Datasheet

LM3243
V
DD
SW
FB
EN
VCON
PGNDSGND
BP
ACB
GPIO
GPIO
MODE
PDM Output
DAC
PV
IN
V
OUT
V
IN
10 µF
10 µF
4.7 µF
1.5 µH
BGND
LM3243
SNVS782B –OCTOBER 2010–REVISED FEBRUARY 2013 www.ti.com
APPLICATION INFORMATION
Setting the Output Voltage
DAC Control
An analog voltage to the VCON pin can dynamically program the output voltage from 0.4V (typ.) to 3.6V (typ.) in
both PFM and PWM modes of operation, without the need for external resistors. The output voltage is governed
by Table 2.
Table 2. Output Voltage Selection
VCON (V) V
OUT
(V)
VCON = 0.16V to 1.44V 2.5 x VCON
Figure 21. Dynamic Adjustment of Output Voltage with DAC or PDM
PDM-Based VCON Signal
Figure 21 shows the application circuit that enables the LM3243 to dynamically adjust the output voltage using a
GPIO pin from the system controller. Figure 22 shows the waveforms when adjusted dynamically. The PDM
signal of the GPIO is filtered using a low-pass filter and fed to the VCON pin. As the bitstream of the PDM signal
changes, the voltage on the VCON pin changes. Thus, the GPIO pin can be used to dynamically adjust the
output voltage. The double low-pass filter reduces the ripple at VCON to avoid any excessive VCON-induced
ripple at the output voltage.
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