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| TLD5085EJ Datasheet, PDF (11/16 Pages) Infineon Technologies AG – 1.8A DC/DC Step-Down Converter Infineon Power LED Driver | |||
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TLD5085EJ
Application Information
8
Application Information
Note: The following information is given as a hint for the implementation of the device only and shall not be
regarded as a description or warranty of a certain functionality, condition or quality of the device.
8.1
Frequency Compensation
The stability of the output voltage can be achieved with a simple RC connected between pin COMP and GND. The
standard configuration using the switching frequency of the internal oscillator is a ceramic capacitor CCOMP = 22nF
and RCOMP = 22kâ¦. By slight modifications to the compensation network the stability can be optimized for different
types of buck capacitors (ceramic or tantalum).
The compensation network is essential for the control loop stability. Leaving pin COMP open might lead to an
instable operation.
8.2
Compensating a tantalum buck capacitor CBU1
The TLD5085EJ control loop is optimized for ceramic buck capacitors CBU. In order to maintain stability also for
tantalum capacitors with ESR up to 300mâ¦, an additional compensation capacitance CCOMP2 at pin COMP to GND
is required. Itâs value calculates:
CCOMP2 = CBU * ESR(CBU) / RCOMP ,
whereas CCOMP2 needs to stay below 5nF.
CCOMP2
COMP
3
CCOMP
RCOMP
Application _C-COMP2.vsd
TLD5085
2
GND
Figure 4 High-ESR buck capacitor compensation
8.3
Freewheeling Diode
In order to minimize losses and for fast recovery, a schottky freewheeling diode is required. Disconnecting the
freewheeling diode during operation might lead to destruction of the IC.
Datasheet
11
Rev. 1.0, 2009-06-04
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