PT7681 Datasheet, PDF (6/12 Pages) Texas Instruments – 30-A Programmable ISR With Margin Up/Down Controls

Application Notes
PT7680 Series
Capacitor Recommendations for the PT7680
Series of 30-A Switching Regulators
Input Capacitor:
The recommended input capacitance is determined by
1.1A minimum ripple current rating and 1500µF mini-
mum capacitance.
Ripple current and <100m. equivalent series resistance
(ESR) values are the major considerations, along with
temperature, when designing with different types of
capacitors. Tantalum capacitors have a recommended
minimum voltage rating of twice the maximum DC
voltage + AC ripple. This is necessary to insure reliabil-
ity for input voltage bus applications.
Output Capacitors:
The ESR of the required capacitors is less than 100m. .
Electrolytic capacitors have marginal ripple performance
at frequencies greater than 400kHz but excellent low
frequency transient response. Above the ripple frequency,
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 2-1.
Tantalum Capacitors( Optional Output 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 rec-
ommended 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 dissipation, and lower ripple current ca-
pability. The TAJ series is also less reliable than the AVX
TPS series when determining power dissipation capa-
bility. Tantalum or Oscon® types are recommended for
applications where ambient temperatures fall below 0°C.
Capacitor Table
Table 2-1 identifies the characteristics of capacitors from a
number of vendors with acceptable ESR and ripple cur-
rent (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 2-1: Input/Output Capacitors
Capacitor
Vendor/
Series
Panasonic
FK (SMT)
FC (Radial)
United LXZ
Chemi -Con
FX
Nichicon
PL Series
NX (SM)
Oscon
SP (Radial)
SVP (SMT)
AVX
Tanatalum
TPS- Series
Sprague
Tantalum
595D/594D
Kemet
Tantalum
T510/T495
Series
Sanyo Poscap
TPB
Working
Voltage
25V
35V
16V
16V
25V
16V
10V
25V
10V
10V
10V
10V
10V
10V
10V
10V
10V
10V
10V
Capacitor Characteristics
Value(µF) (ESR) Equivalent
Series Resistance
2200
330
470
1500
330
1500
680
390
1500
330
0.038.
0.080.
0.090.
0.043.
0.090.
0.038.
0.015.
0.080.
0.050.
0.024.
105°C Maximum
Ripple
Current(Irms)
1800mA
850mA
755mA
1690mA
760mA
1660mA
4735mA
720mA
1330mA
3770mA
470
0.015.
330
0.017.
330
0.10.
330
0.060.
>4510mA
>3950mA
1414mA
1826mA
330 0.045.  4 =0.011.
680
0.09.
>4500mA
>1510mA
330
0.035.
220
0.07.  2 =0.035.
2000mA
>2000mA
220
0.04.
3000mA
Physical
Size(mm)
16x16.5
10x10.2
10x12.5
16x15
10x12.5
12.5x20
10x10.5
12.5x15
16x15
10x8
10x10.5
9x12x8.3
7.3Lx
4.3Wx
4.1H
7.3L x
5.7W x
4.0H
4.3Wx7.3L
x4.0H
7.2L x
4.3W x
3.1H
Quantity
Input
Bus
Output
Bus
Vendor Number
1
1 EEVFK1E222M
1 EEVFK1V331P
1 EEUFC1C471
1
1 EEUFC1C152S
1 LXZ25VB331M10X12LL
1
1 LXZ16VB152M12X20LL
2
1 10FX680M
1 UPL1E391MHH6
1
1 UPL1A152MHH6
5
1 PNX1A331MCR1GS
3
1 10SP470M
4
1 10SVP330M
5
1 TPSV337M010R0100
5
1 TPSV337M010R0060
5
1 594D337X0010R2T
2
1 595D687X0010R2T
(Surface Mount)
5
1 510X337M010AS
6
2 T495X227M010AS
(Surface Mount)
6
2 10TPB220M
(Surface Mount)
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