IFX54441EJV50_15 Datasheet, PDF (20/25 Pages) Infineon Technologies AG – Wide Input Range Low Noise 300mA 5V LDO

IFX54441EJV50
IFX54441LDV50
Application Information
(see Figure 5). Please note that the voltage drop across the external PC trace will add up to the dropout voltage
of the regulator.
V_IN
C_IN
IFX54441
IN OUT
SENSE
EN BYP
GND
R
P
C_OUT
R _Load
R_P
Figure 5 Kelvin Sense Connection
7.2
Bypass Capacitance and Low Noise Performance
The IFX54441 V50 regulator may be used in combination with a bypass capacitor connecting the OUT pin to the
BYP pin in order to minimize output voltage noise¹⁾.This capacitor will bypass the reference of the regulator,
providing a low frequency noise pole. The noise pole provided by such a bypass capacitor will lower the output
voltage noise in the considered bandwidth. For a given output voltage actual numbers of the output voltage noise
will - next to the bypass capacitor itself - be dependent on the capacitance of the applied output capacitor and its
ESR: In case of applying the IFX54441 V50 with a bypass capacitor of 10 nF in combination with a (low ESR)
ceramic C_OUT of 10 µF will result in output voltage noise numbers of typical 55 µV_RMS. This Output Noise level can
be reduced to typical 44 µV_RMS under the same conditions by adding a small resistance of ~250 mΩ in series to
the 10 µF ceramic output capacitor acting as additional ESR. A reduction of the output voltage noise can also be
achieved by increasing capacitance of the output capacitor. For C_OUT = 22 µF (ceramic low ESR) the output
voltage noise will be typical 42 µV_RMS. For output capacitor values of 22 µF or bigger adding resistance in series
to C_OUT does not further lower output noise numbers significantly anymore. For further details please also see
“Output Voltage Noise6)” on Page 10,, of the Electrical Characteristics. Please note that next to reducing the
output voltage noise level the usage of a bypass capacitor has the additional benefit of improving transient
response which will be also explained in the next chapter. However one needs to take into consideration that on
the other hand the regulator start-up time is proportional to the size of the bypass capacitor and slows down to
values around 15 ms when using a 10 nF bypass capacitor in combination with a 10 µF C_OUT output capacitor.
7.3
Output Capacitance Requirements and Transient Response
The IFX54441 V50 is designed to be stable with a wide range of output capacitors. The ESR of the output
capacitor is an essential parameter with regard to stability, most notably with small capacitors. A minimum output
capacitor of 3.3 µF with an ESR of 3 Ω or less is recommended to prevent oscillations. Like in general for LDO’s
the output transient response of the IFX54441 V50 will be a function of the output capacitance. Larger values of
output capacitance decrease peak deviations and thus improve transient response for larger load current
1) a good quality low leakage capacitor is recommended.
Data Sheet
20
Rev. 1.1, 2014-10-30