PT6722 Datasheet, PDF (6/7 Pages) Texas Instruments – 14-A Low-Voltage Programmable Integrated Switching Regulator

Application Notes
PT6721/6722, & PT6725 Series
Capacitor Recommendations for the PT6721,
PT6722, and PT6725 Series of Regulators
Input Capacitors
The recommended input capacitance is determined by 1.6
ampere minimum ripple current rating and 1000µF mini-
mum capacitance. Tantalum capacitors listed below cannot
be used on the input bus since they are not rated for 12V
operation. Ripple current and Equivalent Series Resistance
(ESR) values are the major considerations along with tem-
perature when selecting the proper capacitor.
Output Capacitors
The minimum required output capacitance is 330µF with a
maximum ESR less than or equal to 50mW. Failure to ob-
serve this requirement may lead to regulator instability or
oscillation. Electrolytic capacitors have poor ripple per-
formance at frequencies greater than 400kHz, but excellentlow
frequency transient response. Above the ripple frequency ce-
ramic decoupling capacitors are necessary to improve the
transient response and reduce any microprocessor high
frequency noise components apparent during higher cur-
rent excursions. Preferred low ESR type capacitor part
numbers are identified in the Table 1 below.
Tantalum Characteristics
Tantalum capacitors may be used on the output bus but
only the AVX TPS series, Sprague 593D/594/595 series,
or Kemet T495/T510 series. These capacitors are recom-
mended over many other tantalum types due to their high
surge current, excellent power dissipation and ripple
current ratings. 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 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 necessary to insure both optimum regulator
performance and long capacitor life.
Table 1 Capacitors Characteristic Data
Capacitor
Vendor/
Series
Capacitor Characteristics
Quantity
Panasonic
FC Series/
FA Series
United
Chemi-con
LFVSeries
Nichicon
PL Series/
PM Series
Panasonic
FC Series
Surface Mtg
Oscon-
SS/SV Series
AVX
Tantalum
TPS Series
Kemet
Tantalum
T510/T495
Series
Sprague
Tantalum
594D Series
Working
Voltage
35V
25V
25V
35V
35V
16V
35V
25V
35V
35V
25V
35V
Value(µF) (ESR) Equivalent
Series Resistance
680
1000
1000
680
1000
470
680
1200
1000
1000
1000
470
0.043Ω
0.038Ω
0.038Ω
0.034Ω
0.038Ω
0.084Ω÷2 =0.042Ω
0.036Ω
0.039Ω
0.034Ω
0038Ω
0.038Ω
0.043Ω
105°C Maximum
Ripple
Current(Irms)
1655mA
1655mA
1690mA
1690mA
1630mA
825mA (x2)
1660mA
1600mA
1770mA
2000mA
2000mA
1690mA
10V
330
10V
330
0.025Ω
0.020Ω
3500mA
3800mA
10V
330
0.1Ω÷2 =0.05Ω
>2500mA
10V
330
0.06Ω÷2 =0.03Ω
>3000mA
10V
330
0.033Ω
1400mA
10V
220
0.07Ω÷2 =0.035Ω
>2000mA
10V
330
0.045Ω
2360mA
Physical
Size(mm)
Input
Bus
Output
Bus
Vendor Part Number
12.5x20
12.5x20
16x15
12.5x25
16x20
10x16
12.5x25
18x15
16x20
18x16.5
18x16.5
16x16.5
2
1
1
2
1
N/R(1)
2
1
1
1
1
2
10x10.5 N/R(1)
10.3x10.3 N/R(1)
7.3L x
5.7W x
4.1H
N/R(1)
N/R(1)
4.3Wx7.3L
x4.0H
N/R(1)
N/R(1)
7.2L x
6W x
4.1H
N/R(1)
1 EEUFC1V681
2 EEUFC1E102
1 EEUFC1E102S
1 LXV35VB680M12X25LL
1 LXV35VB102M16X20LL
2 LXV16VB471M10X16LL
1 UPL1V681MHH
1 UPL1E122MHH6
1 UPM1V102MHH6
1 EEVFC1V102N
1 EEVFC1E102N
1 EEVFC1V471N
1 10SS330M (If Vo <5V)
1 10SV330 (If Vo <5V)
Surface Mount (SV)
2 TPSE337M010R0100
2 TPSV337M010R0060
Surface Mount
1 510X337M010AS
2 T495X227M0100AS
Surface Mount
1 594D337X0010R2T
Surface Mount
Note: (N/R) 10V tantalums are not recommend for the input bus.
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