PT6937A Datasheet, PDF (8/14 Pages) Texas Instruments – Internal Sequencing Short Circuit Protection 23-pin Space-Saving Package

Application Notes
PT6935 Series
Not Recommended For New Designs
Capacitor Recommendations for the
Dual-Output PT6935 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: C₂(Required), C₃(Optional)
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 V₂out 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)
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. These capacitors are recommended
over many other tantalum 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 dissipa-
tion, and lower ripple current capability. The TAJ series is
less reliable than the AVX TPS series when determining
power dissipation capability. Tantalum or Oscon® types
are recommended for applications where ambient tem-
peratures 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.
Table 1: Input/Output Capacitors
Capacitor
Vendor/
Component
Series
Working
Voltage
Value(µF)
Capacitor Characteristics
(ESR) Equivalent
Series Resistance
85°C Maximum Ripple
Current(Irms)
Quantity
Physical
Size(mm)
Input Output
Bus Bus
Vendor Number
Panasonic
25V
FC
35V
35V
United
16V
Chemi-Con
35V
LXV/FS/
10V
LXZ
20V
Nichicon
PL/ PM
35V
35V
50V
Panasonic
10V
FC
35V
(Surface Mtg)
16V
Oscon- SS
10V
SV
10V
20V
560µF
390µF
330µF
330µF
470µF
330µF
150µF
560µF
330µF
470µF
1000µF
330µF
330µF
330µF
330µF
150µF
0.0065Ω
0.065Ω
0.117Ω
0.120Ω
0.052Ω
0.025Ω
0.030÷2 Ω
0.048Ω
0.065÷2 Ω
0.046Ω
0.043Ω
0.065Ω
0.150Ω
0.025Ω
0.025Ω
0.024÷2 Ω
1205mA
1205mA
555mA
555mA
1220mA
3500mA
3200mA
1360mA
1020mA
1470mA
1205mA
1205mA
670mA
>3500mA
>3800mA
3600mA
12.5x15
1
12.5x15
2
8x11.5
N/R
8x12
N/R
10x20
1
10x10.5
1
10x10.5
2
16x15
1
12.5x15
1
18x15
1
12x16.5
1
12.5x16
1
10x10.2
N/R
10.0x10.5
1
10.3x10.3
1
10.3x10.3
2
AVX
Tantalum
TPS
Kemet
T510/
T495
Sprague
594D
10V
330µF
10V
330µF
10V
220µF
0.100÷2 Ω
0.100÷2 Ω
0.095Ω
10V
330µF
0.033Ω
10V
220µF
0.07Ω÷2 =0.035Ω
10V
330µF
10V
220µF
0.045Ω
0.065Ω
>2500mA
>3000mA
>2000mA
1400mA
>2000mA
2350mA
>2000mA
7.3Lx
2
4.3Wx
2
4.1H
2
7.3Lx5.7W
2
x 4.0H
2
7.3Lx
6.0Wx
4.1H
2
2
N/R –Not recommended. The voltage rating does not meet the minimum operating limits.
1 EEUFC1E561S
1 EEUFC1V391S
1 EEUFC1C331
1 LXZ16VB331M8X12LL
1 LXZ35VB471M10X20LL
1 10FS330M
2 20FS150M
1 UPL1V561MHH6
1 UPL1V331MHH6
1 UPM1H4711MHH6
1 EEVFC1A102LQ
1 EEVFC1V331LQ
1 EEVFC1C331P
1 10SS330M
1 10SV300M
2 20SV150M
SV= Surface Mount
1 TPSV337M010R0100
1 TPSV337M010R0060
2 TPSV227M0105R0100
1 T510X337M010AS
2 T495X227M010AS
1 4D337X0010R2T
2 594D227X0010D2T
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