PT8125 Datasheet, PDF (7/10 Pages) Texas Instruments – 30-A 12-V Input Programmable Integrated Switching Regulator

Application Notes
PT8120 Series & PT8139
Capacitor Recommendations for the
PT8120 Series of Programmable ISRs
Input Capacitors
The recommended input capacitor(s) is determined by
1.6 Arms minimum ripple current rating and 1,500µF
minimum capacitance. Ripple current and Equivalent
Series Resistance (ESR) values are the major considerations
along with temperature when selecting the proper capaci-
tor. The tantalum capacitors listed below cannot be used
on the input bus since they are not rated for 12V operation.
Output Capacitors
The minimum required output capacitance is 660µF
(organic/polymer), or 1,200 (aluminum electrolytic) with
a maximum ESR less than or equal to 50mΩ. Failure to
observe this requirement may lead to regulator instabil-
ity or oscillation. Electrolytic capacitors have poor ripple
performance at frequencies greater than 400kHz, but
excellent low frequency transient response. Above the
ripple frequency ceramic decoupling capacitors are nec-
essary to improve the transient response and reduce any
microprocessor high frequency noise components apparent
during higher current excursions. Preferred low ESR type
capacitor part numbers are identified in the Table 1 below.
Tantalum Characteristics
Tantalum capacitors are recommended on the output bus
but only AVX TPS Series, Sprague 593D/594/595 Series,
or Kemet T495/T510,520 Series. These capacitors are
recommended over other types due to their higher surge
current, excellent power dissipation and ripple current
ratings. As a caution, the TAJ Series by AVX is not rec-
ommended. This series exhibits considerably higher ESR,
reduced power dissipation and lower ripple current capa-
bility. The TAJ Series is also 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
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 the
critical parameters are necessary to insure both optimum
regulator performance and long capacitor life.
Table 1 Capacitors Characteristic Data
Capacitor Vendor/
Series
Capacitor Characteristics
Quantity
Working Value(µF) (ESR) Equivalent
Voltage
Series Resistance
Panasonic
35V
FC (Radial)
25V
16V
FC/FK (Surface Mount)
25V
16V
United Chemi-con
35V
LXZ Series
25V
16V
Nichicon
25V
PW Series
25V
PM Series
25V
Os-con:( Organic)
SS
10V
SV (Surface Mount)
10V
AVX Tantalum
10V
TPS (Surface Mount)
10V
1500
1500
4700
2200
2200
1800
1800
2700
1000
1800
1500
0.028Ω
0.029Ω
0.033Ω
0.028Ω
0.038Ω
0.028Ω
0.029Ω
0.029Ω
0.038÷2Ω
0.029Ω
0.034Ω
330
0.025Ω
330
0.020Ω
330
0.1Ω÷2 =0.05Ω
330
0.06Ω÷2 =0.03Ω
105°C Maximum
Ripple
Current(Irms)
2490mA
2205mA
2060mA
2490mA
2000mA
2490mA
2210mA
2210mA
3200mA
2205mA
1770mA
3500mA
3800mA
>2500mA
>3000mA
Kemet
Polymer/Tantalum
T520Series
(Surface Mount)
Sprague Tantalum
594D Series
(Surface Mount)
10V
330
10V
330
10V
330
0.040÷2Ω
0.040÷2Ω
0.045÷2Ω
1800mA
>1800mA
2360mA
Physical
Size(mm)
18× 20
16× 20
18×16.5
18×21.5
18×16.5
18× 20
16×20
16× 20
12.5x20
16x20
16×20
10×10.5
10.3×10.3
7.3L
×5.7W
×4.1H
4.3W
×7.3L
×4.0H
7.2L
×6W
×4.1H
Note: (N/R -Not recommended) The 10V-rated tantalum capacitors cannot be used on the input bus.
Input
Bus
Output
Bus
Vendor Part Number
1
1 EEUFC1V152S
1
1 EEUFC1E152S
1
1 EEVFK1C472M
1
1 EEVFC1E222N
2
1 EEVFC1C222N
1
1 LXZ35VB182M18X20LL
1
1 LXZ25VB182M16X20LL
1
1 LXZ16VB272M16X20LL
2
1 UPW1E102MHH
1
1 UPW1E182MHH6
1
1 UPM1E152MHH6
N/R(1)
N/R(1)
N/R(1)
N/R(1)
N/R(1)
N/R(1)
2 10SS330M (Vo<6V)
2 10SV330 (Vo<6V)
2 TPSE337M010R0100 (Vo<5V)
2 TPSV337M010R0060( Vo<5V)
2 T520X337M010AS (Vo<6V)
2 T520D330M006AS (Vo<4V)
N/R(1)
2 594D337X0010R2T(Vo<5V)
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