L6726A_07 STMICROELECTRONICS [STMicroelectronics], L6726A_07 Datasheet - Page 15

• Manufacturer Part Number: L6726A_07
• Description: Single phase PWM controller
• Manufacturer: STMICROELECTRONICS [STMicroelectronics]

L6726A
8
8.1
8.2
Application details
Output voltage selection
L6726A is capable to precisely regulate an output voltage as low as 0.8V. In fact, the device
comes with a fixed 0.8V internal reference that guarantees the output regulated voltage to
be within ±1% tolerance over line and temperature variations between 0°C and 70°C
(excluding output resistor divider tolerance, when present).
Output voltage higher than 0.8V can be achieved by adding a resistor R
and ground. Referring to
where V
Compensation network
The control loop shown in
transconductance type with fixed gain (3.3mS typ.). The FB voltage is regulated to the
internal reference, thus the output voltage is fixed accordingly to the output resistor divider
(when present).
Transconductance error amplifier output current generates a voltage across Z
compared to oscillator saw-tooth waveform to provide PWM signal to the driver section.
PWM signal is then transferred to the switching node with V
filtered by the output filter.
Figure 8.
The converter transfer function is the small signal transfer function between the voltage at
the output node of the EA (COMP) and V
conjugate) at frequency F
REF
is 0.8V.
PWM control loop
∆V
OSC
OSC
Figure
LC
Figure 8
C
R
depending on the L-C
F
COMPARATOR
F
V
COMP
1, the steady state DC output voltage will be:
OUT
_
+
PWM
is a voltage mode control loop. The error amplifier is a
Z
C
F
=
P
OTA
V
OUT
REF
. This function has a double pole (complex
+
_
⋅
⎛
⎝
V
OUT
1
V
IN
R
REF
FB
+
OS
resonance and a zero at F
---------- -
R
R
L
OS
FB
R
FB
IN
⎞
⎠
amplitude. This waveform is
OUTPUT
DIVIDER
R
C
ESR
OUT
Application details
OS
V
between FB pin
OUT
F
, which is
ESR
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