PT6930 Datasheet, PDF (6/7 Pages) Texas Instruments – 5V TO 3.3V/2.5V 25 WATT DUAL OUTPUT INTEGRATED SWITCHING REGULATOR

Application Notes continued
PT6920/PT6930 Series
Capacitor Recommendations for the Dual-Output
PT6920/30 Regulator Series
Input Capacitors:
The recommended input capacitance is determined by 1.0
ampere minimum ripple current rating and 330µF minimum
capacitance (300µF for Oscon® or low ESR tantalum).
Ripple current and <100mΩ equivalent series resistance
(ESR) values are the major considerations, along with tem-
perature, when designing with different types of capacitors.
Tantalum capacitors have a recommended minimum voltage
rating of 2 × the maximum DC voltage + AC ripple. This is
necessary to insure reliability for input voltage bus applica-
tions.
Output Capacitors: C (Required), C (Optional)
2
3
The ESR of the required capacitor (C₂) must not be greater
than 150mΩ. Electrolytic capacitors have poor ripple per-
formance at frequencies greater than 400kHz but excellent
low frequency transient response. Above the ripple fre-
quency, ceramic capacitors are necessary to improve the
transient response and reduce any high frequency noise
components apparent during higher current excursions.
Preferred low ESR type capacitor part numbers are identified
in Table 1. The optional 100µF capacitor (C₃) for Vo₂ can
have an ESR of up to 200mΩ for optimum performance
and ripple reduction. (Note: Vendor part numbers for the
optional capacitor, C₃, are not identified in the table. Use the
same series selected for C₂)
Table 1: Input/Output Capacitors
Tantalum Capacitors
Tantalum type capacitors can be used for the output but only
the AVX TPS series, Sprague 593D/594/595 series or Kemet
T495/T510 series. The AVX TPS series, Kemet or Sprague
series tantalums are recommended over many other types
due to their higher rated surge, power dissipation, and ripple
current capability. As a caution the TAJ series by AVX is not
recommended. This series has considerably higher ESR,
reduced power dissipation and lower ripple current capability.
The TAJ Series is a less reliable when compared to the AVX
TPS series when determining power dissipation capability.
Tantalum types are recommended for applications where
ambient temperatures fall below 0°C.
Capacitor Table
Table 1 identifies the characteristics of capacitors from a
number of vendors with acceptable ESR and ripple current
(rms) ratings. The number of capacitors required at both the
input and output buses is identified for each capacitor type.
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 performance and
long capacitor life.
Capacitor
Vendor/
Component
Series
Working
Voltage
Panasonic
25V
FC
35V
35V
United
16V
Chemi -con
35V
LXV/FS/
10V
LXZ
20V
Nichicon
35V
PL
35V
PM
50V
Panasonic
10V
FC
35V
Surface Mtg
16V
Oscon- SS
SV
10V
10V
20V
AVX
Tantalum
TPS
10V
10V
10V
Capacitor Characteristics
Value(µF)
(ESR) Equivalent
Series Resistance
560µF
390µF
330µF
330µF
470µF
330µF
150µF
560µF
330µF
470µF
1000µF
330µF
330µF
330µF
330µF
150µF
0.0065W
0.065W
0.117W
0.120W
0.052W
0.025W
0.030/2W
0.048W
0.065/2W
0.046W
0.043W
0.065W
0.150W
0.025W
0.025W
0.024/2W
85°C Maximum
Ripple
Current(Irms)
1205mA
1205mA
555mA
555mA
1220mA
3500mA
3200mA
1360mA
1020mA
1470mA
1205mA
1205mA
670mA
>3500mA
>3800mA
3600mA
330µF
330µF
220µF
0.100/2W
0.100/2W
0.095W
>2500mA
>3000mA
>2000mA
Quantity
Physical Input Output
Size(mm) Bus Bus
Vendor Number
12.5x15
12.5x15
8x11.5
8x12
10x20
10x10.5
10x10.5
16x15
12.5x15
18x15
12x16.5
12.5x16
10x10.2
10.0x10.5
10.3x10.3
10.3x10.3
7.3Lx
4.3Wx
4.1H
1
1
2
1
(a)
1
(a)
1
1
1
1 (N/R)
2 (N/R)
1
1
1
1
1
1
1
1
1
1
(a)
1
1 (N/R)
1 (N/R)
2 (N/R)
2
1
2
1
2
2
EEUFC1E561S
EEUFC1V391S
EEUFC1C331
LXZ16VB331M8X12LL
LXZ35VB471M10X20LL
10FS330M
20FS150M
UPL1V561MHH6
UPL1V331MHH6
UPM1H4711MHH6
EEVFC1A102LQ
EEVFC1V331LQ
EEVFC1C331P
10SS330M
10SV300M
20SV150M
SV= Surface Mount
TPSV337M010R0100
TPSV337M010R0060
TPSV227M0105R0100
Kemet
T510
T495
10V
10V
Sprague
10V
594D
10V
330µF
220µF
0.033W
0.070W/2=0.035W
330µF
220µF
0.0450W
0.065W
1400mA
>2000mA
2350mA
>2000mA
7.3Lx5.7W 2
1
x 4.0H
2
2
7.3Lx
6.0Wx
4.1H
2
2
1
2
T510X337M010AS
T495X227M010AS
4D337X0010R2T
594D227X0010D2T
(a) -Not recommended. The maximum ripple current rating of these capacitors does not meet the operating limits.
(N/R) -Oscon Type Capcitors are not recommended for this application due to extremely low equivatlent series resistance (ESR)
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