TLE8386-2EL Datasheet, PDF (13/32 Pages) Infineon Technologies AG – Basic Smart Boost Controller

TLE8386-2EL
Oscillator and Synchronization
6
Oscillator and Synchronization
6.1
Description
R_OSC vs. switching frequency
The internal oscillator is used to determine the switching frequency of the boost regulator. The switching frequency
can be selected from 100 kHz to 700 kHz with an external resistor to GND. To set the switching frequency with an
external resistor the following formula can be applied.
( ) ( ) ^{( )} [ ] [ ] ^{[ ] [ ] R FREQ}
=
1
141 × 10 ^−12
s
Ω
×
f _FREQ
1
s
− 3 .5 × 10 ³ Ω
Ω
In addition, the oscillator is capable of changing from the frequency set by the external resistor to a synchronized
frequency from an external clock source. If an external clock source is provided on the pin SYNC, the internal
oscillator should adjusted close to this frequency. Then it synchronizes to this external clock frequency and the
boost regulator switches at the synchronized frequency. The synchronization frequency capture range is from 250
kHz to 700 kHz.
VCLK
SYNC
FREQ
R FREQ
Clock Frequency
Detector
Oscillator
TLE8386-2EL
Multiplexer
PWM
Logic
Gate
Driver
SWO
Oscillator_BlkDiag.vsd
Figure 4 Oscillator and Synchronization Block Diagram and Simplified Application Circuit
9_6<1&
9
96<1&+
9 ^96<1&/
W6<1&75
W6<1&75
76<1& I6<1&
W6<1&3:+
Figure 5 Synchronization Timing Diagram
W
2VFLOODWRUB7LPLQJVYJ
Data Sheet
11
Rev. 1.0, 2010-10-25