L6566BH View Datasheet(PDF) - STMicroelectronics
Part Name
Description
MFG CO.
'L6566BH' PDF : 51 Pages View PDF
L6566BH
Application information
The voltage on the pin is clamped upwards at about 3.15 V; then, if the function is not used,
the pin must be connected to Vcc through a resistor (220 to 680 kΩ).
5.13
Slope compensation
The MODE/SC pin (12), when not connected to VREF, provides a voltage ramp during
MOSFET ON-time synchronous to that of the internal oscillator sawtooth, with 0.8 mA
minimum current capability. This ramp is intended for implementing additional slope
compensation on current sense. This is needed to avoid the sub-harmonic oscillation that
arises in all peak-current-mode-controlled converters working at fixed frequency in
continuous conduction mode with a duty cycle close to or exceeding 50%.
Figure 27. Slope compensation waveforms
Internal
oscillator
Note:
GD
t
(pin 4)
MODE/SC
t
(pin 12)
t
AM11503v1
The compensation is realized by connecting a programming resistor between this pin and
the current sense input (pin 7, CS). The CS pin must be connected to the sense resistor with
another resistor to make a summing node on the pin. Since no ramp is delivered during
MOSFET OFF-time (see Figure 27), no external component other than the programming
resistor is needed to ensure a clean operation at light loads.
The addition of the slope compensation ramp reduces the available dynamics of the current
signal; thereby, the value of the sense resistor must be determined taking this into account.
Note also that the burst-mode threshold (in terms of power) is slightly changed.
If slope compensation is not required with FF operation, the pin is left floating.
5.14
Summary of L6566BH power management functions
The device is provided with a number of power management functions: multiple operating
mode upon loading conditions and protection functions. To help the user familiarize
themselves with these functions, in the following tables, all themes are summarized with
their respective activation mechanism and the resulting status of the most important pins.
This can be useful not only for a correct use of the IC but also for diagnostic purposes:
especially at the prototyping/debugging stage, it is quite common to come across unwanted
activation of some function, and these tables can be used as a kind of quick troubleshooting
guide.
Doc ID 16610 Rev 2
39/51
Share Link: 
