PT7708-3.3V Datasheet, PDF (3/4 Pages) Texas Instruments – Integrated Switching Regulator

Application Notes
PT7708/PT7709, PT7742/PT7743
Capacitor Recommendations for the PT7708/09
Regulators and PT7742/43 Current Boosters
Input Capacitors
The recommended input capacitance is determined by
1.4 ampere minimum ripple current rating and 1500µF
minimum capacitance. Capacitors listed below must be
rated for a minimum of 2x the input voltage with +5V
operation. Ripple current and ≤100mΩ Equivalent Series
Resistance (ESR) values are the major considerations along
with temperature when selecting the proper capacitor.
Output Capacitors
The minimum required output capacitance is 330µF with
a maximum ESR less than or equal to 100mΩ. Failure to
observe this requirement may lead to regulator instability
or oscillation. Electrolytic capacitors have poor ripple per-
formance at frequencies greater than 400kHz, but excellent
low frequency transient response. Above the ripple fre-
quency ceramic decoupling capacitors are necessary to
improve the transient response and reduce any microproces-
sor high frequency noise components apparent during
higher current excursions. Preferred low ESR type capaci-
tor part numbers are identified in the Table 1 below.
Table 1 Capacitors Characteristic Data
Tantalum Characteristics
Tantalum capacitors with a minimum 10V rating are
recommended on the output bus, but only the AVX TPS
Series, Sprague 594/595 Series, or Kemet T495/T510 Series.
The AVX TPS Series, Sprague Series or Kemet Series
capacitors are specified over other types due to their
higher surge current, excellent power dissipation and ripple
current ratings. As an example, the TAJ Series by AVX is
not recommended. This series exhibits considerably higher
ESR, reduced power dissipation and lower ripple current
capability. The TAJ Series is a less reliable compared to
the TPS series when determining power dissipation capability.
Capacitor Table
Table 1 identifies the characteristics of capacitors from a
number of vendors with acceptable ESR and ripple current
(rms) ratings. The suggested minimum quantities per regu-
lator for both the input and output buses are identified.
This is not an extensive capacitor list. The table below is a
selection guide for input and output capacitors. Other capacitor
vendors are available with comparable RMS ripple current rating
and ESR (Equivalent Series Resistance at 100kHz). These
critical parameters are necessary to insure both optimum regulator
performance and long capacitor life.
Capacitor
Vendor/
Series
Panasonic
FC
Surface Mtg
FA
United
Chemi -Con
LFVSeries
Nichicon
PL Series
PM Series
Oscon SS
SV
AVX
Tanatalum
TPS- Series
Sprague
Tantalum
595D/594D
Kemet
Tantalum
T510/T495
Series
Sanyo Poscap
TPB
Capacitor Characteristics
Working
Voltage
16V
35V
10V
16V
25V
16V
16V
10V
10V
25V
10V
10V
10V
10V
Value(µF) (ESR) Equivalent
Series Resistance
2200
330
680
1800
330
2200
470
680
1800
330
330
330
330
330
0.038Ω
0.065Ω
0.090Ω
0.032Ω
0.084Ω
0.038Ω
0.084Ω/2=042Ω
0.090Ω
0.044Ω
0.095Ω
0.025W/4=0.006Ω
0.020/4=0.005Ω
0.100/5=20Ω
0.060Ω
105°C Maximum
Ripple
Current(Irms)
2000mA
1205mA
755mA
2000mA
825mA
1630mA
825mA x2
770mA
1420mA
750mA
>9800mA
>9800mA
3500mA
1826mA
10V
330
0.045W/4=0.011Ω
>4500mA
10V
680
0.090Ω
>1660mA
10V
330
0.035Ω
2000mA
10V
220
0.070Ω/2=0.035Ω
>2000mA
10V
220
0.040Ω
3000mA
Physical
Size(mm)
18x16.5
12.5x16.5
10x12.5
18x15
10x16
16x20
10x16
10x15
16x15
10x15
10x10.5
10.3x12.6
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
Note: (N/R) is not recommended for this application, due to extremely low Equivalent Series Resistance (ESR)
Quantity
Input Output
Bus
Bus
Vendor Number
1
1 EEVFC1C222N
1 EEVFC1V331LQ
1 EEUFA1A681
1
1 EEUFA1C182A
1 LXV25VB331M10X16LL
1
1 LXV16VB222M16X20LL
1 LXV16VB471M10X16LL
1 UPL1A681MHH6
1
1 UPL1A182MHH6
1 UPL1E331MPH6
4
N/R 10SS330M
4
(Note) 10SV330M(Sufvace Mtg
5
1 TPSV337M010R0100
5
1 TPSV337M010R0060
5
1 594D337X0010R2T
Surface Mount
2
1 595D687X0010R2T
5
1 510X337M010AS
6
2 T495X227M010AS
Surface Mount
6
2 10TPB220M
Surface Mount
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