ≤ 3 10TPE68M
(SMT) 6.3 V 47 0.074 Ω 1110 mA 5 × 6 1 ≤ 3 6SVP47M
SP 10 V 56 0.045 Ω 1710 mA 6,3 × 5 1 ≤ 3 10SP56M
10 V 47 0.100 Ω 1100 mA 7,3L × 4,3W 1 ≤ 3 TPSD476M010R0100
AVX Tantalum TPS (SMD)
10 V 47 0.060 Ω > 412 mA × 4,1H 1 ≤ 53 TPSB476M010R0500
Kemet T520 (SMD) 10 V 68 0.060 Ω >1200 mA 7,3L × 5,7W 1 ≤ 3 T520V686M010ASE060
AO-CAP 6.3 V 47 0.028 Ω >1100 mA × 4H 1 ≤ 3 A700V476M006AT
Vishay/Sprague 594D/595D 10 V 68 0.100 Ω >1000 mA 7,3L × 6W × 1 ≤ 3 594D686X0010C2T
(SMD) 10 V 68 0.240 Ω 680 mA 4,1H 1 ≤ 3 595D686X0010C2T
94SL 16 V 47 0.070 Ω 1550 mA 8 × 5 1 ≤ 3 94SL476X0016EBP
7,5L × 4,0W
TDK Ceramic X5R (Leaded) 10 V 47 0.005 Ω >1400 mA ≥ 1 ≤ 2 FK22X5R1A476M
× 8,0H
TDK Ceramic X5R 6.3 V 22 0.002 Ω >1400 mA ≥ 2
(4)
≤ 3 C3225X5R0J226KT/MT
1210 case
Murata Ceramic X5R 6.3 V 22 0.002 Ω >1000 mA ≥ 2
(4)
≤ 3 GRM32ER61J223M
3225 mm
Kemet 6.3 V 22 0.002 Ω >1000 mA ≥ 2
(4)
≤ 3 C1210C226K9PAC
TDK Ceramic X5R 6.3 V 47 0.002 Ω >1400 mA ≥ 1 ≤ 2 C3225X5R0J476KT/MT
1210 case
Murata Ceramic X5R 6.3 V 47 0.002 Ω >1000 mA ≥ 1 ≤ 2 GRM32ER60J476M/6.3
3225 mm
Kemet 6.3 V 47 0.002 Ω >1000 mA ≥ 1 ≤ 2 C1210C476K9PAC
(1) Check with capacitor manufacturers for availability and lead-free status.
(2) A ceramic capacitor is required on the input. An electrolytic capacitor can be added to the output for improved transient response.
(3) An optional through-hole capacitor available.
(4) A total capacitance of 44 µF is an acceptable replacement for a single 47-µF capacitor.
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