LMZ31710 Datasheet, PDF (12/33 Pages) Texas Instruments – 10A SIMPLE SWITCHER® Power Module with 2.95V-17V Input and Current Sharing in QFN Package

LMZ31710
SNVS987A – JULY 2013 – REVISED JULY 2013
Capacitor Recommendations for the LMZ31710 Power Supply
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Capacitor Technologies
Electrolytic, Polymer-Electrolytic Capacitors
When using electrolytic capacitors, high-quality, computer-grade electrolytic capacitors are recommended.
Polymer-electrolytic type capacitors are recommended for applications where the ambient operating temperature
is less than 0°C. The Sanyo OS-CON capacitor series is suggested due to the lower ESR, higher rated surge,
power dissipation, ripple current capability, and small package size. Aluminum electrolytic capacitors provide
adequate decoupling over the frequency range of 2 kHz to 150 kHz, and are suitable when ambient temperatures
are above 0°C.
Ceramic Capacitors
The performance of aluminum electrolytic capacitors is less effective than ceramic capacitors above 150 kHz.
Multilayer ceramic capacitors have a low ESR and a resonant frequency higher than the bandwidth of the
regulator. They can be used to reduce the reflected ripple current at the input as well as improve the transient
response of the output.
Tantalum, Polymer-Tantalum Capacitors
Polymer-tantalum type capacitors are recommended for applications where the ambient operating temperature is
less than 0°C. The Sanyo POSCAP series and Kemet T530 capacitor series are recommended rather than many
other tantalum types due to their lower ESR, higher rated surge, power dissipation, ripple current capability, and
small package size. Tantalum capacitors that have no stated ESR or surge current rating are not recommended
for power applications.
Input Capacitor
The LMZ31710 requires a minimum input capacitance of 44 μF of ceramic type. An additional 100 µF of non-
ceramic capacitance is recommended for applications with transient load requirements. The voltage rating of
input capacitors must be greater than the maximum input voltage. At worst case, when operating at 50% duty
cycle and maximum load, the combined ripple current rating of the input capacitors must be at least 5 Arms.
Table 6 includes a preferred list of capacitors by vendor. It is also recommended to place a 0.1 µF ceramic
capacitor directly across the PVIN and PGND pins of the device. When operating with split VIN and PVIN rails,
place 4.7µF of ceramic capacitance directly at the VIN pin.
Output Capacitor
The required output capacitance is determined by the output voltage of the LMZ31710. See Table 5 for the
amount of required capacitance. The effects of temperature and capacitor voltage rating must be considered
when selecting capacitors to meet the minimum required capacitance. The required output capacitance can be
comprised of all ceramic capacitors, or a combination of ceramic and bulk capacitors. The required capacitance
must include at least one 47 µF ceramic. When adding additional non-ceramic bulk capacitors, low-ESR devices
like the ones recommended in Table 6 are required. The required capacitance above the minimum is determined
by actual transient deviation requirements. See Table 7 for typical transient response values for several output
voltage, input voltage and capacitance combinations. Table 6 includes a preferred list of capacitors by vendor.
Table 5. Required Output Capacitance
V_OUT RANGE (V)
MIN
MAX
0.6
< 0.8
0.8
< 1.2
1.2
< 3.0
3.0
< 4.0
4.0
5.5
MINIMUM REQUIRED C_OUT (µF)
500 µF⁽¹⁾
300 µF⁽¹⁾
200 µF⁽¹⁾
100 µF⁽¹⁾
47 µF ceramic
(1) Minimum required must include at least one 47 µF ceramic capacitor.
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