PT6447 Datasheet, PDF (4/8 Pages) Texas Instruments – 6-A 5-V/3.3-V Input Adjustable Integrated Switching Regulator

Application Notes
PT6440 Series
Capacitor Recommendations for the PT6440
Excalibur™ 5V/3.3V Bus Step-Down ISRs
Input Capacitors
The recommended input capacitance is determined by
350 milli-amperes (rms) minimum ripple current rating
and 100µF minimum capacitance. Capacitors placed at
the input must be rated for a minimum of twice the input
voltage with +5V operation. Ripple current and ≤200mΩ
Equivalent Series Resistance (ESR) values are the major
considerations, along with temperature, when selecting
the proper input capacitor.
Output Capacitors
The ESR of the required 330µF output capacitor must
be less than or equal to 100mΩ. Failure to observe this
requirement may lead to regulator instability or oscillation.
Electrolytic capacitors have poor ripple performance at
frequencies greater than 300kHz but excellent low fre-
quency transient response. Above the ripple frequency,
ceramic decoupling capacitors are necessary to improve the
transient response and reduce any high frequency noise
components apparent during higher current excursions.
The preferred low ESR type capacitor part numbers are
identified in Table 1.
Tanatalum Capacitors
Tantalum capacitors are recommended on the output bus
but only the AVX TPS series, Sprague 593D/594/595
series or Kemet T495/T510 series. These capacitors are
specified over many other types due to their higher surge
current, power dissipation and ripple current capability.
As a caution, the TAJ Series by AVX is not recommended.
This series exhibits considerably higher ESR and lower
ripple current capability. The TAJ series is also less reliable
than the TPS series when determining power dissipation
capability. Tantalum or Oscon® types are recommended
in applications where ambient temperatures fall below 0°C.
Capacitor Table
Table 1 identifies vendors with acceptable ESR and
maximum allowable ripple current (rms) ratings. The
suggested minimum quantities per regulator for both
the input and output buses are identified.
This is not an extensive capacitor list. Capacitors from other
vendors are available with comparable specifications. Those
listed are for guidance. The RMS ripple current rating and
ESR (Equivalent Series Resistance at 100kHz) are critical
parameters necessary to insure both optimum regulator perfor-
mance and long capacitor life.
Table 1; Input/Output Capacitors
Capacitor Vendor/
Component
Series
Working
Voltage
Panasonic, FC (Radial)
35V
35V
25V
FC (Surface Mount)
16V
25V
35V
United Chemi-Con
25V
LXV/LXZ
35V
FS
10V
10V
Nichicon, PL (Radial)
35V
UD (Surface Mount)
35V
35V
Oscon, SS (Radial)
10V
SV (Surface Mount)
10V
16V
AVX Tantalum TPS
10V
10V
10V
Kemet, T510
10V
T495
10V
Sprague
10V
594D
10V
Value(µF)
390µF
100µF
330µF
220µF
100µF
330µF
330µF
220µF
330µF
100µF
330µF
330µF
220µF
330µF
330µF
100µF
330µF
330µF
150µF
330µF
220µF
330µF
150µF
Capacitor Characteristics
Quantity
(ESR) Equivalent
Series Resistance
85°C Maximum Ripple
Current(Irms)
Physical
Size(mm)
Input
Bus
Output
Bus
Vendor Number
0.065Ω
0.117Ω
0.090Ω
0.15Ω÷2
0.40Ω
0.065Ω
0.084Ω
0.090Ω÷2
0.025Ω
0.040Ω
0.065Ω
0.090Ω
0.17Ω÷2
0.025Ω
0.025Ω
0.045Ω
0.100Ω
0.060Ω
0.100Ω
0.033Ω
0.070Ω÷2
0.045Ω
0.090Ω
1205mA
555mA
755mA
670mA
450mA
1205mA
825mA
760mA
3500mA
2100mA
1020mA
670mA
450mA
>3500mA
>3800mA
2200mA
1414mA
1826mA
1095mA
1400mA
>2000mA
2350mA
1100mA
12.5×15
8×11.5
10×12.5
1
1 EEUFC1V391S
1
N/R EEUFC1V101
1
1 EEUFC1E331
10×10.2
8×10 2
12×16.5
10×16
10×12.5
1
2 EEVFC1C221P
1
N/R EEVFC1101P
1
1 EEVFC1V471LQ
1
1 LXV25VB331M10X16LL
1
2 LXZ35VB221M10X12LL
10×10.5
6.3×9.8
12.5×15
1
1 10FS330M
1
N/R 10FS100M
1
1 UPL1V331MHH6
10×10
8×10
1
1 UUD1V331MNR1GS
1
2 UUD1V2211MNR1GS
10×10.5
1
1 10SS330M
10.3×10.3
10.3×10.3
1
1 10SV300M
1
N/R 16SV100M
7.3L
1
×4.3W
1
×4.1H
1
7.3L ×5.7W
1
×4.0H
1
1 TPSV337M010R0100
1 TPSV337M010R0060
2 TPSD107M0 0R100
1 T510X337M010AS
2 T495X227M010AS
7.3L ×6W
1
×4.1H
1
1 594D337X0010R2T
2 594D157X0010C2T
For technical support and more information, see inside back cover or visit www.ti.com