IFX 80471SK V50 Infineon Technologies, IFX 80471SK V50 Datasheet - Page 26

• Manufacturer Part Number: IFX 80471SK V50
• Manufacturer: Infineon Technologies

Specifications of IFX 80471SK V50

• Packages: PG-DSO-14
• Comment: Vin up to 60V; external MOS; PG-DSO-14
• Vq (max): 5.0 V
• Iq (max): 2,300.0 mA
• Iq (typ): 130.0 µA
• Output: Buck Converter

From the formula it is recognized that the ESR has a big influence in the total ripple at the output, so low ESR
tantalum or ceramic capacitors are recommended for the application (recommended range: 50mOhm to
150mOhm).
One other important thing to note are the requirements for the resonant frequency of the output LC-combination.
The choice of the components L and C have to meet also the specified range given in
instabilities of the regulation loop might occur.
7.8.5
At high load currents, where the current through the inductance flows continuously, the input capacitor is exposed
to a square wave current with its duty cycle V
low ESR should be used. The maximum RMS current which the capacitor has to withstand is calculated to:
For low ESR an e.g. Al-electrolytic capacitance in parallel to an ceramic capacitance could be used.
7.8.6
For lowest power loss in the freewheeling path Schottky diodes are recommended. With those types the reverse
recovery charge is negligible and a fast hand over from freewheeling to forward conduction mode is possible.
Depending on the application (12V battery systems) 40V types could be also used instead of the 60V diodes. Also
for high temperature operation select a Schottky-diode with low reverse leakage.
A fast recovery diode with recovery times in the range of 30ns can be also used if smaller junction capacitance
values (smaller spikes) are desired.
7.8.7
The voltage at the ceramic capacitor is clamped internally to 7V, a ceramic type with a minimum of 220nF and
voltage class 16V would be sufficient.
7.8.8
At the input of Buck converters a square wave current is observed causing electromagnetic interference on the
battery line. The emission to the battery line consists on one hand of components of the switching frequency
(fundamental wave) and its harmonics and on the other hand of the high frequency components derived from the
current slope. For proper attenuation of those interferers a π-type input filter structure is recommended which is
built up with inductive and capacitive components in addition to the Input caps C
be chosen up to the value of the Buck converter inductance, higher values might not be necessary, the additional
capacitance should be a ceramic type in the range up to 100nF.
Inexpensive input filters show due to their parasitics a notch filter characteristic, which means basically that the
low pass filter acts from a certain frequency as a high pass filter and means further that the high frequency
components are not attenuated properly. To slower down the slopes at the gate of the PMOS switch and get down
the emission in the high frequency range a small gate resistor can be put between GDRV and the PMOS gate.
7.8.9
The external frequency compensation pin should be connected via a 22nF (>10V) ceramic capacitor and a 430 Ω
(1/8W) resistor to GND. This node should be kept free from switching noise.
Data Sheet
Input capacitor (C
Freewheeling diode / catch diode (D1)
Frequency compensation
Buck driver supply capacitor (C
Input pi-filter components for reduced EME
I
IN1
RMS
) selection:
=
I
LOAD
OUT
/V
⋅
I
V
--------------
. To prevent a high ripple to the battery line a capacitor with
V
OUT
BDS
IN
25
⋅
)
1
+
1
-- -
3
⋅
⎛
⎝
-----------------------
2 I
⋅
ΔI
LOAD
⎞
⎠
2
IN1
and C
Application Information
IN2
Chapter 4.2
Rev. 1.0, 2011-02-07
. The inductance can
IFX80471
otherwise