PT6880_09 Datasheet, PDF (4/10 Pages) Texas Instruments – 5A Non-Isolated Output

Application Notes
PT6880 Series
Capacitor Recommendations for the
PT6880 Regulator Series
Input Capacitor:
The required input capacitor is determined by a 1.2Arms
minimum ripple current rating and 560µF capacitance
value. The ripple current rating and <120mΩ equivalent
series resistance (ESR) are the major considerations, along
with temperature, when designing with different types of
capacitors.
Tantalum/Os-Con® capacitors are not recommended
due to a minimum voltage rating of 2× (the maximum
DC voltage + AC ripple). This is necessary to improve
the reliability of these capacitors in high bus applications.
Output Capacitors:
The ESR specification of the output capacitor should be
at least 50mΩ. 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. Electrolytic capacitors with appropriate
ESR values are identified in Table 1-1. In low-temperature
applications (<0°C), a higher capacitance with lower ESR
will improve performance.
Os-Con® and ultra low ESR type capacitors are not recom-
mended on the output bus as they degrade regulator stability.
Tantalum Capacitors (For V_out <5.1V)
Tantalum type capacitors can be used on the output bus
for output voltages less than 5.1V. Voltages higher than this
will exceed the capacitor’s published surge voltage limits.
If tantalum capacitors are located on the output bus, an
appropriate fuse with I²t current derating is recommended
along with an external clamp component. An Output
Over-voltage Clamp (OOVC) will fault the output fuse
protecting the capacitors in event of an over-voltage condi-
tion. The OOVC can be a simple zener high power di-
ode, 3-5W, located on the load side of the output bus. The
zener diode should be rated to 1.3 times the normal out-
put voltage.
Capacitor Table
Table 1-1 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 1-1: Input/Output Capacitors
Capacitor Vendor/
Series
Panasonic
FC (Radial)
FC/FK (Surface Mtg)
United Chemi-con
LXZ/LXV Series
MVY (Surface Mtg)
Nichicon
PM Series
AVX Tantalum
TPS (Surface Mtgt)
Kemet Tantalum (2)
T496 /T495 Series
(Surface Mount)
Sprague Tantalum (2)
594D Series
(Surface Mount)
Capacitor Characteristics
Quantity
Working
Voltage
50V
50V
50V
63V
35V
50V
50V
35V
35V
50V
63V
50V
10V
10V
Value(µF)
560
390
390
680
330
1000
680
330
220
560
560
330
330
330
(ESR) Equivalent
Series Resistance
0.068Ω
0.080Ω
0.080Ω
0080Ω
0.080Ω
0.073Ω
0.048Ω
0.068Ω
0.150Ω
0.044Ω
0.039Ω
0.060Ω
0.10Ω
0.06Ω
105°C Maximum
Ripple
Current(Irms)
1900mA
1610mA
1610mA
1690mA
850mA
1610mA
1840mA
1050mA
670mA
1550mA
1400mA
1210mA
>2500mA
>3000mA
10V
220
10V
220
0.500Ω
0.070Ω
500mA
>2000mA
10V
330
0.130Ω
1393mA
Physical
Size(mm)
18×15
16x15
16×15
18×16.5
10×10.2
16×16.5
16×20
10×16
10×10.3
16×20
18×20
16×15
7.3L
×5.7W
×4.1H
4.3W
×7.3L
×4.0H
7.2L
×6W
×4.1H
Input
Bus
Output
Bus
Vendor Part Number
1
2
2
1
N/R (1)
1
1
N/R (1)
N/R (1)
1
1
2
N/R (1)
N/R (1)
N/R (1)
N/R (1)
N/R (1)
1 EEUFC1H561
1 EEUFC1H391S
1 EEUFC1H391S
1 EEVFK1J681M
1 EEVFK1V331P
1 EEVFK1H102M
1 LXZ50VB681M16X20LL
1 LXV35VB331M10X16LL
2
MVY35VC2211M10X10TP
1 UPM1H561MHH6
1 UPM1J561MHH6
1 UPM1H331MHH6
1
TPSE337M010R0100 (Vo <5.1V)
1
TPSV337M010R0060 (Vo <5.1V)
2
T496X227M010AS (Vo <5.1V)
2
T495X227M0100AS (Vo <5.1V)
1
595D337X0010R2T (Vo <5.1V)
Notes: (1) N/R –Not recommended. The voltage rating does not meet the minimum operating limits.
(2) A fused input bus is recommended when tantalum capacitors are used on the output bus.
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