Datasheet
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Designing for Load Transients
PTN78020A
SLTS244A – APRIL 2005 – REVISED MAY 2005
The transient response of the dc/dc converter has been characterized using a load transient with a di/dt of
1 A/µs. The typical voltage deviation for this load transient is given in the data sheet specification table using the
required 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 of
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.
Table 3. Recommended Input/Output Capacitors
CAPACITOR CHARACTERISTICS QUANTITY
85°C
CAPACITOR VENDOR/
EQUIVALENT
VENDOR
WORKING MAXIMUM PHYSICAL
COMPONENT
VALUE SERIES INPUT OUTPUT
NUMBER
VOLTAGE RIPPLE SIZE
SERIES
(µF) RESISTANCE BUS BUS
(V) CURRENT (mm)
(ESR) ( Ω )
(mArms)
FC( Radial) 35 180 0.090 755 10 × 16 1 1 EEUFC1V331 (V
I
< 30 V)
FK (SMD) 50 330 0.12 900 12,5 × 13,5 1
(1)
1 EEVFK1H181Q
United Chemi-Con PXA (SMD) 16 150 0.026 3430 10 × 12,2 ≤ 1 PXA16VC151MJ80TP (V
I
, |V
O
|
1
(1)
< 14 V)
PS 25 100 0.020 4320 10 × 12,5 1
(1)
≤ 1 25PS100M J12 (V
I
< 20 V)
LXZ 35 220 0.090 760 10 × 12,5 1
(1)
1 LXZ35VB221M10X12LL
MVZ (SMD) 25 470 0.090 670 10 × 10 1 1 MVZ25VC471MJ10TP (V
I
< 20
V)
Nichicon UWG (SMD) 35 330 0.15 670 10 × 10 1 1 UWG1V331MNR1GS
F550 (Tantalum) 10 100 0.055 2000 7,7 × 4,3 N/R
(2)
≤ 3
(3)
F551A107MN (V
O
≤ 5 V)
HD 50 150 0.061 979 10 × 12,5 1 1 UHD1H151MHR
Sanyo Os-Con SVP (SMD) 20 150 0.020 4300 10 × 12,7 1
(1)
≤ 1 20SVP150M (V
I
≤ 16 V)
SP 20 120 0.024 3110 8 × 10,5 1
(1)
≤ 1 20SP180M (V
I
≤ 16 V)
20 100 0.085 1543 7,3 L × 4,3 N/R
(2)
≤ 3 TPSV107M020R0085
W × 4,1 H (|V
O
| ≤ 10 V)
AVX Tantalum TPS (SMD)
20 100 0.200 > 817 3225 N/R
(2)
≤ 3 TPSE107M020R0200
(|V
O
| ≤ 10 V)
Murata X5R Ceramic 6.3 100 0.002 >1000 3225 N/R
(2)
≤ 2 GRM32ER60J107M
(|V
O
| ≤ 5.5 V)
TDK X5R Ceramic 6.3 100 0.002 >1000 3225 N/R
(2)
≤ 2 C3225X5R0J107MT
(|V
O
| ≤ 5.5 V)
Murata X5R Ceramic 16 47 0.002 >1000 3225 4
(1)
≤ 4 GRM32ER61C476M
(|V
o
| ~ V
I
≤ 13.5 V)
Kemet X5R Ceramic 6.3 47 0.002 >1000 3225 N/R
(2)
≤ 4 C1210C476K9PAC
(|V
O
| ≤ 5.5 V)
TDK X5R Ceramic 6.3 47 0.002 >1000 3225 N/R
(2)
≤ 4 C3225X5R0J476MT
(|V
O
| ≤ 5.5 V)
Murata X5R Ceramic 6.3 47 0.002 >1000 3225 N/R
(2)
≤ 4 GRM42-2X5R476M6.3
(|V
O
| ≤ 5.5 V)
TDK X7R Ceramic 25 2.2 0.002 >1000 3225 ≥ 8
(4)
1 C3225X7R1E225KT/MT
(|V
O
| ≤ 20 V)
Murata X7R Ceramic 25 2.2 0.002 >1000 3225 ≥ 8
(4)
1 GRM32RR71E225K
(|V
O
| ≤ 20 V)
Kemet X7R Ceramic 25 2.2 0.002 >1000 3225 ≥ 8
(4)
1 C1210C225K3RAC
(V
I
, |V
O
| ≤ 20 V)
AVX X7R Ceramic 25 2.2 0.002 >1000 3225 ≥ 8
(4)
1 C12103C225KAT2A
(V
I
, |V
O
| ≤ 20 V)
(1) The voltage rating of the input capacitor must be selected for the desired operating input voltage range of the regulator. To operate the
regulator at a higher input voltage, select a capacitor with the next higher voltage rating.
(2) Not recommended (N/R). The voltage rating does not meet the minimum operating limits in most applications.
(3) The maximum voltage rating of the capacitor must be selected for the desired set-point voltage (V
O
). To operate at a higher output
voltage, select a capacitor with a higher voltage rating.
(4) The maximum rating of the ceramic capacitor limits the regulator operating input voltage to 20 V. Select a alternative ceramic
component to operate at a higher input voltage.
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