L6911C Ver la hoja de datos (PDF) - STMicroelectronics
Número de pieza
componentes Descripción
Fabricante
L6911C Datasheet PDF : 20 Pages
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L6911C
fS = 200kH z + -4---.-R3----0T---6-(--k--⋅-Ω--1---0-)---7-
VCC = 12V
fS = 200kH z + 1-R---5-T---(-⋅--k-1--Ω-0----7)-
VCC = 5V
Switching frequency variations vs. RT are reported in Fig.1.
Note that forcing a 50µA current into this pin, the device stops switching because no current is delivered to the
oscillator.
Figure 1.
10000
1000
100
RT to G N D
10
RT to V CC =12V
RT to V CC =5V
10
100
1000
Frequency [kHz]
Digital to Analog Converter
The built-in digital to analog converter allows the adjustment of the output voltage from 1.30V to 2.05V with
50mV binary steps and from 2.10V to 3.50V with 100mV binary steps as shown in the previous table 1. The
internal reference is trimmed to ensure the precision of 1%.
The internal reference voltage for the regulation is programmed by the voltage identification (VID) pins. These
are TTL compatible inputs of an internal DAC that is realized by means of a series of resistors providing a par-
tition of the internal voltage reference. The VID code drives a multiplexer that selects a voltage on a precise
point of the divider. The DAC output is delivered to an amplifier obtaining the VPROG voltage reference (i.e. the
set-point of the error amplifier). Internal pull-ups are provided (realized with a 5µA current generator); in this
way, to program a logic "1" it is enough to leave the pin floating, while to program a logic "0" it is enough to short
the pin to GND.
The voltage identification (VID) pin configuration also sets the power-good thresholds (PGOOD) and the over-
voltage protection (OVP) thresholds.
The VID code "11111" disable the device (as a short on the SS pin) and no output voltage is regulated.
Soft Start and Inhibit
At start-up a ramp is generated charging the external capacitor CSS by means of a 10µA constant current, as
shown in figure 1.
When the voltage across the soft start capacitor (VSS) reaches 0.5V the lower power MOS is turned on to dis-
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