TLF51801ELV Datasheet, PDF (16/29 Pages) Infineon Technologies AG – 10 A synchronous DC/DC Step-Down Controller

TLF51801ELV
Module Oscillator
6
Module Oscillator
6.1
Description
The oscillator supplies the device with a constant frequency. When the device is not operating in pulse skipping
mode, the external MOSFETs are switched on and off with the same constant frequency. Some safety functions
are synchronized also to this frequency.
The internal oscillator is used to determine the switching frequency of the buck regulator. The switching frequency
can be selected from 100 kHz to 700 kHz with an external resistor connected at pin SYNC/FREQ to GND. To set
the switching frequency with an external resistor the following formula can be applied
( ) ( ) ^{( )} [ ] [ ] ^{[ ] [ ] R FREQ}
=
149 × 10 ^−12
1
s
Ω
×
f _FREQ
1
s
− 2 .0 × 10 ³ Ω
Ω
80
70
60
50
40
30
20
10
0
100
200
300
400
500
600
700
Switching Frequency f_FREQ (kHz)
Figure 10 Resistor R_FREQ versus Switching Frequency f_FREQ
The turn-on frequency can optionally be set externally via the pin SYNC/FREQ. In this case the synchronization
of the PWM-on signal refers to the falling edge of the pin SYNC/FREQ input signal.
Data sheet
16
Rev. 1.0.1, 2013-04-15